1 // SPDX-License-Identifier: GPL-2.0-only
5 * Core kernel scheduler code and related syscalls
7 * Copyright (C) 1991-2002 Linus Torvalds
9 #define CREATE_TRACE_POINTS
10 #include <trace/events/sched.h>
11 #undef CREATE_TRACE_POINTS
15 #include <linux/nospec.h>
17 #include <linux/kcov.h>
18 #include <linux/scs.h>
20 #include <asm/switch_to.h>
23 #include "../workqueue_internal.h"
24 #include "../../fs/io-wq.h"
25 #include "../smpboot.h"
31 * Export tracepoints that act as a bare tracehook (ie: have no trace event
32 * associated with them) to allow external modules to probe them.
34 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp
);
35 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp
);
36 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp
);
37 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp
);
38 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp
);
39 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp
);
40 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp
);
41 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp
);
42 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp
);
43 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp
);
45 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq
, runqueues
);
47 #ifdef CONFIG_SCHED_DEBUG
49 * Debugging: various feature bits
51 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
52 * sysctl_sched_features, defined in sched.h, to allow constants propagation
53 * at compile time and compiler optimization based on features default.
55 #define SCHED_FEAT(name, enabled) \
56 (1UL << __SCHED_FEAT_##name) * enabled |
57 const_debug
unsigned int sysctl_sched_features
=
63 * Print a warning if need_resched is set for the given duration (if
64 * LATENCY_WARN is enabled).
66 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
69 __read_mostly
int sysctl_resched_latency_warn_ms
= 100;
70 __read_mostly
int sysctl_resched_latency_warn_once
= 1;
71 #endif /* CONFIG_SCHED_DEBUG */
74 * Number of tasks to iterate in a single balance run.
75 * Limited because this is done with IRQs disabled.
77 const_debug
unsigned int sysctl_sched_nr_migrate
= 32;
80 * period over which we measure -rt task CPU usage in us.
83 unsigned int sysctl_sched_rt_period
= 1000000;
85 __read_mostly
int scheduler_running
;
87 #ifdef CONFIG_SCHED_CORE
89 DEFINE_STATIC_KEY_FALSE(__sched_core_enabled
);
91 /* kernel prio, less is more */
92 static inline int __task_prio(struct task_struct
*p
)
94 if (p
->sched_class
== &stop_sched_class
) /* trumps deadline */
97 if (rt_prio(p
->prio
)) /* includes deadline */
98 return p
->prio
; /* [-1, 99] */
100 if (p
->sched_class
== &idle_sched_class
)
101 return MAX_RT_PRIO
+ NICE_WIDTH
; /* 140 */
103 return MAX_RT_PRIO
+ MAX_NICE
; /* 120, squash fair */
113 /* real prio, less is less */
114 static inline bool prio_less(struct task_struct
*a
, struct task_struct
*b
, bool in_fi
)
117 int pa
= __task_prio(a
), pb
= __task_prio(b
);
125 if (pa
== -1) /* dl_prio() doesn't work because of stop_class above */
126 return !dl_time_before(a
->dl
.deadline
, b
->dl
.deadline
);
128 if (pa
== MAX_RT_PRIO
+ MAX_NICE
) /* fair */
129 return cfs_prio_less(a
, b
, in_fi
);
134 static inline bool __sched_core_less(struct task_struct
*a
, struct task_struct
*b
)
136 if (a
->core_cookie
< b
->core_cookie
)
139 if (a
->core_cookie
> b
->core_cookie
)
142 /* flip prio, so high prio is leftmost */
143 if (prio_less(b
, a
, task_rq(a
)->core
->core_forceidle
))
149 #define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)
151 static inline bool rb_sched_core_less(struct rb_node
*a
, const struct rb_node
*b
)
153 return __sched_core_less(__node_2_sc(a
), __node_2_sc(b
));
156 static inline int rb_sched_core_cmp(const void *key
, const struct rb_node
*node
)
158 const struct task_struct
*p
= __node_2_sc(node
);
159 unsigned long cookie
= (unsigned long)key
;
161 if (cookie
< p
->core_cookie
)
164 if (cookie
> p
->core_cookie
)
170 void sched_core_enqueue(struct rq
*rq
, struct task_struct
*p
)
172 rq
->core
->core_task_seq
++;
177 rb_add(&p
->core_node
, &rq
->core_tree
, rb_sched_core_less
);
180 void sched_core_dequeue(struct rq
*rq
, struct task_struct
*p
)
182 rq
->core
->core_task_seq
++;
184 if (!sched_core_enqueued(p
))
187 rb_erase(&p
->core_node
, &rq
->core_tree
);
188 RB_CLEAR_NODE(&p
->core_node
);
192 * Find left-most (aka, highest priority) task matching @cookie.
194 static struct task_struct
*sched_core_find(struct rq
*rq
, unsigned long cookie
)
196 struct rb_node
*node
;
198 node
= rb_find_first((void *)cookie
, &rq
->core_tree
, rb_sched_core_cmp
);
200 * The idle task always matches any cookie!
203 return idle_sched_class
.pick_task(rq
);
205 return __node_2_sc(node
);
208 static struct task_struct
*sched_core_next(struct task_struct
*p
, unsigned long cookie
)
210 struct rb_node
*node
= &p
->core_node
;
212 node
= rb_next(node
);
216 p
= container_of(node
, struct task_struct
, core_node
);
217 if (p
->core_cookie
!= cookie
)
224 * Magic required such that:
226 * raw_spin_rq_lock(rq);
228 * raw_spin_rq_unlock(rq);
230 * ends up locking and unlocking the _same_ lock, and all CPUs
231 * always agree on what rq has what lock.
233 * XXX entirely possible to selectively enable cores, don't bother for now.
236 static DEFINE_MUTEX(sched_core_mutex
);
237 static atomic_t sched_core_count
;
238 static struct cpumask sched_core_mask
;
240 static void sched_core_lock(int cpu
, unsigned long *flags
)
242 const struct cpumask
*smt_mask
= cpu_smt_mask(cpu
);
245 local_irq_save(*flags
);
246 for_each_cpu(t
, smt_mask
)
247 raw_spin_lock_nested(&cpu_rq(t
)->__lock
, i
++);
250 static void sched_core_unlock(int cpu
, unsigned long *flags
)
252 const struct cpumask
*smt_mask
= cpu_smt_mask(cpu
);
255 for_each_cpu(t
, smt_mask
)
256 raw_spin_unlock(&cpu_rq(t
)->__lock
);
257 local_irq_restore(*flags
);
260 static void __sched_core_flip(bool enabled
)
268 * Toggle the online cores, one by one.
270 cpumask_copy(&sched_core_mask
, cpu_online_mask
);
271 for_each_cpu(cpu
, &sched_core_mask
) {
272 const struct cpumask
*smt_mask
= cpu_smt_mask(cpu
);
274 sched_core_lock(cpu
, &flags
);
276 for_each_cpu(t
, smt_mask
)
277 cpu_rq(t
)->core_enabled
= enabled
;
279 sched_core_unlock(cpu
, &flags
);
281 cpumask_andnot(&sched_core_mask
, &sched_core_mask
, smt_mask
);
285 * Toggle the offline CPUs.
287 cpumask_copy(&sched_core_mask
, cpu_possible_mask
);
288 cpumask_andnot(&sched_core_mask
, &sched_core_mask
, cpu_online_mask
);
290 for_each_cpu(cpu
, &sched_core_mask
)
291 cpu_rq(cpu
)->core_enabled
= enabled
;
296 static void sched_core_assert_empty(void)
300 for_each_possible_cpu(cpu
)
301 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu
)->core_tree
));
304 static void __sched_core_enable(void)
306 static_branch_enable(&__sched_core_enabled
);
308 * Ensure all previous instances of raw_spin_rq_*lock() have finished
309 * and future ones will observe !sched_core_disabled().
312 __sched_core_flip(true);
313 sched_core_assert_empty();
316 static void __sched_core_disable(void)
318 sched_core_assert_empty();
319 __sched_core_flip(false);
320 static_branch_disable(&__sched_core_enabled
);
323 void sched_core_get(void)
325 if (atomic_inc_not_zero(&sched_core_count
))
328 mutex_lock(&sched_core_mutex
);
329 if (!atomic_read(&sched_core_count
))
330 __sched_core_enable();
332 smp_mb__before_atomic();
333 atomic_inc(&sched_core_count
);
334 mutex_unlock(&sched_core_mutex
);
337 static void __sched_core_put(struct work_struct
*work
)
339 if (atomic_dec_and_mutex_lock(&sched_core_count
, &sched_core_mutex
)) {
340 __sched_core_disable();
341 mutex_unlock(&sched_core_mutex
);
345 void sched_core_put(void)
347 static DECLARE_WORK(_work
, __sched_core_put
);
350 * "There can be only one"
352 * Either this is the last one, or we don't actually need to do any
353 * 'work'. If it is the last *again*, we rely on
354 * WORK_STRUCT_PENDING_BIT.
356 if (!atomic_add_unless(&sched_core_count
, -1, 1))
357 schedule_work(&_work
);
360 #else /* !CONFIG_SCHED_CORE */
362 static inline void sched_core_enqueue(struct rq
*rq
, struct task_struct
*p
) { }
363 static inline void sched_core_dequeue(struct rq
*rq
, struct task_struct
*p
) { }
365 #endif /* CONFIG_SCHED_CORE */
368 * part of the period that we allow rt tasks to run in us.
371 int sysctl_sched_rt_runtime
= 950000;
375 * Serialization rules:
381 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
384 * rq2->lock where: rq1 < rq2
388 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
389 * local CPU's rq->lock, it optionally removes the task from the runqueue and
390 * always looks at the local rq data structures to find the most eligible task
393 * Task enqueue is also under rq->lock, possibly taken from another CPU.
394 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
395 * the local CPU to avoid bouncing the runqueue state around [ see
396 * ttwu_queue_wakelist() ]
398 * Task wakeup, specifically wakeups that involve migration, are horribly
399 * complicated to avoid having to take two rq->locks.
403 * System-calls and anything external will use task_rq_lock() which acquires
404 * both p->pi_lock and rq->lock. As a consequence the state they change is
405 * stable while holding either lock:
407 * - sched_setaffinity()/
408 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
409 * - set_user_nice(): p->se.load, p->*prio
410 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
411 * p->se.load, p->rt_priority,
412 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
413 * - sched_setnuma(): p->numa_preferred_nid
414 * - sched_move_task()/
415 * cpu_cgroup_fork(): p->sched_task_group
416 * - uclamp_update_active() p->uclamp*
418 * p->state <- TASK_*:
420 * is changed locklessly using set_current_state(), __set_current_state() or
421 * set_special_state(), see their respective comments, or by
422 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
425 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
427 * is set by activate_task() and cleared by deactivate_task(), under
428 * rq->lock. Non-zero indicates the task is runnable, the special
429 * ON_RQ_MIGRATING state is used for migration without holding both
430 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
432 * p->on_cpu <- { 0, 1 }:
434 * is set by prepare_task() and cleared by finish_task() such that it will be
435 * set before p is scheduled-in and cleared after p is scheduled-out, both
436 * under rq->lock. Non-zero indicates the task is running on its CPU.
438 * [ The astute reader will observe that it is possible for two tasks on one
439 * CPU to have ->on_cpu = 1 at the same time. ]
441 * task_cpu(p): is changed by set_task_cpu(), the rules are:
443 * - Don't call set_task_cpu() on a blocked task:
445 * We don't care what CPU we're not running on, this simplifies hotplug,
446 * the CPU assignment of blocked tasks isn't required to be valid.
448 * - for try_to_wake_up(), called under p->pi_lock:
450 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
452 * - for migration called under rq->lock:
453 * [ see task_on_rq_migrating() in task_rq_lock() ]
455 * o move_queued_task()
458 * - for migration called under double_rq_lock():
460 * o __migrate_swap_task()
461 * o push_rt_task() / pull_rt_task()
462 * o push_dl_task() / pull_dl_task()
463 * o dl_task_offline_migration()
467 void raw_spin_rq_lock_nested(struct rq
*rq
, int subclass
)
469 raw_spinlock_t
*lock
;
471 /* Matches synchronize_rcu() in __sched_core_enable() */
473 if (sched_core_disabled()) {
474 raw_spin_lock_nested(&rq
->__lock
, subclass
);
475 /* preempt_count *MUST* be > 1 */
476 preempt_enable_no_resched();
481 lock
= __rq_lockp(rq
);
482 raw_spin_lock_nested(lock
, subclass
);
483 if (likely(lock
== __rq_lockp(rq
))) {
484 /* preempt_count *MUST* be > 1 */
485 preempt_enable_no_resched();
488 raw_spin_unlock(lock
);
492 bool raw_spin_rq_trylock(struct rq
*rq
)
494 raw_spinlock_t
*lock
;
497 /* Matches synchronize_rcu() in __sched_core_enable() */
499 if (sched_core_disabled()) {
500 ret
= raw_spin_trylock(&rq
->__lock
);
506 lock
= __rq_lockp(rq
);
507 ret
= raw_spin_trylock(lock
);
508 if (!ret
|| (likely(lock
== __rq_lockp(rq
)))) {
512 raw_spin_unlock(lock
);
516 void raw_spin_rq_unlock(struct rq
*rq
)
518 raw_spin_unlock(rq_lockp(rq
));
523 * double_rq_lock - safely lock two runqueues
525 void double_rq_lock(struct rq
*rq1
, struct rq
*rq2
)
527 lockdep_assert_irqs_disabled();
529 if (rq_order_less(rq2
, rq1
))
532 raw_spin_rq_lock(rq1
);
533 if (__rq_lockp(rq1
) == __rq_lockp(rq2
))
536 raw_spin_rq_lock_nested(rq2
, SINGLE_DEPTH_NESTING
);
541 * __task_rq_lock - lock the rq @p resides on.
543 struct rq
*__task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
548 lockdep_assert_held(&p
->pi_lock
);
552 raw_spin_rq_lock(rq
);
553 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
557 raw_spin_rq_unlock(rq
);
559 while (unlikely(task_on_rq_migrating(p
)))
565 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
567 struct rq
*task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
568 __acquires(p
->pi_lock
)
574 raw_spin_lock_irqsave(&p
->pi_lock
, rf
->flags
);
576 raw_spin_rq_lock(rq
);
578 * move_queued_task() task_rq_lock()
581 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
582 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
583 * [S] ->cpu = new_cpu [L] task_rq()
587 * If we observe the old CPU in task_rq_lock(), the acquire of
588 * the old rq->lock will fully serialize against the stores.
590 * If we observe the new CPU in task_rq_lock(), the address
591 * dependency headed by '[L] rq = task_rq()' and the acquire
592 * will pair with the WMB to ensure we then also see migrating.
594 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
598 raw_spin_rq_unlock(rq
);
599 raw_spin_unlock_irqrestore(&p
->pi_lock
, rf
->flags
);
601 while (unlikely(task_on_rq_migrating(p
)))
607 * RQ-clock updating methods:
610 static void update_rq_clock_task(struct rq
*rq
, s64 delta
)
613 * In theory, the compile should just see 0 here, and optimize out the call
614 * to sched_rt_avg_update. But I don't trust it...
616 s64 __maybe_unused steal
= 0, irq_delta
= 0;
618 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
619 irq_delta
= irq_time_read(cpu_of(rq
)) - rq
->prev_irq_time
;
622 * Since irq_time is only updated on {soft,}irq_exit, we might run into
623 * this case when a previous update_rq_clock() happened inside a
626 * When this happens, we stop ->clock_task and only update the
627 * prev_irq_time stamp to account for the part that fit, so that a next
628 * update will consume the rest. This ensures ->clock_task is
631 * It does however cause some slight miss-attribution of {soft,}irq
632 * time, a more accurate solution would be to update the irq_time using
633 * the current rq->clock timestamp, except that would require using
636 if (irq_delta
> delta
)
639 rq
->prev_irq_time
+= irq_delta
;
642 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
643 if (static_key_false((¶virt_steal_rq_enabled
))) {
644 steal
= paravirt_steal_clock(cpu_of(rq
));
645 steal
-= rq
->prev_steal_time_rq
;
647 if (unlikely(steal
> delta
))
650 rq
->prev_steal_time_rq
+= steal
;
655 rq
->clock_task
+= delta
;
657 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
658 if ((irq_delta
+ steal
) && sched_feat(NONTASK_CAPACITY
))
659 update_irq_load_avg(rq
, irq_delta
+ steal
);
661 update_rq_clock_pelt(rq
, delta
);
664 void update_rq_clock(struct rq
*rq
)
668 lockdep_assert_rq_held(rq
);
670 if (rq
->clock_update_flags
& RQCF_ACT_SKIP
)
673 #ifdef CONFIG_SCHED_DEBUG
674 if (sched_feat(WARN_DOUBLE_CLOCK
))
675 SCHED_WARN_ON(rq
->clock_update_flags
& RQCF_UPDATED
);
676 rq
->clock_update_flags
|= RQCF_UPDATED
;
679 delta
= sched_clock_cpu(cpu_of(rq
)) - rq
->clock
;
683 update_rq_clock_task(rq
, delta
);
686 #ifdef CONFIG_SCHED_HRTICK
688 * Use HR-timers to deliver accurate preemption points.
691 static void hrtick_clear(struct rq
*rq
)
693 if (hrtimer_active(&rq
->hrtick_timer
))
694 hrtimer_cancel(&rq
->hrtick_timer
);
698 * High-resolution timer tick.
699 * Runs from hardirq context with interrupts disabled.
701 static enum hrtimer_restart
hrtick(struct hrtimer
*timer
)
703 struct rq
*rq
= container_of(timer
, struct rq
, hrtick_timer
);
706 WARN_ON_ONCE(cpu_of(rq
) != smp_processor_id());
710 rq
->curr
->sched_class
->task_tick(rq
, rq
->curr
, 1);
713 return HRTIMER_NORESTART
;
718 static void __hrtick_restart(struct rq
*rq
)
720 struct hrtimer
*timer
= &rq
->hrtick_timer
;
721 ktime_t time
= rq
->hrtick_time
;
723 hrtimer_start(timer
, time
, HRTIMER_MODE_ABS_PINNED_HARD
);
727 * called from hardirq (IPI) context
729 static void __hrtick_start(void *arg
)
735 __hrtick_restart(rq
);
740 * Called to set the hrtick timer state.
742 * called with rq->lock held and irqs disabled
744 void hrtick_start(struct rq
*rq
, u64 delay
)
746 struct hrtimer
*timer
= &rq
->hrtick_timer
;
750 * Don't schedule slices shorter than 10000ns, that just
751 * doesn't make sense and can cause timer DoS.
753 delta
= max_t(s64
, delay
, 10000LL);
754 rq
->hrtick_time
= ktime_add_ns(timer
->base
->get_time(), delta
);
757 __hrtick_restart(rq
);
759 smp_call_function_single_async(cpu_of(rq
), &rq
->hrtick_csd
);
764 * Called to set the hrtick timer state.
766 * called with rq->lock held and irqs disabled
768 void hrtick_start(struct rq
*rq
, u64 delay
)
771 * Don't schedule slices shorter than 10000ns, that just
772 * doesn't make sense. Rely on vruntime for fairness.
774 delay
= max_t(u64
, delay
, 10000LL);
775 hrtimer_start(&rq
->hrtick_timer
, ns_to_ktime(delay
),
776 HRTIMER_MODE_REL_PINNED_HARD
);
779 #endif /* CONFIG_SMP */
781 static void hrtick_rq_init(struct rq
*rq
)
784 INIT_CSD(&rq
->hrtick_csd
, __hrtick_start
, rq
);
786 hrtimer_init(&rq
->hrtick_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL_HARD
);
787 rq
->hrtick_timer
.function
= hrtick
;
789 #else /* CONFIG_SCHED_HRTICK */
790 static inline void hrtick_clear(struct rq
*rq
)
794 static inline void hrtick_rq_init(struct rq
*rq
)
797 #endif /* CONFIG_SCHED_HRTICK */
800 * cmpxchg based fetch_or, macro so it works for different integer types
802 #define fetch_or(ptr, mask) \
804 typeof(ptr) _ptr = (ptr); \
805 typeof(mask) _mask = (mask); \
806 typeof(*_ptr) _old, _val = *_ptr; \
809 _old = cmpxchg(_ptr, _val, _val | _mask); \
817 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
819 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
820 * this avoids any races wrt polling state changes and thereby avoids
823 static bool set_nr_and_not_polling(struct task_struct
*p
)
825 struct thread_info
*ti
= task_thread_info(p
);
826 return !(fetch_or(&ti
->flags
, _TIF_NEED_RESCHED
) & _TIF_POLLING_NRFLAG
);
830 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
832 * If this returns true, then the idle task promises to call
833 * sched_ttwu_pending() and reschedule soon.
835 static bool set_nr_if_polling(struct task_struct
*p
)
837 struct thread_info
*ti
= task_thread_info(p
);
838 typeof(ti
->flags
) old
, val
= READ_ONCE(ti
->flags
);
841 if (!(val
& _TIF_POLLING_NRFLAG
))
843 if (val
& _TIF_NEED_RESCHED
)
845 old
= cmpxchg(&ti
->flags
, val
, val
| _TIF_NEED_RESCHED
);
854 static bool set_nr_and_not_polling(struct task_struct
*p
)
856 set_tsk_need_resched(p
);
861 static bool set_nr_if_polling(struct task_struct
*p
)
868 static bool __wake_q_add(struct wake_q_head
*head
, struct task_struct
*task
)
870 struct wake_q_node
*node
= &task
->wake_q
;
873 * Atomically grab the task, if ->wake_q is !nil already it means
874 * it's already queued (either by us or someone else) and will get the
875 * wakeup due to that.
877 * In order to ensure that a pending wakeup will observe our pending
878 * state, even in the failed case, an explicit smp_mb() must be used.
880 smp_mb__before_atomic();
881 if (unlikely(cmpxchg_relaxed(&node
->next
, NULL
, WAKE_Q_TAIL
)))
885 * The head is context local, there can be no concurrency.
888 head
->lastp
= &node
->next
;
893 * wake_q_add() - queue a wakeup for 'later' waking.
894 * @head: the wake_q_head to add @task to
895 * @task: the task to queue for 'later' wakeup
897 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
898 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
901 * This function must be used as-if it were wake_up_process(); IOW the task
902 * must be ready to be woken at this location.
904 void wake_q_add(struct wake_q_head
*head
, struct task_struct
*task
)
906 if (__wake_q_add(head
, task
))
907 get_task_struct(task
);
911 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
912 * @head: the wake_q_head to add @task to
913 * @task: the task to queue for 'later' wakeup
915 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
916 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
919 * This function must be used as-if it were wake_up_process(); IOW the task
920 * must be ready to be woken at this location.
922 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
923 * that already hold reference to @task can call the 'safe' version and trust
924 * wake_q to do the right thing depending whether or not the @task is already
927 void wake_q_add_safe(struct wake_q_head
*head
, struct task_struct
*task
)
929 if (!__wake_q_add(head
, task
))
930 put_task_struct(task
);
933 void wake_up_q(struct wake_q_head
*head
)
935 struct wake_q_node
*node
= head
->first
;
937 while (node
!= WAKE_Q_TAIL
) {
938 struct task_struct
*task
;
940 task
= container_of(node
, struct task_struct
, wake_q
);
941 /* Task can safely be re-inserted now: */
943 task
->wake_q
.next
= NULL
;
946 * wake_up_process() executes a full barrier, which pairs with
947 * the queueing in wake_q_add() so as not to miss wakeups.
949 wake_up_process(task
);
950 put_task_struct(task
);
955 * resched_curr - mark rq's current task 'to be rescheduled now'.
957 * On UP this means the setting of the need_resched flag, on SMP it
958 * might also involve a cross-CPU call to trigger the scheduler on
961 void resched_curr(struct rq
*rq
)
963 struct task_struct
*curr
= rq
->curr
;
966 lockdep_assert_rq_held(rq
);
968 if (test_tsk_need_resched(curr
))
973 if (cpu
== smp_processor_id()) {
974 set_tsk_need_resched(curr
);
975 set_preempt_need_resched();
979 if (set_nr_and_not_polling(curr
))
980 smp_send_reschedule(cpu
);
982 trace_sched_wake_idle_without_ipi(cpu
);
985 void resched_cpu(int cpu
)
987 struct rq
*rq
= cpu_rq(cpu
);
990 raw_spin_rq_lock_irqsave(rq
, flags
);
991 if (cpu_online(cpu
) || cpu
== smp_processor_id())
993 raw_spin_rq_unlock_irqrestore(rq
, flags
);
997 #ifdef CONFIG_NO_HZ_COMMON
999 * In the semi idle case, use the nearest busy CPU for migrating timers
1000 * from an idle CPU. This is good for power-savings.
1002 * We don't do similar optimization for completely idle system, as
1003 * selecting an idle CPU will add more delays to the timers than intended
1004 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
1006 int get_nohz_timer_target(void)
1008 int i
, cpu
= smp_processor_id(), default_cpu
= -1;
1009 struct sched_domain
*sd
;
1010 const struct cpumask
*hk_mask
;
1012 if (housekeeping_cpu(cpu
, HK_FLAG_TIMER
)) {
1018 hk_mask
= housekeeping_cpumask(HK_FLAG_TIMER
);
1021 for_each_domain(cpu
, sd
) {
1022 for_each_cpu_and(i
, sched_domain_span(sd
), hk_mask
) {
1033 if (default_cpu
== -1)
1034 default_cpu
= housekeeping_any_cpu(HK_FLAG_TIMER
);
1042 * When add_timer_on() enqueues a timer into the timer wheel of an
1043 * idle CPU then this timer might expire before the next timer event
1044 * which is scheduled to wake up that CPU. In case of a completely
1045 * idle system the next event might even be infinite time into the
1046 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
1047 * leaves the inner idle loop so the newly added timer is taken into
1048 * account when the CPU goes back to idle and evaluates the timer
1049 * wheel for the next timer event.
1051 static void wake_up_idle_cpu(int cpu
)
1053 struct rq
*rq
= cpu_rq(cpu
);
1055 if (cpu
== smp_processor_id())
1058 if (set_nr_and_not_polling(rq
->idle
))
1059 smp_send_reschedule(cpu
);
1061 trace_sched_wake_idle_without_ipi(cpu
);
1064 static bool wake_up_full_nohz_cpu(int cpu
)
1067 * We just need the target to call irq_exit() and re-evaluate
1068 * the next tick. The nohz full kick at least implies that.
1069 * If needed we can still optimize that later with an
1072 if (cpu_is_offline(cpu
))
1073 return true; /* Don't try to wake offline CPUs. */
1074 if (tick_nohz_full_cpu(cpu
)) {
1075 if (cpu
!= smp_processor_id() ||
1076 tick_nohz_tick_stopped())
1077 tick_nohz_full_kick_cpu(cpu
);
1085 * Wake up the specified CPU. If the CPU is going offline, it is the
1086 * caller's responsibility to deal with the lost wakeup, for example,
1087 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
1089 void wake_up_nohz_cpu(int cpu
)
1091 if (!wake_up_full_nohz_cpu(cpu
))
1092 wake_up_idle_cpu(cpu
);
1095 static void nohz_csd_func(void *info
)
1097 struct rq
*rq
= info
;
1098 int cpu
= cpu_of(rq
);
1102 * Release the rq::nohz_csd.
1104 flags
= atomic_fetch_andnot(NOHZ_KICK_MASK
| NOHZ_NEWILB_KICK
, nohz_flags(cpu
));
1105 WARN_ON(!(flags
& NOHZ_KICK_MASK
));
1107 rq
->idle_balance
= idle_cpu(cpu
);
1108 if (rq
->idle_balance
&& !need_resched()) {
1109 rq
->nohz_idle_balance
= flags
;
1110 raise_softirq_irqoff(SCHED_SOFTIRQ
);
1114 #endif /* CONFIG_NO_HZ_COMMON */
1116 #ifdef CONFIG_NO_HZ_FULL
1117 bool sched_can_stop_tick(struct rq
*rq
)
1119 int fifo_nr_running
;
1121 /* Deadline tasks, even if single, need the tick */
1122 if (rq
->dl
.dl_nr_running
)
1126 * If there are more than one RR tasks, we need the tick to affect the
1127 * actual RR behaviour.
1129 if (rq
->rt
.rr_nr_running
) {
1130 if (rq
->rt
.rr_nr_running
== 1)
1137 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
1138 * forced preemption between FIFO tasks.
1140 fifo_nr_running
= rq
->rt
.rt_nr_running
- rq
->rt
.rr_nr_running
;
1141 if (fifo_nr_running
)
1145 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
1146 * if there's more than one we need the tick for involuntary
1149 if (rq
->nr_running
> 1)
1154 #endif /* CONFIG_NO_HZ_FULL */
1155 #endif /* CONFIG_SMP */
1157 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
1158 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
1160 * Iterate task_group tree rooted at *from, calling @down when first entering a
1161 * node and @up when leaving it for the final time.
1163 * Caller must hold rcu_lock or sufficient equivalent.
1165 int walk_tg_tree_from(struct task_group
*from
,
1166 tg_visitor down
, tg_visitor up
, void *data
)
1168 struct task_group
*parent
, *child
;
1174 ret
= (*down
)(parent
, data
);
1177 list_for_each_entry_rcu(child
, &parent
->children
, siblings
) {
1184 ret
= (*up
)(parent
, data
);
1185 if (ret
|| parent
== from
)
1189 parent
= parent
->parent
;
1196 int tg_nop(struct task_group
*tg
, void *data
)
1202 static void set_load_weight(struct task_struct
*p
, bool update_load
)
1204 int prio
= p
->static_prio
- MAX_RT_PRIO
;
1205 struct load_weight
*load
= &p
->se
.load
;
1208 * SCHED_IDLE tasks get minimal weight:
1210 if (task_has_idle_policy(p
)) {
1211 load
->weight
= scale_load(WEIGHT_IDLEPRIO
);
1212 load
->inv_weight
= WMULT_IDLEPRIO
;
1217 * SCHED_OTHER tasks have to update their load when changing their
1220 if (update_load
&& p
->sched_class
== &fair_sched_class
) {
1221 reweight_task(p
, prio
);
1223 load
->weight
= scale_load(sched_prio_to_weight
[prio
]);
1224 load
->inv_weight
= sched_prio_to_wmult
[prio
];
1228 #ifdef CONFIG_UCLAMP_TASK
1230 * Serializes updates of utilization clamp values
1232 * The (slow-path) user-space triggers utilization clamp value updates which
1233 * can require updates on (fast-path) scheduler's data structures used to
1234 * support enqueue/dequeue operations.
1235 * While the per-CPU rq lock protects fast-path update operations, user-space
1236 * requests are serialized using a mutex to reduce the risk of conflicting
1237 * updates or API abuses.
1239 static DEFINE_MUTEX(uclamp_mutex
);
1241 /* Max allowed minimum utilization */
1242 unsigned int sysctl_sched_uclamp_util_min
= SCHED_CAPACITY_SCALE
;
1244 /* Max allowed maximum utilization */
1245 unsigned int sysctl_sched_uclamp_util_max
= SCHED_CAPACITY_SCALE
;
1248 * By default RT tasks run at the maximum performance point/capacity of the
1249 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
1250 * SCHED_CAPACITY_SCALE.
1252 * This knob allows admins to change the default behavior when uclamp is being
1253 * used. In battery powered devices, particularly, running at the maximum
1254 * capacity and frequency will increase energy consumption and shorten the
1257 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
1259 * This knob will not override the system default sched_util_clamp_min defined
1262 unsigned int sysctl_sched_uclamp_util_min_rt_default
= SCHED_CAPACITY_SCALE
;
1264 /* All clamps are required to be less or equal than these values */
1265 static struct uclamp_se uclamp_default
[UCLAMP_CNT
];
1268 * This static key is used to reduce the uclamp overhead in the fast path. It
1269 * primarily disables the call to uclamp_rq_{inc, dec}() in
1270 * enqueue/dequeue_task().
1272 * This allows users to continue to enable uclamp in their kernel config with
1273 * minimum uclamp overhead in the fast path.
1275 * As soon as userspace modifies any of the uclamp knobs, the static key is
1276 * enabled, since we have an actual users that make use of uclamp
1279 * The knobs that would enable this static key are:
1281 * * A task modifying its uclamp value with sched_setattr().
1282 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
1283 * * An admin modifying the cgroup cpu.uclamp.{min, max}
1285 DEFINE_STATIC_KEY_FALSE(sched_uclamp_used
);
1287 /* Integer rounded range for each bucket */
1288 #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
1290 #define for_each_clamp_id(clamp_id) \
1291 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
1293 static inline unsigned int uclamp_bucket_id(unsigned int clamp_value
)
1295 return min_t(unsigned int, clamp_value
/ UCLAMP_BUCKET_DELTA
, UCLAMP_BUCKETS
- 1);
1298 static inline unsigned int uclamp_none(enum uclamp_id clamp_id
)
1300 if (clamp_id
== UCLAMP_MIN
)
1302 return SCHED_CAPACITY_SCALE
;
1305 static inline void uclamp_se_set(struct uclamp_se
*uc_se
,
1306 unsigned int value
, bool user_defined
)
1308 uc_se
->value
= value
;
1309 uc_se
->bucket_id
= uclamp_bucket_id(value
);
1310 uc_se
->user_defined
= user_defined
;
1313 static inline unsigned int
1314 uclamp_idle_value(struct rq
*rq
, enum uclamp_id clamp_id
,
1315 unsigned int clamp_value
)
1318 * Avoid blocked utilization pushing up the frequency when we go
1319 * idle (which drops the max-clamp) by retaining the last known
1322 if (clamp_id
== UCLAMP_MAX
) {
1323 rq
->uclamp_flags
|= UCLAMP_FLAG_IDLE
;
1327 return uclamp_none(UCLAMP_MIN
);
1330 static inline void uclamp_idle_reset(struct rq
*rq
, enum uclamp_id clamp_id
,
1331 unsigned int clamp_value
)
1333 /* Reset max-clamp retention only on idle exit */
1334 if (!(rq
->uclamp_flags
& UCLAMP_FLAG_IDLE
))
1337 WRITE_ONCE(rq
->uclamp
[clamp_id
].value
, clamp_value
);
1341 unsigned int uclamp_rq_max_value(struct rq
*rq
, enum uclamp_id clamp_id
,
1342 unsigned int clamp_value
)
1344 struct uclamp_bucket
*bucket
= rq
->uclamp
[clamp_id
].bucket
;
1345 int bucket_id
= UCLAMP_BUCKETS
- 1;
1348 * Since both min and max clamps are max aggregated, find the
1349 * top most bucket with tasks in.
1351 for ( ; bucket_id
>= 0; bucket_id
--) {
1352 if (!bucket
[bucket_id
].tasks
)
1354 return bucket
[bucket_id
].value
;
1357 /* No tasks -- default clamp values */
1358 return uclamp_idle_value(rq
, clamp_id
, clamp_value
);
1361 static void __uclamp_update_util_min_rt_default(struct task_struct
*p
)
1363 unsigned int default_util_min
;
1364 struct uclamp_se
*uc_se
;
1366 lockdep_assert_held(&p
->pi_lock
);
1368 uc_se
= &p
->uclamp_req
[UCLAMP_MIN
];
1370 /* Only sync if user didn't override the default */
1371 if (uc_se
->user_defined
)
1374 default_util_min
= sysctl_sched_uclamp_util_min_rt_default
;
1375 uclamp_se_set(uc_se
, default_util_min
, false);
1378 static void uclamp_update_util_min_rt_default(struct task_struct
*p
)
1386 /* Protect updates to p->uclamp_* */
1387 rq
= task_rq_lock(p
, &rf
);
1388 __uclamp_update_util_min_rt_default(p
);
1389 task_rq_unlock(rq
, p
, &rf
);
1392 static void uclamp_sync_util_min_rt_default(void)
1394 struct task_struct
*g
, *p
;
1397 * copy_process() sysctl_uclamp
1398 * uclamp_min_rt = X;
1399 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1400 * // link thread smp_mb__after_spinlock()
1401 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1402 * sched_post_fork() for_each_process_thread()
1403 * __uclamp_sync_rt() __uclamp_sync_rt()
1405 * Ensures that either sched_post_fork() will observe the new
1406 * uclamp_min_rt or for_each_process_thread() will observe the new
1409 read_lock(&tasklist_lock
);
1410 smp_mb__after_spinlock();
1411 read_unlock(&tasklist_lock
);
1414 for_each_process_thread(g
, p
)
1415 uclamp_update_util_min_rt_default(p
);
1419 static inline struct uclamp_se
1420 uclamp_tg_restrict(struct task_struct
*p
, enum uclamp_id clamp_id
)
1422 /* Copy by value as we could modify it */
1423 struct uclamp_se uc_req
= p
->uclamp_req
[clamp_id
];
1424 #ifdef CONFIG_UCLAMP_TASK_GROUP
1425 unsigned int tg_min
, tg_max
, value
;
1428 * Tasks in autogroups or root task group will be
1429 * restricted by system defaults.
1431 if (task_group_is_autogroup(task_group(p
)))
1433 if (task_group(p
) == &root_task_group
)
1436 tg_min
= task_group(p
)->uclamp
[UCLAMP_MIN
].value
;
1437 tg_max
= task_group(p
)->uclamp
[UCLAMP_MAX
].value
;
1438 value
= uc_req
.value
;
1439 value
= clamp(value
, tg_min
, tg_max
);
1440 uclamp_se_set(&uc_req
, value
, false);
1447 * The effective clamp bucket index of a task depends on, by increasing
1449 * - the task specific clamp value, when explicitly requested from userspace
1450 * - the task group effective clamp value, for tasks not either in the root
1451 * group or in an autogroup
1452 * - the system default clamp value, defined by the sysadmin
1454 static inline struct uclamp_se
1455 uclamp_eff_get(struct task_struct
*p
, enum uclamp_id clamp_id
)
1457 struct uclamp_se uc_req
= uclamp_tg_restrict(p
, clamp_id
);
1458 struct uclamp_se uc_max
= uclamp_default
[clamp_id
];
1460 /* System default restrictions always apply */
1461 if (unlikely(uc_req
.value
> uc_max
.value
))
1467 unsigned long uclamp_eff_value(struct task_struct
*p
, enum uclamp_id clamp_id
)
1469 struct uclamp_se uc_eff
;
1471 /* Task currently refcounted: use back-annotated (effective) value */
1472 if (p
->uclamp
[clamp_id
].active
)
1473 return (unsigned long)p
->uclamp
[clamp_id
].value
;
1475 uc_eff
= uclamp_eff_get(p
, clamp_id
);
1477 return (unsigned long)uc_eff
.value
;
1481 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1482 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1483 * updates the rq's clamp value if required.
1485 * Tasks can have a task-specific value requested from user-space, track
1486 * within each bucket the maximum value for tasks refcounted in it.
1487 * This "local max aggregation" allows to track the exact "requested" value
1488 * for each bucket when all its RUNNABLE tasks require the same clamp.
1490 static inline void uclamp_rq_inc_id(struct rq
*rq
, struct task_struct
*p
,
1491 enum uclamp_id clamp_id
)
1493 struct uclamp_rq
*uc_rq
= &rq
->uclamp
[clamp_id
];
1494 struct uclamp_se
*uc_se
= &p
->uclamp
[clamp_id
];
1495 struct uclamp_bucket
*bucket
;
1497 lockdep_assert_rq_held(rq
);
1499 /* Update task effective clamp */
1500 p
->uclamp
[clamp_id
] = uclamp_eff_get(p
, clamp_id
);
1502 bucket
= &uc_rq
->bucket
[uc_se
->bucket_id
];
1504 uc_se
->active
= true;
1506 uclamp_idle_reset(rq
, clamp_id
, uc_se
->value
);
1509 * Local max aggregation: rq buckets always track the max
1510 * "requested" clamp value of its RUNNABLE tasks.
1512 if (bucket
->tasks
== 1 || uc_se
->value
> bucket
->value
)
1513 bucket
->value
= uc_se
->value
;
1515 if (uc_se
->value
> READ_ONCE(uc_rq
->value
))
1516 WRITE_ONCE(uc_rq
->value
, uc_se
->value
);
1520 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1521 * is released. If this is the last task reference counting the rq's max
1522 * active clamp value, then the rq's clamp value is updated.
1524 * Both refcounted tasks and rq's cached clamp values are expected to be
1525 * always valid. If it's detected they are not, as defensive programming,
1526 * enforce the expected state and warn.
1528 static inline void uclamp_rq_dec_id(struct rq
*rq
, struct task_struct
*p
,
1529 enum uclamp_id clamp_id
)
1531 struct uclamp_rq
*uc_rq
= &rq
->uclamp
[clamp_id
];
1532 struct uclamp_se
*uc_se
= &p
->uclamp
[clamp_id
];
1533 struct uclamp_bucket
*bucket
;
1534 unsigned int bkt_clamp
;
1535 unsigned int rq_clamp
;
1537 lockdep_assert_rq_held(rq
);
1540 * If sched_uclamp_used was enabled after task @p was enqueued,
1541 * we could end up with unbalanced call to uclamp_rq_dec_id().
1543 * In this case the uc_se->active flag should be false since no uclamp
1544 * accounting was performed at enqueue time and we can just return
1547 * Need to be careful of the following enqueue/dequeue ordering
1551 * // sched_uclamp_used gets enabled
1554 * // Must not decrement bucket->tasks here
1557 * where we could end up with stale data in uc_se and
1558 * bucket[uc_se->bucket_id].
1560 * The following check here eliminates the possibility of such race.
1562 if (unlikely(!uc_se
->active
))
1565 bucket
= &uc_rq
->bucket
[uc_se
->bucket_id
];
1567 SCHED_WARN_ON(!bucket
->tasks
);
1568 if (likely(bucket
->tasks
))
1571 uc_se
->active
= false;
1574 * Keep "local max aggregation" simple and accept to (possibly)
1575 * overboost some RUNNABLE tasks in the same bucket.
1576 * The rq clamp bucket value is reset to its base value whenever
1577 * there are no more RUNNABLE tasks refcounting it.
1579 if (likely(bucket
->tasks
))
1582 rq_clamp
= READ_ONCE(uc_rq
->value
);
1584 * Defensive programming: this should never happen. If it happens,
1585 * e.g. due to future modification, warn and fixup the expected value.
1587 SCHED_WARN_ON(bucket
->value
> rq_clamp
);
1588 if (bucket
->value
>= rq_clamp
) {
1589 bkt_clamp
= uclamp_rq_max_value(rq
, clamp_id
, uc_se
->value
);
1590 WRITE_ONCE(uc_rq
->value
, bkt_clamp
);
1594 static inline void uclamp_rq_inc(struct rq
*rq
, struct task_struct
*p
)
1596 enum uclamp_id clamp_id
;
1599 * Avoid any overhead until uclamp is actually used by the userspace.
1601 * The condition is constructed such that a NOP is generated when
1602 * sched_uclamp_used is disabled.
1604 if (!static_branch_unlikely(&sched_uclamp_used
))
1607 if (unlikely(!p
->sched_class
->uclamp_enabled
))
1610 for_each_clamp_id(clamp_id
)
1611 uclamp_rq_inc_id(rq
, p
, clamp_id
);
1613 /* Reset clamp idle holding when there is one RUNNABLE task */
1614 if (rq
->uclamp_flags
& UCLAMP_FLAG_IDLE
)
1615 rq
->uclamp_flags
&= ~UCLAMP_FLAG_IDLE
;
1618 static inline void uclamp_rq_dec(struct rq
*rq
, struct task_struct
*p
)
1620 enum uclamp_id clamp_id
;
1623 * Avoid any overhead until uclamp is actually used by the userspace.
1625 * The condition is constructed such that a NOP is generated when
1626 * sched_uclamp_used is disabled.
1628 if (!static_branch_unlikely(&sched_uclamp_used
))
1631 if (unlikely(!p
->sched_class
->uclamp_enabled
))
1634 for_each_clamp_id(clamp_id
)
1635 uclamp_rq_dec_id(rq
, p
, clamp_id
);
1638 static inline void uclamp_rq_reinc_id(struct rq
*rq
, struct task_struct
*p
,
1639 enum uclamp_id clamp_id
)
1641 if (!p
->uclamp
[clamp_id
].active
)
1644 uclamp_rq_dec_id(rq
, p
, clamp_id
);
1645 uclamp_rq_inc_id(rq
, p
, clamp_id
);
1648 * Make sure to clear the idle flag if we've transiently reached 0
1649 * active tasks on rq.
1651 if (clamp_id
== UCLAMP_MAX
&& (rq
->uclamp_flags
& UCLAMP_FLAG_IDLE
))
1652 rq
->uclamp_flags
&= ~UCLAMP_FLAG_IDLE
;
1656 uclamp_update_active(struct task_struct
*p
)
1658 enum uclamp_id clamp_id
;
1663 * Lock the task and the rq where the task is (or was) queued.
1665 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1666 * price to pay to safely serialize util_{min,max} updates with
1667 * enqueues, dequeues and migration operations.
1668 * This is the same locking schema used by __set_cpus_allowed_ptr().
1670 rq
= task_rq_lock(p
, &rf
);
1673 * Setting the clamp bucket is serialized by task_rq_lock().
1674 * If the task is not yet RUNNABLE and its task_struct is not
1675 * affecting a valid clamp bucket, the next time it's enqueued,
1676 * it will already see the updated clamp bucket value.
1678 for_each_clamp_id(clamp_id
)
1679 uclamp_rq_reinc_id(rq
, p
, clamp_id
);
1681 task_rq_unlock(rq
, p
, &rf
);
1684 #ifdef CONFIG_UCLAMP_TASK_GROUP
1686 uclamp_update_active_tasks(struct cgroup_subsys_state
*css
)
1688 struct css_task_iter it
;
1689 struct task_struct
*p
;
1691 css_task_iter_start(css
, 0, &it
);
1692 while ((p
= css_task_iter_next(&it
)))
1693 uclamp_update_active(p
);
1694 css_task_iter_end(&it
);
1697 static void cpu_util_update_eff(struct cgroup_subsys_state
*css
);
1698 static void uclamp_update_root_tg(void)
1700 struct task_group
*tg
= &root_task_group
;
1702 uclamp_se_set(&tg
->uclamp_req
[UCLAMP_MIN
],
1703 sysctl_sched_uclamp_util_min
, false);
1704 uclamp_se_set(&tg
->uclamp_req
[UCLAMP_MAX
],
1705 sysctl_sched_uclamp_util_max
, false);
1708 cpu_util_update_eff(&root_task_group
.css
);
1712 static void uclamp_update_root_tg(void) { }
1715 int sysctl_sched_uclamp_handler(struct ctl_table
*table
, int write
,
1716 void *buffer
, size_t *lenp
, loff_t
*ppos
)
1718 bool update_root_tg
= false;
1719 int old_min
, old_max
, old_min_rt
;
1722 mutex_lock(&uclamp_mutex
);
1723 old_min
= sysctl_sched_uclamp_util_min
;
1724 old_max
= sysctl_sched_uclamp_util_max
;
1725 old_min_rt
= sysctl_sched_uclamp_util_min_rt_default
;
1727 result
= proc_dointvec(table
, write
, buffer
, lenp
, ppos
);
1733 if (sysctl_sched_uclamp_util_min
> sysctl_sched_uclamp_util_max
||
1734 sysctl_sched_uclamp_util_max
> SCHED_CAPACITY_SCALE
||
1735 sysctl_sched_uclamp_util_min_rt_default
> SCHED_CAPACITY_SCALE
) {
1741 if (old_min
!= sysctl_sched_uclamp_util_min
) {
1742 uclamp_se_set(&uclamp_default
[UCLAMP_MIN
],
1743 sysctl_sched_uclamp_util_min
, false);
1744 update_root_tg
= true;
1746 if (old_max
!= sysctl_sched_uclamp_util_max
) {
1747 uclamp_se_set(&uclamp_default
[UCLAMP_MAX
],
1748 sysctl_sched_uclamp_util_max
, false);
1749 update_root_tg
= true;
1752 if (update_root_tg
) {
1753 static_branch_enable(&sched_uclamp_used
);
1754 uclamp_update_root_tg();
1757 if (old_min_rt
!= sysctl_sched_uclamp_util_min_rt_default
) {
1758 static_branch_enable(&sched_uclamp_used
);
1759 uclamp_sync_util_min_rt_default();
1763 * We update all RUNNABLE tasks only when task groups are in use.
1764 * Otherwise, keep it simple and do just a lazy update at each next
1765 * task enqueue time.
1771 sysctl_sched_uclamp_util_min
= old_min
;
1772 sysctl_sched_uclamp_util_max
= old_max
;
1773 sysctl_sched_uclamp_util_min_rt_default
= old_min_rt
;
1775 mutex_unlock(&uclamp_mutex
);
1780 static int uclamp_validate(struct task_struct
*p
,
1781 const struct sched_attr
*attr
)
1783 int util_min
= p
->uclamp_req
[UCLAMP_MIN
].value
;
1784 int util_max
= p
->uclamp_req
[UCLAMP_MAX
].value
;
1786 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MIN
) {
1787 util_min
= attr
->sched_util_min
;
1789 if (util_min
+ 1 > SCHED_CAPACITY_SCALE
+ 1)
1793 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MAX
) {
1794 util_max
= attr
->sched_util_max
;
1796 if (util_max
+ 1 > SCHED_CAPACITY_SCALE
+ 1)
1800 if (util_min
!= -1 && util_max
!= -1 && util_min
> util_max
)
1804 * We have valid uclamp attributes; make sure uclamp is enabled.
1806 * We need to do that here, because enabling static branches is a
1807 * blocking operation which obviously cannot be done while holding
1810 static_branch_enable(&sched_uclamp_used
);
1815 static bool uclamp_reset(const struct sched_attr
*attr
,
1816 enum uclamp_id clamp_id
,
1817 struct uclamp_se
*uc_se
)
1819 /* Reset on sched class change for a non user-defined clamp value. */
1820 if (likely(!(attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP
)) &&
1821 !uc_se
->user_defined
)
1824 /* Reset on sched_util_{min,max} == -1. */
1825 if (clamp_id
== UCLAMP_MIN
&&
1826 attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MIN
&&
1827 attr
->sched_util_min
== -1) {
1831 if (clamp_id
== UCLAMP_MAX
&&
1832 attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MAX
&&
1833 attr
->sched_util_max
== -1) {
1840 static void __setscheduler_uclamp(struct task_struct
*p
,
1841 const struct sched_attr
*attr
)
1843 enum uclamp_id clamp_id
;
1845 for_each_clamp_id(clamp_id
) {
1846 struct uclamp_se
*uc_se
= &p
->uclamp_req
[clamp_id
];
1849 if (!uclamp_reset(attr
, clamp_id
, uc_se
))
1853 * RT by default have a 100% boost value that could be modified
1856 if (unlikely(rt_task(p
) && clamp_id
== UCLAMP_MIN
))
1857 value
= sysctl_sched_uclamp_util_min_rt_default
;
1859 value
= uclamp_none(clamp_id
);
1861 uclamp_se_set(uc_se
, value
, false);
1865 if (likely(!(attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP
)))
1868 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MIN
&&
1869 attr
->sched_util_min
!= -1) {
1870 uclamp_se_set(&p
->uclamp_req
[UCLAMP_MIN
],
1871 attr
->sched_util_min
, true);
1874 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP_MAX
&&
1875 attr
->sched_util_max
!= -1) {
1876 uclamp_se_set(&p
->uclamp_req
[UCLAMP_MAX
],
1877 attr
->sched_util_max
, true);
1881 static void uclamp_fork(struct task_struct
*p
)
1883 enum uclamp_id clamp_id
;
1886 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
1887 * as the task is still at its early fork stages.
1889 for_each_clamp_id(clamp_id
)
1890 p
->uclamp
[clamp_id
].active
= false;
1892 if (likely(!p
->sched_reset_on_fork
))
1895 for_each_clamp_id(clamp_id
) {
1896 uclamp_se_set(&p
->uclamp_req
[clamp_id
],
1897 uclamp_none(clamp_id
), false);
1901 static void uclamp_post_fork(struct task_struct
*p
)
1903 uclamp_update_util_min_rt_default(p
);
1906 static void __init
init_uclamp_rq(struct rq
*rq
)
1908 enum uclamp_id clamp_id
;
1909 struct uclamp_rq
*uc_rq
= rq
->uclamp
;
1911 for_each_clamp_id(clamp_id
) {
1912 uc_rq
[clamp_id
] = (struct uclamp_rq
) {
1913 .value
= uclamp_none(clamp_id
)
1917 rq
->uclamp_flags
= UCLAMP_FLAG_IDLE
;
1920 static void __init
init_uclamp(void)
1922 struct uclamp_se uc_max
= {};
1923 enum uclamp_id clamp_id
;
1926 for_each_possible_cpu(cpu
)
1927 init_uclamp_rq(cpu_rq(cpu
));
1929 for_each_clamp_id(clamp_id
) {
1930 uclamp_se_set(&init_task
.uclamp_req
[clamp_id
],
1931 uclamp_none(clamp_id
), false);
1934 /* System defaults allow max clamp values for both indexes */
1935 uclamp_se_set(&uc_max
, uclamp_none(UCLAMP_MAX
), false);
1936 for_each_clamp_id(clamp_id
) {
1937 uclamp_default
[clamp_id
] = uc_max
;
1938 #ifdef CONFIG_UCLAMP_TASK_GROUP
1939 root_task_group
.uclamp_req
[clamp_id
] = uc_max
;
1940 root_task_group
.uclamp
[clamp_id
] = uc_max
;
1945 #else /* CONFIG_UCLAMP_TASK */
1946 static inline void uclamp_rq_inc(struct rq
*rq
, struct task_struct
*p
) { }
1947 static inline void uclamp_rq_dec(struct rq
*rq
, struct task_struct
*p
) { }
1948 static inline int uclamp_validate(struct task_struct
*p
,
1949 const struct sched_attr
*attr
)
1953 static void __setscheduler_uclamp(struct task_struct
*p
,
1954 const struct sched_attr
*attr
) { }
1955 static inline void uclamp_fork(struct task_struct
*p
) { }
1956 static inline void uclamp_post_fork(struct task_struct
*p
) { }
1957 static inline void init_uclamp(void) { }
1958 #endif /* CONFIG_UCLAMP_TASK */
1960 bool sched_task_on_rq(struct task_struct
*p
)
1962 return task_on_rq_queued(p
);
1965 static inline void enqueue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
1967 if (!(flags
& ENQUEUE_NOCLOCK
))
1968 update_rq_clock(rq
);
1970 if (!(flags
& ENQUEUE_RESTORE
)) {
1971 sched_info_enqueue(rq
, p
);
1972 psi_enqueue(p
, flags
& ENQUEUE_WAKEUP
);
1975 uclamp_rq_inc(rq
, p
);
1976 p
->sched_class
->enqueue_task(rq
, p
, flags
);
1978 if (sched_core_enabled(rq
))
1979 sched_core_enqueue(rq
, p
);
1982 static inline void dequeue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
1984 if (sched_core_enabled(rq
))
1985 sched_core_dequeue(rq
, p
);
1987 if (!(flags
& DEQUEUE_NOCLOCK
))
1988 update_rq_clock(rq
);
1990 if (!(flags
& DEQUEUE_SAVE
)) {
1991 sched_info_dequeue(rq
, p
);
1992 psi_dequeue(p
, flags
& DEQUEUE_SLEEP
);
1995 uclamp_rq_dec(rq
, p
);
1996 p
->sched_class
->dequeue_task(rq
, p
, flags
);
1999 void activate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
2001 enqueue_task(rq
, p
, flags
);
2003 p
->on_rq
= TASK_ON_RQ_QUEUED
;
2006 void deactivate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
2008 p
->on_rq
= (flags
& DEQUEUE_SLEEP
) ? 0 : TASK_ON_RQ_MIGRATING
;
2010 dequeue_task(rq
, p
, flags
);
2013 static inline int __normal_prio(int policy
, int rt_prio
, int nice
)
2017 if (dl_policy(policy
))
2018 prio
= MAX_DL_PRIO
- 1;
2019 else if (rt_policy(policy
))
2020 prio
= MAX_RT_PRIO
- 1 - rt_prio
;
2022 prio
= NICE_TO_PRIO(nice
);
2028 * Calculate the expected normal priority: i.e. priority
2029 * without taking RT-inheritance into account. Might be
2030 * boosted by interactivity modifiers. Changes upon fork,
2031 * setprio syscalls, and whenever the interactivity
2032 * estimator recalculates.
2034 static inline int normal_prio(struct task_struct
*p
)
2036 return __normal_prio(p
->policy
, p
->rt_priority
, PRIO_TO_NICE(p
->static_prio
));
2040 * Calculate the current priority, i.e. the priority
2041 * taken into account by the scheduler. This value might
2042 * be boosted by RT tasks, or might be boosted by
2043 * interactivity modifiers. Will be RT if the task got
2044 * RT-boosted. If not then it returns p->normal_prio.
2046 static int effective_prio(struct task_struct
*p
)
2048 p
->normal_prio
= normal_prio(p
);
2050 * If we are RT tasks or we were boosted to RT priority,
2051 * keep the priority unchanged. Otherwise, update priority
2052 * to the normal priority:
2054 if (!rt_prio(p
->prio
))
2055 return p
->normal_prio
;
2060 * task_curr - is this task currently executing on a CPU?
2061 * @p: the task in question.
2063 * Return: 1 if the task is currently executing. 0 otherwise.
2065 inline int task_curr(const struct task_struct
*p
)
2067 return cpu_curr(task_cpu(p
)) == p
;
2071 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
2072 * use the balance_callback list if you want balancing.
2074 * this means any call to check_class_changed() must be followed by a call to
2075 * balance_callback().
2077 static inline void check_class_changed(struct rq
*rq
, struct task_struct
*p
,
2078 const struct sched_class
*prev_class
,
2081 if (prev_class
!= p
->sched_class
) {
2082 if (prev_class
->switched_from
)
2083 prev_class
->switched_from(rq
, p
);
2085 p
->sched_class
->switched_to(rq
, p
);
2086 } else if (oldprio
!= p
->prio
|| dl_task(p
))
2087 p
->sched_class
->prio_changed(rq
, p
, oldprio
);
2090 void check_preempt_curr(struct rq
*rq
, struct task_struct
*p
, int flags
)
2092 if (p
->sched_class
== rq
->curr
->sched_class
)
2093 rq
->curr
->sched_class
->check_preempt_curr(rq
, p
, flags
);
2094 else if (p
->sched_class
> rq
->curr
->sched_class
)
2098 * A queue event has occurred, and we're going to schedule. In
2099 * this case, we can save a useless back to back clock update.
2101 if (task_on_rq_queued(rq
->curr
) && test_tsk_need_resched(rq
->curr
))
2102 rq_clock_skip_update(rq
);
2108 __do_set_cpus_allowed(struct task_struct
*p
, const struct cpumask
*new_mask
, u32 flags
);
2110 static int __set_cpus_allowed_ptr(struct task_struct
*p
,
2111 const struct cpumask
*new_mask
,
2114 static void migrate_disable_switch(struct rq
*rq
, struct task_struct
*p
)
2116 if (likely(!p
->migration_disabled
))
2119 if (p
->cpus_ptr
!= &p
->cpus_mask
)
2123 * Violates locking rules! see comment in __do_set_cpus_allowed().
2125 __do_set_cpus_allowed(p
, cpumask_of(rq
->cpu
), SCA_MIGRATE_DISABLE
);
2128 void migrate_disable(void)
2130 struct task_struct
*p
= current
;
2132 if (p
->migration_disabled
) {
2133 p
->migration_disabled
++;
2138 this_rq()->nr_pinned
++;
2139 p
->migration_disabled
= 1;
2142 EXPORT_SYMBOL_GPL(migrate_disable
);
2144 void migrate_enable(void)
2146 struct task_struct
*p
= current
;
2148 if (p
->migration_disabled
> 1) {
2149 p
->migration_disabled
--;
2154 * Ensure stop_task runs either before or after this, and that
2155 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
2158 if (p
->cpus_ptr
!= &p
->cpus_mask
)
2159 __set_cpus_allowed_ptr(p
, &p
->cpus_mask
, SCA_MIGRATE_ENABLE
);
2161 * Mustn't clear migration_disabled() until cpus_ptr points back at the
2162 * regular cpus_mask, otherwise things that race (eg.
2163 * select_fallback_rq) get confused.
2166 p
->migration_disabled
= 0;
2167 this_rq()->nr_pinned
--;
2170 EXPORT_SYMBOL_GPL(migrate_enable
);
2172 static inline bool rq_has_pinned_tasks(struct rq
*rq
)
2174 return rq
->nr_pinned
;
2178 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
2179 * __set_cpus_allowed_ptr() and select_fallback_rq().
2181 static inline bool is_cpu_allowed(struct task_struct
*p
, int cpu
)
2183 /* When not in the task's cpumask, no point in looking further. */
2184 if (!cpumask_test_cpu(cpu
, p
->cpus_ptr
))
2187 /* migrate_disabled() must be allowed to finish. */
2188 if (is_migration_disabled(p
))
2189 return cpu_online(cpu
);
2191 /* Non kernel threads are not allowed during either online or offline. */
2192 if (!(p
->flags
& PF_KTHREAD
))
2193 return cpu_active(cpu
) && task_cpu_possible(cpu
, p
);
2195 /* KTHREAD_IS_PER_CPU is always allowed. */
2196 if (kthread_is_per_cpu(p
))
2197 return cpu_online(cpu
);
2199 /* Regular kernel threads don't get to stay during offline. */
2203 /* But are allowed during online. */
2204 return cpu_online(cpu
);
2208 * This is how migration works:
2210 * 1) we invoke migration_cpu_stop() on the target CPU using
2212 * 2) stopper starts to run (implicitly forcing the migrated thread
2214 * 3) it checks whether the migrated task is still in the wrong runqueue.
2215 * 4) if it's in the wrong runqueue then the migration thread removes
2216 * it and puts it into the right queue.
2217 * 5) stopper completes and stop_one_cpu() returns and the migration
2222 * move_queued_task - move a queued task to new rq.
2224 * Returns (locked) new rq. Old rq's lock is released.
2226 static struct rq
*move_queued_task(struct rq
*rq
, struct rq_flags
*rf
,
2227 struct task_struct
*p
, int new_cpu
)
2229 lockdep_assert_rq_held(rq
);
2231 deactivate_task(rq
, p
, DEQUEUE_NOCLOCK
);
2232 set_task_cpu(p
, new_cpu
);
2235 rq
= cpu_rq(new_cpu
);
2238 BUG_ON(task_cpu(p
) != new_cpu
);
2239 activate_task(rq
, p
, 0);
2240 check_preempt_curr(rq
, p
, 0);
2245 struct migration_arg
{
2246 struct task_struct
*task
;
2248 struct set_affinity_pending
*pending
;
2252 * @refs: number of wait_for_completion()
2253 * @stop_pending: is @stop_work in use
2255 struct set_affinity_pending
{
2257 unsigned int stop_pending
;
2258 struct completion done
;
2259 struct cpu_stop_work stop_work
;
2260 struct migration_arg arg
;
2264 * Move (not current) task off this CPU, onto the destination CPU. We're doing
2265 * this because either it can't run here any more (set_cpus_allowed()
2266 * away from this CPU, or CPU going down), or because we're
2267 * attempting to rebalance this task on exec (sched_exec).
2269 * So we race with normal scheduler movements, but that's OK, as long
2270 * as the task is no longer on this CPU.
2272 static struct rq
*__migrate_task(struct rq
*rq
, struct rq_flags
*rf
,
2273 struct task_struct
*p
, int dest_cpu
)
2275 /* Affinity changed (again). */
2276 if (!is_cpu_allowed(p
, dest_cpu
))
2279 update_rq_clock(rq
);
2280 rq
= move_queued_task(rq
, rf
, p
, dest_cpu
);
2286 * migration_cpu_stop - this will be executed by a highprio stopper thread
2287 * and performs thread migration by bumping thread off CPU then
2288 * 'pushing' onto another runqueue.
2290 static int migration_cpu_stop(void *data
)
2292 struct migration_arg
*arg
= data
;
2293 struct set_affinity_pending
*pending
= arg
->pending
;
2294 struct task_struct
*p
= arg
->task
;
2295 struct rq
*rq
= this_rq();
2296 bool complete
= false;
2300 * The original target CPU might have gone down and we might
2301 * be on another CPU but it doesn't matter.
2303 local_irq_save(rf
.flags
);
2305 * We need to explicitly wake pending tasks before running
2306 * __migrate_task() such that we will not miss enforcing cpus_ptr
2307 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
2309 flush_smp_call_function_from_idle();
2311 raw_spin_lock(&p
->pi_lock
);
2315 * If we were passed a pending, then ->stop_pending was set, thus
2316 * p->migration_pending must have remained stable.
2318 WARN_ON_ONCE(pending
&& pending
!= p
->migration_pending
);
2321 * If task_rq(p) != rq, it cannot be migrated here, because we're
2322 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
2323 * we're holding p->pi_lock.
2325 if (task_rq(p
) == rq
) {
2326 if (is_migration_disabled(p
))
2330 p
->migration_pending
= NULL
;
2333 if (cpumask_test_cpu(task_cpu(p
), &p
->cpus_mask
))
2337 if (task_on_rq_queued(p
))
2338 rq
= __migrate_task(rq
, &rf
, p
, arg
->dest_cpu
);
2340 p
->wake_cpu
= arg
->dest_cpu
;
2343 * XXX __migrate_task() can fail, at which point we might end
2344 * up running on a dodgy CPU, AFAICT this can only happen
2345 * during CPU hotplug, at which point we'll get pushed out
2346 * anyway, so it's probably not a big deal.
2349 } else if (pending
) {
2351 * This happens when we get migrated between migrate_enable()'s
2352 * preempt_enable() and scheduling the stopper task. At that
2353 * point we're a regular task again and not current anymore.
2355 * A !PREEMPT kernel has a giant hole here, which makes it far
2360 * The task moved before the stopper got to run. We're holding
2361 * ->pi_lock, so the allowed mask is stable - if it got
2362 * somewhere allowed, we're done.
2364 if (cpumask_test_cpu(task_cpu(p
), p
->cpus_ptr
)) {
2365 p
->migration_pending
= NULL
;
2371 * When migrate_enable() hits a rq mis-match we can't reliably
2372 * determine is_migration_disabled() and so have to chase after
2375 WARN_ON_ONCE(!pending
->stop_pending
);
2376 task_rq_unlock(rq
, p
, &rf
);
2377 stop_one_cpu_nowait(task_cpu(p
), migration_cpu_stop
,
2378 &pending
->arg
, &pending
->stop_work
);
2383 pending
->stop_pending
= false;
2384 task_rq_unlock(rq
, p
, &rf
);
2387 complete_all(&pending
->done
);
2392 int push_cpu_stop(void *arg
)
2394 struct rq
*lowest_rq
= NULL
, *rq
= this_rq();
2395 struct task_struct
*p
= arg
;
2397 raw_spin_lock_irq(&p
->pi_lock
);
2398 raw_spin_rq_lock(rq
);
2400 if (task_rq(p
) != rq
)
2403 if (is_migration_disabled(p
)) {
2404 p
->migration_flags
|= MDF_PUSH
;
2408 p
->migration_flags
&= ~MDF_PUSH
;
2410 if (p
->sched_class
->find_lock_rq
)
2411 lowest_rq
= p
->sched_class
->find_lock_rq(p
, rq
);
2416 // XXX validate p is still the highest prio task
2417 if (task_rq(p
) == rq
) {
2418 deactivate_task(rq
, p
, 0);
2419 set_task_cpu(p
, lowest_rq
->cpu
);
2420 activate_task(lowest_rq
, p
, 0);
2421 resched_curr(lowest_rq
);
2424 double_unlock_balance(rq
, lowest_rq
);
2427 rq
->push_busy
= false;
2428 raw_spin_rq_unlock(rq
);
2429 raw_spin_unlock_irq(&p
->pi_lock
);
2436 * sched_class::set_cpus_allowed must do the below, but is not required to
2437 * actually call this function.
2439 void set_cpus_allowed_common(struct task_struct
*p
, const struct cpumask
*new_mask
, u32 flags
)
2441 if (flags
& (SCA_MIGRATE_ENABLE
| SCA_MIGRATE_DISABLE
)) {
2442 p
->cpus_ptr
= new_mask
;
2446 cpumask_copy(&p
->cpus_mask
, new_mask
);
2447 p
->nr_cpus_allowed
= cpumask_weight(new_mask
);
2451 __do_set_cpus_allowed(struct task_struct
*p
, const struct cpumask
*new_mask
, u32 flags
)
2453 struct rq
*rq
= task_rq(p
);
2454 bool queued
, running
;
2457 * This here violates the locking rules for affinity, since we're only
2458 * supposed to change these variables while holding both rq->lock and
2461 * HOWEVER, it magically works, because ttwu() is the only code that
2462 * accesses these variables under p->pi_lock and only does so after
2463 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
2464 * before finish_task().
2466 * XXX do further audits, this smells like something putrid.
2468 if (flags
& SCA_MIGRATE_DISABLE
)
2469 SCHED_WARN_ON(!p
->on_cpu
);
2471 lockdep_assert_held(&p
->pi_lock
);
2473 queued
= task_on_rq_queued(p
);
2474 running
= task_current(rq
, p
);
2478 * Because __kthread_bind() calls this on blocked tasks without
2481 lockdep_assert_rq_held(rq
);
2482 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
2485 put_prev_task(rq
, p
);
2487 p
->sched_class
->set_cpus_allowed(p
, new_mask
, flags
);
2490 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
2492 set_next_task(rq
, p
);
2495 void do_set_cpus_allowed(struct task_struct
*p
, const struct cpumask
*new_mask
)
2497 __do_set_cpus_allowed(p
, new_mask
, 0);
2500 int dup_user_cpus_ptr(struct task_struct
*dst
, struct task_struct
*src
,
2503 if (!src
->user_cpus_ptr
)
2506 dst
->user_cpus_ptr
= kmalloc_node(cpumask_size(), GFP_KERNEL
, node
);
2507 if (!dst
->user_cpus_ptr
)
2510 cpumask_copy(dst
->user_cpus_ptr
, src
->user_cpus_ptr
);
2514 static inline struct cpumask
*clear_user_cpus_ptr(struct task_struct
*p
)
2516 struct cpumask
*user_mask
= NULL
;
2518 swap(p
->user_cpus_ptr
, user_mask
);
2523 void release_user_cpus_ptr(struct task_struct
*p
)
2525 kfree(clear_user_cpus_ptr(p
));
2529 * This function is wildly self concurrent; here be dragons.
2532 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
2533 * designated task is enqueued on an allowed CPU. If that task is currently
2534 * running, we have to kick it out using the CPU stopper.
2536 * Migrate-Disable comes along and tramples all over our nice sandcastle.
2539 * Initial conditions: P0->cpus_mask = [0, 1]
2543 * migrate_disable();
2545 * set_cpus_allowed_ptr(P0, [1]);
2547 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
2548 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
2549 * This means we need the following scheme:
2553 * migrate_disable();
2555 * set_cpus_allowed_ptr(P0, [1]);
2559 * __set_cpus_allowed_ptr();
2560 * <wakes local stopper>
2561 * `--> <woken on migration completion>
2563 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
2564 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
2565 * task p are serialized by p->pi_lock, which we can leverage: the one that
2566 * should come into effect at the end of the Migrate-Disable region is the last
2567 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
2568 * but we still need to properly signal those waiting tasks at the appropriate
2571 * This is implemented using struct set_affinity_pending. The first
2572 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
2573 * setup an instance of that struct and install it on the targeted task_struct.
2574 * Any and all further callers will reuse that instance. Those then wait for
2575 * a completion signaled at the tail of the CPU stopper callback (1), triggered
2576 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
2579 * (1) In the cases covered above. There is one more where the completion is
2580 * signaled within affine_move_task() itself: when a subsequent affinity request
2581 * occurs after the stopper bailed out due to the targeted task still being
2582 * Migrate-Disable. Consider:
2584 * Initial conditions: P0->cpus_mask = [0, 1]
2588 * migrate_disable();
2590 * set_cpus_allowed_ptr(P0, [1]);
2593 * migration_cpu_stop()
2594 * is_migration_disabled()
2596 * set_cpus_allowed_ptr(P0, [0, 1]);
2597 * <signal completion>
2600 * Note that the above is safe vs a concurrent migrate_enable(), as any
2601 * pending affinity completion is preceded by an uninstallation of
2602 * p->migration_pending done with p->pi_lock held.
2604 static int affine_move_task(struct rq
*rq
, struct task_struct
*p
, struct rq_flags
*rf
,
2605 int dest_cpu
, unsigned int flags
)
2607 struct set_affinity_pending my_pending
= { }, *pending
= NULL
;
2608 bool stop_pending
, complete
= false;
2610 /* Can the task run on the task's current CPU? If so, we're done */
2611 if (cpumask_test_cpu(task_cpu(p
), &p
->cpus_mask
)) {
2612 struct task_struct
*push_task
= NULL
;
2614 if ((flags
& SCA_MIGRATE_ENABLE
) &&
2615 (p
->migration_flags
& MDF_PUSH
) && !rq
->push_busy
) {
2616 rq
->push_busy
= true;
2617 push_task
= get_task_struct(p
);
2621 * If there are pending waiters, but no pending stop_work,
2622 * then complete now.
2624 pending
= p
->migration_pending
;
2625 if (pending
&& !pending
->stop_pending
) {
2626 p
->migration_pending
= NULL
;
2630 task_rq_unlock(rq
, p
, rf
);
2633 stop_one_cpu_nowait(rq
->cpu
, push_cpu_stop
,
2638 complete_all(&pending
->done
);
2643 if (!(flags
& SCA_MIGRATE_ENABLE
)) {
2644 /* serialized by p->pi_lock */
2645 if (!p
->migration_pending
) {
2646 /* Install the request */
2647 refcount_set(&my_pending
.refs
, 1);
2648 init_completion(&my_pending
.done
);
2649 my_pending
.arg
= (struct migration_arg
) {
2651 .dest_cpu
= dest_cpu
,
2652 .pending
= &my_pending
,
2655 p
->migration_pending
= &my_pending
;
2657 pending
= p
->migration_pending
;
2658 refcount_inc(&pending
->refs
);
2660 * Affinity has changed, but we've already installed a
2661 * pending. migration_cpu_stop() *must* see this, else
2662 * we risk a completion of the pending despite having a
2663 * task on a disallowed CPU.
2665 * Serialized by p->pi_lock, so this is safe.
2667 pending
->arg
.dest_cpu
= dest_cpu
;
2670 pending
= p
->migration_pending
;
2672 * - !MIGRATE_ENABLE:
2673 * we'll have installed a pending if there wasn't one already.
2676 * we're here because the current CPU isn't matching anymore,
2677 * the only way that can happen is because of a concurrent
2678 * set_cpus_allowed_ptr() call, which should then still be
2679 * pending completion.
2681 * Either way, we really should have a @pending here.
2683 if (WARN_ON_ONCE(!pending
)) {
2684 task_rq_unlock(rq
, p
, rf
);
2688 if (task_running(rq
, p
) || READ_ONCE(p
->__state
) == TASK_WAKING
) {
2690 * MIGRATE_ENABLE gets here because 'p == current', but for
2691 * anything else we cannot do is_migration_disabled(), punt
2692 * and have the stopper function handle it all race-free.
2694 stop_pending
= pending
->stop_pending
;
2696 pending
->stop_pending
= true;
2698 if (flags
& SCA_MIGRATE_ENABLE
)
2699 p
->migration_flags
&= ~MDF_PUSH
;
2701 task_rq_unlock(rq
, p
, rf
);
2703 if (!stop_pending
) {
2704 stop_one_cpu_nowait(cpu_of(rq
), migration_cpu_stop
,
2705 &pending
->arg
, &pending
->stop_work
);
2708 if (flags
& SCA_MIGRATE_ENABLE
)
2712 if (!is_migration_disabled(p
)) {
2713 if (task_on_rq_queued(p
))
2714 rq
= move_queued_task(rq
, rf
, p
, dest_cpu
);
2716 if (!pending
->stop_pending
) {
2717 p
->migration_pending
= NULL
;
2721 task_rq_unlock(rq
, p
, rf
);
2724 complete_all(&pending
->done
);
2727 wait_for_completion(&pending
->done
);
2729 if (refcount_dec_and_test(&pending
->refs
))
2730 wake_up_var(&pending
->refs
); /* No UaF, just an address */
2733 * Block the original owner of &pending until all subsequent callers
2734 * have seen the completion and decremented the refcount
2736 wait_var_event(&my_pending
.refs
, !refcount_read(&my_pending
.refs
));
2739 WARN_ON_ONCE(my_pending
.stop_pending
);
2745 * Called with both p->pi_lock and rq->lock held; drops both before returning.
2747 static int __set_cpus_allowed_ptr_locked(struct task_struct
*p
,
2748 const struct cpumask
*new_mask
,
2751 struct rq_flags
*rf
)
2752 __releases(rq
->lock
)
2753 __releases(p
->pi_lock
)
2755 const struct cpumask
*cpu_allowed_mask
= task_cpu_possible_mask(p
);
2756 const struct cpumask
*cpu_valid_mask
= cpu_active_mask
;
2757 bool kthread
= p
->flags
& PF_KTHREAD
;
2758 struct cpumask
*user_mask
= NULL
;
2759 unsigned int dest_cpu
;
2762 update_rq_clock(rq
);
2764 if (kthread
|| is_migration_disabled(p
)) {
2766 * Kernel threads are allowed on online && !active CPUs,
2767 * however, during cpu-hot-unplug, even these might get pushed
2768 * away if not KTHREAD_IS_PER_CPU.
2770 * Specifically, migration_disabled() tasks must not fail the
2771 * cpumask_any_and_distribute() pick below, esp. so on
2772 * SCA_MIGRATE_ENABLE, otherwise we'll not call
2773 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
2775 cpu_valid_mask
= cpu_online_mask
;
2778 if (!kthread
&& !cpumask_subset(new_mask
, cpu_allowed_mask
)) {
2784 * Must re-check here, to close a race against __kthread_bind(),
2785 * sched_setaffinity() is not guaranteed to observe the flag.
2787 if ((flags
& SCA_CHECK
) && (p
->flags
& PF_NO_SETAFFINITY
)) {
2792 if (!(flags
& SCA_MIGRATE_ENABLE
)) {
2793 if (cpumask_equal(&p
->cpus_mask
, new_mask
))
2796 if (WARN_ON_ONCE(p
== current
&&
2797 is_migration_disabled(p
) &&
2798 !cpumask_test_cpu(task_cpu(p
), new_mask
))) {
2805 * Picking a ~random cpu helps in cases where we are changing affinity
2806 * for groups of tasks (ie. cpuset), so that load balancing is not
2807 * immediately required to distribute the tasks within their new mask.
2809 dest_cpu
= cpumask_any_and_distribute(cpu_valid_mask
, new_mask
);
2810 if (dest_cpu
>= nr_cpu_ids
) {
2815 __do_set_cpus_allowed(p
, new_mask
, flags
);
2817 if (flags
& SCA_USER
)
2818 user_mask
= clear_user_cpus_ptr(p
);
2820 ret
= affine_move_task(rq
, p
, rf
, dest_cpu
, flags
);
2827 task_rq_unlock(rq
, p
, rf
);
2833 * Change a given task's CPU affinity. Migrate the thread to a
2834 * proper CPU and schedule it away if the CPU it's executing on
2835 * is removed from the allowed bitmask.
2837 * NOTE: the caller must have a valid reference to the task, the
2838 * task must not exit() & deallocate itself prematurely. The
2839 * call is not atomic; no spinlocks may be held.
2841 static int __set_cpus_allowed_ptr(struct task_struct
*p
,
2842 const struct cpumask
*new_mask
, u32 flags
)
2847 rq
= task_rq_lock(p
, &rf
);
2848 return __set_cpus_allowed_ptr_locked(p
, new_mask
, flags
, rq
, &rf
);
2851 int set_cpus_allowed_ptr(struct task_struct
*p
, const struct cpumask
*new_mask
)
2853 return __set_cpus_allowed_ptr(p
, new_mask
, 0);
2855 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr
);
2858 * Change a given task's CPU affinity to the intersection of its current
2859 * affinity mask and @subset_mask, writing the resulting mask to @new_mask
2860 * and pointing @p->user_cpus_ptr to a copy of the old mask.
2861 * If the resulting mask is empty, leave the affinity unchanged and return
2864 static int restrict_cpus_allowed_ptr(struct task_struct
*p
,
2865 struct cpumask
*new_mask
,
2866 const struct cpumask
*subset_mask
)
2868 struct cpumask
*user_mask
= NULL
;
2873 if (!p
->user_cpus_ptr
) {
2874 user_mask
= kmalloc(cpumask_size(), GFP_KERNEL
);
2879 rq
= task_rq_lock(p
, &rf
);
2882 * Forcefully restricting the affinity of a deadline task is
2883 * likely to cause problems, so fail and noisily override the
2886 if (task_has_dl_policy(p
) && dl_bandwidth_enabled()) {
2891 if (!cpumask_and(new_mask
, &p
->cpus_mask
, subset_mask
)) {
2897 * We're about to butcher the task affinity, so keep track of what
2898 * the user asked for in case we're able to restore it later on.
2901 cpumask_copy(user_mask
, p
->cpus_ptr
);
2902 p
->user_cpus_ptr
= user_mask
;
2905 return __set_cpus_allowed_ptr_locked(p
, new_mask
, 0, rq
, &rf
);
2908 task_rq_unlock(rq
, p
, &rf
);
2914 * Restrict the CPU affinity of task @p so that it is a subset of
2915 * task_cpu_possible_mask() and point @p->user_cpu_ptr to a copy of the
2916 * old affinity mask. If the resulting mask is empty, we warn and walk
2917 * up the cpuset hierarchy until we find a suitable mask.
2919 void force_compatible_cpus_allowed_ptr(struct task_struct
*p
)
2921 cpumask_var_t new_mask
;
2922 const struct cpumask
*override_mask
= task_cpu_possible_mask(p
);
2924 alloc_cpumask_var(&new_mask
, GFP_KERNEL
);
2927 * __migrate_task() can fail silently in the face of concurrent
2928 * offlining of the chosen destination CPU, so take the hotplug
2929 * lock to ensure that the migration succeeds.
2932 if (!cpumask_available(new_mask
))
2935 if (!restrict_cpus_allowed_ptr(p
, new_mask
, override_mask
))
2939 * We failed to find a valid subset of the affinity mask for the
2940 * task, so override it based on its cpuset hierarchy.
2942 cpuset_cpus_allowed(p
, new_mask
);
2943 override_mask
= new_mask
;
2946 if (printk_ratelimit()) {
2947 printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
2948 task_pid_nr(p
), p
->comm
,
2949 cpumask_pr_args(override_mask
));
2952 WARN_ON(set_cpus_allowed_ptr(p
, override_mask
));
2955 free_cpumask_var(new_mask
);
2959 __sched_setaffinity(struct task_struct
*p
, const struct cpumask
*mask
);
2962 * Restore the affinity of a task @p which was previously restricted by a
2963 * call to force_compatible_cpus_allowed_ptr(). This will clear (and free)
2964 * @p->user_cpus_ptr.
2966 * It is the caller's responsibility to serialise this with any calls to
2967 * force_compatible_cpus_allowed_ptr(@p).
2969 void relax_compatible_cpus_allowed_ptr(struct task_struct
*p
)
2971 struct cpumask
*user_mask
= p
->user_cpus_ptr
;
2972 unsigned long flags
;
2975 * Try to restore the old affinity mask. If this fails, then
2976 * we free the mask explicitly to avoid it being inherited across
2977 * a subsequent fork().
2979 if (!user_mask
|| !__sched_setaffinity(p
, user_mask
))
2982 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
2983 user_mask
= clear_user_cpus_ptr(p
);
2984 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2989 void set_task_cpu(struct task_struct
*p
, unsigned int new_cpu
)
2991 #ifdef CONFIG_SCHED_DEBUG
2992 unsigned int state
= READ_ONCE(p
->__state
);
2995 * We should never call set_task_cpu() on a blocked task,
2996 * ttwu() will sort out the placement.
2998 WARN_ON_ONCE(state
!= TASK_RUNNING
&& state
!= TASK_WAKING
&& !p
->on_rq
);
3001 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
3002 * because schedstat_wait_{start,end} rebase migrating task's wait_start
3003 * time relying on p->on_rq.
3005 WARN_ON_ONCE(state
== TASK_RUNNING
&&
3006 p
->sched_class
== &fair_sched_class
&&
3007 (p
->on_rq
&& !task_on_rq_migrating(p
)));
3009 #ifdef CONFIG_LOCKDEP
3011 * The caller should hold either p->pi_lock or rq->lock, when changing
3012 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
3014 * sched_move_task() holds both and thus holding either pins the cgroup,
3017 * Furthermore, all task_rq users should acquire both locks, see
3020 WARN_ON_ONCE(debug_locks
&& !(lockdep_is_held(&p
->pi_lock
) ||
3021 lockdep_is_held(__rq_lockp(task_rq(p
)))));
3024 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
3026 WARN_ON_ONCE(!cpu_online(new_cpu
));
3028 WARN_ON_ONCE(is_migration_disabled(p
));
3031 trace_sched_migrate_task(p
, new_cpu
);
3033 if (task_cpu(p
) != new_cpu
) {
3034 if (p
->sched_class
->migrate_task_rq
)
3035 p
->sched_class
->migrate_task_rq(p
, new_cpu
);
3036 p
->se
.nr_migrations
++;
3038 perf_event_task_migrate(p
);
3041 __set_task_cpu(p
, new_cpu
);
3044 #ifdef CONFIG_NUMA_BALANCING
3045 static void __migrate_swap_task(struct task_struct
*p
, int cpu
)
3047 if (task_on_rq_queued(p
)) {
3048 struct rq
*src_rq
, *dst_rq
;
3049 struct rq_flags srf
, drf
;
3051 src_rq
= task_rq(p
);
3052 dst_rq
= cpu_rq(cpu
);
3054 rq_pin_lock(src_rq
, &srf
);
3055 rq_pin_lock(dst_rq
, &drf
);
3057 deactivate_task(src_rq
, p
, 0);
3058 set_task_cpu(p
, cpu
);
3059 activate_task(dst_rq
, p
, 0);
3060 check_preempt_curr(dst_rq
, p
, 0);
3062 rq_unpin_lock(dst_rq
, &drf
);
3063 rq_unpin_lock(src_rq
, &srf
);
3067 * Task isn't running anymore; make it appear like we migrated
3068 * it before it went to sleep. This means on wakeup we make the
3069 * previous CPU our target instead of where it really is.
3075 struct migration_swap_arg
{
3076 struct task_struct
*src_task
, *dst_task
;
3077 int src_cpu
, dst_cpu
;
3080 static int migrate_swap_stop(void *data
)
3082 struct migration_swap_arg
*arg
= data
;
3083 struct rq
*src_rq
, *dst_rq
;
3086 if (!cpu_active(arg
->src_cpu
) || !cpu_active(arg
->dst_cpu
))
3089 src_rq
= cpu_rq(arg
->src_cpu
);
3090 dst_rq
= cpu_rq(arg
->dst_cpu
);
3092 double_raw_lock(&arg
->src_task
->pi_lock
,
3093 &arg
->dst_task
->pi_lock
);
3094 double_rq_lock(src_rq
, dst_rq
);
3096 if (task_cpu(arg
->dst_task
) != arg
->dst_cpu
)
3099 if (task_cpu(arg
->src_task
) != arg
->src_cpu
)
3102 if (!cpumask_test_cpu(arg
->dst_cpu
, arg
->src_task
->cpus_ptr
))
3105 if (!cpumask_test_cpu(arg
->src_cpu
, arg
->dst_task
->cpus_ptr
))
3108 __migrate_swap_task(arg
->src_task
, arg
->dst_cpu
);
3109 __migrate_swap_task(arg
->dst_task
, arg
->src_cpu
);
3114 double_rq_unlock(src_rq
, dst_rq
);
3115 raw_spin_unlock(&arg
->dst_task
->pi_lock
);
3116 raw_spin_unlock(&arg
->src_task
->pi_lock
);
3122 * Cross migrate two tasks
3124 int migrate_swap(struct task_struct
*cur
, struct task_struct
*p
,
3125 int target_cpu
, int curr_cpu
)
3127 struct migration_swap_arg arg
;
3130 arg
= (struct migration_swap_arg
){
3132 .src_cpu
= curr_cpu
,
3134 .dst_cpu
= target_cpu
,
3137 if (arg
.src_cpu
== arg
.dst_cpu
)
3141 * These three tests are all lockless; this is OK since all of them
3142 * will be re-checked with proper locks held further down the line.
3144 if (!cpu_active(arg
.src_cpu
) || !cpu_active(arg
.dst_cpu
))
3147 if (!cpumask_test_cpu(arg
.dst_cpu
, arg
.src_task
->cpus_ptr
))
3150 if (!cpumask_test_cpu(arg
.src_cpu
, arg
.dst_task
->cpus_ptr
))
3153 trace_sched_swap_numa(cur
, arg
.src_cpu
, p
, arg
.dst_cpu
);
3154 ret
= stop_two_cpus(arg
.dst_cpu
, arg
.src_cpu
, migrate_swap_stop
, &arg
);
3159 #endif /* CONFIG_NUMA_BALANCING */
3162 * wait_task_inactive - wait for a thread to unschedule.
3164 * If @match_state is nonzero, it's the @p->state value just checked and
3165 * not expected to change. If it changes, i.e. @p might have woken up,
3166 * then return zero. When we succeed in waiting for @p to be off its CPU,
3167 * we return a positive number (its total switch count). If a second call
3168 * a short while later returns the same number, the caller can be sure that
3169 * @p has remained unscheduled the whole time.
3171 * The caller must ensure that the task *will* unschedule sometime soon,
3172 * else this function might spin for a *long* time. This function can't
3173 * be called with interrupts off, or it may introduce deadlock with
3174 * smp_call_function() if an IPI is sent by the same process we are
3175 * waiting to become inactive.
3177 unsigned long wait_task_inactive(struct task_struct
*p
, unsigned int match_state
)
3179 int running
, queued
;
3186 * We do the initial early heuristics without holding
3187 * any task-queue locks at all. We'll only try to get
3188 * the runqueue lock when things look like they will
3194 * If the task is actively running on another CPU
3195 * still, just relax and busy-wait without holding
3198 * NOTE! Since we don't hold any locks, it's not
3199 * even sure that "rq" stays as the right runqueue!
3200 * But we don't care, since "task_running()" will
3201 * return false if the runqueue has changed and p
3202 * is actually now running somewhere else!
3204 while (task_running(rq
, p
)) {
3205 if (match_state
&& unlikely(READ_ONCE(p
->__state
) != match_state
))
3211 * Ok, time to look more closely! We need the rq
3212 * lock now, to be *sure*. If we're wrong, we'll
3213 * just go back and repeat.
3215 rq
= task_rq_lock(p
, &rf
);
3216 trace_sched_wait_task(p
);
3217 running
= task_running(rq
, p
);
3218 queued
= task_on_rq_queued(p
);
3220 if (!match_state
|| READ_ONCE(p
->__state
) == match_state
)
3221 ncsw
= p
->nvcsw
| LONG_MIN
; /* sets MSB */
3222 task_rq_unlock(rq
, p
, &rf
);
3225 * If it changed from the expected state, bail out now.
3227 if (unlikely(!ncsw
))
3231 * Was it really running after all now that we
3232 * checked with the proper locks actually held?
3234 * Oops. Go back and try again..
3236 if (unlikely(running
)) {
3242 * It's not enough that it's not actively running,
3243 * it must be off the runqueue _entirely_, and not
3246 * So if it was still runnable (but just not actively
3247 * running right now), it's preempted, and we should
3248 * yield - it could be a while.
3250 if (unlikely(queued
)) {
3251 ktime_t to
= NSEC_PER_SEC
/ HZ
;
3253 set_current_state(TASK_UNINTERRUPTIBLE
);
3254 schedule_hrtimeout(&to
, HRTIMER_MODE_REL
);
3259 * Ahh, all good. It wasn't running, and it wasn't
3260 * runnable, which means that it will never become
3261 * running in the future either. We're all done!
3270 * kick_process - kick a running thread to enter/exit the kernel
3271 * @p: the to-be-kicked thread
3273 * Cause a process which is running on another CPU to enter
3274 * kernel-mode, without any delay. (to get signals handled.)
3276 * NOTE: this function doesn't have to take the runqueue lock,
3277 * because all it wants to ensure is that the remote task enters
3278 * the kernel. If the IPI races and the task has been migrated
3279 * to another CPU then no harm is done and the purpose has been
3282 void kick_process(struct task_struct
*p
)
3288 if ((cpu
!= smp_processor_id()) && task_curr(p
))
3289 smp_send_reschedule(cpu
);
3292 EXPORT_SYMBOL_GPL(kick_process
);
3295 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
3297 * A few notes on cpu_active vs cpu_online:
3299 * - cpu_active must be a subset of cpu_online
3301 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
3302 * see __set_cpus_allowed_ptr(). At this point the newly online
3303 * CPU isn't yet part of the sched domains, and balancing will not
3306 * - on CPU-down we clear cpu_active() to mask the sched domains and
3307 * avoid the load balancer to place new tasks on the to be removed
3308 * CPU. Existing tasks will remain running there and will be taken
3311 * This means that fallback selection must not select !active CPUs.
3312 * And can assume that any active CPU must be online. Conversely
3313 * select_task_rq() below may allow selection of !active CPUs in order
3314 * to satisfy the above rules.
3316 static int select_fallback_rq(int cpu
, struct task_struct
*p
)
3318 int nid
= cpu_to_node(cpu
);
3319 const struct cpumask
*nodemask
= NULL
;
3320 enum { cpuset
, possible
, fail
} state
= cpuset
;
3324 * If the node that the CPU is on has been offlined, cpu_to_node()
3325 * will return -1. There is no CPU on the node, and we should
3326 * select the CPU on the other node.
3329 nodemask
= cpumask_of_node(nid
);
3331 /* Look for allowed, online CPU in same node. */
3332 for_each_cpu(dest_cpu
, nodemask
) {
3333 if (is_cpu_allowed(p
, dest_cpu
))
3339 /* Any allowed, online CPU? */
3340 for_each_cpu(dest_cpu
, p
->cpus_ptr
) {
3341 if (!is_cpu_allowed(p
, dest_cpu
))
3347 /* No more Mr. Nice Guy. */
3350 if (cpuset_cpus_allowed_fallback(p
)) {
3357 * XXX When called from select_task_rq() we only
3358 * hold p->pi_lock and again violate locking order.
3360 * More yuck to audit.
3362 do_set_cpus_allowed(p
, task_cpu_possible_mask(p
));
3372 if (state
!= cpuset
) {
3374 * Don't tell them about moving exiting tasks or
3375 * kernel threads (both mm NULL), since they never
3378 if (p
->mm
&& printk_ratelimit()) {
3379 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
3380 task_pid_nr(p
), p
->comm
, cpu
);
3388 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
3391 int select_task_rq(struct task_struct
*p
, int cpu
, int wake_flags
)
3393 lockdep_assert_held(&p
->pi_lock
);
3395 if (p
->nr_cpus_allowed
> 1 && !is_migration_disabled(p
))
3396 cpu
= p
->sched_class
->select_task_rq(p
, cpu
, wake_flags
);
3398 cpu
= cpumask_any(p
->cpus_ptr
);
3401 * In order not to call set_task_cpu() on a blocking task we need
3402 * to rely on ttwu() to place the task on a valid ->cpus_ptr
3405 * Since this is common to all placement strategies, this lives here.
3407 * [ this allows ->select_task() to simply return task_cpu(p) and
3408 * not worry about this generic constraint ]
3410 if (unlikely(!is_cpu_allowed(p
, cpu
)))
3411 cpu
= select_fallback_rq(task_cpu(p
), p
);
3416 void sched_set_stop_task(int cpu
, struct task_struct
*stop
)
3418 static struct lock_class_key stop_pi_lock
;
3419 struct sched_param param
= { .sched_priority
= MAX_RT_PRIO
- 1 };
3420 struct task_struct
*old_stop
= cpu_rq(cpu
)->stop
;
3424 * Make it appear like a SCHED_FIFO task, its something
3425 * userspace knows about and won't get confused about.
3427 * Also, it will make PI more or less work without too
3428 * much confusion -- but then, stop work should not
3429 * rely on PI working anyway.
3431 sched_setscheduler_nocheck(stop
, SCHED_FIFO
, ¶m
);
3433 stop
->sched_class
= &stop_sched_class
;
3436 * The PI code calls rt_mutex_setprio() with ->pi_lock held to
3437 * adjust the effective priority of a task. As a result,
3438 * rt_mutex_setprio() can trigger (RT) balancing operations,
3439 * which can then trigger wakeups of the stop thread to push
3440 * around the current task.
3442 * The stop task itself will never be part of the PI-chain, it
3443 * never blocks, therefore that ->pi_lock recursion is safe.
3444 * Tell lockdep about this by placing the stop->pi_lock in its
3447 lockdep_set_class(&stop
->pi_lock
, &stop_pi_lock
);
3450 cpu_rq(cpu
)->stop
= stop
;
3454 * Reset it back to a normal scheduling class so that
3455 * it can die in pieces.
3457 old_stop
->sched_class
= &rt_sched_class
;
3461 #else /* CONFIG_SMP */
3463 static inline int __set_cpus_allowed_ptr(struct task_struct
*p
,
3464 const struct cpumask
*new_mask
,
3467 return set_cpus_allowed_ptr(p
, new_mask
);
3470 static inline void migrate_disable_switch(struct rq
*rq
, struct task_struct
*p
) { }
3472 static inline bool rq_has_pinned_tasks(struct rq
*rq
)
3477 #endif /* !CONFIG_SMP */
3480 ttwu_stat(struct task_struct
*p
, int cpu
, int wake_flags
)
3484 if (!schedstat_enabled())
3490 if (cpu
== rq
->cpu
) {
3491 __schedstat_inc(rq
->ttwu_local
);
3492 __schedstat_inc(p
->se
.statistics
.nr_wakeups_local
);
3494 struct sched_domain
*sd
;
3496 __schedstat_inc(p
->se
.statistics
.nr_wakeups_remote
);
3498 for_each_domain(rq
->cpu
, sd
) {
3499 if (cpumask_test_cpu(cpu
, sched_domain_span(sd
))) {
3500 __schedstat_inc(sd
->ttwu_wake_remote
);
3507 if (wake_flags
& WF_MIGRATED
)
3508 __schedstat_inc(p
->se
.statistics
.nr_wakeups_migrate
);
3509 #endif /* CONFIG_SMP */
3511 __schedstat_inc(rq
->ttwu_count
);
3512 __schedstat_inc(p
->se
.statistics
.nr_wakeups
);
3514 if (wake_flags
& WF_SYNC
)
3515 __schedstat_inc(p
->se
.statistics
.nr_wakeups_sync
);
3519 * Mark the task runnable and perform wakeup-preemption.
3521 static void ttwu_do_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
3522 struct rq_flags
*rf
)
3524 check_preempt_curr(rq
, p
, wake_flags
);
3525 WRITE_ONCE(p
->__state
, TASK_RUNNING
);
3526 trace_sched_wakeup(p
);
3529 if (p
->sched_class
->task_woken
) {
3531 * Our task @p is fully woken up and running; so it's safe to
3532 * drop the rq->lock, hereafter rq is only used for statistics.
3534 rq_unpin_lock(rq
, rf
);
3535 p
->sched_class
->task_woken(rq
, p
);
3536 rq_repin_lock(rq
, rf
);
3539 if (rq
->idle_stamp
) {
3540 u64 delta
= rq_clock(rq
) - rq
->idle_stamp
;
3541 u64 max
= 2*rq
->max_idle_balance_cost
;
3543 update_avg(&rq
->avg_idle
, delta
);
3545 if (rq
->avg_idle
> max
)
3548 rq
->wake_stamp
= jiffies
;
3549 rq
->wake_avg_idle
= rq
->avg_idle
/ 2;
3557 ttwu_do_activate(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
3558 struct rq_flags
*rf
)
3560 int en_flags
= ENQUEUE_WAKEUP
| ENQUEUE_NOCLOCK
;
3562 lockdep_assert_rq_held(rq
);
3564 if (p
->sched_contributes_to_load
)
3565 rq
->nr_uninterruptible
--;
3568 if (wake_flags
& WF_MIGRATED
)
3569 en_flags
|= ENQUEUE_MIGRATED
;
3573 delayacct_blkio_end(p
);
3574 atomic_dec(&task_rq(p
)->nr_iowait
);
3577 activate_task(rq
, p
, en_flags
);
3578 ttwu_do_wakeup(rq
, p
, wake_flags
, rf
);
3582 * Consider @p being inside a wait loop:
3585 * set_current_state(TASK_UNINTERRUPTIBLE);
3592 * __set_current_state(TASK_RUNNING);
3594 * between set_current_state() and schedule(). In this case @p is still
3595 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
3598 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
3599 * then schedule() must still happen and p->state can be changed to
3600 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
3601 * need to do a full wakeup with enqueue.
3603 * Returns: %true when the wakeup is done,
3606 static int ttwu_runnable(struct task_struct
*p
, int wake_flags
)
3612 rq
= __task_rq_lock(p
, &rf
);
3613 if (task_on_rq_queued(p
)) {
3614 /* check_preempt_curr() may use rq clock */
3615 update_rq_clock(rq
);
3616 ttwu_do_wakeup(rq
, p
, wake_flags
, &rf
);
3619 __task_rq_unlock(rq
, &rf
);
3625 void sched_ttwu_pending(void *arg
)
3627 struct llist_node
*llist
= arg
;
3628 struct rq
*rq
= this_rq();
3629 struct task_struct
*p
, *t
;
3636 * rq::ttwu_pending racy indication of out-standing wakeups.
3637 * Races such that false-negatives are possible, since they
3638 * are shorter lived that false-positives would be.
3640 WRITE_ONCE(rq
->ttwu_pending
, 0);
3642 rq_lock_irqsave(rq
, &rf
);
3643 update_rq_clock(rq
);
3645 llist_for_each_entry_safe(p
, t
, llist
, wake_entry
.llist
) {
3646 if (WARN_ON_ONCE(p
->on_cpu
))
3647 smp_cond_load_acquire(&p
->on_cpu
, !VAL
);
3649 if (WARN_ON_ONCE(task_cpu(p
) != cpu_of(rq
)))
3650 set_task_cpu(p
, cpu_of(rq
));
3652 ttwu_do_activate(rq
, p
, p
->sched_remote_wakeup
? WF_MIGRATED
: 0, &rf
);
3655 rq_unlock_irqrestore(rq
, &rf
);
3658 void send_call_function_single_ipi(int cpu
)
3660 struct rq
*rq
= cpu_rq(cpu
);
3662 if (!set_nr_if_polling(rq
->idle
))
3663 arch_send_call_function_single_ipi(cpu
);
3665 trace_sched_wake_idle_without_ipi(cpu
);
3669 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
3670 * necessary. The wakee CPU on receipt of the IPI will queue the task
3671 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
3672 * of the wakeup instead of the waker.
3674 static void __ttwu_queue_wakelist(struct task_struct
*p
, int cpu
, int wake_flags
)
3676 struct rq
*rq
= cpu_rq(cpu
);
3678 p
->sched_remote_wakeup
= !!(wake_flags
& WF_MIGRATED
);
3680 WRITE_ONCE(rq
->ttwu_pending
, 1);
3681 __smp_call_single_queue(cpu
, &p
->wake_entry
.llist
);
3684 void wake_up_if_idle(int cpu
)
3686 struct rq
*rq
= cpu_rq(cpu
);
3691 if (!is_idle_task(rcu_dereference(rq
->curr
)))
3694 if (set_nr_if_polling(rq
->idle
)) {
3695 trace_sched_wake_idle_without_ipi(cpu
);
3697 rq_lock_irqsave(rq
, &rf
);
3698 if (is_idle_task(rq
->curr
))
3699 smp_send_reschedule(cpu
);
3700 /* Else CPU is not idle, do nothing here: */
3701 rq_unlock_irqrestore(rq
, &rf
);
3708 bool cpus_share_cache(int this_cpu
, int that_cpu
)
3710 if (this_cpu
== that_cpu
)
3713 return per_cpu(sd_llc_id
, this_cpu
) == per_cpu(sd_llc_id
, that_cpu
);
3716 static inline bool ttwu_queue_cond(int cpu
, int wake_flags
)
3719 * Do not complicate things with the async wake_list while the CPU is
3722 if (!cpu_active(cpu
))
3726 * If the CPU does not share cache, then queue the task on the
3727 * remote rqs wakelist to avoid accessing remote data.
3729 if (!cpus_share_cache(smp_processor_id(), cpu
))
3733 * If the task is descheduling and the only running task on the
3734 * CPU then use the wakelist to offload the task activation to
3735 * the soon-to-be-idle CPU as the current CPU is likely busy.
3736 * nr_running is checked to avoid unnecessary task stacking.
3738 if ((wake_flags
& WF_ON_CPU
) && cpu_rq(cpu
)->nr_running
<= 1)
3744 static bool ttwu_queue_wakelist(struct task_struct
*p
, int cpu
, int wake_flags
)
3746 if (sched_feat(TTWU_QUEUE
) && ttwu_queue_cond(cpu
, wake_flags
)) {
3747 if (WARN_ON_ONCE(cpu
== smp_processor_id()))
3750 sched_clock_cpu(cpu
); /* Sync clocks across CPUs */
3751 __ttwu_queue_wakelist(p
, cpu
, wake_flags
);
3758 #else /* !CONFIG_SMP */
3760 static inline bool ttwu_queue_wakelist(struct task_struct
*p
, int cpu
, int wake_flags
)
3765 #endif /* CONFIG_SMP */
3767 static void ttwu_queue(struct task_struct
*p
, int cpu
, int wake_flags
)
3769 struct rq
*rq
= cpu_rq(cpu
);
3772 if (ttwu_queue_wakelist(p
, cpu
, wake_flags
))
3776 update_rq_clock(rq
);
3777 ttwu_do_activate(rq
, p
, wake_flags
, &rf
);
3782 * Invoked from try_to_wake_up() to check whether the task can be woken up.
3784 * The caller holds p::pi_lock if p != current or has preemption
3785 * disabled when p == current.
3787 * The rules of PREEMPT_RT saved_state:
3789 * The related locking code always holds p::pi_lock when updating
3790 * p::saved_state, which means the code is fully serialized in both cases.
3792 * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other
3793 * bits set. This allows to distinguish all wakeup scenarios.
3795 static __always_inline
3796 bool ttwu_state_match(struct task_struct
*p
, unsigned int state
, int *success
)
3798 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)) {
3799 WARN_ON_ONCE((state
& TASK_RTLOCK_WAIT
) &&
3800 state
!= TASK_RTLOCK_WAIT
);
3803 if (READ_ONCE(p
->__state
) & state
) {
3808 #ifdef CONFIG_PREEMPT_RT
3810 * Saved state preserves the task state across blocking on
3811 * an RT lock. If the state matches, set p::saved_state to
3812 * TASK_RUNNING, but do not wake the task because it waits
3813 * for a lock wakeup. Also indicate success because from
3814 * the regular waker's point of view this has succeeded.
3816 * After acquiring the lock the task will restore p::__state
3817 * from p::saved_state which ensures that the regular
3818 * wakeup is not lost. The restore will also set
3819 * p::saved_state to TASK_RUNNING so any further tests will
3820 * not result in false positives vs. @success
3822 if (p
->saved_state
& state
) {
3823 p
->saved_state
= TASK_RUNNING
;
3831 * Notes on Program-Order guarantees on SMP systems.
3835 * The basic program-order guarantee on SMP systems is that when a task [t]
3836 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
3837 * execution on its new CPU [c1].
3839 * For migration (of runnable tasks) this is provided by the following means:
3841 * A) UNLOCK of the rq(c0)->lock scheduling out task t
3842 * B) migration for t is required to synchronize *both* rq(c0)->lock and
3843 * rq(c1)->lock (if not at the same time, then in that order).
3844 * C) LOCK of the rq(c1)->lock scheduling in task
3846 * Release/acquire chaining guarantees that B happens after A and C after B.
3847 * Note: the CPU doing B need not be c0 or c1
3856 * UNLOCK rq(0)->lock
3858 * LOCK rq(0)->lock // orders against CPU0
3860 * UNLOCK rq(0)->lock
3864 * UNLOCK rq(1)->lock
3866 * LOCK rq(1)->lock // orders against CPU2
3869 * UNLOCK rq(1)->lock
3872 * BLOCKING -- aka. SLEEP + WAKEUP
3874 * For blocking we (obviously) need to provide the same guarantee as for
3875 * migration. However the means are completely different as there is no lock
3876 * chain to provide order. Instead we do:
3878 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
3879 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
3883 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
3885 * LOCK rq(0)->lock LOCK X->pi_lock
3888 * smp_store_release(X->on_cpu, 0);
3890 * smp_cond_load_acquire(&X->on_cpu, !VAL);
3896 * X->state = RUNNING
3897 * UNLOCK rq(2)->lock
3899 * LOCK rq(2)->lock // orders against CPU1
3902 * UNLOCK rq(2)->lock
3905 * UNLOCK rq(0)->lock
3908 * However, for wakeups there is a second guarantee we must provide, namely we
3909 * must ensure that CONDITION=1 done by the caller can not be reordered with
3910 * accesses to the task state; see try_to_wake_up() and set_current_state().
3914 * try_to_wake_up - wake up a thread
3915 * @p: the thread to be awakened
3916 * @state: the mask of task states that can be woken
3917 * @wake_flags: wake modifier flags (WF_*)
3919 * Conceptually does:
3921 * If (@state & @p->state) @p->state = TASK_RUNNING.
3923 * If the task was not queued/runnable, also place it back on a runqueue.
3925 * This function is atomic against schedule() which would dequeue the task.
3927 * It issues a full memory barrier before accessing @p->state, see the comment
3928 * with set_current_state().
3930 * Uses p->pi_lock to serialize against concurrent wake-ups.
3932 * Relies on p->pi_lock stabilizing:
3935 * - p->sched_task_group
3936 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
3938 * Tries really hard to only take one task_rq(p)->lock for performance.
3939 * Takes rq->lock in:
3940 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
3941 * - ttwu_queue() -- new rq, for enqueue of the task;
3942 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
3944 * As a consequence we race really badly with just about everything. See the
3945 * many memory barriers and their comments for details.
3947 * Return: %true if @p->state changes (an actual wakeup was done),
3951 try_to_wake_up(struct task_struct
*p
, unsigned int state
, int wake_flags
)
3953 unsigned long flags
;
3954 int cpu
, success
= 0;
3959 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
3960 * == smp_processor_id()'. Together this means we can special
3961 * case the whole 'p->on_rq && ttwu_runnable()' case below
3962 * without taking any locks.
3965 * - we rely on Program-Order guarantees for all the ordering,
3966 * - we're serialized against set_special_state() by virtue of
3967 * it disabling IRQs (this allows not taking ->pi_lock).
3969 if (!ttwu_state_match(p
, state
, &success
))
3972 trace_sched_waking(p
);
3973 WRITE_ONCE(p
->__state
, TASK_RUNNING
);
3974 trace_sched_wakeup(p
);
3979 * If we are going to wake up a thread waiting for CONDITION we
3980 * need to ensure that CONDITION=1 done by the caller can not be
3981 * reordered with p->state check below. This pairs with smp_store_mb()
3982 * in set_current_state() that the waiting thread does.
3984 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
3985 smp_mb__after_spinlock();
3986 if (!ttwu_state_match(p
, state
, &success
))
3989 trace_sched_waking(p
);
3992 * Ensure we load p->on_rq _after_ p->state, otherwise it would
3993 * be possible to, falsely, observe p->on_rq == 0 and get stuck
3994 * in smp_cond_load_acquire() below.
3996 * sched_ttwu_pending() try_to_wake_up()
3997 * STORE p->on_rq = 1 LOAD p->state
4000 * __schedule() (switch to task 'p')
4001 * LOCK rq->lock smp_rmb();
4002 * smp_mb__after_spinlock();
4006 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
4008 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4009 * __schedule(). See the comment for smp_mb__after_spinlock().
4011 * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
4014 if (READ_ONCE(p
->on_rq
) && ttwu_runnable(p
, wake_flags
))
4019 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
4020 * possible to, falsely, observe p->on_cpu == 0.
4022 * One must be running (->on_cpu == 1) in order to remove oneself
4023 * from the runqueue.
4025 * __schedule() (switch to task 'p') try_to_wake_up()
4026 * STORE p->on_cpu = 1 LOAD p->on_rq
4029 * __schedule() (put 'p' to sleep)
4030 * LOCK rq->lock smp_rmb();
4031 * smp_mb__after_spinlock();
4032 * STORE p->on_rq = 0 LOAD p->on_cpu
4034 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4035 * __schedule(). See the comment for smp_mb__after_spinlock().
4037 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
4038 * schedule()'s deactivate_task() has 'happened' and p will no longer
4039 * care about it's own p->state. See the comment in __schedule().
4041 smp_acquire__after_ctrl_dep();
4044 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
4045 * == 0), which means we need to do an enqueue, change p->state to
4046 * TASK_WAKING such that we can unlock p->pi_lock before doing the
4047 * enqueue, such as ttwu_queue_wakelist().
4049 WRITE_ONCE(p
->__state
, TASK_WAKING
);
4052 * If the owning (remote) CPU is still in the middle of schedule() with
4053 * this task as prev, considering queueing p on the remote CPUs wake_list
4054 * which potentially sends an IPI instead of spinning on p->on_cpu to
4055 * let the waker make forward progress. This is safe because IRQs are
4056 * disabled and the IPI will deliver after on_cpu is cleared.
4058 * Ensure we load task_cpu(p) after p->on_cpu:
4060 * set_task_cpu(p, cpu);
4061 * STORE p->cpu = @cpu
4062 * __schedule() (switch to task 'p')
4064 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
4065 * STORE p->on_cpu = 1 LOAD p->cpu
4067 * to ensure we observe the correct CPU on which the task is currently
4070 if (smp_load_acquire(&p
->on_cpu
) &&
4071 ttwu_queue_wakelist(p
, task_cpu(p
), wake_flags
| WF_ON_CPU
))
4075 * If the owning (remote) CPU is still in the middle of schedule() with
4076 * this task as prev, wait until it's done referencing the task.
4078 * Pairs with the smp_store_release() in finish_task().
4080 * This ensures that tasks getting woken will be fully ordered against
4081 * their previous state and preserve Program Order.
4083 smp_cond_load_acquire(&p
->on_cpu
, !VAL
);
4085 cpu
= select_task_rq(p
, p
->wake_cpu
, wake_flags
| WF_TTWU
);
4086 if (task_cpu(p
) != cpu
) {
4088 delayacct_blkio_end(p
);
4089 atomic_dec(&task_rq(p
)->nr_iowait
);
4092 wake_flags
|= WF_MIGRATED
;
4093 psi_ttwu_dequeue(p
);
4094 set_task_cpu(p
, cpu
);
4098 #endif /* CONFIG_SMP */
4100 ttwu_queue(p
, cpu
, wake_flags
);
4102 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
4105 ttwu_stat(p
, task_cpu(p
), wake_flags
);
4112 * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
4113 * @p: Process for which the function is to be invoked, can be @current.
4114 * @func: Function to invoke.
4115 * @arg: Argument to function.
4117 * If the specified task can be quickly locked into a definite state
4118 * (either sleeping or on a given runqueue), arrange to keep it in that
4119 * state while invoking @func(@arg). This function can use ->on_rq and
4120 * task_curr() to work out what the state is, if required. Given that
4121 * @func can be invoked with a runqueue lock held, it had better be quite
4125 * @false if the task slipped out from under the locks.
4126 * @true if the task was locked onto a runqueue or is sleeping.
4127 * However, @func can override this by returning @false.
4129 bool try_invoke_on_locked_down_task(struct task_struct
*p
, bool (*func
)(struct task_struct
*t
, void *arg
), void *arg
)
4135 raw_spin_lock_irqsave(&p
->pi_lock
, rf
.flags
);
4137 rq
= __task_rq_lock(p
, &rf
);
4138 if (task_rq(p
) == rq
)
4142 switch (READ_ONCE(p
->__state
)) {
4147 smp_rmb(); // See smp_rmb() comment in try_to_wake_up().
4152 raw_spin_unlock_irqrestore(&p
->pi_lock
, rf
.flags
);
4157 * wake_up_process - Wake up a specific process
4158 * @p: The process to be woken up.
4160 * Attempt to wake up the nominated process and move it to the set of runnable
4163 * Return: 1 if the process was woken up, 0 if it was already running.
4165 * This function executes a full memory barrier before accessing the task state.
4167 int wake_up_process(struct task_struct
*p
)
4169 return try_to_wake_up(p
, TASK_NORMAL
, 0);
4171 EXPORT_SYMBOL(wake_up_process
);
4173 int wake_up_state(struct task_struct
*p
, unsigned int state
)
4175 return try_to_wake_up(p
, state
, 0);
4179 * Perform scheduler related setup for a newly forked process p.
4180 * p is forked by current.
4182 * __sched_fork() is basic setup used by init_idle() too:
4184 static void __sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
4189 p
->se
.exec_start
= 0;
4190 p
->se
.sum_exec_runtime
= 0;
4191 p
->se
.prev_sum_exec_runtime
= 0;
4192 p
->se
.nr_migrations
= 0;
4194 INIT_LIST_HEAD(&p
->se
.group_node
);
4196 #ifdef CONFIG_FAIR_GROUP_SCHED
4197 p
->se
.cfs_rq
= NULL
;
4200 #ifdef CONFIG_SCHEDSTATS
4201 /* Even if schedstat is disabled, there should not be garbage */
4202 memset(&p
->se
.statistics
, 0, sizeof(p
->se
.statistics
));
4205 RB_CLEAR_NODE(&p
->dl
.rb_node
);
4206 init_dl_task_timer(&p
->dl
);
4207 init_dl_inactive_task_timer(&p
->dl
);
4208 __dl_clear_params(p
);
4210 INIT_LIST_HEAD(&p
->rt
.run_list
);
4212 p
->rt
.time_slice
= sched_rr_timeslice
;
4216 #ifdef CONFIG_PREEMPT_NOTIFIERS
4217 INIT_HLIST_HEAD(&p
->preempt_notifiers
);
4220 #ifdef CONFIG_COMPACTION
4221 p
->capture_control
= NULL
;
4223 init_numa_balancing(clone_flags
, p
);
4225 p
->wake_entry
.u_flags
= CSD_TYPE_TTWU
;
4226 p
->migration_pending
= NULL
;
4230 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing
);
4232 #ifdef CONFIG_NUMA_BALANCING
4234 void set_numabalancing_state(bool enabled
)
4237 static_branch_enable(&sched_numa_balancing
);
4239 static_branch_disable(&sched_numa_balancing
);
4242 #ifdef CONFIG_PROC_SYSCTL
4243 int sysctl_numa_balancing(struct ctl_table
*table
, int write
,
4244 void *buffer
, size_t *lenp
, loff_t
*ppos
)
4248 int state
= static_branch_likely(&sched_numa_balancing
);
4250 if (write
&& !capable(CAP_SYS_ADMIN
))
4255 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
4259 set_numabalancing_state(state
);
4265 #ifdef CONFIG_SCHEDSTATS
4267 DEFINE_STATIC_KEY_FALSE(sched_schedstats
);
4269 static void set_schedstats(bool enabled
)
4272 static_branch_enable(&sched_schedstats
);
4274 static_branch_disable(&sched_schedstats
);
4277 void force_schedstat_enabled(void)
4279 if (!schedstat_enabled()) {
4280 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
4281 static_branch_enable(&sched_schedstats
);
4285 static int __init
setup_schedstats(char *str
)
4291 if (!strcmp(str
, "enable")) {
4292 set_schedstats(true);
4294 } else if (!strcmp(str
, "disable")) {
4295 set_schedstats(false);
4300 pr_warn("Unable to parse schedstats=\n");
4304 __setup("schedstats=", setup_schedstats
);
4306 #ifdef CONFIG_PROC_SYSCTL
4307 int sysctl_schedstats(struct ctl_table
*table
, int write
, void *buffer
,
4308 size_t *lenp
, loff_t
*ppos
)
4312 int state
= static_branch_likely(&sched_schedstats
);
4314 if (write
&& !capable(CAP_SYS_ADMIN
))
4319 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
4323 set_schedstats(state
);
4326 #endif /* CONFIG_PROC_SYSCTL */
4327 #endif /* CONFIG_SCHEDSTATS */
4330 * fork()/clone()-time setup:
4332 int sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
4334 __sched_fork(clone_flags
, p
);
4336 * We mark the process as NEW here. This guarantees that
4337 * nobody will actually run it, and a signal or other external
4338 * event cannot wake it up and insert it on the runqueue either.
4340 p
->__state
= TASK_NEW
;
4343 * Make sure we do not leak PI boosting priority to the child.
4345 p
->prio
= current
->normal_prio
;
4350 * Revert to default priority/policy on fork if requested.
4352 if (unlikely(p
->sched_reset_on_fork
)) {
4353 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
4354 p
->policy
= SCHED_NORMAL
;
4355 p
->static_prio
= NICE_TO_PRIO(0);
4357 } else if (PRIO_TO_NICE(p
->static_prio
) < 0)
4358 p
->static_prio
= NICE_TO_PRIO(0);
4360 p
->prio
= p
->normal_prio
= p
->static_prio
;
4361 set_load_weight(p
, false);
4364 * We don't need the reset flag anymore after the fork. It has
4365 * fulfilled its duty:
4367 p
->sched_reset_on_fork
= 0;
4370 if (dl_prio(p
->prio
))
4372 else if (rt_prio(p
->prio
))
4373 p
->sched_class
= &rt_sched_class
;
4375 p
->sched_class
= &fair_sched_class
;
4377 init_entity_runnable_average(&p
->se
);
4379 #ifdef CONFIG_SCHED_INFO
4380 if (likely(sched_info_on()))
4381 memset(&p
->sched_info
, 0, sizeof(p
->sched_info
));
4383 #if defined(CONFIG_SMP)
4386 init_task_preempt_count(p
);
4388 plist_node_init(&p
->pushable_tasks
, MAX_PRIO
);
4389 RB_CLEAR_NODE(&p
->pushable_dl_tasks
);
4394 void sched_post_fork(struct task_struct
*p
, struct kernel_clone_args
*kargs
)
4396 unsigned long flags
;
4397 #ifdef CONFIG_CGROUP_SCHED
4398 struct task_group
*tg
;
4401 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
4402 #ifdef CONFIG_CGROUP_SCHED
4403 tg
= container_of(kargs
->cset
->subsys
[cpu_cgrp_id
],
4404 struct task_group
, css
);
4405 p
->sched_task_group
= autogroup_task_group(p
, tg
);
4409 * We're setting the CPU for the first time, we don't migrate,
4410 * so use __set_task_cpu().
4412 __set_task_cpu(p
, smp_processor_id());
4413 if (p
->sched_class
->task_fork
)
4414 p
->sched_class
->task_fork(p
);
4415 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
4417 uclamp_post_fork(p
);
4420 unsigned long to_ratio(u64 period
, u64 runtime
)
4422 if (runtime
== RUNTIME_INF
)
4426 * Doing this here saves a lot of checks in all
4427 * the calling paths, and returning zero seems
4428 * safe for them anyway.
4433 return div64_u64(runtime
<< BW_SHIFT
, period
);
4437 * wake_up_new_task - wake up a newly created task for the first time.
4439 * This function will do some initial scheduler statistics housekeeping
4440 * that must be done for every newly created context, then puts the task
4441 * on the runqueue and wakes it.
4443 void wake_up_new_task(struct task_struct
*p
)
4448 raw_spin_lock_irqsave(&p
->pi_lock
, rf
.flags
);
4449 WRITE_ONCE(p
->__state
, TASK_RUNNING
);
4452 * Fork balancing, do it here and not earlier because:
4453 * - cpus_ptr can change in the fork path
4454 * - any previously selected CPU might disappear through hotplug
4456 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
4457 * as we're not fully set-up yet.
4459 p
->recent_used_cpu
= task_cpu(p
);
4461 __set_task_cpu(p
, select_task_rq(p
, task_cpu(p
), WF_FORK
));
4463 rq
= __task_rq_lock(p
, &rf
);
4464 update_rq_clock(rq
);
4465 post_init_entity_util_avg(p
);
4467 activate_task(rq
, p
, ENQUEUE_NOCLOCK
);
4468 trace_sched_wakeup_new(p
);
4469 check_preempt_curr(rq
, p
, WF_FORK
);
4471 if (p
->sched_class
->task_woken
) {
4473 * Nothing relies on rq->lock after this, so it's fine to
4476 rq_unpin_lock(rq
, &rf
);
4477 p
->sched_class
->task_woken(rq
, p
);
4478 rq_repin_lock(rq
, &rf
);
4481 task_rq_unlock(rq
, p
, &rf
);
4484 #ifdef CONFIG_PREEMPT_NOTIFIERS
4486 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key
);
4488 void preempt_notifier_inc(void)
4490 static_branch_inc(&preempt_notifier_key
);
4492 EXPORT_SYMBOL_GPL(preempt_notifier_inc
);
4494 void preempt_notifier_dec(void)
4496 static_branch_dec(&preempt_notifier_key
);
4498 EXPORT_SYMBOL_GPL(preempt_notifier_dec
);
4501 * preempt_notifier_register - tell me when current is being preempted & rescheduled
4502 * @notifier: notifier struct to register
4504 void preempt_notifier_register(struct preempt_notifier
*notifier
)
4506 if (!static_branch_unlikely(&preempt_notifier_key
))
4507 WARN(1, "registering preempt_notifier while notifiers disabled\n");
4509 hlist_add_head(¬ifier
->link
, ¤t
->preempt_notifiers
);
4511 EXPORT_SYMBOL_GPL(preempt_notifier_register
);
4514 * preempt_notifier_unregister - no longer interested in preemption notifications
4515 * @notifier: notifier struct to unregister
4517 * This is *not* safe to call from within a preemption notifier.
4519 void preempt_notifier_unregister(struct preempt_notifier
*notifier
)
4521 hlist_del(¬ifier
->link
);
4523 EXPORT_SYMBOL_GPL(preempt_notifier_unregister
);
4525 static void __fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
4527 struct preempt_notifier
*notifier
;
4529 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
4530 notifier
->ops
->sched_in(notifier
, raw_smp_processor_id());
4533 static __always_inline
void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
4535 if (static_branch_unlikely(&preempt_notifier_key
))
4536 __fire_sched_in_preempt_notifiers(curr
);
4540 __fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
4541 struct task_struct
*next
)
4543 struct preempt_notifier
*notifier
;
4545 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
4546 notifier
->ops
->sched_out(notifier
, next
);
4549 static __always_inline
void
4550 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
4551 struct task_struct
*next
)
4553 if (static_branch_unlikely(&preempt_notifier_key
))
4554 __fire_sched_out_preempt_notifiers(curr
, next
);
4557 #else /* !CONFIG_PREEMPT_NOTIFIERS */
4559 static inline void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
4564 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
4565 struct task_struct
*next
)
4569 #endif /* CONFIG_PREEMPT_NOTIFIERS */
4571 static inline void prepare_task(struct task_struct
*next
)
4575 * Claim the task as running, we do this before switching to it
4576 * such that any running task will have this set.
4578 * See the ttwu() WF_ON_CPU case and its ordering comment.
4580 WRITE_ONCE(next
->on_cpu
, 1);
4584 static inline void finish_task(struct task_struct
*prev
)
4588 * This must be the very last reference to @prev from this CPU. After
4589 * p->on_cpu is cleared, the task can be moved to a different CPU. We
4590 * must ensure this doesn't happen until the switch is completely
4593 * In particular, the load of prev->state in finish_task_switch() must
4594 * happen before this.
4596 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
4598 smp_store_release(&prev
->on_cpu
, 0);
4604 static void do_balance_callbacks(struct rq
*rq
, struct callback_head
*head
)
4606 void (*func
)(struct rq
*rq
);
4607 struct callback_head
*next
;
4609 lockdep_assert_rq_held(rq
);
4612 func
= (void (*)(struct rq
*))head
->func
;
4621 static void balance_push(struct rq
*rq
);
4623 struct callback_head balance_push_callback
= {
4625 .func
= (void (*)(struct callback_head
*))balance_push
,
4628 static inline struct callback_head
*splice_balance_callbacks(struct rq
*rq
)
4630 struct callback_head
*head
= rq
->balance_callback
;
4632 lockdep_assert_rq_held(rq
);
4634 rq
->balance_callback
= NULL
;
4639 static void __balance_callbacks(struct rq
*rq
)
4641 do_balance_callbacks(rq
, splice_balance_callbacks(rq
));
4644 static inline void balance_callbacks(struct rq
*rq
, struct callback_head
*head
)
4646 unsigned long flags
;
4648 if (unlikely(head
)) {
4649 raw_spin_rq_lock_irqsave(rq
, flags
);
4650 do_balance_callbacks(rq
, head
);
4651 raw_spin_rq_unlock_irqrestore(rq
, flags
);
4657 static inline void __balance_callbacks(struct rq
*rq
)
4661 static inline struct callback_head
*splice_balance_callbacks(struct rq
*rq
)
4666 static inline void balance_callbacks(struct rq
*rq
, struct callback_head
*head
)
4673 prepare_lock_switch(struct rq
*rq
, struct task_struct
*next
, struct rq_flags
*rf
)
4676 * Since the runqueue lock will be released by the next
4677 * task (which is an invalid locking op but in the case
4678 * of the scheduler it's an obvious special-case), so we
4679 * do an early lockdep release here:
4681 rq_unpin_lock(rq
, rf
);
4682 spin_release(&__rq_lockp(rq
)->dep_map
, _THIS_IP_
);
4683 #ifdef CONFIG_DEBUG_SPINLOCK
4684 /* this is a valid case when another task releases the spinlock */
4685 rq_lockp(rq
)->owner
= next
;
4689 static inline void finish_lock_switch(struct rq
*rq
)
4692 * If we are tracking spinlock dependencies then we have to
4693 * fix up the runqueue lock - which gets 'carried over' from
4694 * prev into current:
4696 spin_acquire(&__rq_lockp(rq
)->dep_map
, 0, 0, _THIS_IP_
);
4697 __balance_callbacks(rq
);
4698 raw_spin_rq_unlock_irq(rq
);
4702 * NOP if the arch has not defined these:
4705 #ifndef prepare_arch_switch
4706 # define prepare_arch_switch(next) do { } while (0)
4709 #ifndef finish_arch_post_lock_switch
4710 # define finish_arch_post_lock_switch() do { } while (0)
4713 static inline void kmap_local_sched_out(void)
4715 #ifdef CONFIG_KMAP_LOCAL
4716 if (unlikely(current
->kmap_ctrl
.idx
))
4717 __kmap_local_sched_out();
4721 static inline void kmap_local_sched_in(void)
4723 #ifdef CONFIG_KMAP_LOCAL
4724 if (unlikely(current
->kmap_ctrl
.idx
))
4725 __kmap_local_sched_in();
4730 * prepare_task_switch - prepare to switch tasks
4731 * @rq: the runqueue preparing to switch
4732 * @prev: the current task that is being switched out
4733 * @next: the task we are going to switch to.
4735 * This is called with the rq lock held and interrupts off. It must
4736 * be paired with a subsequent finish_task_switch after the context
4739 * prepare_task_switch sets up locking and calls architecture specific
4743 prepare_task_switch(struct rq
*rq
, struct task_struct
*prev
,
4744 struct task_struct
*next
)
4746 kcov_prepare_switch(prev
);
4747 sched_info_switch(rq
, prev
, next
);
4748 perf_event_task_sched_out(prev
, next
);
4750 fire_sched_out_preempt_notifiers(prev
, next
);
4751 kmap_local_sched_out();
4753 prepare_arch_switch(next
);
4757 * finish_task_switch - clean up after a task-switch
4758 * @prev: the thread we just switched away from.
4760 * finish_task_switch must be called after the context switch, paired
4761 * with a prepare_task_switch call before the context switch.
4762 * finish_task_switch will reconcile locking set up by prepare_task_switch,
4763 * and do any other architecture-specific cleanup actions.
4765 * Note that we may have delayed dropping an mm in context_switch(). If
4766 * so, we finish that here outside of the runqueue lock. (Doing it
4767 * with the lock held can cause deadlocks; see schedule() for
4770 * The context switch have flipped the stack from under us and restored the
4771 * local variables which were saved when this task called schedule() in the
4772 * past. prev == current is still correct but we need to recalculate this_rq
4773 * because prev may have moved to another CPU.
4775 static struct rq
*finish_task_switch(struct task_struct
*prev
)
4776 __releases(rq
->lock
)
4778 struct rq
*rq
= this_rq();
4779 struct mm_struct
*mm
= rq
->prev_mm
;
4783 * The previous task will have left us with a preempt_count of 2
4784 * because it left us after:
4787 * preempt_disable(); // 1
4789 * raw_spin_lock_irq(&rq->lock) // 2
4791 * Also, see FORK_PREEMPT_COUNT.
4793 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET
,
4794 "corrupted preempt_count: %s/%d/0x%x\n",
4795 current
->comm
, current
->pid
, preempt_count()))
4796 preempt_count_set(FORK_PREEMPT_COUNT
);
4801 * A task struct has one reference for the use as "current".
4802 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
4803 * schedule one last time. The schedule call will never return, and
4804 * the scheduled task must drop that reference.
4806 * We must observe prev->state before clearing prev->on_cpu (in
4807 * finish_task), otherwise a concurrent wakeup can get prev
4808 * running on another CPU and we could rave with its RUNNING -> DEAD
4809 * transition, resulting in a double drop.
4811 prev_state
= READ_ONCE(prev
->__state
);
4812 vtime_task_switch(prev
);
4813 perf_event_task_sched_in(prev
, current
);
4815 tick_nohz_task_switch();
4816 finish_lock_switch(rq
);
4817 finish_arch_post_lock_switch();
4818 kcov_finish_switch(current
);
4820 * kmap_local_sched_out() is invoked with rq::lock held and
4821 * interrupts disabled. There is no requirement for that, but the
4822 * sched out code does not have an interrupt enabled section.
4823 * Restoring the maps on sched in does not require interrupts being
4826 kmap_local_sched_in();
4828 fire_sched_in_preempt_notifiers(current
);
4830 * When switching through a kernel thread, the loop in
4831 * membarrier_{private,global}_expedited() may have observed that
4832 * kernel thread and not issued an IPI. It is therefore possible to
4833 * schedule between user->kernel->user threads without passing though
4834 * switch_mm(). Membarrier requires a barrier after storing to
4835 * rq->curr, before returning to userspace, so provide them here:
4837 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
4838 * provided by mmdrop(),
4839 * - a sync_core for SYNC_CORE.
4842 membarrier_mm_sync_core_before_usermode(mm
);
4845 if (unlikely(prev_state
== TASK_DEAD
)) {
4846 if (prev
->sched_class
->task_dead
)
4847 prev
->sched_class
->task_dead(prev
);
4850 * Remove function-return probe instances associated with this
4851 * task and put them back on the free list.
4853 kprobe_flush_task(prev
);
4855 /* Task is done with its stack. */
4856 put_task_stack(prev
);
4858 put_task_struct_rcu_user(prev
);
4865 * schedule_tail - first thing a freshly forked thread must call.
4866 * @prev: the thread we just switched away from.
4868 asmlinkage __visible
void schedule_tail(struct task_struct
*prev
)
4869 __releases(rq
->lock
)
4872 * New tasks start with FORK_PREEMPT_COUNT, see there and
4873 * finish_task_switch() for details.
4875 * finish_task_switch() will drop rq->lock() and lower preempt_count
4876 * and the preempt_enable() will end up enabling preemption (on
4877 * PREEMPT_COUNT kernels).
4880 finish_task_switch(prev
);
4883 if (current
->set_child_tid
)
4884 put_user(task_pid_vnr(current
), current
->set_child_tid
);
4886 calculate_sigpending();
4890 * context_switch - switch to the new MM and the new thread's register state.
4892 static __always_inline
struct rq
*
4893 context_switch(struct rq
*rq
, struct task_struct
*prev
,
4894 struct task_struct
*next
, struct rq_flags
*rf
)
4896 prepare_task_switch(rq
, prev
, next
);
4899 * For paravirt, this is coupled with an exit in switch_to to
4900 * combine the page table reload and the switch backend into
4903 arch_start_context_switch(prev
);
4906 * kernel -> kernel lazy + transfer active
4907 * user -> kernel lazy + mmgrab() active
4909 * kernel -> user switch + mmdrop() active
4910 * user -> user switch
4912 if (!next
->mm
) { // to kernel
4913 enter_lazy_tlb(prev
->active_mm
, next
);
4915 next
->active_mm
= prev
->active_mm
;
4916 if (prev
->mm
) // from user
4917 mmgrab(prev
->active_mm
);
4919 prev
->active_mm
= NULL
;
4921 membarrier_switch_mm(rq
, prev
->active_mm
, next
->mm
);
4923 * sys_membarrier() requires an smp_mb() between setting
4924 * rq->curr / membarrier_switch_mm() and returning to userspace.
4926 * The below provides this either through switch_mm(), or in
4927 * case 'prev->active_mm == next->mm' through
4928 * finish_task_switch()'s mmdrop().
4930 switch_mm_irqs_off(prev
->active_mm
, next
->mm
, next
);
4932 if (!prev
->mm
) { // from kernel
4933 /* will mmdrop() in finish_task_switch(). */
4934 rq
->prev_mm
= prev
->active_mm
;
4935 prev
->active_mm
= NULL
;
4939 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
4941 prepare_lock_switch(rq
, next
, rf
);
4943 /* Here we just switch the register state and the stack. */
4944 switch_to(prev
, next
, prev
);
4947 return finish_task_switch(prev
);
4951 * nr_running and nr_context_switches:
4953 * externally visible scheduler statistics: current number of runnable
4954 * threads, total number of context switches performed since bootup.
4956 unsigned int nr_running(void)
4958 unsigned int i
, sum
= 0;
4960 for_each_online_cpu(i
)
4961 sum
+= cpu_rq(i
)->nr_running
;
4967 * Check if only the current task is running on the CPU.
4969 * Caution: this function does not check that the caller has disabled
4970 * preemption, thus the result might have a time-of-check-to-time-of-use
4971 * race. The caller is responsible to use it correctly, for example:
4973 * - from a non-preemptible section (of course)
4975 * - from a thread that is bound to a single CPU
4977 * - in a loop with very short iterations (e.g. a polling loop)
4979 bool single_task_running(void)
4981 return raw_rq()->nr_running
== 1;
4983 EXPORT_SYMBOL(single_task_running
);
4985 unsigned long long nr_context_switches(void)
4988 unsigned long long sum
= 0;
4990 for_each_possible_cpu(i
)
4991 sum
+= cpu_rq(i
)->nr_switches
;
4997 * Consumers of these two interfaces, like for example the cpuidle menu
4998 * governor, are using nonsensical data. Preferring shallow idle state selection
4999 * for a CPU that has IO-wait which might not even end up running the task when
5000 * it does become runnable.
5003 unsigned int nr_iowait_cpu(int cpu
)
5005 return atomic_read(&cpu_rq(cpu
)->nr_iowait
);
5009 * IO-wait accounting, and how it's mostly bollocks (on SMP).
5011 * The idea behind IO-wait account is to account the idle time that we could
5012 * have spend running if it were not for IO. That is, if we were to improve the
5013 * storage performance, we'd have a proportional reduction in IO-wait time.
5015 * This all works nicely on UP, where, when a task blocks on IO, we account
5016 * idle time as IO-wait, because if the storage were faster, it could've been
5017 * running and we'd not be idle.
5019 * This has been extended to SMP, by doing the same for each CPU. This however
5022 * Imagine for instance the case where two tasks block on one CPU, only the one
5023 * CPU will have IO-wait accounted, while the other has regular idle. Even
5024 * though, if the storage were faster, both could've ran at the same time,
5025 * utilising both CPUs.
5027 * This means, that when looking globally, the current IO-wait accounting on
5028 * SMP is a lower bound, by reason of under accounting.
5030 * Worse, since the numbers are provided per CPU, they are sometimes
5031 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
5032 * associated with any one particular CPU, it can wake to another CPU than it
5033 * blocked on. This means the per CPU IO-wait number is meaningless.
5035 * Task CPU affinities can make all that even more 'interesting'.
5038 unsigned int nr_iowait(void)
5040 unsigned int i
, sum
= 0;
5042 for_each_possible_cpu(i
)
5043 sum
+= nr_iowait_cpu(i
);
5051 * sched_exec - execve() is a valuable balancing opportunity, because at
5052 * this point the task has the smallest effective memory and cache footprint.
5054 void sched_exec(void)
5056 struct task_struct
*p
= current
;
5057 unsigned long flags
;
5060 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
5061 dest_cpu
= p
->sched_class
->select_task_rq(p
, task_cpu(p
), WF_EXEC
);
5062 if (dest_cpu
== smp_processor_id())
5065 if (likely(cpu_active(dest_cpu
))) {
5066 struct migration_arg arg
= { p
, dest_cpu
};
5068 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
5069 stop_one_cpu(task_cpu(p
), migration_cpu_stop
, &arg
);
5073 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
5078 DEFINE_PER_CPU(struct kernel_stat
, kstat
);
5079 DEFINE_PER_CPU(struct kernel_cpustat
, kernel_cpustat
);
5081 EXPORT_PER_CPU_SYMBOL(kstat
);
5082 EXPORT_PER_CPU_SYMBOL(kernel_cpustat
);
5085 * The function fair_sched_class.update_curr accesses the struct curr
5086 * and its field curr->exec_start; when called from task_sched_runtime(),
5087 * we observe a high rate of cache misses in practice.
5088 * Prefetching this data results in improved performance.
5090 static inline void prefetch_curr_exec_start(struct task_struct
*p
)
5092 #ifdef CONFIG_FAIR_GROUP_SCHED
5093 struct sched_entity
*curr
= (&p
->se
)->cfs_rq
->curr
;
5095 struct sched_entity
*curr
= (&task_rq(p
)->cfs
)->curr
;
5098 prefetch(&curr
->exec_start
);
5102 * Return accounted runtime for the task.
5103 * In case the task is currently running, return the runtime plus current's
5104 * pending runtime that have not been accounted yet.
5106 unsigned long long task_sched_runtime(struct task_struct
*p
)
5112 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
5114 * 64-bit doesn't need locks to atomically read a 64-bit value.
5115 * So we have a optimization chance when the task's delta_exec is 0.
5116 * Reading ->on_cpu is racy, but this is ok.
5118 * If we race with it leaving CPU, we'll take a lock. So we're correct.
5119 * If we race with it entering CPU, unaccounted time is 0. This is
5120 * indistinguishable from the read occurring a few cycles earlier.
5121 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
5122 * been accounted, so we're correct here as well.
5124 if (!p
->on_cpu
|| !task_on_rq_queued(p
))
5125 return p
->se
.sum_exec_runtime
;
5128 rq
= task_rq_lock(p
, &rf
);
5130 * Must be ->curr _and_ ->on_rq. If dequeued, we would
5131 * project cycles that may never be accounted to this
5132 * thread, breaking clock_gettime().
5134 if (task_current(rq
, p
) && task_on_rq_queued(p
)) {
5135 prefetch_curr_exec_start(p
);
5136 update_rq_clock(rq
);
5137 p
->sched_class
->update_curr(rq
);
5139 ns
= p
->se
.sum_exec_runtime
;
5140 task_rq_unlock(rq
, p
, &rf
);
5145 #ifdef CONFIG_SCHED_DEBUG
5146 static u64
cpu_resched_latency(struct rq
*rq
)
5148 int latency_warn_ms
= READ_ONCE(sysctl_resched_latency_warn_ms
);
5149 u64 resched_latency
, now
= rq_clock(rq
);
5150 static bool warned_once
;
5152 if (sysctl_resched_latency_warn_once
&& warned_once
)
5155 if (!need_resched() || !latency_warn_ms
)
5158 if (system_state
== SYSTEM_BOOTING
)
5161 if (!rq
->last_seen_need_resched_ns
) {
5162 rq
->last_seen_need_resched_ns
= now
;
5163 rq
->ticks_without_resched
= 0;
5167 rq
->ticks_without_resched
++;
5168 resched_latency
= now
- rq
->last_seen_need_resched_ns
;
5169 if (resched_latency
<= latency_warn_ms
* NSEC_PER_MSEC
)
5174 return resched_latency
;
5177 static int __init
setup_resched_latency_warn_ms(char *str
)
5181 if ((kstrtol(str
, 0, &val
))) {
5182 pr_warn("Unable to set resched_latency_warn_ms\n");
5186 sysctl_resched_latency_warn_ms
= val
;
5189 __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms
);
5191 static inline u64
cpu_resched_latency(struct rq
*rq
) { return 0; }
5192 #endif /* CONFIG_SCHED_DEBUG */
5195 * This function gets called by the timer code, with HZ frequency.
5196 * We call it with interrupts disabled.
5198 void scheduler_tick(void)
5200 int cpu
= smp_processor_id();
5201 struct rq
*rq
= cpu_rq(cpu
);
5202 struct task_struct
*curr
= rq
->curr
;
5204 unsigned long thermal_pressure
;
5205 u64 resched_latency
;
5207 arch_scale_freq_tick();
5212 update_rq_clock(rq
);
5213 thermal_pressure
= arch_scale_thermal_pressure(cpu_of(rq
));
5214 update_thermal_load_avg(rq_clock_thermal(rq
), rq
, thermal_pressure
);
5215 curr
->sched_class
->task_tick(rq
, curr
, 0);
5216 if (sched_feat(LATENCY_WARN
))
5217 resched_latency
= cpu_resched_latency(rq
);
5218 calc_global_load_tick(rq
);
5222 if (sched_feat(LATENCY_WARN
) && resched_latency
)
5223 resched_latency_warn(cpu
, resched_latency
);
5225 perf_event_task_tick();
5228 rq
->idle_balance
= idle_cpu(cpu
);
5229 trigger_load_balance(rq
);
5233 #ifdef CONFIG_NO_HZ_FULL
5238 struct delayed_work work
;
5240 /* Values for ->state, see diagram below. */
5241 #define TICK_SCHED_REMOTE_OFFLINE 0
5242 #define TICK_SCHED_REMOTE_OFFLINING 1
5243 #define TICK_SCHED_REMOTE_RUNNING 2
5246 * State diagram for ->state:
5249 * TICK_SCHED_REMOTE_OFFLINE
5252 * | | sched_tick_remote()
5255 * +--TICK_SCHED_REMOTE_OFFLINING
5258 * sched_tick_start() | | sched_tick_stop()
5261 * TICK_SCHED_REMOTE_RUNNING
5264 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
5265 * and sched_tick_start() are happy to leave the state in RUNNING.
5268 static struct tick_work __percpu
*tick_work_cpu
;
5270 static void sched_tick_remote(struct work_struct
*work
)
5272 struct delayed_work
*dwork
= to_delayed_work(work
);
5273 struct tick_work
*twork
= container_of(dwork
, struct tick_work
, work
);
5274 int cpu
= twork
->cpu
;
5275 struct rq
*rq
= cpu_rq(cpu
);
5276 struct task_struct
*curr
;
5282 * Handle the tick only if it appears the remote CPU is running in full
5283 * dynticks mode. The check is racy by nature, but missing a tick or
5284 * having one too much is no big deal because the scheduler tick updates
5285 * statistics and checks timeslices in a time-independent way, regardless
5286 * of when exactly it is running.
5288 if (!tick_nohz_tick_stopped_cpu(cpu
))
5291 rq_lock_irq(rq
, &rf
);
5293 if (cpu_is_offline(cpu
))
5296 update_rq_clock(rq
);
5298 if (!is_idle_task(curr
)) {
5300 * Make sure the next tick runs within a reasonable
5303 delta
= rq_clock_task(rq
) - curr
->se
.exec_start
;
5304 WARN_ON_ONCE(delta
> (u64
)NSEC_PER_SEC
* 3);
5306 curr
->sched_class
->task_tick(rq
, curr
, 0);
5308 calc_load_nohz_remote(rq
);
5310 rq_unlock_irq(rq
, &rf
);
5314 * Run the remote tick once per second (1Hz). This arbitrary
5315 * frequency is large enough to avoid overload but short enough
5316 * to keep scheduler internal stats reasonably up to date. But
5317 * first update state to reflect hotplug activity if required.
5319 os
= atomic_fetch_add_unless(&twork
->state
, -1, TICK_SCHED_REMOTE_RUNNING
);
5320 WARN_ON_ONCE(os
== TICK_SCHED_REMOTE_OFFLINE
);
5321 if (os
== TICK_SCHED_REMOTE_RUNNING
)
5322 queue_delayed_work(system_unbound_wq
, dwork
, HZ
);
5325 static void sched_tick_start(int cpu
)
5328 struct tick_work
*twork
;
5330 if (housekeeping_cpu(cpu
, HK_FLAG_TICK
))
5333 WARN_ON_ONCE(!tick_work_cpu
);
5335 twork
= per_cpu_ptr(tick_work_cpu
, cpu
);
5336 os
= atomic_xchg(&twork
->state
, TICK_SCHED_REMOTE_RUNNING
);
5337 WARN_ON_ONCE(os
== TICK_SCHED_REMOTE_RUNNING
);
5338 if (os
== TICK_SCHED_REMOTE_OFFLINE
) {
5340 INIT_DELAYED_WORK(&twork
->work
, sched_tick_remote
);
5341 queue_delayed_work(system_unbound_wq
, &twork
->work
, HZ
);
5345 #ifdef CONFIG_HOTPLUG_CPU
5346 static void sched_tick_stop(int cpu
)
5348 struct tick_work
*twork
;
5351 if (housekeeping_cpu(cpu
, HK_FLAG_TICK
))
5354 WARN_ON_ONCE(!tick_work_cpu
);
5356 twork
= per_cpu_ptr(tick_work_cpu
, cpu
);
5357 /* There cannot be competing actions, but don't rely on stop-machine. */
5358 os
= atomic_xchg(&twork
->state
, TICK_SCHED_REMOTE_OFFLINING
);
5359 WARN_ON_ONCE(os
!= TICK_SCHED_REMOTE_RUNNING
);
5360 /* Don't cancel, as this would mess up the state machine. */
5362 #endif /* CONFIG_HOTPLUG_CPU */
5364 int __init
sched_tick_offload_init(void)
5366 tick_work_cpu
= alloc_percpu(struct tick_work
);
5367 BUG_ON(!tick_work_cpu
);
5371 #else /* !CONFIG_NO_HZ_FULL */
5372 static inline void sched_tick_start(int cpu
) { }
5373 static inline void sched_tick_stop(int cpu
) { }
5376 #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
5377 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
5379 * If the value passed in is equal to the current preempt count
5380 * then we just disabled preemption. Start timing the latency.
5382 static inline void preempt_latency_start(int val
)
5384 if (preempt_count() == val
) {
5385 unsigned long ip
= get_lock_parent_ip();
5386 #ifdef CONFIG_DEBUG_PREEMPT
5387 current
->preempt_disable_ip
= ip
;
5389 trace_preempt_off(CALLER_ADDR0
, ip
);
5393 void preempt_count_add(int val
)
5395 #ifdef CONFIG_DEBUG_PREEMPT
5399 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
5402 __preempt_count_add(val
);
5403 #ifdef CONFIG_DEBUG_PREEMPT
5405 * Spinlock count overflowing soon?
5407 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK
) >=
5410 preempt_latency_start(val
);
5412 EXPORT_SYMBOL(preempt_count_add
);
5413 NOKPROBE_SYMBOL(preempt_count_add
);
5416 * If the value passed in equals to the current preempt count
5417 * then we just enabled preemption. Stop timing the latency.
5419 static inline void preempt_latency_stop(int val
)
5421 if (preempt_count() == val
)
5422 trace_preempt_on(CALLER_ADDR0
, get_lock_parent_ip());
5425 void preempt_count_sub(int val
)
5427 #ifdef CONFIG_DEBUG_PREEMPT
5431 if (DEBUG_LOCKS_WARN_ON(val
> preempt_count()))
5434 * Is the spinlock portion underflowing?
5436 if (DEBUG_LOCKS_WARN_ON((val
< PREEMPT_MASK
) &&
5437 !(preempt_count() & PREEMPT_MASK
)))
5441 preempt_latency_stop(val
);
5442 __preempt_count_sub(val
);
5444 EXPORT_SYMBOL(preempt_count_sub
);
5445 NOKPROBE_SYMBOL(preempt_count_sub
);
5448 static inline void preempt_latency_start(int val
) { }
5449 static inline void preempt_latency_stop(int val
) { }
5452 static inline unsigned long get_preempt_disable_ip(struct task_struct
*p
)
5454 #ifdef CONFIG_DEBUG_PREEMPT
5455 return p
->preempt_disable_ip
;
5462 * Print scheduling while atomic bug:
5464 static noinline
void __schedule_bug(struct task_struct
*prev
)
5466 /* Save this before calling printk(), since that will clobber it */
5467 unsigned long preempt_disable_ip
= get_preempt_disable_ip(current
);
5469 if (oops_in_progress
)
5472 printk(KERN_ERR
"BUG: scheduling while atomic: %s/%d/0x%08x\n",
5473 prev
->comm
, prev
->pid
, preempt_count());
5475 debug_show_held_locks(prev
);
5477 if (irqs_disabled())
5478 print_irqtrace_events(prev
);
5479 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
5480 && in_atomic_preempt_off()) {
5481 pr_err("Preemption disabled at:");
5482 print_ip_sym(KERN_ERR
, preempt_disable_ip
);
5485 panic("scheduling while atomic\n");
5488 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
5492 * Various schedule()-time debugging checks and statistics:
5494 static inline void schedule_debug(struct task_struct
*prev
, bool preempt
)
5496 #ifdef CONFIG_SCHED_STACK_END_CHECK
5497 if (task_stack_end_corrupted(prev
))
5498 panic("corrupted stack end detected inside scheduler\n");
5500 if (task_scs_end_corrupted(prev
))
5501 panic("corrupted shadow stack detected inside scheduler\n");
5504 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5505 if (!preempt
&& READ_ONCE(prev
->__state
) && prev
->non_block_count
) {
5506 printk(KERN_ERR
"BUG: scheduling in a non-blocking section: %s/%d/%i\n",
5507 prev
->comm
, prev
->pid
, prev
->non_block_count
);
5509 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
5513 if (unlikely(in_atomic_preempt_off())) {
5514 __schedule_bug(prev
);
5515 preempt_count_set(PREEMPT_DISABLED
);
5518 SCHED_WARN_ON(ct_state() == CONTEXT_USER
);
5520 profile_hit(SCHED_PROFILING
, __builtin_return_address(0));
5522 schedstat_inc(this_rq()->sched_count
);
5525 static void put_prev_task_balance(struct rq
*rq
, struct task_struct
*prev
,
5526 struct rq_flags
*rf
)
5529 const struct sched_class
*class;
5531 * We must do the balancing pass before put_prev_task(), such
5532 * that when we release the rq->lock the task is in the same
5533 * state as before we took rq->lock.
5535 * We can terminate the balance pass as soon as we know there is
5536 * a runnable task of @class priority or higher.
5538 for_class_range(class, prev
->sched_class
, &idle_sched_class
) {
5539 if (class->balance(rq
, prev
, rf
))
5544 put_prev_task(rq
, prev
);
5548 * Pick up the highest-prio task:
5550 static inline struct task_struct
*
5551 __pick_next_task(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
5553 const struct sched_class
*class;
5554 struct task_struct
*p
;
5557 * Optimization: we know that if all tasks are in the fair class we can
5558 * call that function directly, but only if the @prev task wasn't of a
5559 * higher scheduling class, because otherwise those lose the
5560 * opportunity to pull in more work from other CPUs.
5562 if (likely(prev
->sched_class
<= &fair_sched_class
&&
5563 rq
->nr_running
== rq
->cfs
.h_nr_running
)) {
5565 p
= pick_next_task_fair(rq
, prev
, rf
);
5566 if (unlikely(p
== RETRY_TASK
))
5569 /* Assume the next prioritized class is idle_sched_class */
5571 put_prev_task(rq
, prev
);
5572 p
= pick_next_task_idle(rq
);
5579 put_prev_task_balance(rq
, prev
, rf
);
5581 for_each_class(class) {
5582 p
= class->pick_next_task(rq
);
5587 /* The idle class should always have a runnable task: */
5591 #ifdef CONFIG_SCHED_CORE
5592 static inline bool is_task_rq_idle(struct task_struct
*t
)
5594 return (task_rq(t
)->idle
== t
);
5597 static inline bool cookie_equals(struct task_struct
*a
, unsigned long cookie
)
5599 return is_task_rq_idle(a
) || (a
->core_cookie
== cookie
);
5602 static inline bool cookie_match(struct task_struct
*a
, struct task_struct
*b
)
5604 if (is_task_rq_idle(a
) || is_task_rq_idle(b
))
5607 return a
->core_cookie
== b
->core_cookie
;
5610 // XXX fairness/fwd progress conditions
5613 * - NULL if there is no runnable task for this class.
5614 * - the highest priority task for this runqueue if it matches
5615 * rq->core->core_cookie or its priority is greater than max.
5616 * - Else returns idle_task.
5618 static struct task_struct
*
5619 pick_task(struct rq
*rq
, const struct sched_class
*class, struct task_struct
*max
, bool in_fi
)
5621 struct task_struct
*class_pick
, *cookie_pick
;
5622 unsigned long cookie
= rq
->core
->core_cookie
;
5624 class_pick
= class->pick_task(rq
);
5630 * If class_pick is tagged, return it only if it has
5631 * higher priority than max.
5633 if (max
&& class_pick
->core_cookie
&&
5634 prio_less(class_pick
, max
, in_fi
))
5635 return idle_sched_class
.pick_task(rq
);
5641 * If class_pick is idle or matches cookie, return early.
5643 if (cookie_equals(class_pick
, cookie
))
5646 cookie_pick
= sched_core_find(rq
, cookie
);
5649 * If class > max && class > cookie, it is the highest priority task on
5650 * the core (so far) and it must be selected, otherwise we must go with
5651 * the cookie pick in order to satisfy the constraint.
5653 if (prio_less(cookie_pick
, class_pick
, in_fi
) &&
5654 (!max
|| prio_less(max
, class_pick
, in_fi
)))
5660 extern void task_vruntime_update(struct rq
*rq
, struct task_struct
*p
, bool in_fi
);
5662 static struct task_struct
*
5663 pick_next_task(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
5665 struct task_struct
*next
, *max
= NULL
;
5666 const struct sched_class
*class;
5667 const struct cpumask
*smt_mask
;
5668 bool fi_before
= false;
5669 int i
, j
, cpu
, occ
= 0;
5672 if (!sched_core_enabled(rq
))
5673 return __pick_next_task(rq
, prev
, rf
);
5677 /* Stopper task is switching into idle, no need core-wide selection. */
5678 if (cpu_is_offline(cpu
)) {
5680 * Reset core_pick so that we don't enter the fastpath when
5681 * coming online. core_pick would already be migrated to
5682 * another cpu during offline.
5684 rq
->core_pick
= NULL
;
5685 return __pick_next_task(rq
, prev
, rf
);
5689 * If there were no {en,de}queues since we picked (IOW, the task
5690 * pointers are all still valid), and we haven't scheduled the last
5691 * pick yet, do so now.
5693 * rq->core_pick can be NULL if no selection was made for a CPU because
5694 * it was either offline or went offline during a sibling's core-wide
5695 * selection. In this case, do a core-wide selection.
5697 if (rq
->core
->core_pick_seq
== rq
->core
->core_task_seq
&&
5698 rq
->core
->core_pick_seq
!= rq
->core_sched_seq
&&
5700 WRITE_ONCE(rq
->core_sched_seq
, rq
->core
->core_pick_seq
);
5702 next
= rq
->core_pick
;
5704 put_prev_task(rq
, prev
);
5705 set_next_task(rq
, next
);
5708 rq
->core_pick
= NULL
;
5712 put_prev_task_balance(rq
, prev
, rf
);
5714 smt_mask
= cpu_smt_mask(cpu
);
5715 need_sync
= !!rq
->core
->core_cookie
;
5718 rq
->core
->core_cookie
= 0UL;
5719 if (rq
->core
->core_forceidle
) {
5722 rq
->core
->core_forceidle
= false;
5726 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
5728 * @task_seq guards the task state ({en,de}queues)
5729 * @pick_seq is the @task_seq we did a selection on
5730 * @sched_seq is the @pick_seq we scheduled
5732 * However, preemptions can cause multiple picks on the same task set.
5733 * 'Fix' this by also increasing @task_seq for every pick.
5735 rq
->core
->core_task_seq
++;
5738 * Optimize for common case where this CPU has no cookies
5739 * and there are no cookied tasks running on siblings.
5742 for_each_class(class) {
5743 next
= class->pick_task(rq
);
5748 if (!next
->core_cookie
) {
5749 rq
->core_pick
= NULL
;
5751 * For robustness, update the min_vruntime_fi for
5752 * unconstrained picks as well.
5754 WARN_ON_ONCE(fi_before
);
5755 task_vruntime_update(rq
, next
, false);
5760 for_each_cpu(i
, smt_mask
) {
5761 struct rq
*rq_i
= cpu_rq(i
);
5763 rq_i
->core_pick
= NULL
;
5766 update_rq_clock(rq_i
);
5770 * Try and select tasks for each sibling in descending sched_class
5773 for_each_class(class) {
5775 for_each_cpu_wrap(i
, smt_mask
, cpu
) {
5776 struct rq
*rq_i
= cpu_rq(i
);
5777 struct task_struct
*p
;
5779 if (rq_i
->core_pick
)
5783 * If this sibling doesn't yet have a suitable task to
5784 * run; ask for the most eligible task, given the
5785 * highest priority task already selected for this
5788 p
= pick_task(rq_i
, class, max
, fi_before
);
5792 if (!is_task_rq_idle(p
))
5795 rq_i
->core_pick
= p
;
5796 if (rq_i
->idle
== p
&& rq_i
->nr_running
) {
5797 rq
->core
->core_forceidle
= true;
5799 rq
->core
->core_forceidle_seq
++;
5803 * If this new candidate is of higher priority than the
5804 * previous; and they're incompatible; we need to wipe
5805 * the slate and start over. pick_task makes sure that
5806 * p's priority is more than max if it doesn't match
5809 * NOTE: this is a linear max-filter and is thus bounded
5810 * in execution time.
5812 if (!max
|| !cookie_match(max
, p
)) {
5813 struct task_struct
*old_max
= max
;
5815 rq
->core
->core_cookie
= p
->core_cookie
;
5819 rq
->core
->core_forceidle
= false;
5820 for_each_cpu(j
, smt_mask
) {
5824 cpu_rq(j
)->core_pick
= NULL
;
5833 rq
->core
->core_pick_seq
= rq
->core
->core_task_seq
;
5834 next
= rq
->core_pick
;
5835 rq
->core_sched_seq
= rq
->core
->core_pick_seq
;
5837 /* Something should have been selected for current CPU */
5838 WARN_ON_ONCE(!next
);
5841 * Reschedule siblings
5843 * NOTE: L1TF -- at this point we're no longer running the old task and
5844 * sending an IPI (below) ensures the sibling will no longer be running
5845 * their task. This ensures there is no inter-sibling overlap between
5846 * non-matching user state.
5848 for_each_cpu(i
, smt_mask
) {
5849 struct rq
*rq_i
= cpu_rq(i
);
5852 * An online sibling might have gone offline before a task
5853 * could be picked for it, or it might be offline but later
5854 * happen to come online, but its too late and nothing was
5855 * picked for it. That's Ok - it will pick tasks for itself,
5858 if (!rq_i
->core_pick
)
5862 * Update for new !FI->FI transitions, or if continuing to be in !FI:
5863 * fi_before fi update?
5869 if (!(fi_before
&& rq
->core
->core_forceidle
))
5870 task_vruntime_update(rq_i
, rq_i
->core_pick
, rq
->core
->core_forceidle
);
5872 rq_i
->core_pick
->core_occupation
= occ
;
5875 rq_i
->core_pick
= NULL
;
5879 /* Did we break L1TF mitigation requirements? */
5880 WARN_ON_ONCE(!cookie_match(next
, rq_i
->core_pick
));
5882 if (rq_i
->curr
== rq_i
->core_pick
) {
5883 rq_i
->core_pick
= NULL
;
5891 set_next_task(rq
, next
);
5895 static bool try_steal_cookie(int this, int that
)
5897 struct rq
*dst
= cpu_rq(this), *src
= cpu_rq(that
);
5898 struct task_struct
*p
;
5899 unsigned long cookie
;
5900 bool success
= false;
5902 local_irq_disable();
5903 double_rq_lock(dst
, src
);
5905 cookie
= dst
->core
->core_cookie
;
5909 if (dst
->curr
!= dst
->idle
)
5912 p
= sched_core_find(src
, cookie
);
5917 if (p
== src
->core_pick
|| p
== src
->curr
)
5920 if (!cpumask_test_cpu(this, &p
->cpus_mask
))
5923 if (p
->core_occupation
> dst
->idle
->core_occupation
)
5926 deactivate_task(src
, p
, 0);
5927 set_task_cpu(p
, this);
5928 activate_task(dst
, p
, 0);
5936 p
= sched_core_next(p
, cookie
);
5940 double_rq_unlock(dst
, src
);
5946 static bool steal_cookie_task(int cpu
, struct sched_domain
*sd
)
5950 for_each_cpu_wrap(i
, sched_domain_span(sd
), cpu
) {
5957 if (try_steal_cookie(cpu
, i
))
5964 static void sched_core_balance(struct rq
*rq
)
5966 struct sched_domain
*sd
;
5967 int cpu
= cpu_of(rq
);
5971 raw_spin_rq_unlock_irq(rq
);
5972 for_each_domain(cpu
, sd
) {
5976 if (steal_cookie_task(cpu
, sd
))
5979 raw_spin_rq_lock_irq(rq
);
5984 static DEFINE_PER_CPU(struct callback_head
, core_balance_head
);
5986 void queue_core_balance(struct rq
*rq
)
5988 if (!sched_core_enabled(rq
))
5991 if (!rq
->core
->core_cookie
)
5994 if (!rq
->nr_running
) /* not forced idle */
5997 queue_balance_callback(rq
, &per_cpu(core_balance_head
, rq
->cpu
), sched_core_balance
);
6000 static void sched_core_cpu_starting(unsigned int cpu
)
6002 const struct cpumask
*smt_mask
= cpu_smt_mask(cpu
);
6003 struct rq
*rq
= cpu_rq(cpu
), *core_rq
= NULL
;
6004 unsigned long flags
;
6007 sched_core_lock(cpu
, &flags
);
6009 WARN_ON_ONCE(rq
->core
!= rq
);
6011 /* if we're the first, we'll be our own leader */
6012 if (cpumask_weight(smt_mask
) == 1)
6015 /* find the leader */
6016 for_each_cpu(t
, smt_mask
) {
6020 if (rq
->core
== rq
) {
6026 if (WARN_ON_ONCE(!core_rq
)) /* whoopsie */
6029 /* install and validate core_rq */
6030 for_each_cpu(t
, smt_mask
) {
6036 WARN_ON_ONCE(rq
->core
!= core_rq
);
6040 sched_core_unlock(cpu
, &flags
);
6043 static void sched_core_cpu_deactivate(unsigned int cpu
)
6045 const struct cpumask
*smt_mask
= cpu_smt_mask(cpu
);
6046 struct rq
*rq
= cpu_rq(cpu
), *core_rq
= NULL
;
6047 unsigned long flags
;
6050 sched_core_lock(cpu
, &flags
);
6052 /* if we're the last man standing, nothing to do */
6053 if (cpumask_weight(smt_mask
) == 1) {
6054 WARN_ON_ONCE(rq
->core
!= rq
);
6058 /* if we're not the leader, nothing to do */
6062 /* find a new leader */
6063 for_each_cpu(t
, smt_mask
) {
6066 core_rq
= cpu_rq(t
);
6070 if (WARN_ON_ONCE(!core_rq
)) /* impossible */
6073 /* copy the shared state to the new leader */
6074 core_rq
->core_task_seq
= rq
->core_task_seq
;
6075 core_rq
->core_pick_seq
= rq
->core_pick_seq
;
6076 core_rq
->core_cookie
= rq
->core_cookie
;
6077 core_rq
->core_forceidle
= rq
->core_forceidle
;
6078 core_rq
->core_forceidle_seq
= rq
->core_forceidle_seq
;
6080 /* install new leader */
6081 for_each_cpu(t
, smt_mask
) {
6087 sched_core_unlock(cpu
, &flags
);
6090 static inline void sched_core_cpu_dying(unsigned int cpu
)
6092 struct rq
*rq
= cpu_rq(cpu
);
6098 #else /* !CONFIG_SCHED_CORE */
6100 static inline void sched_core_cpu_starting(unsigned int cpu
) {}
6101 static inline void sched_core_cpu_deactivate(unsigned int cpu
) {}
6102 static inline void sched_core_cpu_dying(unsigned int cpu
) {}
6104 static struct task_struct
*
6105 pick_next_task(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
6107 return __pick_next_task(rq
, prev
, rf
);
6110 #endif /* CONFIG_SCHED_CORE */
6113 * Constants for the sched_mode argument of __schedule().
6115 * The mode argument allows RT enabled kernels to differentiate a
6116 * preemption from blocking on an 'sleeping' spin/rwlock. Note that
6117 * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
6118 * optimize the AND operation out and just check for zero.
6121 #define SM_PREEMPT 0x1
6122 #define SM_RTLOCK_WAIT 0x2
6124 #ifndef CONFIG_PREEMPT_RT
6125 # define SM_MASK_PREEMPT (~0U)
6127 # define SM_MASK_PREEMPT SM_PREEMPT
6131 * __schedule() is the main scheduler function.
6133 * The main means of driving the scheduler and thus entering this function are:
6135 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
6137 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
6138 * paths. For example, see arch/x86/entry_64.S.
6140 * To drive preemption between tasks, the scheduler sets the flag in timer
6141 * interrupt handler scheduler_tick().
6143 * 3. Wakeups don't really cause entry into schedule(). They add a
6144 * task to the run-queue and that's it.
6146 * Now, if the new task added to the run-queue preempts the current
6147 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
6148 * called on the nearest possible occasion:
6150 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
6152 * - in syscall or exception context, at the next outmost
6153 * preempt_enable(). (this might be as soon as the wake_up()'s
6156 * - in IRQ context, return from interrupt-handler to
6157 * preemptible context
6159 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
6162 * - cond_resched() call
6163 * - explicit schedule() call
6164 * - return from syscall or exception to user-space
6165 * - return from interrupt-handler to user-space
6167 * WARNING: must be called with preemption disabled!
6169 static void __sched notrace
__schedule(unsigned int sched_mode
)
6171 struct task_struct
*prev
, *next
;
6172 unsigned long *switch_count
;
6173 unsigned long prev_state
;
6178 cpu
= smp_processor_id();
6182 schedule_debug(prev
, !!sched_mode
);
6184 if (sched_feat(HRTICK
) || sched_feat(HRTICK_DL
))
6187 local_irq_disable();
6188 rcu_note_context_switch(!!sched_mode
);
6191 * Make sure that signal_pending_state()->signal_pending() below
6192 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
6193 * done by the caller to avoid the race with signal_wake_up():
6195 * __set_current_state(@state) signal_wake_up()
6196 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
6197 * wake_up_state(p, state)
6198 * LOCK rq->lock LOCK p->pi_state
6199 * smp_mb__after_spinlock() smp_mb__after_spinlock()
6200 * if (signal_pending_state()) if (p->state & @state)
6202 * Also, the membarrier system call requires a full memory barrier
6203 * after coming from user-space, before storing to rq->curr.
6206 smp_mb__after_spinlock();
6208 /* Promote REQ to ACT */
6209 rq
->clock_update_flags
<<= 1;
6210 update_rq_clock(rq
);
6212 switch_count
= &prev
->nivcsw
;
6215 * We must load prev->state once (task_struct::state is volatile), such
6218 * - we form a control dependency vs deactivate_task() below.
6219 * - ptrace_{,un}freeze_traced() can change ->state underneath us.
6221 prev_state
= READ_ONCE(prev
->__state
);
6222 if (!(sched_mode
& SM_MASK_PREEMPT
) && prev_state
) {
6223 if (signal_pending_state(prev_state
, prev
)) {
6224 WRITE_ONCE(prev
->__state
, TASK_RUNNING
);
6226 prev
->sched_contributes_to_load
=
6227 (prev_state
& TASK_UNINTERRUPTIBLE
) &&
6228 !(prev_state
& TASK_NOLOAD
) &&
6229 !(prev
->flags
& PF_FROZEN
);
6231 if (prev
->sched_contributes_to_load
)
6232 rq
->nr_uninterruptible
++;
6235 * __schedule() ttwu()
6236 * prev_state = prev->state; if (p->on_rq && ...)
6237 * if (prev_state) goto out;
6238 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
6239 * p->state = TASK_WAKING
6241 * Where __schedule() and ttwu() have matching control dependencies.
6243 * After this, schedule() must not care about p->state any more.
6245 deactivate_task(rq
, prev
, DEQUEUE_SLEEP
| DEQUEUE_NOCLOCK
);
6247 if (prev
->in_iowait
) {
6248 atomic_inc(&rq
->nr_iowait
);
6249 delayacct_blkio_start();
6252 switch_count
= &prev
->nvcsw
;
6255 next
= pick_next_task(rq
, prev
, &rf
);
6256 clear_tsk_need_resched(prev
);
6257 clear_preempt_need_resched();
6258 #ifdef CONFIG_SCHED_DEBUG
6259 rq
->last_seen_need_resched_ns
= 0;
6262 if (likely(prev
!= next
)) {
6265 * RCU users of rcu_dereference(rq->curr) may not see
6266 * changes to task_struct made by pick_next_task().
6268 RCU_INIT_POINTER(rq
->curr
, next
);
6270 * The membarrier system call requires each architecture
6271 * to have a full memory barrier after updating
6272 * rq->curr, before returning to user-space.
6274 * Here are the schemes providing that barrier on the
6275 * various architectures:
6276 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
6277 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
6278 * - finish_lock_switch() for weakly-ordered
6279 * architectures where spin_unlock is a full barrier,
6280 * - switch_to() for arm64 (weakly-ordered, spin_unlock
6281 * is a RELEASE barrier),
6285 migrate_disable_switch(rq
, prev
);
6286 psi_sched_switch(prev
, next
, !task_on_rq_queued(prev
));
6288 trace_sched_switch(sched_mode
& SM_MASK_PREEMPT
, prev
, next
);
6290 /* Also unlocks the rq: */
6291 rq
= context_switch(rq
, prev
, next
, &rf
);
6293 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
6295 rq_unpin_lock(rq
, &rf
);
6296 __balance_callbacks(rq
);
6297 raw_spin_rq_unlock_irq(rq
);
6301 void __noreturn
do_task_dead(void)
6303 /* Causes final put_task_struct in finish_task_switch(): */
6304 set_special_state(TASK_DEAD
);
6306 /* Tell freezer to ignore us: */
6307 current
->flags
|= PF_NOFREEZE
;
6309 __schedule(SM_NONE
);
6312 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
6317 static inline void sched_submit_work(struct task_struct
*tsk
)
6319 unsigned int task_flags
;
6321 if (task_is_running(tsk
))
6324 task_flags
= tsk
->flags
;
6326 * If a worker went to sleep, notify and ask workqueue whether
6327 * it wants to wake up a task to maintain concurrency.
6328 * As this function is called inside the schedule() context,
6329 * we disable preemption to avoid it calling schedule() again
6330 * in the possible wakeup of a kworker and because wq_worker_sleeping()
6333 if (task_flags
& (PF_WQ_WORKER
| PF_IO_WORKER
)) {
6335 if (task_flags
& PF_WQ_WORKER
)
6336 wq_worker_sleeping(tsk
);
6338 io_wq_worker_sleeping(tsk
);
6339 preempt_enable_no_resched();
6342 if (tsk_is_pi_blocked(tsk
))
6346 * If we are going to sleep and we have plugged IO queued,
6347 * make sure to submit it to avoid deadlocks.
6349 if (blk_needs_flush_plug(tsk
))
6350 blk_schedule_flush_plug(tsk
);
6353 static void sched_update_worker(struct task_struct
*tsk
)
6355 if (tsk
->flags
& (PF_WQ_WORKER
| PF_IO_WORKER
)) {
6356 if (tsk
->flags
& PF_WQ_WORKER
)
6357 wq_worker_running(tsk
);
6359 io_wq_worker_running(tsk
);
6363 asmlinkage __visible
void __sched
schedule(void)
6365 struct task_struct
*tsk
= current
;
6367 sched_submit_work(tsk
);
6370 __schedule(SM_NONE
);
6371 sched_preempt_enable_no_resched();
6372 } while (need_resched());
6373 sched_update_worker(tsk
);
6375 EXPORT_SYMBOL(schedule
);
6378 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
6379 * state (have scheduled out non-voluntarily) by making sure that all
6380 * tasks have either left the run queue or have gone into user space.
6381 * As idle tasks do not do either, they must not ever be preempted
6382 * (schedule out non-voluntarily).
6384 * schedule_idle() is similar to schedule_preempt_disable() except that it
6385 * never enables preemption because it does not call sched_submit_work().
6387 void __sched
schedule_idle(void)
6390 * As this skips calling sched_submit_work(), which the idle task does
6391 * regardless because that function is a nop when the task is in a
6392 * TASK_RUNNING state, make sure this isn't used someplace that the
6393 * current task can be in any other state. Note, idle is always in the
6394 * TASK_RUNNING state.
6396 WARN_ON_ONCE(current
->__state
);
6398 __schedule(SM_NONE
);
6399 } while (need_resched());
6402 #if defined(CONFIG_CONTEXT_TRACKING) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK)
6403 asmlinkage __visible
void __sched
schedule_user(void)
6406 * If we come here after a random call to set_need_resched(),
6407 * or we have been woken up remotely but the IPI has not yet arrived,
6408 * we haven't yet exited the RCU idle mode. Do it here manually until
6409 * we find a better solution.
6411 * NB: There are buggy callers of this function. Ideally we
6412 * should warn if prev_state != CONTEXT_USER, but that will trigger
6413 * too frequently to make sense yet.
6415 enum ctx_state prev_state
= exception_enter();
6417 exception_exit(prev_state
);
6422 * schedule_preempt_disabled - called with preemption disabled
6424 * Returns with preemption disabled. Note: preempt_count must be 1
6426 void __sched
schedule_preempt_disabled(void)
6428 sched_preempt_enable_no_resched();
6433 #ifdef CONFIG_PREEMPT_RT
6434 void __sched notrace
schedule_rtlock(void)
6438 __schedule(SM_RTLOCK_WAIT
);
6439 sched_preempt_enable_no_resched();
6440 } while (need_resched());
6442 NOKPROBE_SYMBOL(schedule_rtlock
);
6445 static void __sched notrace
preempt_schedule_common(void)
6449 * Because the function tracer can trace preempt_count_sub()
6450 * and it also uses preempt_enable/disable_notrace(), if
6451 * NEED_RESCHED is set, the preempt_enable_notrace() called
6452 * by the function tracer will call this function again and
6453 * cause infinite recursion.
6455 * Preemption must be disabled here before the function
6456 * tracer can trace. Break up preempt_disable() into two
6457 * calls. One to disable preemption without fear of being
6458 * traced. The other to still record the preemption latency,
6459 * which can also be traced by the function tracer.
6461 preempt_disable_notrace();
6462 preempt_latency_start(1);
6463 __schedule(SM_PREEMPT
);
6464 preempt_latency_stop(1);
6465 preempt_enable_no_resched_notrace();
6468 * Check again in case we missed a preemption opportunity
6469 * between schedule and now.
6471 } while (need_resched());
6474 #ifdef CONFIG_PREEMPTION
6476 * This is the entry point to schedule() from in-kernel preemption
6477 * off of preempt_enable.
6479 asmlinkage __visible
void __sched notrace
preempt_schedule(void)
6482 * If there is a non-zero preempt_count or interrupts are disabled,
6483 * we do not want to preempt the current task. Just return..
6485 if (likely(!preemptible()))
6488 preempt_schedule_common();
6490 NOKPROBE_SYMBOL(preempt_schedule
);
6491 EXPORT_SYMBOL(preempt_schedule
);
6493 #ifdef CONFIG_PREEMPT_DYNAMIC
6494 DEFINE_STATIC_CALL(preempt_schedule
, __preempt_schedule_func
);
6495 EXPORT_STATIC_CALL_TRAMP(preempt_schedule
);
6500 * preempt_schedule_notrace - preempt_schedule called by tracing
6502 * The tracing infrastructure uses preempt_enable_notrace to prevent
6503 * recursion and tracing preempt enabling caused by the tracing
6504 * infrastructure itself. But as tracing can happen in areas coming
6505 * from userspace or just about to enter userspace, a preempt enable
6506 * can occur before user_exit() is called. This will cause the scheduler
6507 * to be called when the system is still in usermode.
6509 * To prevent this, the preempt_enable_notrace will use this function
6510 * instead of preempt_schedule() to exit user context if needed before
6511 * calling the scheduler.
6513 asmlinkage __visible
void __sched notrace
preempt_schedule_notrace(void)
6515 enum ctx_state prev_ctx
;
6517 if (likely(!preemptible()))
6522 * Because the function tracer can trace preempt_count_sub()
6523 * and it also uses preempt_enable/disable_notrace(), if
6524 * NEED_RESCHED is set, the preempt_enable_notrace() called
6525 * by the function tracer will call this function again and
6526 * cause infinite recursion.
6528 * Preemption must be disabled here before the function
6529 * tracer can trace. Break up preempt_disable() into two
6530 * calls. One to disable preemption without fear of being
6531 * traced. The other to still record the preemption latency,
6532 * which can also be traced by the function tracer.
6534 preempt_disable_notrace();
6535 preempt_latency_start(1);
6537 * Needs preempt disabled in case user_exit() is traced
6538 * and the tracer calls preempt_enable_notrace() causing
6539 * an infinite recursion.
6541 prev_ctx
= exception_enter();
6542 __schedule(SM_PREEMPT
);
6543 exception_exit(prev_ctx
);
6545 preempt_latency_stop(1);
6546 preempt_enable_no_resched_notrace();
6547 } while (need_resched());
6549 EXPORT_SYMBOL_GPL(preempt_schedule_notrace
);
6551 #ifdef CONFIG_PREEMPT_DYNAMIC
6552 DEFINE_STATIC_CALL(preempt_schedule_notrace
, __preempt_schedule_notrace_func
);
6553 EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace
);
6556 #endif /* CONFIG_PREEMPTION */
6558 #ifdef CONFIG_PREEMPT_DYNAMIC
6560 #include <linux/entry-common.h>
6565 * SC:preempt_schedule
6566 * SC:preempt_schedule_notrace
6567 * SC:irqentry_exit_cond_resched
6571 * cond_resched <- __cond_resched
6572 * might_resched <- RET0
6573 * preempt_schedule <- NOP
6574 * preempt_schedule_notrace <- NOP
6575 * irqentry_exit_cond_resched <- NOP
6578 * cond_resched <- __cond_resched
6579 * might_resched <- __cond_resched
6580 * preempt_schedule <- NOP
6581 * preempt_schedule_notrace <- NOP
6582 * irqentry_exit_cond_resched <- NOP
6585 * cond_resched <- RET0
6586 * might_resched <- RET0
6587 * preempt_schedule <- preempt_schedule
6588 * preempt_schedule_notrace <- preempt_schedule_notrace
6589 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched
6593 preempt_dynamic_none
= 0,
6594 preempt_dynamic_voluntary
,
6595 preempt_dynamic_full
,
6598 int preempt_dynamic_mode
= preempt_dynamic_full
;
6600 int sched_dynamic_mode(const char *str
)
6602 if (!strcmp(str
, "none"))
6603 return preempt_dynamic_none
;
6605 if (!strcmp(str
, "voluntary"))
6606 return preempt_dynamic_voluntary
;
6608 if (!strcmp(str
, "full"))
6609 return preempt_dynamic_full
;
6614 void sched_dynamic_update(int mode
)
6617 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
6618 * the ZERO state, which is invalid.
6620 static_call_update(cond_resched
, __cond_resched
);
6621 static_call_update(might_resched
, __cond_resched
);
6622 static_call_update(preempt_schedule
, __preempt_schedule_func
);
6623 static_call_update(preempt_schedule_notrace
, __preempt_schedule_notrace_func
);
6624 static_call_update(irqentry_exit_cond_resched
, irqentry_exit_cond_resched
);
6627 case preempt_dynamic_none
:
6628 static_call_update(cond_resched
, __cond_resched
);
6629 static_call_update(might_resched
, (void *)&__static_call_return0
);
6630 static_call_update(preempt_schedule
, NULL
);
6631 static_call_update(preempt_schedule_notrace
, NULL
);
6632 static_call_update(irqentry_exit_cond_resched
, NULL
);
6633 pr_info("Dynamic Preempt: none\n");
6636 case preempt_dynamic_voluntary
:
6637 static_call_update(cond_resched
, __cond_resched
);
6638 static_call_update(might_resched
, __cond_resched
);
6639 static_call_update(preempt_schedule
, NULL
);
6640 static_call_update(preempt_schedule_notrace
, NULL
);
6641 static_call_update(irqentry_exit_cond_resched
, NULL
);
6642 pr_info("Dynamic Preempt: voluntary\n");
6645 case preempt_dynamic_full
:
6646 static_call_update(cond_resched
, (void *)&__static_call_return0
);
6647 static_call_update(might_resched
, (void *)&__static_call_return0
);
6648 static_call_update(preempt_schedule
, __preempt_schedule_func
);
6649 static_call_update(preempt_schedule_notrace
, __preempt_schedule_notrace_func
);
6650 static_call_update(irqentry_exit_cond_resched
, irqentry_exit_cond_resched
);
6651 pr_info("Dynamic Preempt: full\n");
6655 preempt_dynamic_mode
= mode
;
6658 static int __init
setup_preempt_mode(char *str
)
6660 int mode
= sched_dynamic_mode(str
);
6662 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str
);
6666 sched_dynamic_update(mode
);
6669 __setup("preempt=", setup_preempt_mode
);
6671 #endif /* CONFIG_PREEMPT_DYNAMIC */
6674 * This is the entry point to schedule() from kernel preemption
6675 * off of irq context.
6676 * Note, that this is called and return with irqs disabled. This will
6677 * protect us against recursive calling from irq.
6679 asmlinkage __visible
void __sched
preempt_schedule_irq(void)
6681 enum ctx_state prev_state
;
6683 /* Catch callers which need to be fixed */
6684 BUG_ON(preempt_count() || !irqs_disabled());
6686 prev_state
= exception_enter();
6691 __schedule(SM_PREEMPT
);
6692 local_irq_disable();
6693 sched_preempt_enable_no_resched();
6694 } while (need_resched());
6696 exception_exit(prev_state
);
6699 int default_wake_function(wait_queue_entry_t
*curr
, unsigned mode
, int wake_flags
,
6702 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG
) && wake_flags
& ~WF_SYNC
);
6703 return try_to_wake_up(curr
->private, mode
, wake_flags
);
6705 EXPORT_SYMBOL(default_wake_function
);
6707 static void __setscheduler_prio(struct task_struct
*p
, int prio
)
6710 p
->sched_class
= &dl_sched_class
;
6711 else if (rt_prio(prio
))
6712 p
->sched_class
= &rt_sched_class
;
6714 p
->sched_class
= &fair_sched_class
;
6719 #ifdef CONFIG_RT_MUTEXES
6721 static inline int __rt_effective_prio(struct task_struct
*pi_task
, int prio
)
6724 prio
= min(prio
, pi_task
->prio
);
6729 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
6731 struct task_struct
*pi_task
= rt_mutex_get_top_task(p
);
6733 return __rt_effective_prio(pi_task
, prio
);
6737 * rt_mutex_setprio - set the current priority of a task
6739 * @pi_task: donor task
6741 * This function changes the 'effective' priority of a task. It does
6742 * not touch ->normal_prio like __setscheduler().
6744 * Used by the rt_mutex code to implement priority inheritance
6745 * logic. Call site only calls if the priority of the task changed.
6747 void rt_mutex_setprio(struct task_struct
*p
, struct task_struct
*pi_task
)
6749 int prio
, oldprio
, queued
, running
, queue_flag
=
6750 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
6751 const struct sched_class
*prev_class
;
6755 /* XXX used to be waiter->prio, not waiter->task->prio */
6756 prio
= __rt_effective_prio(pi_task
, p
->normal_prio
);
6759 * If nothing changed; bail early.
6761 if (p
->pi_top_task
== pi_task
&& prio
== p
->prio
&& !dl_prio(prio
))
6764 rq
= __task_rq_lock(p
, &rf
);
6765 update_rq_clock(rq
);
6767 * Set under pi_lock && rq->lock, such that the value can be used under
6770 * Note that there is loads of tricky to make this pointer cache work
6771 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
6772 * ensure a task is de-boosted (pi_task is set to NULL) before the
6773 * task is allowed to run again (and can exit). This ensures the pointer
6774 * points to a blocked task -- which guarantees the task is present.
6776 p
->pi_top_task
= pi_task
;
6779 * For FIFO/RR we only need to set prio, if that matches we're done.
6781 if (prio
== p
->prio
&& !dl_prio(prio
))
6785 * Idle task boosting is a nono in general. There is one
6786 * exception, when PREEMPT_RT and NOHZ is active:
6788 * The idle task calls get_next_timer_interrupt() and holds
6789 * the timer wheel base->lock on the CPU and another CPU wants
6790 * to access the timer (probably to cancel it). We can safely
6791 * ignore the boosting request, as the idle CPU runs this code
6792 * with interrupts disabled and will complete the lock
6793 * protected section without being interrupted. So there is no
6794 * real need to boost.
6796 if (unlikely(p
== rq
->idle
)) {
6797 WARN_ON(p
!= rq
->curr
);
6798 WARN_ON(p
->pi_blocked_on
);
6802 trace_sched_pi_setprio(p
, pi_task
);
6805 if (oldprio
== prio
)
6806 queue_flag
&= ~DEQUEUE_MOVE
;
6808 prev_class
= p
->sched_class
;
6809 queued
= task_on_rq_queued(p
);
6810 running
= task_current(rq
, p
);
6812 dequeue_task(rq
, p
, queue_flag
);
6814 put_prev_task(rq
, p
);
6817 * Boosting condition are:
6818 * 1. -rt task is running and holds mutex A
6819 * --> -dl task blocks on mutex A
6821 * 2. -dl task is running and holds mutex A
6822 * --> -dl task blocks on mutex A and could preempt the
6825 if (dl_prio(prio
)) {
6826 if (!dl_prio(p
->normal_prio
) ||
6827 (pi_task
&& dl_prio(pi_task
->prio
) &&
6828 dl_entity_preempt(&pi_task
->dl
, &p
->dl
))) {
6829 p
->dl
.pi_se
= pi_task
->dl
.pi_se
;
6830 queue_flag
|= ENQUEUE_REPLENISH
;
6832 p
->dl
.pi_se
= &p
->dl
;
6834 } else if (rt_prio(prio
)) {
6835 if (dl_prio(oldprio
))
6836 p
->dl
.pi_se
= &p
->dl
;
6838 queue_flag
|= ENQUEUE_HEAD
;
6840 if (dl_prio(oldprio
))
6841 p
->dl
.pi_se
= &p
->dl
;
6842 if (rt_prio(oldprio
))
6846 __setscheduler_prio(p
, prio
);
6849 enqueue_task(rq
, p
, queue_flag
);
6851 set_next_task(rq
, p
);
6853 check_class_changed(rq
, p
, prev_class
, oldprio
);
6855 /* Avoid rq from going away on us: */
6858 rq_unpin_lock(rq
, &rf
);
6859 __balance_callbacks(rq
);
6860 raw_spin_rq_unlock(rq
);
6865 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
6871 void set_user_nice(struct task_struct
*p
, long nice
)
6873 bool queued
, running
;
6878 if (task_nice(p
) == nice
|| nice
< MIN_NICE
|| nice
> MAX_NICE
)
6881 * We have to be careful, if called from sys_setpriority(),
6882 * the task might be in the middle of scheduling on another CPU.
6884 rq
= task_rq_lock(p
, &rf
);
6885 update_rq_clock(rq
);
6888 * The RT priorities are set via sched_setscheduler(), but we still
6889 * allow the 'normal' nice value to be set - but as expected
6890 * it won't have any effect on scheduling until the task is
6891 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
6893 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
6894 p
->static_prio
= NICE_TO_PRIO(nice
);
6897 queued
= task_on_rq_queued(p
);
6898 running
= task_current(rq
, p
);
6900 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
6902 put_prev_task(rq
, p
);
6904 p
->static_prio
= NICE_TO_PRIO(nice
);
6905 set_load_weight(p
, true);
6907 p
->prio
= effective_prio(p
);
6910 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
6912 set_next_task(rq
, p
);
6915 * If the task increased its priority or is running and
6916 * lowered its priority, then reschedule its CPU:
6918 p
->sched_class
->prio_changed(rq
, p
, old_prio
);
6921 task_rq_unlock(rq
, p
, &rf
);
6923 EXPORT_SYMBOL(set_user_nice
);
6926 * can_nice - check if a task can reduce its nice value
6930 int can_nice(const struct task_struct
*p
, const int nice
)
6932 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
6933 int nice_rlim
= nice_to_rlimit(nice
);
6935 return (nice_rlim
<= task_rlimit(p
, RLIMIT_NICE
) ||
6936 capable(CAP_SYS_NICE
));
6938 EXPORT_SYMBOL(can_nice
);
6940 #ifdef __ARCH_WANT_SYS_NICE
6943 * sys_nice - change the priority of the current process.
6944 * @increment: priority increment
6946 * sys_setpriority is a more generic, but much slower function that
6947 * does similar things.
6949 SYSCALL_DEFINE1(nice
, int, increment
)
6954 * Setpriority might change our priority at the same moment.
6955 * We don't have to worry. Conceptually one call occurs first
6956 * and we have a single winner.
6958 increment
= clamp(increment
, -NICE_WIDTH
, NICE_WIDTH
);
6959 nice
= task_nice(current
) + increment
;
6961 nice
= clamp_val(nice
, MIN_NICE
, MAX_NICE
);
6962 if (increment
< 0 && !can_nice(current
, nice
))
6965 retval
= security_task_setnice(current
, nice
);
6969 set_user_nice(current
, nice
);
6976 * task_prio - return the priority value of a given task.
6977 * @p: the task in question.
6979 * Return: The priority value as seen by users in /proc.
6981 * sched policy return value kernel prio user prio/nice
6983 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
6984 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
6985 * deadline -101 -1 0
6987 int task_prio(const struct task_struct
*p
)
6989 return p
->prio
- MAX_RT_PRIO
;
6993 * idle_cpu - is a given CPU idle currently?
6994 * @cpu: the processor in question.
6996 * Return: 1 if the CPU is currently idle. 0 otherwise.
6998 int idle_cpu(int cpu
)
7000 struct rq
*rq
= cpu_rq(cpu
);
7002 if (rq
->curr
!= rq
->idle
)
7009 if (rq
->ttwu_pending
)
7017 * available_idle_cpu - is a given CPU idle for enqueuing work.
7018 * @cpu: the CPU in question.
7020 * Return: 1 if the CPU is currently idle. 0 otherwise.
7022 int available_idle_cpu(int cpu
)
7027 if (vcpu_is_preempted(cpu
))
7034 * idle_task - return the idle task for a given CPU.
7035 * @cpu: the processor in question.
7037 * Return: The idle task for the CPU @cpu.
7039 struct task_struct
*idle_task(int cpu
)
7041 return cpu_rq(cpu
)->idle
;
7046 * This function computes an effective utilization for the given CPU, to be
7047 * used for frequency selection given the linear relation: f = u * f_max.
7049 * The scheduler tracks the following metrics:
7051 * cpu_util_{cfs,rt,dl,irq}()
7054 * Where the cfs,rt and dl util numbers are tracked with the same metric and
7055 * synchronized windows and are thus directly comparable.
7057 * The cfs,rt,dl utilization are the running times measured with rq->clock_task
7058 * which excludes things like IRQ and steal-time. These latter are then accrued
7059 * in the irq utilization.
7061 * The DL bandwidth number otoh is not a measured metric but a value computed
7062 * based on the task model parameters and gives the minimal utilization
7063 * required to meet deadlines.
7065 unsigned long effective_cpu_util(int cpu
, unsigned long util_cfs
,
7066 unsigned long max
, enum cpu_util_type type
,
7067 struct task_struct
*p
)
7069 unsigned long dl_util
, util
, irq
;
7070 struct rq
*rq
= cpu_rq(cpu
);
7072 if (!uclamp_is_used() &&
7073 type
== FREQUENCY_UTIL
&& rt_rq_is_runnable(&rq
->rt
)) {
7078 * Early check to see if IRQ/steal time saturates the CPU, can be
7079 * because of inaccuracies in how we track these -- see
7080 * update_irq_load_avg().
7082 irq
= cpu_util_irq(rq
);
7083 if (unlikely(irq
>= max
))
7087 * Because the time spend on RT/DL tasks is visible as 'lost' time to
7088 * CFS tasks and we use the same metric to track the effective
7089 * utilization (PELT windows are synchronized) we can directly add them
7090 * to obtain the CPU's actual utilization.
7092 * CFS and RT utilization can be boosted or capped, depending on
7093 * utilization clamp constraints requested by currently RUNNABLE
7095 * When there are no CFS RUNNABLE tasks, clamps are released and
7096 * frequency will be gracefully reduced with the utilization decay.
7098 util
= util_cfs
+ cpu_util_rt(rq
);
7099 if (type
== FREQUENCY_UTIL
)
7100 util
= uclamp_rq_util_with(rq
, util
, p
);
7102 dl_util
= cpu_util_dl(rq
);
7105 * For frequency selection we do not make cpu_util_dl() a permanent part
7106 * of this sum because we want to use cpu_bw_dl() later on, but we need
7107 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
7108 * that we select f_max when there is no idle time.
7110 * NOTE: numerical errors or stop class might cause us to not quite hit
7111 * saturation when we should -- something for later.
7113 if (util
+ dl_util
>= max
)
7117 * OTOH, for energy computation we need the estimated running time, so
7118 * include util_dl and ignore dl_bw.
7120 if (type
== ENERGY_UTIL
)
7124 * There is still idle time; further improve the number by using the
7125 * irq metric. Because IRQ/steal time is hidden from the task clock we
7126 * need to scale the task numbers:
7129 * U' = irq + --------- * U
7132 util
= scale_irq_capacity(util
, irq
, max
);
7136 * Bandwidth required by DEADLINE must always be granted while, for
7137 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
7138 * to gracefully reduce the frequency when no tasks show up for longer
7141 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
7142 * bw_dl as requested freq. However, cpufreq is not yet ready for such
7143 * an interface. So, we only do the latter for now.
7145 if (type
== FREQUENCY_UTIL
)
7146 util
+= cpu_bw_dl(rq
);
7148 return min(max
, util
);
7151 unsigned long sched_cpu_util(int cpu
, unsigned long max
)
7153 return effective_cpu_util(cpu
, cpu_util_cfs(cpu_rq(cpu
)), max
,
7156 #endif /* CONFIG_SMP */
7159 * find_process_by_pid - find a process with a matching PID value.
7160 * @pid: the pid in question.
7162 * The task of @pid, if found. %NULL otherwise.
7164 static struct task_struct
*find_process_by_pid(pid_t pid
)
7166 return pid
? find_task_by_vpid(pid
) : current
;
7170 * sched_setparam() passes in -1 for its policy, to let the functions
7171 * it calls know not to change it.
7173 #define SETPARAM_POLICY -1
7175 static void __setscheduler_params(struct task_struct
*p
,
7176 const struct sched_attr
*attr
)
7178 int policy
= attr
->sched_policy
;
7180 if (policy
== SETPARAM_POLICY
)
7185 if (dl_policy(policy
))
7186 __setparam_dl(p
, attr
);
7187 else if (fair_policy(policy
))
7188 p
->static_prio
= NICE_TO_PRIO(attr
->sched_nice
);
7191 * __sched_setscheduler() ensures attr->sched_priority == 0 when
7192 * !rt_policy. Always setting this ensures that things like
7193 * getparam()/getattr() don't report silly values for !rt tasks.
7195 p
->rt_priority
= attr
->sched_priority
;
7196 p
->normal_prio
= normal_prio(p
);
7197 set_load_weight(p
, true);
7201 * Check the target process has a UID that matches the current process's:
7203 static bool check_same_owner(struct task_struct
*p
)
7205 const struct cred
*cred
= current_cred(), *pcred
;
7209 pcred
= __task_cred(p
);
7210 match
= (uid_eq(cred
->euid
, pcred
->euid
) ||
7211 uid_eq(cred
->euid
, pcred
->uid
));
7216 static int __sched_setscheduler(struct task_struct
*p
,
7217 const struct sched_attr
*attr
,
7220 int oldpolicy
= -1, policy
= attr
->sched_policy
;
7221 int retval
, oldprio
, newprio
, queued
, running
;
7222 const struct sched_class
*prev_class
;
7223 struct callback_head
*head
;
7226 int queue_flags
= DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
7229 /* The pi code expects interrupts enabled */
7230 BUG_ON(pi
&& in_interrupt());
7232 /* Double check policy once rq lock held: */
7234 reset_on_fork
= p
->sched_reset_on_fork
;
7235 policy
= oldpolicy
= p
->policy
;
7237 reset_on_fork
= !!(attr
->sched_flags
& SCHED_FLAG_RESET_ON_FORK
);
7239 if (!valid_policy(policy
))
7243 if (attr
->sched_flags
& ~(SCHED_FLAG_ALL
| SCHED_FLAG_SUGOV
))
7247 * Valid priorities for SCHED_FIFO and SCHED_RR are
7248 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
7249 * SCHED_BATCH and SCHED_IDLE is 0.
7251 if (attr
->sched_priority
> MAX_RT_PRIO
-1)
7253 if ((dl_policy(policy
) && !__checkparam_dl(attr
)) ||
7254 (rt_policy(policy
) != (attr
->sched_priority
!= 0)))
7258 * Allow unprivileged RT tasks to decrease priority:
7260 if (user
&& !capable(CAP_SYS_NICE
)) {
7261 if (fair_policy(policy
)) {
7262 if (attr
->sched_nice
< task_nice(p
) &&
7263 !can_nice(p
, attr
->sched_nice
))
7267 if (rt_policy(policy
)) {
7268 unsigned long rlim_rtprio
=
7269 task_rlimit(p
, RLIMIT_RTPRIO
);
7271 /* Can't set/change the rt policy: */
7272 if (policy
!= p
->policy
&& !rlim_rtprio
)
7275 /* Can't increase priority: */
7276 if (attr
->sched_priority
> p
->rt_priority
&&
7277 attr
->sched_priority
> rlim_rtprio
)
7282 * Can't set/change SCHED_DEADLINE policy at all for now
7283 * (safest behavior); in the future we would like to allow
7284 * unprivileged DL tasks to increase their relative deadline
7285 * or reduce their runtime (both ways reducing utilization)
7287 if (dl_policy(policy
))
7291 * Treat SCHED_IDLE as nice 20. Only allow a switch to
7292 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
7294 if (task_has_idle_policy(p
) && !idle_policy(policy
)) {
7295 if (!can_nice(p
, task_nice(p
)))
7299 /* Can't change other user's priorities: */
7300 if (!check_same_owner(p
))
7303 /* Normal users shall not reset the sched_reset_on_fork flag: */
7304 if (p
->sched_reset_on_fork
&& !reset_on_fork
)
7309 if (attr
->sched_flags
& SCHED_FLAG_SUGOV
)
7312 retval
= security_task_setscheduler(p
);
7317 /* Update task specific "requested" clamps */
7318 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP
) {
7319 retval
= uclamp_validate(p
, attr
);
7328 * Make sure no PI-waiters arrive (or leave) while we are
7329 * changing the priority of the task:
7331 * To be able to change p->policy safely, the appropriate
7332 * runqueue lock must be held.
7334 rq
= task_rq_lock(p
, &rf
);
7335 update_rq_clock(rq
);
7338 * Changing the policy of the stop threads its a very bad idea:
7340 if (p
== rq
->stop
) {
7346 * If not changing anything there's no need to proceed further,
7347 * but store a possible modification of reset_on_fork.
7349 if (unlikely(policy
== p
->policy
)) {
7350 if (fair_policy(policy
) && attr
->sched_nice
!= task_nice(p
))
7352 if (rt_policy(policy
) && attr
->sched_priority
!= p
->rt_priority
)
7354 if (dl_policy(policy
) && dl_param_changed(p
, attr
))
7356 if (attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP
)
7359 p
->sched_reset_on_fork
= reset_on_fork
;
7366 #ifdef CONFIG_RT_GROUP_SCHED
7368 * Do not allow realtime tasks into groups that have no runtime
7371 if (rt_bandwidth_enabled() && rt_policy(policy
) &&
7372 task_group(p
)->rt_bandwidth
.rt_runtime
== 0 &&
7373 !task_group_is_autogroup(task_group(p
))) {
7379 if (dl_bandwidth_enabled() && dl_policy(policy
) &&
7380 !(attr
->sched_flags
& SCHED_FLAG_SUGOV
)) {
7381 cpumask_t
*span
= rq
->rd
->span
;
7384 * Don't allow tasks with an affinity mask smaller than
7385 * the entire root_domain to become SCHED_DEADLINE. We
7386 * will also fail if there's no bandwidth available.
7388 if (!cpumask_subset(span
, p
->cpus_ptr
) ||
7389 rq
->rd
->dl_bw
.bw
== 0) {
7397 /* Re-check policy now with rq lock held: */
7398 if (unlikely(oldpolicy
!= -1 && oldpolicy
!= p
->policy
)) {
7399 policy
= oldpolicy
= -1;
7400 task_rq_unlock(rq
, p
, &rf
);
7402 cpuset_read_unlock();
7407 * If setscheduling to SCHED_DEADLINE (or changing the parameters
7408 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
7411 if ((dl_policy(policy
) || dl_task(p
)) && sched_dl_overflow(p
, policy
, attr
)) {
7416 p
->sched_reset_on_fork
= reset_on_fork
;
7419 newprio
= __normal_prio(policy
, attr
->sched_priority
, attr
->sched_nice
);
7422 * Take priority boosted tasks into account. If the new
7423 * effective priority is unchanged, we just store the new
7424 * normal parameters and do not touch the scheduler class and
7425 * the runqueue. This will be done when the task deboost
7428 newprio
= rt_effective_prio(p
, newprio
);
7429 if (newprio
== oldprio
)
7430 queue_flags
&= ~DEQUEUE_MOVE
;
7433 queued
= task_on_rq_queued(p
);
7434 running
= task_current(rq
, p
);
7436 dequeue_task(rq
, p
, queue_flags
);
7438 put_prev_task(rq
, p
);
7440 prev_class
= p
->sched_class
;
7442 if (!(attr
->sched_flags
& SCHED_FLAG_KEEP_PARAMS
)) {
7443 __setscheduler_params(p
, attr
);
7444 __setscheduler_prio(p
, newprio
);
7446 __setscheduler_uclamp(p
, attr
);
7450 * We enqueue to tail when the priority of a task is
7451 * increased (user space view).
7453 if (oldprio
< p
->prio
)
7454 queue_flags
|= ENQUEUE_HEAD
;
7456 enqueue_task(rq
, p
, queue_flags
);
7459 set_next_task(rq
, p
);
7461 check_class_changed(rq
, p
, prev_class
, oldprio
);
7463 /* Avoid rq from going away on us: */
7465 head
= splice_balance_callbacks(rq
);
7466 task_rq_unlock(rq
, p
, &rf
);
7469 cpuset_read_unlock();
7470 rt_mutex_adjust_pi(p
);
7473 /* Run balance callbacks after we've adjusted the PI chain: */
7474 balance_callbacks(rq
, head
);
7480 task_rq_unlock(rq
, p
, &rf
);
7482 cpuset_read_unlock();
7486 static int _sched_setscheduler(struct task_struct
*p
, int policy
,
7487 const struct sched_param
*param
, bool check
)
7489 struct sched_attr attr
= {
7490 .sched_policy
= policy
,
7491 .sched_priority
= param
->sched_priority
,
7492 .sched_nice
= PRIO_TO_NICE(p
->static_prio
),
7495 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
7496 if ((policy
!= SETPARAM_POLICY
) && (policy
& SCHED_RESET_ON_FORK
)) {
7497 attr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
7498 policy
&= ~SCHED_RESET_ON_FORK
;
7499 attr
.sched_policy
= policy
;
7502 return __sched_setscheduler(p
, &attr
, check
, true);
7505 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
7506 * @p: the task in question.
7507 * @policy: new policy.
7508 * @param: structure containing the new RT priority.
7510 * Use sched_set_fifo(), read its comment.
7512 * Return: 0 on success. An error code otherwise.
7514 * NOTE that the task may be already dead.
7516 int sched_setscheduler(struct task_struct
*p
, int policy
,
7517 const struct sched_param
*param
)
7519 return _sched_setscheduler(p
, policy
, param
, true);
7522 int sched_setattr(struct task_struct
*p
, const struct sched_attr
*attr
)
7524 return __sched_setscheduler(p
, attr
, true, true);
7527 int sched_setattr_nocheck(struct task_struct
*p
, const struct sched_attr
*attr
)
7529 return __sched_setscheduler(p
, attr
, false, true);
7531 EXPORT_SYMBOL_GPL(sched_setattr_nocheck
);
7534 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
7535 * @p: the task in question.
7536 * @policy: new policy.
7537 * @param: structure containing the new RT priority.
7539 * Just like sched_setscheduler, only don't bother checking if the
7540 * current context has permission. For example, this is needed in
7541 * stop_machine(): we create temporary high priority worker threads,
7542 * but our caller might not have that capability.
7544 * Return: 0 on success. An error code otherwise.
7546 int sched_setscheduler_nocheck(struct task_struct
*p
, int policy
,
7547 const struct sched_param
*param
)
7549 return _sched_setscheduler(p
, policy
, param
, false);
7553 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
7554 * incapable of resource management, which is the one thing an OS really should
7557 * This is of course the reason it is limited to privileged users only.
7559 * Worse still; it is fundamentally impossible to compose static priority
7560 * workloads. You cannot take two correctly working static prio workloads
7561 * and smash them together and still expect them to work.
7563 * For this reason 'all' FIFO tasks the kernel creates are basically at:
7567 * The administrator _MUST_ configure the system, the kernel simply doesn't
7568 * know enough information to make a sensible choice.
7570 void sched_set_fifo(struct task_struct
*p
)
7572 struct sched_param sp
= { .sched_priority
= MAX_RT_PRIO
/ 2 };
7573 WARN_ON_ONCE(sched_setscheduler_nocheck(p
, SCHED_FIFO
, &sp
) != 0);
7575 EXPORT_SYMBOL_GPL(sched_set_fifo
);
7578 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
7580 void sched_set_fifo_low(struct task_struct
*p
)
7582 struct sched_param sp
= { .sched_priority
= 1 };
7583 WARN_ON_ONCE(sched_setscheduler_nocheck(p
, SCHED_FIFO
, &sp
) != 0);
7585 EXPORT_SYMBOL_GPL(sched_set_fifo_low
);
7587 void sched_set_normal(struct task_struct
*p
, int nice
)
7589 struct sched_attr attr
= {
7590 .sched_policy
= SCHED_NORMAL
,
7593 WARN_ON_ONCE(sched_setattr_nocheck(p
, &attr
) != 0);
7595 EXPORT_SYMBOL_GPL(sched_set_normal
);
7598 do_sched_setscheduler(pid_t pid
, int policy
, struct sched_param __user
*param
)
7600 struct sched_param lparam
;
7601 struct task_struct
*p
;
7604 if (!param
|| pid
< 0)
7606 if (copy_from_user(&lparam
, param
, sizeof(struct sched_param
)))
7611 p
= find_process_by_pid(pid
);
7617 retval
= sched_setscheduler(p
, policy
, &lparam
);
7625 * Mimics kernel/events/core.c perf_copy_attr().
7627 static int sched_copy_attr(struct sched_attr __user
*uattr
, struct sched_attr
*attr
)
7632 /* Zero the full structure, so that a short copy will be nice: */
7633 memset(attr
, 0, sizeof(*attr
));
7635 ret
= get_user(size
, &uattr
->size
);
7639 /* ABI compatibility quirk: */
7641 size
= SCHED_ATTR_SIZE_VER0
;
7642 if (size
< SCHED_ATTR_SIZE_VER0
|| size
> PAGE_SIZE
)
7645 ret
= copy_struct_from_user(attr
, sizeof(*attr
), uattr
, size
);
7652 if ((attr
->sched_flags
& SCHED_FLAG_UTIL_CLAMP
) &&
7653 size
< SCHED_ATTR_SIZE_VER1
)
7657 * XXX: Do we want to be lenient like existing syscalls; or do we want
7658 * to be strict and return an error on out-of-bounds values?
7660 attr
->sched_nice
= clamp(attr
->sched_nice
, MIN_NICE
, MAX_NICE
);
7665 put_user(sizeof(*attr
), &uattr
->size
);
7669 static void get_params(struct task_struct
*p
, struct sched_attr
*attr
)
7671 if (task_has_dl_policy(p
))
7672 __getparam_dl(p
, attr
);
7673 else if (task_has_rt_policy(p
))
7674 attr
->sched_priority
= p
->rt_priority
;
7676 attr
->sched_nice
= task_nice(p
);
7680 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
7681 * @pid: the pid in question.
7682 * @policy: new policy.
7683 * @param: structure containing the new RT priority.
7685 * Return: 0 on success. An error code otherwise.
7687 SYSCALL_DEFINE3(sched_setscheduler
, pid_t
, pid
, int, policy
, struct sched_param __user
*, param
)
7692 return do_sched_setscheduler(pid
, policy
, param
);
7696 * sys_sched_setparam - set/change the RT priority of a thread
7697 * @pid: the pid in question.
7698 * @param: structure containing the new RT priority.
7700 * Return: 0 on success. An error code otherwise.
7702 SYSCALL_DEFINE2(sched_setparam
, pid_t
, pid
, struct sched_param __user
*, param
)
7704 return do_sched_setscheduler(pid
, SETPARAM_POLICY
, param
);
7708 * sys_sched_setattr - same as above, but with extended sched_attr
7709 * @pid: the pid in question.
7710 * @uattr: structure containing the extended parameters.
7711 * @flags: for future extension.
7713 SYSCALL_DEFINE3(sched_setattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
7714 unsigned int, flags
)
7716 struct sched_attr attr
;
7717 struct task_struct
*p
;
7720 if (!uattr
|| pid
< 0 || flags
)
7723 retval
= sched_copy_attr(uattr
, &attr
);
7727 if ((int)attr
.sched_policy
< 0)
7729 if (attr
.sched_flags
& SCHED_FLAG_KEEP_POLICY
)
7730 attr
.sched_policy
= SETPARAM_POLICY
;
7734 p
= find_process_by_pid(pid
);
7740 if (attr
.sched_flags
& SCHED_FLAG_KEEP_PARAMS
)
7741 get_params(p
, &attr
);
7742 retval
= sched_setattr(p
, &attr
);
7750 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
7751 * @pid: the pid in question.
7753 * Return: On success, the policy of the thread. Otherwise, a negative error
7756 SYSCALL_DEFINE1(sched_getscheduler
, pid_t
, pid
)
7758 struct task_struct
*p
;
7766 p
= find_process_by_pid(pid
);
7768 retval
= security_task_getscheduler(p
);
7771 | (p
->sched_reset_on_fork
? SCHED_RESET_ON_FORK
: 0);
7778 * sys_sched_getparam - get the RT priority of a thread
7779 * @pid: the pid in question.
7780 * @param: structure containing the RT priority.
7782 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
7785 SYSCALL_DEFINE2(sched_getparam
, pid_t
, pid
, struct sched_param __user
*, param
)
7787 struct sched_param lp
= { .sched_priority
= 0 };
7788 struct task_struct
*p
;
7791 if (!param
|| pid
< 0)
7795 p
= find_process_by_pid(pid
);
7800 retval
= security_task_getscheduler(p
);
7804 if (task_has_rt_policy(p
))
7805 lp
.sched_priority
= p
->rt_priority
;
7809 * This one might sleep, we cannot do it with a spinlock held ...
7811 retval
= copy_to_user(param
, &lp
, sizeof(*param
)) ? -EFAULT
: 0;
7821 * Copy the kernel size attribute structure (which might be larger
7822 * than what user-space knows about) to user-space.
7824 * Note that all cases are valid: user-space buffer can be larger or
7825 * smaller than the kernel-space buffer. The usual case is that both
7826 * have the same size.
7829 sched_attr_copy_to_user(struct sched_attr __user
*uattr
,
7830 struct sched_attr
*kattr
,
7833 unsigned int ksize
= sizeof(*kattr
);
7835 if (!access_ok(uattr
, usize
))
7839 * sched_getattr() ABI forwards and backwards compatibility:
7841 * If usize == ksize then we just copy everything to user-space and all is good.
7843 * If usize < ksize then we only copy as much as user-space has space for,
7844 * this keeps ABI compatibility as well. We skip the rest.
7846 * If usize > ksize then user-space is using a newer version of the ABI,
7847 * which part the kernel doesn't know about. Just ignore it - tooling can
7848 * detect the kernel's knowledge of attributes from the attr->size value
7849 * which is set to ksize in this case.
7851 kattr
->size
= min(usize
, ksize
);
7853 if (copy_to_user(uattr
, kattr
, kattr
->size
))
7860 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
7861 * @pid: the pid in question.
7862 * @uattr: structure containing the extended parameters.
7863 * @usize: sizeof(attr) for fwd/bwd comp.
7864 * @flags: for future extension.
7866 SYSCALL_DEFINE4(sched_getattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
7867 unsigned int, usize
, unsigned int, flags
)
7869 struct sched_attr kattr
= { };
7870 struct task_struct
*p
;
7873 if (!uattr
|| pid
< 0 || usize
> PAGE_SIZE
||
7874 usize
< SCHED_ATTR_SIZE_VER0
|| flags
)
7878 p
= find_process_by_pid(pid
);
7883 retval
= security_task_getscheduler(p
);
7887 kattr
.sched_policy
= p
->policy
;
7888 if (p
->sched_reset_on_fork
)
7889 kattr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
7890 get_params(p
, &kattr
);
7891 kattr
.sched_flags
&= SCHED_FLAG_ALL
;
7893 #ifdef CONFIG_UCLAMP_TASK
7895 * This could race with another potential updater, but this is fine
7896 * because it'll correctly read the old or the new value. We don't need
7897 * to guarantee who wins the race as long as it doesn't return garbage.
7899 kattr
.sched_util_min
= p
->uclamp_req
[UCLAMP_MIN
].value
;
7900 kattr
.sched_util_max
= p
->uclamp_req
[UCLAMP_MAX
].value
;
7905 return sched_attr_copy_to_user(uattr
, &kattr
, usize
);
7913 int dl_task_check_affinity(struct task_struct
*p
, const struct cpumask
*mask
)
7918 * If the task isn't a deadline task or admission control is
7919 * disabled then we don't care about affinity changes.
7921 if (!task_has_dl_policy(p
) || !dl_bandwidth_enabled())
7925 * Since bandwidth control happens on root_domain basis,
7926 * if admission test is enabled, we only admit -deadline
7927 * tasks allowed to run on all the CPUs in the task's
7931 if (!cpumask_subset(task_rq(p
)->rd
->span
, mask
))
7939 __sched_setaffinity(struct task_struct
*p
, const struct cpumask
*mask
)
7942 cpumask_var_t cpus_allowed
, new_mask
;
7944 if (!alloc_cpumask_var(&cpus_allowed
, GFP_KERNEL
))
7947 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
)) {
7949 goto out_free_cpus_allowed
;
7952 cpuset_cpus_allowed(p
, cpus_allowed
);
7953 cpumask_and(new_mask
, mask
, cpus_allowed
);
7955 retval
= dl_task_check_affinity(p
, new_mask
);
7957 goto out_free_new_mask
;
7959 retval
= __set_cpus_allowed_ptr(p
, new_mask
, SCA_CHECK
| SCA_USER
);
7961 goto out_free_new_mask
;
7963 cpuset_cpus_allowed(p
, cpus_allowed
);
7964 if (!cpumask_subset(new_mask
, cpus_allowed
)) {
7966 * We must have raced with a concurrent cpuset update.
7967 * Just reset the cpumask to the cpuset's cpus_allowed.
7969 cpumask_copy(new_mask
, cpus_allowed
);
7974 free_cpumask_var(new_mask
);
7975 out_free_cpus_allowed
:
7976 free_cpumask_var(cpus_allowed
);
7980 long sched_setaffinity(pid_t pid
, const struct cpumask
*in_mask
)
7982 struct task_struct
*p
;
7987 p
= find_process_by_pid(pid
);
7993 /* Prevent p going away */
7997 if (p
->flags
& PF_NO_SETAFFINITY
) {
8002 if (!check_same_owner(p
)) {
8004 if (!ns_capable(__task_cred(p
)->user_ns
, CAP_SYS_NICE
)) {
8012 retval
= security_task_setscheduler(p
);
8016 retval
= __sched_setaffinity(p
, in_mask
);
8022 static int get_user_cpu_mask(unsigned long __user
*user_mask_ptr
, unsigned len
,
8023 struct cpumask
*new_mask
)
8025 if (len
< cpumask_size())
8026 cpumask_clear(new_mask
);
8027 else if (len
> cpumask_size())
8028 len
= cpumask_size();
8030 return copy_from_user(new_mask
, user_mask_ptr
, len
) ? -EFAULT
: 0;
8034 * sys_sched_setaffinity - set the CPU affinity of a process
8035 * @pid: pid of the process
8036 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8037 * @user_mask_ptr: user-space pointer to the new CPU mask
8039 * Return: 0 on success. An error code otherwise.
8041 SYSCALL_DEFINE3(sched_setaffinity
, pid_t
, pid
, unsigned int, len
,
8042 unsigned long __user
*, user_mask_ptr
)
8044 cpumask_var_t new_mask
;
8047 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
))
8050 retval
= get_user_cpu_mask(user_mask_ptr
, len
, new_mask
);
8052 retval
= sched_setaffinity(pid
, new_mask
);
8053 free_cpumask_var(new_mask
);
8057 long sched_getaffinity(pid_t pid
, struct cpumask
*mask
)
8059 struct task_struct
*p
;
8060 unsigned long flags
;
8066 p
= find_process_by_pid(pid
);
8070 retval
= security_task_getscheduler(p
);
8074 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
8075 cpumask_and(mask
, &p
->cpus_mask
, cpu_active_mask
);
8076 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
8085 * sys_sched_getaffinity - get the CPU affinity of a process
8086 * @pid: pid of the process
8087 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8088 * @user_mask_ptr: user-space pointer to hold the current CPU mask
8090 * Return: size of CPU mask copied to user_mask_ptr on success. An
8091 * error code otherwise.
8093 SYSCALL_DEFINE3(sched_getaffinity
, pid_t
, pid
, unsigned int, len
,
8094 unsigned long __user
*, user_mask_ptr
)
8099 if ((len
* BITS_PER_BYTE
) < nr_cpu_ids
)
8101 if (len
& (sizeof(unsigned long)-1))
8104 if (!alloc_cpumask_var(&mask
, GFP_KERNEL
))
8107 ret
= sched_getaffinity(pid
, mask
);
8109 unsigned int retlen
= min(len
, cpumask_size());
8111 if (copy_to_user(user_mask_ptr
, mask
, retlen
))
8116 free_cpumask_var(mask
);
8121 static void do_sched_yield(void)
8126 rq
= this_rq_lock_irq(&rf
);
8128 schedstat_inc(rq
->yld_count
);
8129 current
->sched_class
->yield_task(rq
);
8132 rq_unlock_irq(rq
, &rf
);
8133 sched_preempt_enable_no_resched();
8139 * sys_sched_yield - yield the current processor to other threads.
8141 * This function yields the current CPU to other tasks. If there are no
8142 * other threads running on this CPU then this function will return.
8146 SYSCALL_DEFINE0(sched_yield
)
8152 #if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
8153 int __sched
__cond_resched(void)
8155 if (should_resched(0)) {
8156 preempt_schedule_common();
8160 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick
8161 * whether the current CPU is in an RCU read-side critical section,
8162 * so the tick can report quiescent states even for CPUs looping
8163 * in kernel context. In contrast, in non-preemptible kernels,
8164 * RCU readers leave no in-memory hints, which means that CPU-bound
8165 * processes executing in kernel context might never report an
8166 * RCU quiescent state. Therefore, the following code causes
8167 * cond_resched() to report a quiescent state, but only when RCU
8168 * is in urgent need of one.
8170 #ifndef CONFIG_PREEMPT_RCU
8175 EXPORT_SYMBOL(__cond_resched
);
8178 #ifdef CONFIG_PREEMPT_DYNAMIC
8179 DEFINE_STATIC_CALL_RET0(cond_resched
, __cond_resched
);
8180 EXPORT_STATIC_CALL_TRAMP(cond_resched
);
8182 DEFINE_STATIC_CALL_RET0(might_resched
, __cond_resched
);
8183 EXPORT_STATIC_CALL_TRAMP(might_resched
);
8187 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
8188 * call schedule, and on return reacquire the lock.
8190 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
8191 * operations here to prevent schedule() from being called twice (once via
8192 * spin_unlock(), once by hand).
8194 int __cond_resched_lock(spinlock_t
*lock
)
8196 int resched
= should_resched(PREEMPT_LOCK_OFFSET
);
8199 lockdep_assert_held(lock
);
8201 if (spin_needbreak(lock
) || resched
) {
8204 preempt_schedule_common();
8212 EXPORT_SYMBOL(__cond_resched_lock
);
8214 int __cond_resched_rwlock_read(rwlock_t
*lock
)
8216 int resched
= should_resched(PREEMPT_LOCK_OFFSET
);
8219 lockdep_assert_held_read(lock
);
8221 if (rwlock_needbreak(lock
) || resched
) {
8224 preempt_schedule_common();
8232 EXPORT_SYMBOL(__cond_resched_rwlock_read
);
8234 int __cond_resched_rwlock_write(rwlock_t
*lock
)
8236 int resched
= should_resched(PREEMPT_LOCK_OFFSET
);
8239 lockdep_assert_held_write(lock
);
8241 if (rwlock_needbreak(lock
) || resched
) {
8244 preempt_schedule_common();
8252 EXPORT_SYMBOL(__cond_resched_rwlock_write
);
8255 * yield - yield the current processor to other threads.
8257 * Do not ever use this function, there's a 99% chance you're doing it wrong.
8259 * The scheduler is at all times free to pick the calling task as the most
8260 * eligible task to run, if removing the yield() call from your code breaks
8261 * it, it's already broken.
8263 * Typical broken usage is:
8268 * where one assumes that yield() will let 'the other' process run that will
8269 * make event true. If the current task is a SCHED_FIFO task that will never
8270 * happen. Never use yield() as a progress guarantee!!
8272 * If you want to use yield() to wait for something, use wait_event().
8273 * If you want to use yield() to be 'nice' for others, use cond_resched().
8274 * If you still want to use yield(), do not!
8276 void __sched
yield(void)
8278 set_current_state(TASK_RUNNING
);
8281 EXPORT_SYMBOL(yield
);
8284 * yield_to - yield the current processor to another thread in
8285 * your thread group, or accelerate that thread toward the
8286 * processor it's on.
8288 * @preempt: whether task preemption is allowed or not
8290 * It's the caller's job to ensure that the target task struct
8291 * can't go away on us before we can do any checks.
8294 * true (>0) if we indeed boosted the target task.
8295 * false (0) if we failed to boost the target.
8296 * -ESRCH if there's no task to yield to.
8298 int __sched
yield_to(struct task_struct
*p
, bool preempt
)
8300 struct task_struct
*curr
= current
;
8301 struct rq
*rq
, *p_rq
;
8302 unsigned long flags
;
8305 local_irq_save(flags
);
8311 * If we're the only runnable task on the rq and target rq also
8312 * has only one task, there's absolutely no point in yielding.
8314 if (rq
->nr_running
== 1 && p_rq
->nr_running
== 1) {
8319 double_rq_lock(rq
, p_rq
);
8320 if (task_rq(p
) != p_rq
) {
8321 double_rq_unlock(rq
, p_rq
);
8325 if (!curr
->sched_class
->yield_to_task
)
8328 if (curr
->sched_class
!= p
->sched_class
)
8331 if (task_running(p_rq
, p
) || !task_is_running(p
))
8334 yielded
= curr
->sched_class
->yield_to_task(rq
, p
);
8336 schedstat_inc(rq
->yld_count
);
8338 * Make p's CPU reschedule; pick_next_entity takes care of
8341 if (preempt
&& rq
!= p_rq
)
8346 double_rq_unlock(rq
, p_rq
);
8348 local_irq_restore(flags
);
8355 EXPORT_SYMBOL_GPL(yield_to
);
8357 int io_schedule_prepare(void)
8359 int old_iowait
= current
->in_iowait
;
8361 current
->in_iowait
= 1;
8362 blk_schedule_flush_plug(current
);
8367 void io_schedule_finish(int token
)
8369 current
->in_iowait
= token
;
8373 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
8374 * that process accounting knows that this is a task in IO wait state.
8376 long __sched
io_schedule_timeout(long timeout
)
8381 token
= io_schedule_prepare();
8382 ret
= schedule_timeout(timeout
);
8383 io_schedule_finish(token
);
8387 EXPORT_SYMBOL(io_schedule_timeout
);
8389 void __sched
io_schedule(void)
8393 token
= io_schedule_prepare();
8395 io_schedule_finish(token
);
8397 EXPORT_SYMBOL(io_schedule
);
8400 * sys_sched_get_priority_max - return maximum RT priority.
8401 * @policy: scheduling class.
8403 * Return: On success, this syscall returns the maximum
8404 * rt_priority that can be used by a given scheduling class.
8405 * On failure, a negative error code is returned.
8407 SYSCALL_DEFINE1(sched_get_priority_max
, int, policy
)
8414 ret
= MAX_RT_PRIO
-1;
8416 case SCHED_DEADLINE
:
8427 * sys_sched_get_priority_min - return minimum RT priority.
8428 * @policy: scheduling class.
8430 * Return: On success, this syscall returns the minimum
8431 * rt_priority that can be used by a given scheduling class.
8432 * On failure, a negative error code is returned.
8434 SYSCALL_DEFINE1(sched_get_priority_min
, int, policy
)
8443 case SCHED_DEADLINE
:
8452 static int sched_rr_get_interval(pid_t pid
, struct timespec64
*t
)
8454 struct task_struct
*p
;
8455 unsigned int time_slice
;
8465 p
= find_process_by_pid(pid
);
8469 retval
= security_task_getscheduler(p
);
8473 rq
= task_rq_lock(p
, &rf
);
8475 if (p
->sched_class
->get_rr_interval
)
8476 time_slice
= p
->sched_class
->get_rr_interval(rq
, p
);
8477 task_rq_unlock(rq
, p
, &rf
);
8480 jiffies_to_timespec64(time_slice
, t
);
8489 * sys_sched_rr_get_interval - return the default timeslice of a process.
8490 * @pid: pid of the process.
8491 * @interval: userspace pointer to the timeslice value.
8493 * this syscall writes the default timeslice value of a given process
8494 * into the user-space timespec buffer. A value of '0' means infinity.
8496 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
8499 SYSCALL_DEFINE2(sched_rr_get_interval
, pid_t
, pid
,
8500 struct __kernel_timespec __user
*, interval
)
8502 struct timespec64 t
;
8503 int retval
= sched_rr_get_interval(pid
, &t
);
8506 retval
= put_timespec64(&t
, interval
);
8511 #ifdef CONFIG_COMPAT_32BIT_TIME
8512 SYSCALL_DEFINE2(sched_rr_get_interval_time32
, pid_t
, pid
,
8513 struct old_timespec32 __user
*, interval
)
8515 struct timespec64 t
;
8516 int retval
= sched_rr_get_interval(pid
, &t
);
8519 retval
= put_old_timespec32(&t
, interval
);
8524 void sched_show_task(struct task_struct
*p
)
8526 unsigned long free
= 0;
8529 if (!try_get_task_stack(p
))
8532 pr_info("task:%-15.15s state:%c", p
->comm
, task_state_to_char(p
));
8534 if (task_is_running(p
))
8535 pr_cont(" running task ");
8536 #ifdef CONFIG_DEBUG_STACK_USAGE
8537 free
= stack_not_used(p
);
8542 ppid
= task_pid_nr(rcu_dereference(p
->real_parent
));
8544 pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n",
8545 free
, task_pid_nr(p
), ppid
,
8546 (unsigned long)task_thread_info(p
)->flags
);
8548 print_worker_info(KERN_INFO
, p
);
8549 print_stop_info(KERN_INFO
, p
);
8550 show_stack(p
, NULL
, KERN_INFO
);
8553 EXPORT_SYMBOL_GPL(sched_show_task
);
8556 state_filter_match(unsigned long state_filter
, struct task_struct
*p
)
8558 unsigned int state
= READ_ONCE(p
->__state
);
8560 /* no filter, everything matches */
8564 /* filter, but doesn't match */
8565 if (!(state
& state_filter
))
8569 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
8572 if (state_filter
== TASK_UNINTERRUPTIBLE
&& state
== TASK_IDLE
)
8579 void show_state_filter(unsigned int state_filter
)
8581 struct task_struct
*g
, *p
;
8584 for_each_process_thread(g
, p
) {
8586 * reset the NMI-timeout, listing all files on a slow
8587 * console might take a lot of time:
8588 * Also, reset softlockup watchdogs on all CPUs, because
8589 * another CPU might be blocked waiting for us to process
8592 touch_nmi_watchdog();
8593 touch_all_softlockup_watchdogs();
8594 if (state_filter_match(state_filter
, p
))
8598 #ifdef CONFIG_SCHED_DEBUG
8600 sysrq_sched_debug_show();
8604 * Only show locks if all tasks are dumped:
8607 debug_show_all_locks();
8611 * init_idle - set up an idle thread for a given CPU
8612 * @idle: task in question
8613 * @cpu: CPU the idle task belongs to
8615 * NOTE: this function does not set the idle thread's NEED_RESCHED
8616 * flag, to make booting more robust.
8618 void __init
init_idle(struct task_struct
*idle
, int cpu
)
8620 struct rq
*rq
= cpu_rq(cpu
);
8621 unsigned long flags
;
8623 __sched_fork(0, idle
);
8626 * The idle task doesn't need the kthread struct to function, but it
8627 * is dressed up as a per-CPU kthread and thus needs to play the part
8628 * if we want to avoid special-casing it in code that deals with per-CPU
8631 set_kthread_struct(idle
);
8633 raw_spin_lock_irqsave(&idle
->pi_lock
, flags
);
8634 raw_spin_rq_lock(rq
);
8636 idle
->__state
= TASK_RUNNING
;
8637 idle
->se
.exec_start
= sched_clock();
8639 * PF_KTHREAD should already be set at this point; regardless, make it
8640 * look like a proper per-CPU kthread.
8642 idle
->flags
|= PF_IDLE
| PF_KTHREAD
| PF_NO_SETAFFINITY
;
8643 kthread_set_per_cpu(idle
, cpu
);
8647 * It's possible that init_idle() gets called multiple times on a task,
8648 * in that case do_set_cpus_allowed() will not do the right thing.
8650 * And since this is boot we can forgo the serialization.
8652 set_cpus_allowed_common(idle
, cpumask_of(cpu
), 0);
8655 * We're having a chicken and egg problem, even though we are
8656 * holding rq->lock, the CPU isn't yet set to this CPU so the
8657 * lockdep check in task_group() will fail.
8659 * Similar case to sched_fork(). / Alternatively we could
8660 * use task_rq_lock() here and obtain the other rq->lock.
8665 __set_task_cpu(idle
, cpu
);
8669 rcu_assign_pointer(rq
->curr
, idle
);
8670 idle
->on_rq
= TASK_ON_RQ_QUEUED
;
8674 raw_spin_rq_unlock(rq
);
8675 raw_spin_unlock_irqrestore(&idle
->pi_lock
, flags
);
8677 /* Set the preempt count _outside_ the spinlocks! */
8678 init_idle_preempt_count(idle
, cpu
);
8681 * The idle tasks have their own, simple scheduling class:
8683 idle
->sched_class
= &idle_sched_class
;
8684 ftrace_graph_init_idle_task(idle
, cpu
);
8685 vtime_init_idle(idle
, cpu
);
8687 sprintf(idle
->comm
, "%s/%d", INIT_TASK_COMM
, cpu
);
8693 int cpuset_cpumask_can_shrink(const struct cpumask
*cur
,
8694 const struct cpumask
*trial
)
8698 if (!cpumask_weight(cur
))
8701 ret
= dl_cpuset_cpumask_can_shrink(cur
, trial
);
8706 int task_can_attach(struct task_struct
*p
,
8707 const struct cpumask
*cs_cpus_allowed
)
8712 * Kthreads which disallow setaffinity shouldn't be moved
8713 * to a new cpuset; we don't want to change their CPU
8714 * affinity and isolating such threads by their set of
8715 * allowed nodes is unnecessary. Thus, cpusets are not
8716 * applicable for such threads. This prevents checking for
8717 * success of set_cpus_allowed_ptr() on all attached tasks
8718 * before cpus_mask may be changed.
8720 if (p
->flags
& PF_NO_SETAFFINITY
) {
8725 if (dl_task(p
) && !cpumask_intersects(task_rq(p
)->rd
->span
,
8727 ret
= dl_task_can_attach(p
, cs_cpus_allowed
);
8733 bool sched_smp_initialized __read_mostly
;
8735 #ifdef CONFIG_NUMA_BALANCING
8736 /* Migrate current task p to target_cpu */
8737 int migrate_task_to(struct task_struct
*p
, int target_cpu
)
8739 struct migration_arg arg
= { p
, target_cpu
};
8740 int curr_cpu
= task_cpu(p
);
8742 if (curr_cpu
== target_cpu
)
8745 if (!cpumask_test_cpu(target_cpu
, p
->cpus_ptr
))
8748 /* TODO: This is not properly updating schedstats */
8750 trace_sched_move_numa(p
, curr_cpu
, target_cpu
);
8751 return stop_one_cpu(curr_cpu
, migration_cpu_stop
, &arg
);
8755 * Requeue a task on a given node and accurately track the number of NUMA
8756 * tasks on the runqueues
8758 void sched_setnuma(struct task_struct
*p
, int nid
)
8760 bool queued
, running
;
8764 rq
= task_rq_lock(p
, &rf
);
8765 queued
= task_on_rq_queued(p
);
8766 running
= task_current(rq
, p
);
8769 dequeue_task(rq
, p
, DEQUEUE_SAVE
);
8771 put_prev_task(rq
, p
);
8773 p
->numa_preferred_nid
= nid
;
8776 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
8778 set_next_task(rq
, p
);
8779 task_rq_unlock(rq
, p
, &rf
);
8781 #endif /* CONFIG_NUMA_BALANCING */
8783 #ifdef CONFIG_HOTPLUG_CPU
8785 * Ensure that the idle task is using init_mm right before its CPU goes
8788 void idle_task_exit(void)
8790 struct mm_struct
*mm
= current
->active_mm
;
8792 BUG_ON(cpu_online(smp_processor_id()));
8793 BUG_ON(current
!= this_rq()->idle
);
8795 if (mm
!= &init_mm
) {
8796 switch_mm(mm
, &init_mm
, current
);
8797 finish_arch_post_lock_switch();
8800 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
8803 static int __balance_push_cpu_stop(void *arg
)
8805 struct task_struct
*p
= arg
;
8806 struct rq
*rq
= this_rq();
8810 raw_spin_lock_irq(&p
->pi_lock
);
8813 update_rq_clock(rq
);
8815 if (task_rq(p
) == rq
&& task_on_rq_queued(p
)) {
8816 cpu
= select_fallback_rq(rq
->cpu
, p
);
8817 rq
= __migrate_task(rq
, &rf
, p
, cpu
);
8821 raw_spin_unlock_irq(&p
->pi_lock
);
8828 static DEFINE_PER_CPU(struct cpu_stop_work
, push_work
);
8831 * Ensure we only run per-cpu kthreads once the CPU goes !active.
8833 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
8834 * effective when the hotplug motion is down.
8836 static void balance_push(struct rq
*rq
)
8838 struct task_struct
*push_task
= rq
->curr
;
8840 lockdep_assert_rq_held(rq
);
8843 * Ensure the thing is persistent until balance_push_set(.on = false);
8845 rq
->balance_callback
= &balance_push_callback
;
8848 * Only active while going offline and when invoked on the outgoing
8851 if (!cpu_dying(rq
->cpu
) || rq
!= this_rq())
8855 * Both the cpu-hotplug and stop task are in this case and are
8856 * required to complete the hotplug process.
8858 if (kthread_is_per_cpu(push_task
) ||
8859 is_migration_disabled(push_task
)) {
8862 * If this is the idle task on the outgoing CPU try to wake
8863 * up the hotplug control thread which might wait for the
8864 * last task to vanish. The rcuwait_active() check is
8865 * accurate here because the waiter is pinned on this CPU
8866 * and can't obviously be running in parallel.
8868 * On RT kernels this also has to check whether there are
8869 * pinned and scheduled out tasks on the runqueue. They
8870 * need to leave the migrate disabled section first.
8872 if (!rq
->nr_running
&& !rq_has_pinned_tasks(rq
) &&
8873 rcuwait_active(&rq
->hotplug_wait
)) {
8874 raw_spin_rq_unlock(rq
);
8875 rcuwait_wake_up(&rq
->hotplug_wait
);
8876 raw_spin_rq_lock(rq
);
8881 get_task_struct(push_task
);
8883 * Temporarily drop rq->lock such that we can wake-up the stop task.
8884 * Both preemption and IRQs are still disabled.
8886 raw_spin_rq_unlock(rq
);
8887 stop_one_cpu_nowait(rq
->cpu
, __balance_push_cpu_stop
, push_task
,
8888 this_cpu_ptr(&push_work
));
8890 * At this point need_resched() is true and we'll take the loop in
8891 * schedule(). The next pick is obviously going to be the stop task
8892 * which kthread_is_per_cpu() and will push this task away.
8894 raw_spin_rq_lock(rq
);
8897 static void balance_push_set(int cpu
, bool on
)
8899 struct rq
*rq
= cpu_rq(cpu
);
8902 rq_lock_irqsave(rq
, &rf
);
8904 WARN_ON_ONCE(rq
->balance_callback
);
8905 rq
->balance_callback
= &balance_push_callback
;
8906 } else if (rq
->balance_callback
== &balance_push_callback
) {
8907 rq
->balance_callback
= NULL
;
8909 rq_unlock_irqrestore(rq
, &rf
);
8913 * Invoked from a CPUs hotplug control thread after the CPU has been marked
8914 * inactive. All tasks which are not per CPU kernel threads are either
8915 * pushed off this CPU now via balance_push() or placed on a different CPU
8916 * during wakeup. Wait until the CPU is quiescent.
8918 static void balance_hotplug_wait(void)
8920 struct rq
*rq
= this_rq();
8922 rcuwait_wait_event(&rq
->hotplug_wait
,
8923 rq
->nr_running
== 1 && !rq_has_pinned_tasks(rq
),
8924 TASK_UNINTERRUPTIBLE
);
8929 static inline void balance_push(struct rq
*rq
)
8933 static inline void balance_push_set(int cpu
, bool on
)
8937 static inline void balance_hotplug_wait(void)
8941 #endif /* CONFIG_HOTPLUG_CPU */
8943 void set_rq_online(struct rq
*rq
)
8946 const struct sched_class
*class;
8948 cpumask_set_cpu(rq
->cpu
, rq
->rd
->online
);
8951 for_each_class(class) {
8952 if (class->rq_online
)
8953 class->rq_online(rq
);
8958 void set_rq_offline(struct rq
*rq
)
8961 const struct sched_class
*class;
8963 for_each_class(class) {
8964 if (class->rq_offline
)
8965 class->rq_offline(rq
);
8968 cpumask_clear_cpu(rq
->cpu
, rq
->rd
->online
);
8974 * used to mark begin/end of suspend/resume:
8976 static int num_cpus_frozen
;
8979 * Update cpusets according to cpu_active mask. If cpusets are
8980 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
8981 * around partition_sched_domains().
8983 * If we come here as part of a suspend/resume, don't touch cpusets because we
8984 * want to restore it back to its original state upon resume anyway.
8986 static void cpuset_cpu_active(void)
8988 if (cpuhp_tasks_frozen
) {
8990 * num_cpus_frozen tracks how many CPUs are involved in suspend
8991 * resume sequence. As long as this is not the last online
8992 * operation in the resume sequence, just build a single sched
8993 * domain, ignoring cpusets.
8995 partition_sched_domains(1, NULL
, NULL
);
8996 if (--num_cpus_frozen
)
8999 * This is the last CPU online operation. So fall through and
9000 * restore the original sched domains by considering the
9001 * cpuset configurations.
9003 cpuset_force_rebuild();
9005 cpuset_update_active_cpus();
9008 static int cpuset_cpu_inactive(unsigned int cpu
)
9010 if (!cpuhp_tasks_frozen
) {
9011 if (dl_cpu_busy(cpu
))
9013 cpuset_update_active_cpus();
9016 partition_sched_domains(1, NULL
, NULL
);
9021 int sched_cpu_activate(unsigned int cpu
)
9023 struct rq
*rq
= cpu_rq(cpu
);
9027 * Clear the balance_push callback and prepare to schedule
9030 balance_push_set(cpu
, false);
9032 #ifdef CONFIG_SCHED_SMT
9034 * When going up, increment the number of cores with SMT present.
9036 if (cpumask_weight(cpu_smt_mask(cpu
)) == 2)
9037 static_branch_inc_cpuslocked(&sched_smt_present
);
9039 set_cpu_active(cpu
, true);
9041 if (sched_smp_initialized
) {
9042 sched_domains_numa_masks_set(cpu
);
9043 cpuset_cpu_active();
9047 * Put the rq online, if not already. This happens:
9049 * 1) In the early boot process, because we build the real domains
9050 * after all CPUs have been brought up.
9052 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
9055 rq_lock_irqsave(rq
, &rf
);
9057 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
9060 rq_unlock_irqrestore(rq
, &rf
);
9065 int sched_cpu_deactivate(unsigned int cpu
)
9067 struct rq
*rq
= cpu_rq(cpu
);
9072 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
9073 * load balancing when not active
9075 nohz_balance_exit_idle(rq
);
9077 set_cpu_active(cpu
, false);
9080 * From this point forward, this CPU will refuse to run any task that
9081 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
9082 * push those tasks away until this gets cleared, see
9083 * sched_cpu_dying().
9085 balance_push_set(cpu
, true);
9088 * We've cleared cpu_active_mask / set balance_push, wait for all
9089 * preempt-disabled and RCU users of this state to go away such that
9090 * all new such users will observe it.
9092 * Specifically, we rely on ttwu to no longer target this CPU, see
9093 * ttwu_queue_cond() and is_cpu_allowed().
9095 * Do sync before park smpboot threads to take care the rcu boost case.
9099 rq_lock_irqsave(rq
, &rf
);
9101 update_rq_clock(rq
);
9102 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
9105 rq_unlock_irqrestore(rq
, &rf
);
9107 #ifdef CONFIG_SCHED_SMT
9109 * When going down, decrement the number of cores with SMT present.
9111 if (cpumask_weight(cpu_smt_mask(cpu
)) == 2)
9112 static_branch_dec_cpuslocked(&sched_smt_present
);
9114 sched_core_cpu_deactivate(cpu
);
9117 if (!sched_smp_initialized
)
9120 ret
= cpuset_cpu_inactive(cpu
);
9122 balance_push_set(cpu
, false);
9123 set_cpu_active(cpu
, true);
9126 sched_domains_numa_masks_clear(cpu
);
9130 static void sched_rq_cpu_starting(unsigned int cpu
)
9132 struct rq
*rq
= cpu_rq(cpu
);
9134 rq
->calc_load_update
= calc_load_update
;
9135 update_max_interval();
9138 int sched_cpu_starting(unsigned int cpu
)
9140 sched_core_cpu_starting(cpu
);
9141 sched_rq_cpu_starting(cpu
);
9142 sched_tick_start(cpu
);
9146 #ifdef CONFIG_HOTPLUG_CPU
9149 * Invoked immediately before the stopper thread is invoked to bring the
9150 * CPU down completely. At this point all per CPU kthreads except the
9151 * hotplug thread (current) and the stopper thread (inactive) have been
9152 * either parked or have been unbound from the outgoing CPU. Ensure that
9153 * any of those which might be on the way out are gone.
9155 * If after this point a bound task is being woken on this CPU then the
9156 * responsible hotplug callback has failed to do it's job.
9157 * sched_cpu_dying() will catch it with the appropriate fireworks.
9159 int sched_cpu_wait_empty(unsigned int cpu
)
9161 balance_hotplug_wait();
9166 * Since this CPU is going 'away' for a while, fold any nr_active delta we
9167 * might have. Called from the CPU stopper task after ensuring that the
9168 * stopper is the last running task on the CPU, so nr_active count is
9169 * stable. We need to take the teardown thread which is calling this into
9170 * account, so we hand in adjust = 1 to the load calculation.
9172 * Also see the comment "Global load-average calculations".
9174 static void calc_load_migrate(struct rq
*rq
)
9176 long delta
= calc_load_fold_active(rq
, 1);
9179 atomic_long_add(delta
, &calc_load_tasks
);
9182 static void dump_rq_tasks(struct rq
*rq
, const char *loglvl
)
9184 struct task_struct
*g
, *p
;
9185 int cpu
= cpu_of(rq
);
9187 lockdep_assert_rq_held(rq
);
9189 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl
, cpu
, rq
->nr_running
);
9190 for_each_process_thread(g
, p
) {
9191 if (task_cpu(p
) != cpu
)
9194 if (!task_on_rq_queued(p
))
9197 printk("%s\tpid: %d, name: %s\n", loglvl
, p
->pid
, p
->comm
);
9201 int sched_cpu_dying(unsigned int cpu
)
9203 struct rq
*rq
= cpu_rq(cpu
);
9206 /* Handle pending wakeups and then migrate everything off */
9207 sched_tick_stop(cpu
);
9209 rq_lock_irqsave(rq
, &rf
);
9210 if (rq
->nr_running
!= 1 || rq_has_pinned_tasks(rq
)) {
9211 WARN(true, "Dying CPU not properly vacated!");
9212 dump_rq_tasks(rq
, KERN_WARNING
);
9214 rq_unlock_irqrestore(rq
, &rf
);
9216 calc_load_migrate(rq
);
9217 update_max_interval();
9219 sched_core_cpu_dying(cpu
);
9224 void __init
sched_init_smp(void)
9229 * There's no userspace yet to cause hotplug operations; hence all the
9230 * CPU masks are stable and all blatant races in the below code cannot
9233 mutex_lock(&sched_domains_mutex
);
9234 sched_init_domains(cpu_active_mask
);
9235 mutex_unlock(&sched_domains_mutex
);
9237 /* Move init over to a non-isolated CPU */
9238 if (set_cpus_allowed_ptr(current
, housekeeping_cpumask(HK_FLAG_DOMAIN
)) < 0)
9240 current
->flags
&= ~PF_NO_SETAFFINITY
;
9241 sched_init_granularity();
9243 init_sched_rt_class();
9244 init_sched_dl_class();
9246 sched_smp_initialized
= true;
9249 static int __init
migration_init(void)
9251 sched_cpu_starting(smp_processor_id());
9254 early_initcall(migration_init
);
9257 void __init
sched_init_smp(void)
9259 sched_init_granularity();
9261 #endif /* CONFIG_SMP */
9263 int in_sched_functions(unsigned long addr
)
9265 return in_lock_functions(addr
) ||
9266 (addr
>= (unsigned long)__sched_text_start
9267 && addr
< (unsigned long)__sched_text_end
);
9270 #ifdef CONFIG_CGROUP_SCHED
9272 * Default task group.
9273 * Every task in system belongs to this group at bootup.
9275 struct task_group root_task_group
;
9276 LIST_HEAD(task_groups
);
9278 /* Cacheline aligned slab cache for task_group */
9279 static struct kmem_cache
*task_group_cache __read_mostly
;
9282 DECLARE_PER_CPU(cpumask_var_t
, load_balance_mask
);
9283 DECLARE_PER_CPU(cpumask_var_t
, select_idle_mask
);
9285 void __init
sched_init(void)
9287 unsigned long ptr
= 0;
9290 /* Make sure the linker didn't screw up */
9291 BUG_ON(&idle_sched_class
+ 1 != &fair_sched_class
||
9292 &fair_sched_class
+ 1 != &rt_sched_class
||
9293 &rt_sched_class
+ 1 != &dl_sched_class
);
9295 BUG_ON(&dl_sched_class
+ 1 != &stop_sched_class
);
9300 #ifdef CONFIG_FAIR_GROUP_SCHED
9301 ptr
+= 2 * nr_cpu_ids
* sizeof(void **);
9303 #ifdef CONFIG_RT_GROUP_SCHED
9304 ptr
+= 2 * nr_cpu_ids
* sizeof(void **);
9307 ptr
= (unsigned long)kzalloc(ptr
, GFP_NOWAIT
);
9309 #ifdef CONFIG_FAIR_GROUP_SCHED
9310 root_task_group
.se
= (struct sched_entity
**)ptr
;
9311 ptr
+= nr_cpu_ids
* sizeof(void **);
9313 root_task_group
.cfs_rq
= (struct cfs_rq
**)ptr
;
9314 ptr
+= nr_cpu_ids
* sizeof(void **);
9316 root_task_group
.shares
= ROOT_TASK_GROUP_LOAD
;
9317 init_cfs_bandwidth(&root_task_group
.cfs_bandwidth
);
9318 #endif /* CONFIG_FAIR_GROUP_SCHED */
9319 #ifdef CONFIG_RT_GROUP_SCHED
9320 root_task_group
.rt_se
= (struct sched_rt_entity
**)ptr
;
9321 ptr
+= nr_cpu_ids
* sizeof(void **);
9323 root_task_group
.rt_rq
= (struct rt_rq
**)ptr
;
9324 ptr
+= nr_cpu_ids
* sizeof(void **);
9326 #endif /* CONFIG_RT_GROUP_SCHED */
9328 #ifdef CONFIG_CPUMASK_OFFSTACK
9329 for_each_possible_cpu(i
) {
9330 per_cpu(load_balance_mask
, i
) = (cpumask_var_t
)kzalloc_node(
9331 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
9332 per_cpu(select_idle_mask
, i
) = (cpumask_var_t
)kzalloc_node(
9333 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
9335 #endif /* CONFIG_CPUMASK_OFFSTACK */
9337 init_rt_bandwidth(&def_rt_bandwidth
, global_rt_period(), global_rt_runtime());
9338 init_dl_bandwidth(&def_dl_bandwidth
, global_rt_period(), global_rt_runtime());
9341 init_defrootdomain();
9344 #ifdef CONFIG_RT_GROUP_SCHED
9345 init_rt_bandwidth(&root_task_group
.rt_bandwidth
,
9346 global_rt_period(), global_rt_runtime());
9347 #endif /* CONFIG_RT_GROUP_SCHED */
9349 #ifdef CONFIG_CGROUP_SCHED
9350 task_group_cache
= KMEM_CACHE(task_group
, 0);
9352 list_add(&root_task_group
.list
, &task_groups
);
9353 INIT_LIST_HEAD(&root_task_group
.children
);
9354 INIT_LIST_HEAD(&root_task_group
.siblings
);
9355 autogroup_init(&init_task
);
9356 #endif /* CONFIG_CGROUP_SCHED */
9358 for_each_possible_cpu(i
) {
9362 raw_spin_lock_init(&rq
->__lock
);
9364 rq
->calc_load_active
= 0;
9365 rq
->calc_load_update
= jiffies
+ LOAD_FREQ
;
9366 init_cfs_rq(&rq
->cfs
);
9367 init_rt_rq(&rq
->rt
);
9368 init_dl_rq(&rq
->dl
);
9369 #ifdef CONFIG_FAIR_GROUP_SCHED
9370 INIT_LIST_HEAD(&rq
->leaf_cfs_rq_list
);
9371 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
9373 * How much CPU bandwidth does root_task_group get?
9375 * In case of task-groups formed thr' the cgroup filesystem, it
9376 * gets 100% of the CPU resources in the system. This overall
9377 * system CPU resource is divided among the tasks of
9378 * root_task_group and its child task-groups in a fair manner,
9379 * based on each entity's (task or task-group's) weight
9380 * (se->load.weight).
9382 * In other words, if root_task_group has 10 tasks of weight
9383 * 1024) and two child groups A0 and A1 (of weight 1024 each),
9384 * then A0's share of the CPU resource is:
9386 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
9388 * We achieve this by letting root_task_group's tasks sit
9389 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
9391 init_tg_cfs_entry(&root_task_group
, &rq
->cfs
, NULL
, i
, NULL
);
9392 #endif /* CONFIG_FAIR_GROUP_SCHED */
9394 rq
->rt
.rt_runtime
= def_rt_bandwidth
.rt_runtime
;
9395 #ifdef CONFIG_RT_GROUP_SCHED
9396 init_tg_rt_entry(&root_task_group
, &rq
->rt
, NULL
, i
, NULL
);
9401 rq
->cpu_capacity
= rq
->cpu_capacity_orig
= SCHED_CAPACITY_SCALE
;
9402 rq
->balance_callback
= &balance_push_callback
;
9403 rq
->active_balance
= 0;
9404 rq
->next_balance
= jiffies
;
9409 rq
->avg_idle
= 2*sysctl_sched_migration_cost
;
9410 rq
->wake_stamp
= jiffies
;
9411 rq
->wake_avg_idle
= rq
->avg_idle
;
9412 rq
->max_idle_balance_cost
= sysctl_sched_migration_cost
;
9414 INIT_LIST_HEAD(&rq
->cfs_tasks
);
9416 rq_attach_root(rq
, &def_root_domain
);
9417 #ifdef CONFIG_NO_HZ_COMMON
9418 rq
->last_blocked_load_update_tick
= jiffies
;
9419 atomic_set(&rq
->nohz_flags
, 0);
9421 INIT_CSD(&rq
->nohz_csd
, nohz_csd_func
, rq
);
9423 #ifdef CONFIG_HOTPLUG_CPU
9424 rcuwait_init(&rq
->hotplug_wait
);
9426 #endif /* CONFIG_SMP */
9428 atomic_set(&rq
->nr_iowait
, 0);
9430 #ifdef CONFIG_SCHED_CORE
9432 rq
->core_pick
= NULL
;
9433 rq
->core_enabled
= 0;
9434 rq
->core_tree
= RB_ROOT
;
9435 rq
->core_forceidle
= false;
9437 rq
->core_cookie
= 0UL;
9441 set_load_weight(&init_task
, false);
9444 * The boot idle thread does lazy MMU switching as well:
9447 enter_lazy_tlb(&init_mm
, current
);
9450 * Make us the idle thread. Technically, schedule() should not be
9451 * called from this thread, however somewhere below it might be,
9452 * but because we are the idle thread, we just pick up running again
9453 * when this runqueue becomes "idle".
9455 init_idle(current
, smp_processor_id());
9457 calc_load_update
= jiffies
+ LOAD_FREQ
;
9460 idle_thread_set_boot_cpu();
9461 balance_push_set(smp_processor_id(), false);
9463 init_sched_fair_class();
9469 scheduler_running
= 1;
9472 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
9473 static inline int preempt_count_equals(int preempt_offset
)
9475 int nested
= preempt_count() + rcu_preempt_depth();
9477 return (nested
== preempt_offset
);
9480 void __might_sleep(const char *file
, int line
, int preempt_offset
)
9482 unsigned int state
= get_current_state();
9484 * Blocking primitives will set (and therefore destroy) current->state,
9485 * since we will exit with TASK_RUNNING make sure we enter with it,
9486 * otherwise we will destroy state.
9488 WARN_ONCE(state
!= TASK_RUNNING
&& current
->task_state_change
,
9489 "do not call blocking ops when !TASK_RUNNING; "
9490 "state=%x set at [<%p>] %pS\n", state
,
9491 (void *)current
->task_state_change
,
9492 (void *)current
->task_state_change
);
9494 ___might_sleep(file
, line
, preempt_offset
);
9496 EXPORT_SYMBOL(__might_sleep
);
9498 void ___might_sleep(const char *file
, int line
, int preempt_offset
)
9500 /* Ratelimiting timestamp: */
9501 static unsigned long prev_jiffy
;
9503 unsigned long preempt_disable_ip
;
9505 /* WARN_ON_ONCE() by default, no rate limit required: */
9508 if ((preempt_count_equals(preempt_offset
) && !irqs_disabled() &&
9509 !is_idle_task(current
) && !current
->non_block_count
) ||
9510 system_state
== SYSTEM_BOOTING
|| system_state
> SYSTEM_RUNNING
||
9514 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
9516 prev_jiffy
= jiffies
;
9518 /* Save this before calling printk(), since that will clobber it: */
9519 preempt_disable_ip
= get_preempt_disable_ip(current
);
9522 "BUG: sleeping function called from invalid context at %s:%d\n",
9525 "in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
9526 in_atomic(), irqs_disabled(), current
->non_block_count
,
9527 current
->pid
, current
->comm
);
9529 if (task_stack_end_corrupted(current
))
9530 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
9532 debug_show_held_locks(current
);
9533 if (irqs_disabled())
9534 print_irqtrace_events(current
);
9535 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
9536 && !preempt_count_equals(preempt_offset
)) {
9537 pr_err("Preemption disabled at:");
9538 print_ip_sym(KERN_ERR
, preempt_disable_ip
);
9541 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
9543 EXPORT_SYMBOL(___might_sleep
);
9545 void __cant_sleep(const char *file
, int line
, int preempt_offset
)
9547 static unsigned long prev_jiffy
;
9549 if (irqs_disabled())
9552 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT
))
9555 if (preempt_count() > preempt_offset
)
9558 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
9560 prev_jiffy
= jiffies
;
9562 printk(KERN_ERR
"BUG: assuming atomic context at %s:%d\n", file
, line
);
9563 printk(KERN_ERR
"in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
9564 in_atomic(), irqs_disabled(),
9565 current
->pid
, current
->comm
);
9567 debug_show_held_locks(current
);
9569 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
9571 EXPORT_SYMBOL_GPL(__cant_sleep
);
9574 void __cant_migrate(const char *file
, int line
)
9576 static unsigned long prev_jiffy
;
9578 if (irqs_disabled())
9581 if (is_migration_disabled(current
))
9584 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT
))
9587 if (preempt_count() > 0)
9590 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
9592 prev_jiffy
= jiffies
;
9594 pr_err("BUG: assuming non migratable context at %s:%d\n", file
, line
);
9595 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
9596 in_atomic(), irqs_disabled(), is_migration_disabled(current
),
9597 current
->pid
, current
->comm
);
9599 debug_show_held_locks(current
);
9601 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
9603 EXPORT_SYMBOL_GPL(__cant_migrate
);
9607 #ifdef CONFIG_MAGIC_SYSRQ
9608 void normalize_rt_tasks(void)
9610 struct task_struct
*g
, *p
;
9611 struct sched_attr attr
= {
9612 .sched_policy
= SCHED_NORMAL
,
9615 read_lock(&tasklist_lock
);
9616 for_each_process_thread(g
, p
) {
9618 * Only normalize user tasks:
9620 if (p
->flags
& PF_KTHREAD
)
9623 p
->se
.exec_start
= 0;
9624 schedstat_set(p
->se
.statistics
.wait_start
, 0);
9625 schedstat_set(p
->se
.statistics
.sleep_start
, 0);
9626 schedstat_set(p
->se
.statistics
.block_start
, 0);
9628 if (!dl_task(p
) && !rt_task(p
)) {
9630 * Renice negative nice level userspace
9633 if (task_nice(p
) < 0)
9634 set_user_nice(p
, 0);
9638 __sched_setscheduler(p
, &attr
, false, false);
9640 read_unlock(&tasklist_lock
);
9643 #endif /* CONFIG_MAGIC_SYSRQ */
9645 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
9647 * These functions are only useful for the IA64 MCA handling, or kdb.
9649 * They can only be called when the whole system has been
9650 * stopped - every CPU needs to be quiescent, and no scheduling
9651 * activity can take place. Using them for anything else would
9652 * be a serious bug, and as a result, they aren't even visible
9653 * under any other configuration.
9657 * curr_task - return the current task for a given CPU.
9658 * @cpu: the processor in question.
9660 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
9662 * Return: The current task for @cpu.
9664 struct task_struct
*curr_task(int cpu
)
9666 return cpu_curr(cpu
);
9669 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
9673 * ia64_set_curr_task - set the current task for a given CPU.
9674 * @cpu: the processor in question.
9675 * @p: the task pointer to set.
9677 * Description: This function must only be used when non-maskable interrupts
9678 * are serviced on a separate stack. It allows the architecture to switch the
9679 * notion of the current task on a CPU in a non-blocking manner. This function
9680 * must be called with all CPU's synchronized, and interrupts disabled, the
9681 * and caller must save the original value of the current task (see
9682 * curr_task() above) and restore that value before reenabling interrupts and
9683 * re-starting the system.
9685 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
9687 void ia64_set_curr_task(int cpu
, struct task_struct
*p
)
9694 #ifdef CONFIG_CGROUP_SCHED
9695 /* task_group_lock serializes the addition/removal of task groups */
9696 static DEFINE_SPINLOCK(task_group_lock
);
9698 static inline void alloc_uclamp_sched_group(struct task_group
*tg
,
9699 struct task_group
*parent
)
9701 #ifdef CONFIG_UCLAMP_TASK_GROUP
9702 enum uclamp_id clamp_id
;
9704 for_each_clamp_id(clamp_id
) {
9705 uclamp_se_set(&tg
->uclamp_req
[clamp_id
],
9706 uclamp_none(clamp_id
), false);
9707 tg
->uclamp
[clamp_id
] = parent
->uclamp
[clamp_id
];
9712 static void sched_free_group(struct task_group
*tg
)
9714 free_fair_sched_group(tg
);
9715 free_rt_sched_group(tg
);
9717 kmem_cache_free(task_group_cache
, tg
);
9720 static void sched_free_group_rcu(struct rcu_head
*rcu
)
9722 sched_free_group(container_of(rcu
, struct task_group
, rcu
));
9725 static void sched_unregister_group(struct task_group
*tg
)
9727 unregister_fair_sched_group(tg
);
9728 unregister_rt_sched_group(tg
);
9730 * We have to wait for yet another RCU grace period to expire, as
9731 * print_cfs_stats() might run concurrently.
9733 call_rcu(&tg
->rcu
, sched_free_group_rcu
);
9736 /* allocate runqueue etc for a new task group */
9737 struct task_group
*sched_create_group(struct task_group
*parent
)
9739 struct task_group
*tg
;
9741 tg
= kmem_cache_alloc(task_group_cache
, GFP_KERNEL
| __GFP_ZERO
);
9743 return ERR_PTR(-ENOMEM
);
9745 if (!alloc_fair_sched_group(tg
, parent
))
9748 if (!alloc_rt_sched_group(tg
, parent
))
9751 alloc_uclamp_sched_group(tg
, parent
);
9756 sched_free_group(tg
);
9757 return ERR_PTR(-ENOMEM
);
9760 void sched_online_group(struct task_group
*tg
, struct task_group
*parent
)
9762 unsigned long flags
;
9764 spin_lock_irqsave(&task_group_lock
, flags
);
9765 list_add_rcu(&tg
->list
, &task_groups
);
9767 /* Root should already exist: */
9770 tg
->parent
= parent
;
9771 INIT_LIST_HEAD(&tg
->children
);
9772 list_add_rcu(&tg
->siblings
, &parent
->children
);
9773 spin_unlock_irqrestore(&task_group_lock
, flags
);
9775 online_fair_sched_group(tg
);
9778 /* rcu callback to free various structures associated with a task group */
9779 static void sched_unregister_group_rcu(struct rcu_head
*rhp
)
9781 /* Now it should be safe to free those cfs_rqs: */
9782 sched_unregister_group(container_of(rhp
, struct task_group
, rcu
));
9785 void sched_destroy_group(struct task_group
*tg
)
9787 /* Wait for possible concurrent references to cfs_rqs complete: */
9788 call_rcu(&tg
->rcu
, sched_unregister_group_rcu
);
9791 void sched_release_group(struct task_group
*tg
)
9793 unsigned long flags
;
9796 * Unlink first, to avoid walk_tg_tree_from() from finding us (via
9797 * sched_cfs_period_timer()).
9799 * For this to be effective, we have to wait for all pending users of
9800 * this task group to leave their RCU critical section to ensure no new
9801 * user will see our dying task group any more. Specifically ensure
9802 * that tg_unthrottle_up() won't add decayed cfs_rq's to it.
9804 * We therefore defer calling unregister_fair_sched_group() to
9805 * sched_unregister_group() which is guarantied to get called only after the
9806 * current RCU grace period has expired.
9808 spin_lock_irqsave(&task_group_lock
, flags
);
9809 list_del_rcu(&tg
->list
);
9810 list_del_rcu(&tg
->siblings
);
9811 spin_unlock_irqrestore(&task_group_lock
, flags
);
9814 static void sched_change_group(struct task_struct
*tsk
, int type
)
9816 struct task_group
*tg
;
9819 * All callers are synchronized by task_rq_lock(); we do not use RCU
9820 * which is pointless here. Thus, we pass "true" to task_css_check()
9821 * to prevent lockdep warnings.
9823 tg
= container_of(task_css_check(tsk
, cpu_cgrp_id
, true),
9824 struct task_group
, css
);
9825 tg
= autogroup_task_group(tsk
, tg
);
9826 tsk
->sched_task_group
= tg
;
9828 #ifdef CONFIG_FAIR_GROUP_SCHED
9829 if (tsk
->sched_class
->task_change_group
)
9830 tsk
->sched_class
->task_change_group(tsk
, type
);
9833 set_task_rq(tsk
, task_cpu(tsk
));
9837 * Change task's runqueue when it moves between groups.
9839 * The caller of this function should have put the task in its new group by
9840 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
9843 void sched_move_task(struct task_struct
*tsk
)
9845 int queued
, running
, queue_flags
=
9846 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
9850 rq
= task_rq_lock(tsk
, &rf
);
9851 update_rq_clock(rq
);
9853 running
= task_current(rq
, tsk
);
9854 queued
= task_on_rq_queued(tsk
);
9857 dequeue_task(rq
, tsk
, queue_flags
);
9859 put_prev_task(rq
, tsk
);
9861 sched_change_group(tsk
, TASK_MOVE_GROUP
);
9864 enqueue_task(rq
, tsk
, queue_flags
);
9866 set_next_task(rq
, tsk
);
9868 * After changing group, the running task may have joined a
9869 * throttled one but it's still the running task. Trigger a
9870 * resched to make sure that task can still run.
9875 task_rq_unlock(rq
, tsk
, &rf
);
9878 static inline struct task_group
*css_tg(struct cgroup_subsys_state
*css
)
9880 return css
? container_of(css
, struct task_group
, css
) : NULL
;
9883 static struct cgroup_subsys_state
*
9884 cpu_cgroup_css_alloc(struct cgroup_subsys_state
*parent_css
)
9886 struct task_group
*parent
= css_tg(parent_css
);
9887 struct task_group
*tg
;
9890 /* This is early initialization for the top cgroup */
9891 return &root_task_group
.css
;
9894 tg
= sched_create_group(parent
);
9896 return ERR_PTR(-ENOMEM
);
9901 /* Expose task group only after completing cgroup initialization */
9902 static int cpu_cgroup_css_online(struct cgroup_subsys_state
*css
)
9904 struct task_group
*tg
= css_tg(css
);
9905 struct task_group
*parent
= css_tg(css
->parent
);
9908 sched_online_group(tg
, parent
);
9910 #ifdef CONFIG_UCLAMP_TASK_GROUP
9911 /* Propagate the effective uclamp value for the new group */
9912 mutex_lock(&uclamp_mutex
);
9914 cpu_util_update_eff(css
);
9916 mutex_unlock(&uclamp_mutex
);
9922 static void cpu_cgroup_css_released(struct cgroup_subsys_state
*css
)
9924 struct task_group
*tg
= css_tg(css
);
9926 sched_release_group(tg
);
9929 static void cpu_cgroup_css_free(struct cgroup_subsys_state
*css
)
9931 struct task_group
*tg
= css_tg(css
);
9934 * Relies on the RCU grace period between css_released() and this.
9936 sched_unregister_group(tg
);
9940 * This is called before wake_up_new_task(), therefore we really only
9941 * have to set its group bits, all the other stuff does not apply.
9943 static void cpu_cgroup_fork(struct task_struct
*task
)
9948 rq
= task_rq_lock(task
, &rf
);
9950 update_rq_clock(rq
);
9951 sched_change_group(task
, TASK_SET_GROUP
);
9953 task_rq_unlock(rq
, task
, &rf
);
9956 static int cpu_cgroup_can_attach(struct cgroup_taskset
*tset
)
9958 struct task_struct
*task
;
9959 struct cgroup_subsys_state
*css
;
9962 cgroup_taskset_for_each(task
, css
, tset
) {
9963 #ifdef CONFIG_RT_GROUP_SCHED
9964 if (!sched_rt_can_attach(css_tg(css
), task
))
9968 * Serialize against wake_up_new_task() such that if it's
9969 * running, we're sure to observe its full state.
9971 raw_spin_lock_irq(&task
->pi_lock
);
9973 * Avoid calling sched_move_task() before wake_up_new_task()
9974 * has happened. This would lead to problems with PELT, due to
9975 * move wanting to detach+attach while we're not attached yet.
9977 if (READ_ONCE(task
->__state
) == TASK_NEW
)
9979 raw_spin_unlock_irq(&task
->pi_lock
);
9987 static void cpu_cgroup_attach(struct cgroup_taskset
*tset
)
9989 struct task_struct
*task
;
9990 struct cgroup_subsys_state
*css
;
9992 cgroup_taskset_for_each(task
, css
, tset
)
9993 sched_move_task(task
);
9996 #ifdef CONFIG_UCLAMP_TASK_GROUP
9997 static void cpu_util_update_eff(struct cgroup_subsys_state
*css
)
9999 struct cgroup_subsys_state
*top_css
= css
;
10000 struct uclamp_se
*uc_parent
= NULL
;
10001 struct uclamp_se
*uc_se
= NULL
;
10002 unsigned int eff
[UCLAMP_CNT
];
10003 enum uclamp_id clamp_id
;
10004 unsigned int clamps
;
10006 lockdep_assert_held(&uclamp_mutex
);
10007 SCHED_WARN_ON(!rcu_read_lock_held());
10009 css_for_each_descendant_pre(css
, top_css
) {
10010 uc_parent
= css_tg(css
)->parent
10011 ? css_tg(css
)->parent
->uclamp
: NULL
;
10013 for_each_clamp_id(clamp_id
) {
10014 /* Assume effective clamps matches requested clamps */
10015 eff
[clamp_id
] = css_tg(css
)->uclamp_req
[clamp_id
].value
;
10016 /* Cap effective clamps with parent's effective clamps */
10018 eff
[clamp_id
] > uc_parent
[clamp_id
].value
) {
10019 eff
[clamp_id
] = uc_parent
[clamp_id
].value
;
10022 /* Ensure protection is always capped by limit */
10023 eff
[UCLAMP_MIN
] = min(eff
[UCLAMP_MIN
], eff
[UCLAMP_MAX
]);
10025 /* Propagate most restrictive effective clamps */
10027 uc_se
= css_tg(css
)->uclamp
;
10028 for_each_clamp_id(clamp_id
) {
10029 if (eff
[clamp_id
] == uc_se
[clamp_id
].value
)
10031 uc_se
[clamp_id
].value
= eff
[clamp_id
];
10032 uc_se
[clamp_id
].bucket_id
= uclamp_bucket_id(eff
[clamp_id
]);
10033 clamps
|= (0x1 << clamp_id
);
10036 css
= css_rightmost_descendant(css
);
10040 /* Immediately update descendants RUNNABLE tasks */
10041 uclamp_update_active_tasks(css
);
10046 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
10047 * C expression. Since there is no way to convert a macro argument (N) into a
10048 * character constant, use two levels of macros.
10050 #define _POW10(exp) ((unsigned int)1e##exp)
10051 #define POW10(exp) _POW10(exp)
10053 struct uclamp_request
{
10054 #define UCLAMP_PERCENT_SHIFT 2
10055 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
10061 static inline struct uclamp_request
10062 capacity_from_percent(char *buf
)
10064 struct uclamp_request req
= {
10065 .percent
= UCLAMP_PERCENT_SCALE
,
10066 .util
= SCHED_CAPACITY_SCALE
,
10071 if (strcmp(buf
, "max")) {
10072 req
.ret
= cgroup_parse_float(buf
, UCLAMP_PERCENT_SHIFT
,
10076 if ((u64
)req
.percent
> UCLAMP_PERCENT_SCALE
) {
10081 req
.util
= req
.percent
<< SCHED_CAPACITY_SHIFT
;
10082 req
.util
= DIV_ROUND_CLOSEST_ULL(req
.util
, UCLAMP_PERCENT_SCALE
);
10088 static ssize_t
cpu_uclamp_write(struct kernfs_open_file
*of
, char *buf
,
10089 size_t nbytes
, loff_t off
,
10090 enum uclamp_id clamp_id
)
10092 struct uclamp_request req
;
10093 struct task_group
*tg
;
10095 req
= capacity_from_percent(buf
);
10099 static_branch_enable(&sched_uclamp_used
);
10101 mutex_lock(&uclamp_mutex
);
10104 tg
= css_tg(of_css(of
));
10105 if (tg
->uclamp_req
[clamp_id
].value
!= req
.util
)
10106 uclamp_se_set(&tg
->uclamp_req
[clamp_id
], req
.util
, false);
10109 * Because of not recoverable conversion rounding we keep track of the
10110 * exact requested value
10112 tg
->uclamp_pct
[clamp_id
] = req
.percent
;
10114 /* Update effective clamps to track the most restrictive value */
10115 cpu_util_update_eff(of_css(of
));
10118 mutex_unlock(&uclamp_mutex
);
10123 static ssize_t
cpu_uclamp_min_write(struct kernfs_open_file
*of
,
10124 char *buf
, size_t nbytes
,
10127 return cpu_uclamp_write(of
, buf
, nbytes
, off
, UCLAMP_MIN
);
10130 static ssize_t
cpu_uclamp_max_write(struct kernfs_open_file
*of
,
10131 char *buf
, size_t nbytes
,
10134 return cpu_uclamp_write(of
, buf
, nbytes
, off
, UCLAMP_MAX
);
10137 static inline void cpu_uclamp_print(struct seq_file
*sf
,
10138 enum uclamp_id clamp_id
)
10140 struct task_group
*tg
;
10146 tg
= css_tg(seq_css(sf
));
10147 util_clamp
= tg
->uclamp_req
[clamp_id
].value
;
10150 if (util_clamp
== SCHED_CAPACITY_SCALE
) {
10151 seq_puts(sf
, "max\n");
10155 percent
= tg
->uclamp_pct
[clamp_id
];
10156 percent
= div_u64_rem(percent
, POW10(UCLAMP_PERCENT_SHIFT
), &rem
);
10157 seq_printf(sf
, "%llu.%0*u\n", percent
, UCLAMP_PERCENT_SHIFT
, rem
);
10160 static int cpu_uclamp_min_show(struct seq_file
*sf
, void *v
)
10162 cpu_uclamp_print(sf
, UCLAMP_MIN
);
10166 static int cpu_uclamp_max_show(struct seq_file
*sf
, void *v
)
10168 cpu_uclamp_print(sf
, UCLAMP_MAX
);
10171 #endif /* CONFIG_UCLAMP_TASK_GROUP */
10173 #ifdef CONFIG_FAIR_GROUP_SCHED
10174 static int cpu_shares_write_u64(struct cgroup_subsys_state
*css
,
10175 struct cftype
*cftype
, u64 shareval
)
10177 if (shareval
> scale_load_down(ULONG_MAX
))
10178 shareval
= MAX_SHARES
;
10179 return sched_group_set_shares(css_tg(css
), scale_load(shareval
));
10182 static u64
cpu_shares_read_u64(struct cgroup_subsys_state
*css
,
10183 struct cftype
*cft
)
10185 struct task_group
*tg
= css_tg(css
);
10187 return (u64
) scale_load_down(tg
->shares
);
10190 #ifdef CONFIG_CFS_BANDWIDTH
10191 static DEFINE_MUTEX(cfs_constraints_mutex
);
10193 const u64 max_cfs_quota_period
= 1 * NSEC_PER_SEC
; /* 1s */
10194 static const u64 min_cfs_quota_period
= 1 * NSEC_PER_MSEC
; /* 1ms */
10195 /* More than 203 days if BW_SHIFT equals 20. */
10196 static const u64 max_cfs_runtime
= MAX_BW
* NSEC_PER_USEC
;
10198 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 runtime
);
10200 static int tg_set_cfs_bandwidth(struct task_group
*tg
, u64 period
, u64 quota
,
10203 int i
, ret
= 0, runtime_enabled
, runtime_was_enabled
;
10204 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
10206 if (tg
== &root_task_group
)
10210 * Ensure we have at some amount of bandwidth every period. This is
10211 * to prevent reaching a state of large arrears when throttled via
10212 * entity_tick() resulting in prolonged exit starvation.
10214 if (quota
< min_cfs_quota_period
|| period
< min_cfs_quota_period
)
10218 * Likewise, bound things on the other side by preventing insane quota
10219 * periods. This also allows us to normalize in computing quota
10222 if (period
> max_cfs_quota_period
)
10226 * Bound quota to defend quota against overflow during bandwidth shift.
10228 if (quota
!= RUNTIME_INF
&& quota
> max_cfs_runtime
)
10231 if (quota
!= RUNTIME_INF
&& (burst
> quota
||
10232 burst
+ quota
> max_cfs_runtime
))
10236 * Prevent race between setting of cfs_rq->runtime_enabled and
10237 * unthrottle_offline_cfs_rqs().
10240 mutex_lock(&cfs_constraints_mutex
);
10241 ret
= __cfs_schedulable(tg
, period
, quota
);
10245 runtime_enabled
= quota
!= RUNTIME_INF
;
10246 runtime_was_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
10248 * If we need to toggle cfs_bandwidth_used, off->on must occur
10249 * before making related changes, and on->off must occur afterwards
10251 if (runtime_enabled
&& !runtime_was_enabled
)
10252 cfs_bandwidth_usage_inc();
10253 raw_spin_lock_irq(&cfs_b
->lock
);
10254 cfs_b
->period
= ns_to_ktime(period
);
10255 cfs_b
->quota
= quota
;
10256 cfs_b
->burst
= burst
;
10258 __refill_cfs_bandwidth_runtime(cfs_b
);
10260 /* Restart the period timer (if active) to handle new period expiry: */
10261 if (runtime_enabled
)
10262 start_cfs_bandwidth(cfs_b
);
10264 raw_spin_unlock_irq(&cfs_b
->lock
);
10266 for_each_online_cpu(i
) {
10267 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[i
];
10268 struct rq
*rq
= cfs_rq
->rq
;
10269 struct rq_flags rf
;
10271 rq_lock_irq(rq
, &rf
);
10272 cfs_rq
->runtime_enabled
= runtime_enabled
;
10273 cfs_rq
->runtime_remaining
= 0;
10275 if (cfs_rq
->throttled
)
10276 unthrottle_cfs_rq(cfs_rq
);
10277 rq_unlock_irq(rq
, &rf
);
10279 if (runtime_was_enabled
&& !runtime_enabled
)
10280 cfs_bandwidth_usage_dec();
10282 mutex_unlock(&cfs_constraints_mutex
);
10283 cpus_read_unlock();
10288 static int tg_set_cfs_quota(struct task_group
*tg
, long cfs_quota_us
)
10290 u64 quota
, period
, burst
;
10292 period
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
10293 burst
= tg
->cfs_bandwidth
.burst
;
10294 if (cfs_quota_us
< 0)
10295 quota
= RUNTIME_INF
;
10296 else if ((u64
)cfs_quota_us
<= U64_MAX
/ NSEC_PER_USEC
)
10297 quota
= (u64
)cfs_quota_us
* NSEC_PER_USEC
;
10301 return tg_set_cfs_bandwidth(tg
, period
, quota
, burst
);
10304 static long tg_get_cfs_quota(struct task_group
*tg
)
10308 if (tg
->cfs_bandwidth
.quota
== RUNTIME_INF
)
10311 quota_us
= tg
->cfs_bandwidth
.quota
;
10312 do_div(quota_us
, NSEC_PER_USEC
);
10317 static int tg_set_cfs_period(struct task_group
*tg
, long cfs_period_us
)
10319 u64 quota
, period
, burst
;
10321 if ((u64
)cfs_period_us
> U64_MAX
/ NSEC_PER_USEC
)
10324 period
= (u64
)cfs_period_us
* NSEC_PER_USEC
;
10325 quota
= tg
->cfs_bandwidth
.quota
;
10326 burst
= tg
->cfs_bandwidth
.burst
;
10328 return tg_set_cfs_bandwidth(tg
, period
, quota
, burst
);
10331 static long tg_get_cfs_period(struct task_group
*tg
)
10335 cfs_period_us
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
10336 do_div(cfs_period_us
, NSEC_PER_USEC
);
10338 return cfs_period_us
;
10341 static int tg_set_cfs_burst(struct task_group
*tg
, long cfs_burst_us
)
10343 u64 quota
, period
, burst
;
10345 if ((u64
)cfs_burst_us
> U64_MAX
/ NSEC_PER_USEC
)
10348 burst
= (u64
)cfs_burst_us
* NSEC_PER_USEC
;
10349 period
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
10350 quota
= tg
->cfs_bandwidth
.quota
;
10352 return tg_set_cfs_bandwidth(tg
, period
, quota
, burst
);
10355 static long tg_get_cfs_burst(struct task_group
*tg
)
10359 burst_us
= tg
->cfs_bandwidth
.burst
;
10360 do_div(burst_us
, NSEC_PER_USEC
);
10365 static s64
cpu_cfs_quota_read_s64(struct cgroup_subsys_state
*css
,
10366 struct cftype
*cft
)
10368 return tg_get_cfs_quota(css_tg(css
));
10371 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state
*css
,
10372 struct cftype
*cftype
, s64 cfs_quota_us
)
10374 return tg_set_cfs_quota(css_tg(css
), cfs_quota_us
);
10377 static u64
cpu_cfs_period_read_u64(struct cgroup_subsys_state
*css
,
10378 struct cftype
*cft
)
10380 return tg_get_cfs_period(css_tg(css
));
10383 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state
*css
,
10384 struct cftype
*cftype
, u64 cfs_period_us
)
10386 return tg_set_cfs_period(css_tg(css
), cfs_period_us
);
10389 static u64
cpu_cfs_burst_read_u64(struct cgroup_subsys_state
*css
,
10390 struct cftype
*cft
)
10392 return tg_get_cfs_burst(css_tg(css
));
10395 static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state
*css
,
10396 struct cftype
*cftype
, u64 cfs_burst_us
)
10398 return tg_set_cfs_burst(css_tg(css
), cfs_burst_us
);
10401 struct cfs_schedulable_data
{
10402 struct task_group
*tg
;
10407 * normalize group quota/period to be quota/max_period
10408 * note: units are usecs
10410 static u64
normalize_cfs_quota(struct task_group
*tg
,
10411 struct cfs_schedulable_data
*d
)
10416 period
= d
->period
;
10419 period
= tg_get_cfs_period(tg
);
10420 quota
= tg_get_cfs_quota(tg
);
10423 /* note: these should typically be equivalent */
10424 if (quota
== RUNTIME_INF
|| quota
== -1)
10425 return RUNTIME_INF
;
10427 return to_ratio(period
, quota
);
10430 static int tg_cfs_schedulable_down(struct task_group
*tg
, void *data
)
10432 struct cfs_schedulable_data
*d
= data
;
10433 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
10434 s64 quota
= 0, parent_quota
= -1;
10437 quota
= RUNTIME_INF
;
10439 struct cfs_bandwidth
*parent_b
= &tg
->parent
->cfs_bandwidth
;
10441 quota
= normalize_cfs_quota(tg
, d
);
10442 parent_quota
= parent_b
->hierarchical_quota
;
10445 * Ensure max(child_quota) <= parent_quota. On cgroup2,
10446 * always take the min. On cgroup1, only inherit when no
10449 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys
)) {
10450 quota
= min(quota
, parent_quota
);
10452 if (quota
== RUNTIME_INF
)
10453 quota
= parent_quota
;
10454 else if (parent_quota
!= RUNTIME_INF
&& quota
> parent_quota
)
10458 cfs_b
->hierarchical_quota
= quota
;
10463 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 quota
)
10466 struct cfs_schedulable_data data
= {
10472 if (quota
!= RUNTIME_INF
) {
10473 do_div(data
.period
, NSEC_PER_USEC
);
10474 do_div(data
.quota
, NSEC_PER_USEC
);
10478 ret
= walk_tg_tree(tg_cfs_schedulable_down
, tg_nop
, &data
);
10484 static int cpu_cfs_stat_show(struct seq_file
*sf
, void *v
)
10486 struct task_group
*tg
= css_tg(seq_css(sf
));
10487 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
10489 seq_printf(sf
, "nr_periods %d\n", cfs_b
->nr_periods
);
10490 seq_printf(sf
, "nr_throttled %d\n", cfs_b
->nr_throttled
);
10491 seq_printf(sf
, "throttled_time %llu\n", cfs_b
->throttled_time
);
10493 if (schedstat_enabled() && tg
!= &root_task_group
) {
10497 for_each_possible_cpu(i
)
10498 ws
+= schedstat_val(tg
->se
[i
]->statistics
.wait_sum
);
10500 seq_printf(sf
, "wait_sum %llu\n", ws
);
10505 #endif /* CONFIG_CFS_BANDWIDTH */
10506 #endif /* CONFIG_FAIR_GROUP_SCHED */
10508 #ifdef CONFIG_RT_GROUP_SCHED
10509 static int cpu_rt_runtime_write(struct cgroup_subsys_state
*css
,
10510 struct cftype
*cft
, s64 val
)
10512 return sched_group_set_rt_runtime(css_tg(css
), val
);
10515 static s64
cpu_rt_runtime_read(struct cgroup_subsys_state
*css
,
10516 struct cftype
*cft
)
10518 return sched_group_rt_runtime(css_tg(css
));
10521 static int cpu_rt_period_write_uint(struct cgroup_subsys_state
*css
,
10522 struct cftype
*cftype
, u64 rt_period_us
)
10524 return sched_group_set_rt_period(css_tg(css
), rt_period_us
);
10527 static u64
cpu_rt_period_read_uint(struct cgroup_subsys_state
*css
,
10528 struct cftype
*cft
)
10530 return sched_group_rt_period(css_tg(css
));
10532 #endif /* CONFIG_RT_GROUP_SCHED */
10534 #ifdef CONFIG_FAIR_GROUP_SCHED
10535 static s64
cpu_idle_read_s64(struct cgroup_subsys_state
*css
,
10536 struct cftype
*cft
)
10538 return css_tg(css
)->idle
;
10541 static int cpu_idle_write_s64(struct cgroup_subsys_state
*css
,
10542 struct cftype
*cft
, s64 idle
)
10544 return sched_group_set_idle(css_tg(css
), idle
);
10548 static struct cftype cpu_legacy_files
[] = {
10549 #ifdef CONFIG_FAIR_GROUP_SCHED
10552 .read_u64
= cpu_shares_read_u64
,
10553 .write_u64
= cpu_shares_write_u64
,
10557 .read_s64
= cpu_idle_read_s64
,
10558 .write_s64
= cpu_idle_write_s64
,
10561 #ifdef CONFIG_CFS_BANDWIDTH
10563 .name
= "cfs_quota_us",
10564 .read_s64
= cpu_cfs_quota_read_s64
,
10565 .write_s64
= cpu_cfs_quota_write_s64
,
10568 .name
= "cfs_period_us",
10569 .read_u64
= cpu_cfs_period_read_u64
,
10570 .write_u64
= cpu_cfs_period_write_u64
,
10573 .name
= "cfs_burst_us",
10574 .read_u64
= cpu_cfs_burst_read_u64
,
10575 .write_u64
= cpu_cfs_burst_write_u64
,
10579 .seq_show
= cpu_cfs_stat_show
,
10582 #ifdef CONFIG_RT_GROUP_SCHED
10584 .name
= "rt_runtime_us",
10585 .read_s64
= cpu_rt_runtime_read
,
10586 .write_s64
= cpu_rt_runtime_write
,
10589 .name
= "rt_period_us",
10590 .read_u64
= cpu_rt_period_read_uint
,
10591 .write_u64
= cpu_rt_period_write_uint
,
10594 #ifdef CONFIG_UCLAMP_TASK_GROUP
10596 .name
= "uclamp.min",
10597 .flags
= CFTYPE_NOT_ON_ROOT
,
10598 .seq_show
= cpu_uclamp_min_show
,
10599 .write
= cpu_uclamp_min_write
,
10602 .name
= "uclamp.max",
10603 .flags
= CFTYPE_NOT_ON_ROOT
,
10604 .seq_show
= cpu_uclamp_max_show
,
10605 .write
= cpu_uclamp_max_write
,
10608 { } /* Terminate */
10611 static int cpu_extra_stat_show(struct seq_file
*sf
,
10612 struct cgroup_subsys_state
*css
)
10614 #ifdef CONFIG_CFS_BANDWIDTH
10616 struct task_group
*tg
= css_tg(css
);
10617 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
10618 u64 throttled_usec
;
10620 throttled_usec
= cfs_b
->throttled_time
;
10621 do_div(throttled_usec
, NSEC_PER_USEC
);
10623 seq_printf(sf
, "nr_periods %d\n"
10624 "nr_throttled %d\n"
10625 "throttled_usec %llu\n",
10626 cfs_b
->nr_periods
, cfs_b
->nr_throttled
,
10633 #ifdef CONFIG_FAIR_GROUP_SCHED
10634 static u64
cpu_weight_read_u64(struct cgroup_subsys_state
*css
,
10635 struct cftype
*cft
)
10637 struct task_group
*tg
= css_tg(css
);
10638 u64 weight
= scale_load_down(tg
->shares
);
10640 return DIV_ROUND_CLOSEST_ULL(weight
* CGROUP_WEIGHT_DFL
, 1024);
10643 static int cpu_weight_write_u64(struct cgroup_subsys_state
*css
,
10644 struct cftype
*cft
, u64 weight
)
10647 * cgroup weight knobs should use the common MIN, DFL and MAX
10648 * values which are 1, 100 and 10000 respectively. While it loses
10649 * a bit of range on both ends, it maps pretty well onto the shares
10650 * value used by scheduler and the round-trip conversions preserve
10651 * the original value over the entire range.
10653 if (weight
< CGROUP_WEIGHT_MIN
|| weight
> CGROUP_WEIGHT_MAX
)
10656 weight
= DIV_ROUND_CLOSEST_ULL(weight
* 1024, CGROUP_WEIGHT_DFL
);
10658 return sched_group_set_shares(css_tg(css
), scale_load(weight
));
10661 static s64
cpu_weight_nice_read_s64(struct cgroup_subsys_state
*css
,
10662 struct cftype
*cft
)
10664 unsigned long weight
= scale_load_down(css_tg(css
)->shares
);
10665 int last_delta
= INT_MAX
;
10668 /* find the closest nice value to the current weight */
10669 for (prio
= 0; prio
< ARRAY_SIZE(sched_prio_to_weight
); prio
++) {
10670 delta
= abs(sched_prio_to_weight
[prio
] - weight
);
10671 if (delta
>= last_delta
)
10673 last_delta
= delta
;
10676 return PRIO_TO_NICE(prio
- 1 + MAX_RT_PRIO
);
10679 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state
*css
,
10680 struct cftype
*cft
, s64 nice
)
10682 unsigned long weight
;
10685 if (nice
< MIN_NICE
|| nice
> MAX_NICE
)
10688 idx
= NICE_TO_PRIO(nice
) - MAX_RT_PRIO
;
10689 idx
= array_index_nospec(idx
, 40);
10690 weight
= sched_prio_to_weight
[idx
];
10692 return sched_group_set_shares(css_tg(css
), scale_load(weight
));
10696 static void __maybe_unused
cpu_period_quota_print(struct seq_file
*sf
,
10697 long period
, long quota
)
10700 seq_puts(sf
, "max");
10702 seq_printf(sf
, "%ld", quota
);
10704 seq_printf(sf
, " %ld\n", period
);
10707 /* caller should put the current value in *@periodp before calling */
10708 static int __maybe_unused
cpu_period_quota_parse(char *buf
,
10709 u64
*periodp
, u64
*quotap
)
10711 char tok
[21]; /* U64_MAX */
10713 if (sscanf(buf
, "%20s %llu", tok
, periodp
) < 1)
10716 *periodp
*= NSEC_PER_USEC
;
10718 if (sscanf(tok
, "%llu", quotap
))
10719 *quotap
*= NSEC_PER_USEC
;
10720 else if (!strcmp(tok
, "max"))
10721 *quotap
= RUNTIME_INF
;
10728 #ifdef CONFIG_CFS_BANDWIDTH
10729 static int cpu_max_show(struct seq_file
*sf
, void *v
)
10731 struct task_group
*tg
= css_tg(seq_css(sf
));
10733 cpu_period_quota_print(sf
, tg_get_cfs_period(tg
), tg_get_cfs_quota(tg
));
10737 static ssize_t
cpu_max_write(struct kernfs_open_file
*of
,
10738 char *buf
, size_t nbytes
, loff_t off
)
10740 struct task_group
*tg
= css_tg(of_css(of
));
10741 u64 period
= tg_get_cfs_period(tg
);
10742 u64 burst
= tg_get_cfs_burst(tg
);
10746 ret
= cpu_period_quota_parse(buf
, &period
, "a
);
10748 ret
= tg_set_cfs_bandwidth(tg
, period
, quota
, burst
);
10749 return ret
?: nbytes
;
10753 static struct cftype cpu_files
[] = {
10754 #ifdef CONFIG_FAIR_GROUP_SCHED
10757 .flags
= CFTYPE_NOT_ON_ROOT
,
10758 .read_u64
= cpu_weight_read_u64
,
10759 .write_u64
= cpu_weight_write_u64
,
10762 .name
= "weight.nice",
10763 .flags
= CFTYPE_NOT_ON_ROOT
,
10764 .read_s64
= cpu_weight_nice_read_s64
,
10765 .write_s64
= cpu_weight_nice_write_s64
,
10769 .flags
= CFTYPE_NOT_ON_ROOT
,
10770 .read_s64
= cpu_idle_read_s64
,
10771 .write_s64
= cpu_idle_write_s64
,
10774 #ifdef CONFIG_CFS_BANDWIDTH
10777 .flags
= CFTYPE_NOT_ON_ROOT
,
10778 .seq_show
= cpu_max_show
,
10779 .write
= cpu_max_write
,
10782 .name
= "max.burst",
10783 .flags
= CFTYPE_NOT_ON_ROOT
,
10784 .read_u64
= cpu_cfs_burst_read_u64
,
10785 .write_u64
= cpu_cfs_burst_write_u64
,
10788 #ifdef CONFIG_UCLAMP_TASK_GROUP
10790 .name
= "uclamp.min",
10791 .flags
= CFTYPE_NOT_ON_ROOT
,
10792 .seq_show
= cpu_uclamp_min_show
,
10793 .write
= cpu_uclamp_min_write
,
10796 .name
= "uclamp.max",
10797 .flags
= CFTYPE_NOT_ON_ROOT
,
10798 .seq_show
= cpu_uclamp_max_show
,
10799 .write
= cpu_uclamp_max_write
,
10802 { } /* terminate */
10805 struct cgroup_subsys cpu_cgrp_subsys
= {
10806 .css_alloc
= cpu_cgroup_css_alloc
,
10807 .css_online
= cpu_cgroup_css_online
,
10808 .css_released
= cpu_cgroup_css_released
,
10809 .css_free
= cpu_cgroup_css_free
,
10810 .css_extra_stat_show
= cpu_extra_stat_show
,
10811 .fork
= cpu_cgroup_fork
,
10812 .can_attach
= cpu_cgroup_can_attach
,
10813 .attach
= cpu_cgroup_attach
,
10814 .legacy_cftypes
= cpu_legacy_files
,
10815 .dfl_cftypes
= cpu_files
,
10816 .early_init
= true,
10820 #endif /* CONFIG_CGROUP_SCHED */
10822 void dump_cpu_task(int cpu
)
10824 pr_info("Task dump for CPU %d:\n", cpu
);
10825 sched_show_task(cpu_curr(cpu
));
10829 * Nice levels are multiplicative, with a gentle 10% change for every
10830 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
10831 * nice 1, it will get ~10% less CPU time than another CPU-bound task
10832 * that remained on nice 0.
10834 * The "10% effect" is relative and cumulative: from _any_ nice level,
10835 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
10836 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
10837 * If a task goes up by ~10% and another task goes down by ~10% then
10838 * the relative distance between them is ~25%.)
10840 const int sched_prio_to_weight
[40] = {
10841 /* -20 */ 88761, 71755, 56483, 46273, 36291,
10842 /* -15 */ 29154, 23254, 18705, 14949, 11916,
10843 /* -10 */ 9548, 7620, 6100, 4904, 3906,
10844 /* -5 */ 3121, 2501, 1991, 1586, 1277,
10845 /* 0 */ 1024, 820, 655, 526, 423,
10846 /* 5 */ 335, 272, 215, 172, 137,
10847 /* 10 */ 110, 87, 70, 56, 45,
10848 /* 15 */ 36, 29, 23, 18, 15,
10852 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
10854 * In cases where the weight does not change often, we can use the
10855 * precalculated inverse to speed up arithmetics by turning divisions
10856 * into multiplications:
10858 const u32 sched_prio_to_wmult
[40] = {
10859 /* -20 */ 48388, 59856, 76040, 92818, 118348,
10860 /* -15 */ 147320, 184698, 229616, 287308, 360437,
10861 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
10862 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
10863 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
10864 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
10865 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
10866 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
10869 void call_trace_sched_update_nr_running(struct rq
*rq
, int count
)
10871 trace_sched_update_nr_running_tp(rq
, count
);