4 * Core kernel scheduler code and related syscalls
6 * Copyright (C) 1991-2002 Linus Torvalds
8 #include <linux/sched.h>
9 #include <linux/sched/clock.h>
10 #include <uapi/linux/sched/types.h>
11 #include <linux/sched/loadavg.h>
12 #include <linux/sched/hotplug.h>
13 #include <linux/wait_bit.h>
14 #include <linux/cpuset.h>
15 #include <linux/delayacct.h>
16 #include <linux/init_task.h>
17 #include <linux/context_tracking.h>
18 #include <linux/rcupdate_wait.h>
20 #include <linux/blkdev.h>
21 #include <linux/kprobes.h>
22 #include <linux/mmu_context.h>
23 #include <linux/module.h>
24 #include <linux/nmi.h>
25 #include <linux/prefetch.h>
26 #include <linux/profile.h>
27 #include <linux/security.h>
28 #include <linux/syscalls.h>
30 #include <asm/switch_to.h>
32 #ifdef CONFIG_PARAVIRT
33 #include <asm/paravirt.h>
37 #include "../workqueue_internal.h"
38 #include "../smpboot.h"
40 #define CREATE_TRACE_POINTS
41 #include <trace/events/sched.h>
43 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq
, runqueues
);
46 * Debugging: various feature bits
49 #define SCHED_FEAT(name, enabled) \
50 (1UL << __SCHED_FEAT_##name) * enabled |
52 const_debug
unsigned int sysctl_sched_features
=
59 * Number of tasks to iterate in a single balance run.
60 * Limited because this is done with IRQs disabled.
62 const_debug
unsigned int sysctl_sched_nr_migrate
= 32;
65 * period over which we average the RT time consumption, measured
70 const_debug
unsigned int sysctl_sched_time_avg
= MSEC_PER_SEC
;
73 * period over which we measure -rt task CPU usage in us.
76 unsigned int sysctl_sched_rt_period
= 1000000;
78 __read_mostly
int scheduler_running
;
81 * part of the period that we allow rt tasks to run in us.
84 int sysctl_sched_rt_runtime
= 950000;
86 /* CPUs with isolated domains */
87 cpumask_var_t cpu_isolated_map
;
90 * __task_rq_lock - lock the rq @p resides on.
92 struct rq
*__task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
97 lockdep_assert_held(&p
->pi_lock
);
101 raw_spin_lock(&rq
->lock
);
102 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
106 raw_spin_unlock(&rq
->lock
);
108 while (unlikely(task_on_rq_migrating(p
)))
114 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
116 struct rq
*task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
117 __acquires(p
->pi_lock
)
123 raw_spin_lock_irqsave(&p
->pi_lock
, rf
->flags
);
125 raw_spin_lock(&rq
->lock
);
127 * move_queued_task() task_rq_lock()
130 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
131 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
132 * [S] ->cpu = new_cpu [L] task_rq()
136 * If we observe the old cpu in task_rq_lock, the acquire of
137 * the old rq->lock will fully serialize against the stores.
139 * If we observe the new CPU in task_rq_lock, the acquire will
140 * pair with the WMB to ensure we must then also see migrating.
142 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
146 raw_spin_unlock(&rq
->lock
);
147 raw_spin_unlock_irqrestore(&p
->pi_lock
, rf
->flags
);
149 while (unlikely(task_on_rq_migrating(p
)))
155 * RQ-clock updating methods:
158 static void update_rq_clock_task(struct rq
*rq
, s64 delta
)
161 * In theory, the compile should just see 0 here, and optimize out the call
162 * to sched_rt_avg_update. But I don't trust it...
164 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
165 s64 steal
= 0, irq_delta
= 0;
167 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
168 irq_delta
= irq_time_read(cpu_of(rq
)) - rq
->prev_irq_time
;
171 * Since irq_time is only updated on {soft,}irq_exit, we might run into
172 * this case when a previous update_rq_clock() happened inside a
175 * When this happens, we stop ->clock_task and only update the
176 * prev_irq_time stamp to account for the part that fit, so that a next
177 * update will consume the rest. This ensures ->clock_task is
180 * It does however cause some slight miss-attribution of {soft,}irq
181 * time, a more accurate solution would be to update the irq_time using
182 * the current rq->clock timestamp, except that would require using
185 if (irq_delta
> delta
)
188 rq
->prev_irq_time
+= irq_delta
;
191 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
192 if (static_key_false((¶virt_steal_rq_enabled
))) {
193 steal
= paravirt_steal_clock(cpu_of(rq
));
194 steal
-= rq
->prev_steal_time_rq
;
196 if (unlikely(steal
> delta
))
199 rq
->prev_steal_time_rq
+= steal
;
204 rq
->clock_task
+= delta
;
206 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
207 if ((irq_delta
+ steal
) && sched_feat(NONTASK_CAPACITY
))
208 sched_rt_avg_update(rq
, irq_delta
+ steal
);
212 void update_rq_clock(struct rq
*rq
)
216 lockdep_assert_held(&rq
->lock
);
218 if (rq
->clock_update_flags
& RQCF_ACT_SKIP
)
221 #ifdef CONFIG_SCHED_DEBUG
222 if (sched_feat(WARN_DOUBLE_CLOCK
))
223 SCHED_WARN_ON(rq
->clock_update_flags
& RQCF_UPDATED
);
224 rq
->clock_update_flags
|= RQCF_UPDATED
;
227 delta
= sched_clock_cpu(cpu_of(rq
)) - rq
->clock
;
231 update_rq_clock_task(rq
, delta
);
235 #ifdef CONFIG_SCHED_HRTICK
237 * Use HR-timers to deliver accurate preemption points.
240 static void hrtick_clear(struct rq
*rq
)
242 if (hrtimer_active(&rq
->hrtick_timer
))
243 hrtimer_cancel(&rq
->hrtick_timer
);
247 * High-resolution timer tick.
248 * Runs from hardirq context with interrupts disabled.
250 static enum hrtimer_restart
hrtick(struct hrtimer
*timer
)
252 struct rq
*rq
= container_of(timer
, struct rq
, hrtick_timer
);
255 WARN_ON_ONCE(cpu_of(rq
) != smp_processor_id());
259 rq
->curr
->sched_class
->task_tick(rq
, rq
->curr
, 1);
262 return HRTIMER_NORESTART
;
267 static void __hrtick_restart(struct rq
*rq
)
269 struct hrtimer
*timer
= &rq
->hrtick_timer
;
271 hrtimer_start_expires(timer
, HRTIMER_MODE_ABS_PINNED
);
275 * called from hardirq (IPI) context
277 static void __hrtick_start(void *arg
)
283 __hrtick_restart(rq
);
284 rq
->hrtick_csd_pending
= 0;
289 * Called to set the hrtick timer state.
291 * called with rq->lock held and irqs disabled
293 void hrtick_start(struct rq
*rq
, u64 delay
)
295 struct hrtimer
*timer
= &rq
->hrtick_timer
;
300 * Don't schedule slices shorter than 10000ns, that just
301 * doesn't make sense and can cause timer DoS.
303 delta
= max_t(s64
, delay
, 10000LL);
304 time
= ktime_add_ns(timer
->base
->get_time(), delta
);
306 hrtimer_set_expires(timer
, time
);
308 if (rq
== this_rq()) {
309 __hrtick_restart(rq
);
310 } else if (!rq
->hrtick_csd_pending
) {
311 smp_call_function_single_async(cpu_of(rq
), &rq
->hrtick_csd
);
312 rq
->hrtick_csd_pending
= 1;
318 * Called to set the hrtick timer state.
320 * called with rq->lock held and irqs disabled
322 void hrtick_start(struct rq
*rq
, u64 delay
)
325 * Don't schedule slices shorter than 10000ns, that just
326 * doesn't make sense. Rely on vruntime for fairness.
328 delay
= max_t(u64
, delay
, 10000LL);
329 hrtimer_start(&rq
->hrtick_timer
, ns_to_ktime(delay
),
330 HRTIMER_MODE_REL_PINNED
);
332 #endif /* CONFIG_SMP */
334 static void init_rq_hrtick(struct rq
*rq
)
337 rq
->hrtick_csd_pending
= 0;
339 rq
->hrtick_csd
.flags
= 0;
340 rq
->hrtick_csd
.func
= __hrtick_start
;
341 rq
->hrtick_csd
.info
= rq
;
344 hrtimer_init(&rq
->hrtick_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
345 rq
->hrtick_timer
.function
= hrtick
;
347 #else /* CONFIG_SCHED_HRTICK */
348 static inline void hrtick_clear(struct rq
*rq
)
352 static inline void init_rq_hrtick(struct rq
*rq
)
355 #endif /* CONFIG_SCHED_HRTICK */
358 * cmpxchg based fetch_or, macro so it works for different integer types
360 #define fetch_or(ptr, mask) \
362 typeof(ptr) _ptr = (ptr); \
363 typeof(mask) _mask = (mask); \
364 typeof(*_ptr) _old, _val = *_ptr; \
367 _old = cmpxchg(_ptr, _val, _val | _mask); \
375 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
377 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
378 * this avoids any races wrt polling state changes and thereby avoids
381 static bool set_nr_and_not_polling(struct task_struct
*p
)
383 struct thread_info
*ti
= task_thread_info(p
);
384 return !(fetch_or(&ti
->flags
, _TIF_NEED_RESCHED
) & _TIF_POLLING_NRFLAG
);
388 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
390 * If this returns true, then the idle task promises to call
391 * sched_ttwu_pending() and reschedule soon.
393 static bool set_nr_if_polling(struct task_struct
*p
)
395 struct thread_info
*ti
= task_thread_info(p
);
396 typeof(ti
->flags
) old
, val
= READ_ONCE(ti
->flags
);
399 if (!(val
& _TIF_POLLING_NRFLAG
))
401 if (val
& _TIF_NEED_RESCHED
)
403 old
= cmpxchg(&ti
->flags
, val
, val
| _TIF_NEED_RESCHED
);
412 static bool set_nr_and_not_polling(struct task_struct
*p
)
414 set_tsk_need_resched(p
);
419 static bool set_nr_if_polling(struct task_struct
*p
)
426 void wake_q_add(struct wake_q_head
*head
, struct task_struct
*task
)
428 struct wake_q_node
*node
= &task
->wake_q
;
431 * Atomically grab the task, if ->wake_q is !nil already it means
432 * its already queued (either by us or someone else) and will get the
433 * wakeup due to that.
435 * This cmpxchg() implies a full barrier, which pairs with the write
436 * barrier implied by the wakeup in wake_up_q().
438 if (cmpxchg(&node
->next
, NULL
, WAKE_Q_TAIL
))
441 get_task_struct(task
);
444 * The head is context local, there can be no concurrency.
447 head
->lastp
= &node
->next
;
450 void wake_up_q(struct wake_q_head
*head
)
452 struct wake_q_node
*node
= head
->first
;
454 while (node
!= WAKE_Q_TAIL
) {
455 struct task_struct
*task
;
457 task
= container_of(node
, struct task_struct
, wake_q
);
459 /* Task can safely be re-inserted now: */
461 task
->wake_q
.next
= NULL
;
464 * wake_up_process() implies a wmb() to pair with the queueing
465 * in wake_q_add() so as not to miss wakeups.
467 wake_up_process(task
);
468 put_task_struct(task
);
473 * resched_curr - mark rq's current task 'to be rescheduled now'.
475 * On UP this means the setting of the need_resched flag, on SMP it
476 * might also involve a cross-CPU call to trigger the scheduler on
479 void resched_curr(struct rq
*rq
)
481 struct task_struct
*curr
= rq
->curr
;
484 lockdep_assert_held(&rq
->lock
);
486 if (test_tsk_need_resched(curr
))
491 if (cpu
== smp_processor_id()) {
492 set_tsk_need_resched(curr
);
493 set_preempt_need_resched();
497 if (set_nr_and_not_polling(curr
))
498 smp_send_reschedule(cpu
);
500 trace_sched_wake_idle_without_ipi(cpu
);
503 void resched_cpu(int cpu
)
505 struct rq
*rq
= cpu_rq(cpu
);
508 if (!raw_spin_trylock_irqsave(&rq
->lock
, flags
))
511 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
515 #ifdef CONFIG_NO_HZ_COMMON
517 * In the semi idle case, use the nearest busy CPU for migrating timers
518 * from an idle CPU. This is good for power-savings.
520 * We don't do similar optimization for completely idle system, as
521 * selecting an idle CPU will add more delays to the timers than intended
522 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
524 int get_nohz_timer_target(void)
526 int i
, cpu
= smp_processor_id();
527 struct sched_domain
*sd
;
529 if (!idle_cpu(cpu
) && is_housekeeping_cpu(cpu
))
533 for_each_domain(cpu
, sd
) {
534 for_each_cpu(i
, sched_domain_span(sd
)) {
538 if (!idle_cpu(i
) && is_housekeeping_cpu(i
)) {
545 if (!is_housekeeping_cpu(cpu
))
546 cpu
= housekeeping_any_cpu();
553 * When add_timer_on() enqueues a timer into the timer wheel of an
554 * idle CPU then this timer might expire before the next timer event
555 * which is scheduled to wake up that CPU. In case of a completely
556 * idle system the next event might even be infinite time into the
557 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
558 * leaves the inner idle loop so the newly added timer is taken into
559 * account when the CPU goes back to idle and evaluates the timer
560 * wheel for the next timer event.
562 static void wake_up_idle_cpu(int cpu
)
564 struct rq
*rq
= cpu_rq(cpu
);
566 if (cpu
== smp_processor_id())
569 if (set_nr_and_not_polling(rq
->idle
))
570 smp_send_reschedule(cpu
);
572 trace_sched_wake_idle_without_ipi(cpu
);
575 static bool wake_up_full_nohz_cpu(int cpu
)
578 * We just need the target to call irq_exit() and re-evaluate
579 * the next tick. The nohz full kick at least implies that.
580 * If needed we can still optimize that later with an
583 if (cpu_is_offline(cpu
))
584 return true; /* Don't try to wake offline CPUs. */
585 if (tick_nohz_full_cpu(cpu
)) {
586 if (cpu
!= smp_processor_id() ||
587 tick_nohz_tick_stopped())
588 tick_nohz_full_kick_cpu(cpu
);
596 * Wake up the specified CPU. If the CPU is going offline, it is the
597 * caller's responsibility to deal with the lost wakeup, for example,
598 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
600 void wake_up_nohz_cpu(int cpu
)
602 if (!wake_up_full_nohz_cpu(cpu
))
603 wake_up_idle_cpu(cpu
);
606 static inline bool got_nohz_idle_kick(void)
608 int cpu
= smp_processor_id();
610 if (!test_bit(NOHZ_BALANCE_KICK
, nohz_flags(cpu
)))
613 if (idle_cpu(cpu
) && !need_resched())
617 * We can't run Idle Load Balance on this CPU for this time so we
618 * cancel it and clear NOHZ_BALANCE_KICK
620 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(cpu
));
624 #else /* CONFIG_NO_HZ_COMMON */
626 static inline bool got_nohz_idle_kick(void)
631 #endif /* CONFIG_NO_HZ_COMMON */
633 #ifdef CONFIG_NO_HZ_FULL
634 bool sched_can_stop_tick(struct rq
*rq
)
638 /* Deadline tasks, even if single, need the tick */
639 if (rq
->dl
.dl_nr_running
)
643 * If there are more than one RR tasks, we need the tick to effect the
644 * actual RR behaviour.
646 if (rq
->rt
.rr_nr_running
) {
647 if (rq
->rt
.rr_nr_running
== 1)
654 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
655 * forced preemption between FIFO tasks.
657 fifo_nr_running
= rq
->rt
.rt_nr_running
- rq
->rt
.rr_nr_running
;
662 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
663 * if there's more than one we need the tick for involuntary
666 if (rq
->nr_running
> 1)
671 #endif /* CONFIG_NO_HZ_FULL */
673 void sched_avg_update(struct rq
*rq
)
675 s64 period
= sched_avg_period();
677 while ((s64
)(rq_clock(rq
) - rq
->age_stamp
) > period
) {
679 * Inline assembly required to prevent the compiler
680 * optimising this loop into a divmod call.
681 * See __iter_div_u64_rem() for another example of this.
683 asm("" : "+rm" (rq
->age_stamp
));
684 rq
->age_stamp
+= period
;
689 #endif /* CONFIG_SMP */
691 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
692 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
694 * Iterate task_group tree rooted at *from, calling @down when first entering a
695 * node and @up when leaving it for the final time.
697 * Caller must hold rcu_lock or sufficient equivalent.
699 int walk_tg_tree_from(struct task_group
*from
,
700 tg_visitor down
, tg_visitor up
, void *data
)
702 struct task_group
*parent
, *child
;
708 ret
= (*down
)(parent
, data
);
711 list_for_each_entry_rcu(child
, &parent
->children
, siblings
) {
718 ret
= (*up
)(parent
, data
);
719 if (ret
|| parent
== from
)
723 parent
= parent
->parent
;
730 int tg_nop(struct task_group
*tg
, void *data
)
736 static void set_load_weight(struct task_struct
*p
)
738 int prio
= p
->static_prio
- MAX_RT_PRIO
;
739 struct load_weight
*load
= &p
->se
.load
;
742 * SCHED_IDLE tasks get minimal weight:
744 if (idle_policy(p
->policy
)) {
745 load
->weight
= scale_load(WEIGHT_IDLEPRIO
);
746 load
->inv_weight
= WMULT_IDLEPRIO
;
750 load
->weight
= scale_load(sched_prio_to_weight
[prio
]);
751 load
->inv_weight
= sched_prio_to_wmult
[prio
];
754 static inline void enqueue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
756 if (!(flags
& ENQUEUE_NOCLOCK
))
759 if (!(flags
& ENQUEUE_RESTORE
))
760 sched_info_queued(rq
, p
);
762 p
->sched_class
->enqueue_task(rq
, p
, flags
);
765 static inline void dequeue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
767 if (!(flags
& DEQUEUE_NOCLOCK
))
770 if (!(flags
& DEQUEUE_SAVE
))
771 sched_info_dequeued(rq
, p
);
773 p
->sched_class
->dequeue_task(rq
, p
, flags
);
776 void activate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
778 if (task_contributes_to_load(p
))
779 rq
->nr_uninterruptible
--;
781 enqueue_task(rq
, p
, flags
);
784 void deactivate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
786 if (task_contributes_to_load(p
))
787 rq
->nr_uninterruptible
++;
789 dequeue_task(rq
, p
, flags
);
793 * __normal_prio - return the priority that is based on the static prio
795 static inline int __normal_prio(struct task_struct
*p
)
797 return p
->static_prio
;
801 * Calculate the expected normal priority: i.e. priority
802 * without taking RT-inheritance into account. Might be
803 * boosted by interactivity modifiers. Changes upon fork,
804 * setprio syscalls, and whenever the interactivity
805 * estimator recalculates.
807 static inline int normal_prio(struct task_struct
*p
)
811 if (task_has_dl_policy(p
))
812 prio
= MAX_DL_PRIO
-1;
813 else if (task_has_rt_policy(p
))
814 prio
= MAX_RT_PRIO
-1 - p
->rt_priority
;
816 prio
= __normal_prio(p
);
821 * Calculate the current priority, i.e. the priority
822 * taken into account by the scheduler. This value might
823 * be boosted by RT tasks, or might be boosted by
824 * interactivity modifiers. Will be RT if the task got
825 * RT-boosted. If not then it returns p->normal_prio.
827 static int effective_prio(struct task_struct
*p
)
829 p
->normal_prio
= normal_prio(p
);
831 * If we are RT tasks or we were boosted to RT priority,
832 * keep the priority unchanged. Otherwise, update priority
833 * to the normal priority:
835 if (!rt_prio(p
->prio
))
836 return p
->normal_prio
;
841 * task_curr - is this task currently executing on a CPU?
842 * @p: the task in question.
844 * Return: 1 if the task is currently executing. 0 otherwise.
846 inline int task_curr(const struct task_struct
*p
)
848 return cpu_curr(task_cpu(p
)) == p
;
852 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
853 * use the balance_callback list if you want balancing.
855 * this means any call to check_class_changed() must be followed by a call to
856 * balance_callback().
858 static inline void check_class_changed(struct rq
*rq
, struct task_struct
*p
,
859 const struct sched_class
*prev_class
,
862 if (prev_class
!= p
->sched_class
) {
863 if (prev_class
->switched_from
)
864 prev_class
->switched_from(rq
, p
);
866 p
->sched_class
->switched_to(rq
, p
);
867 } else if (oldprio
!= p
->prio
|| dl_task(p
))
868 p
->sched_class
->prio_changed(rq
, p
, oldprio
);
871 void check_preempt_curr(struct rq
*rq
, struct task_struct
*p
, int flags
)
873 const struct sched_class
*class;
875 if (p
->sched_class
== rq
->curr
->sched_class
) {
876 rq
->curr
->sched_class
->check_preempt_curr(rq
, p
, flags
);
878 for_each_class(class) {
879 if (class == rq
->curr
->sched_class
)
881 if (class == p
->sched_class
) {
889 * A queue event has occurred, and we're going to schedule. In
890 * this case, we can save a useless back to back clock update.
892 if (task_on_rq_queued(rq
->curr
) && test_tsk_need_resched(rq
->curr
))
893 rq_clock_skip_update(rq
, true);
898 * This is how migration works:
900 * 1) we invoke migration_cpu_stop() on the target CPU using
902 * 2) stopper starts to run (implicitly forcing the migrated thread
904 * 3) it checks whether the migrated task is still in the wrong runqueue.
905 * 4) if it's in the wrong runqueue then the migration thread removes
906 * it and puts it into the right queue.
907 * 5) stopper completes and stop_one_cpu() returns and the migration
912 * move_queued_task - move a queued task to new rq.
914 * Returns (locked) new rq. Old rq's lock is released.
916 static struct rq
*move_queued_task(struct rq
*rq
, struct rq_flags
*rf
,
917 struct task_struct
*p
, int new_cpu
)
919 lockdep_assert_held(&rq
->lock
);
921 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
922 dequeue_task(rq
, p
, DEQUEUE_NOCLOCK
);
923 set_task_cpu(p
, new_cpu
);
926 rq
= cpu_rq(new_cpu
);
929 BUG_ON(task_cpu(p
) != new_cpu
);
930 enqueue_task(rq
, p
, 0);
931 p
->on_rq
= TASK_ON_RQ_QUEUED
;
932 check_preempt_curr(rq
, p
, 0);
937 struct migration_arg
{
938 struct task_struct
*task
;
943 * Move (not current) task off this CPU, onto the destination CPU. We're doing
944 * this because either it can't run here any more (set_cpus_allowed()
945 * away from this CPU, or CPU going down), or because we're
946 * attempting to rebalance this task on exec (sched_exec).
948 * So we race with normal scheduler movements, but that's OK, as long
949 * as the task is no longer on this CPU.
951 static struct rq
*__migrate_task(struct rq
*rq
, struct rq_flags
*rf
,
952 struct task_struct
*p
, int dest_cpu
)
954 if (p
->flags
& PF_KTHREAD
) {
955 if (unlikely(!cpu_online(dest_cpu
)))
958 if (unlikely(!cpu_active(dest_cpu
)))
962 /* Affinity changed (again). */
963 if (!cpumask_test_cpu(dest_cpu
, &p
->cpus_allowed
))
967 rq
= move_queued_task(rq
, rf
, p
, dest_cpu
);
973 * migration_cpu_stop - this will be executed by a highprio stopper thread
974 * and performs thread migration by bumping thread off CPU then
975 * 'pushing' onto another runqueue.
977 static int migration_cpu_stop(void *data
)
979 struct migration_arg
*arg
= data
;
980 struct task_struct
*p
= arg
->task
;
981 struct rq
*rq
= this_rq();
985 * The original target CPU might have gone down and we might
986 * be on another CPU but it doesn't matter.
990 * We need to explicitly wake pending tasks before running
991 * __migrate_task() such that we will not miss enforcing cpus_allowed
992 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
994 sched_ttwu_pending();
996 raw_spin_lock(&p
->pi_lock
);
999 * If task_rq(p) != rq, it cannot be migrated here, because we're
1000 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1001 * we're holding p->pi_lock.
1003 if (task_rq(p
) == rq
) {
1004 if (task_on_rq_queued(p
))
1005 rq
= __migrate_task(rq
, &rf
, p
, arg
->dest_cpu
);
1007 p
->wake_cpu
= arg
->dest_cpu
;
1010 raw_spin_unlock(&p
->pi_lock
);
1017 * sched_class::set_cpus_allowed must do the below, but is not required to
1018 * actually call this function.
1020 void set_cpus_allowed_common(struct task_struct
*p
, const struct cpumask
*new_mask
)
1022 cpumask_copy(&p
->cpus_allowed
, new_mask
);
1023 p
->nr_cpus_allowed
= cpumask_weight(new_mask
);
1026 void do_set_cpus_allowed(struct task_struct
*p
, const struct cpumask
*new_mask
)
1028 struct rq
*rq
= task_rq(p
);
1029 bool queued
, running
;
1031 lockdep_assert_held(&p
->pi_lock
);
1033 queued
= task_on_rq_queued(p
);
1034 running
= task_current(rq
, p
);
1038 * Because __kthread_bind() calls this on blocked tasks without
1041 lockdep_assert_held(&rq
->lock
);
1042 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
1045 put_prev_task(rq
, p
);
1047 p
->sched_class
->set_cpus_allowed(p
, new_mask
);
1050 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
1052 set_curr_task(rq
, p
);
1056 * Change a given task's CPU affinity. Migrate the thread to a
1057 * proper CPU and schedule it away if the CPU it's executing on
1058 * is removed from the allowed bitmask.
1060 * NOTE: the caller must have a valid reference to the task, the
1061 * task must not exit() & deallocate itself prematurely. The
1062 * call is not atomic; no spinlocks may be held.
1064 static int __set_cpus_allowed_ptr(struct task_struct
*p
,
1065 const struct cpumask
*new_mask
, bool check
)
1067 const struct cpumask
*cpu_valid_mask
= cpu_active_mask
;
1068 unsigned int dest_cpu
;
1073 rq
= task_rq_lock(p
, &rf
);
1074 update_rq_clock(rq
);
1076 if (p
->flags
& PF_KTHREAD
) {
1078 * Kernel threads are allowed on online && !active CPUs
1080 cpu_valid_mask
= cpu_online_mask
;
1084 * Must re-check here, to close a race against __kthread_bind(),
1085 * sched_setaffinity() is not guaranteed to observe the flag.
1087 if (check
&& (p
->flags
& PF_NO_SETAFFINITY
)) {
1092 if (cpumask_equal(&p
->cpus_allowed
, new_mask
))
1095 if (!cpumask_intersects(new_mask
, cpu_valid_mask
)) {
1100 do_set_cpus_allowed(p
, new_mask
);
1102 if (p
->flags
& PF_KTHREAD
) {
1104 * For kernel threads that do indeed end up on online &&
1105 * !active we want to ensure they are strict per-CPU threads.
1107 WARN_ON(cpumask_intersects(new_mask
, cpu_online_mask
) &&
1108 !cpumask_intersects(new_mask
, cpu_active_mask
) &&
1109 p
->nr_cpus_allowed
!= 1);
1112 /* Can the task run on the task's current CPU? If so, we're done */
1113 if (cpumask_test_cpu(task_cpu(p
), new_mask
))
1116 dest_cpu
= cpumask_any_and(cpu_valid_mask
, new_mask
);
1117 if (task_running(rq
, p
) || p
->state
== TASK_WAKING
) {
1118 struct migration_arg arg
= { p
, dest_cpu
};
1119 /* Need help from migration thread: drop lock and wait. */
1120 task_rq_unlock(rq
, p
, &rf
);
1121 stop_one_cpu(cpu_of(rq
), migration_cpu_stop
, &arg
);
1122 tlb_migrate_finish(p
->mm
);
1124 } else if (task_on_rq_queued(p
)) {
1126 * OK, since we're going to drop the lock immediately
1127 * afterwards anyway.
1129 rq
= move_queued_task(rq
, &rf
, p
, dest_cpu
);
1132 task_rq_unlock(rq
, p
, &rf
);
1137 int set_cpus_allowed_ptr(struct task_struct
*p
, const struct cpumask
*new_mask
)
1139 return __set_cpus_allowed_ptr(p
, new_mask
, false);
1141 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr
);
1143 void set_task_cpu(struct task_struct
*p
, unsigned int new_cpu
)
1145 #ifdef CONFIG_SCHED_DEBUG
1147 * We should never call set_task_cpu() on a blocked task,
1148 * ttwu() will sort out the placement.
1150 WARN_ON_ONCE(p
->state
!= TASK_RUNNING
&& p
->state
!= TASK_WAKING
&&
1154 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1155 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1156 * time relying on p->on_rq.
1158 WARN_ON_ONCE(p
->state
== TASK_RUNNING
&&
1159 p
->sched_class
== &fair_sched_class
&&
1160 (p
->on_rq
&& !task_on_rq_migrating(p
)));
1162 #ifdef CONFIG_LOCKDEP
1164 * The caller should hold either p->pi_lock or rq->lock, when changing
1165 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1167 * sched_move_task() holds both and thus holding either pins the cgroup,
1170 * Furthermore, all task_rq users should acquire both locks, see
1173 WARN_ON_ONCE(debug_locks
&& !(lockdep_is_held(&p
->pi_lock
) ||
1174 lockdep_is_held(&task_rq(p
)->lock
)));
1178 trace_sched_migrate_task(p
, new_cpu
);
1180 if (task_cpu(p
) != new_cpu
) {
1181 if (p
->sched_class
->migrate_task_rq
)
1182 p
->sched_class
->migrate_task_rq(p
);
1183 p
->se
.nr_migrations
++;
1184 perf_event_task_migrate(p
);
1187 __set_task_cpu(p
, new_cpu
);
1190 static void __migrate_swap_task(struct task_struct
*p
, int cpu
)
1192 if (task_on_rq_queued(p
)) {
1193 struct rq
*src_rq
, *dst_rq
;
1194 struct rq_flags srf
, drf
;
1196 src_rq
= task_rq(p
);
1197 dst_rq
= cpu_rq(cpu
);
1199 rq_pin_lock(src_rq
, &srf
);
1200 rq_pin_lock(dst_rq
, &drf
);
1202 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
1203 deactivate_task(src_rq
, p
, 0);
1204 set_task_cpu(p
, cpu
);
1205 activate_task(dst_rq
, p
, 0);
1206 p
->on_rq
= TASK_ON_RQ_QUEUED
;
1207 check_preempt_curr(dst_rq
, p
, 0);
1209 rq_unpin_lock(dst_rq
, &drf
);
1210 rq_unpin_lock(src_rq
, &srf
);
1214 * Task isn't running anymore; make it appear like we migrated
1215 * it before it went to sleep. This means on wakeup we make the
1216 * previous CPU our target instead of where it really is.
1222 struct migration_swap_arg
{
1223 struct task_struct
*src_task
, *dst_task
;
1224 int src_cpu
, dst_cpu
;
1227 static int migrate_swap_stop(void *data
)
1229 struct migration_swap_arg
*arg
= data
;
1230 struct rq
*src_rq
, *dst_rq
;
1233 if (!cpu_active(arg
->src_cpu
) || !cpu_active(arg
->dst_cpu
))
1236 src_rq
= cpu_rq(arg
->src_cpu
);
1237 dst_rq
= cpu_rq(arg
->dst_cpu
);
1239 double_raw_lock(&arg
->src_task
->pi_lock
,
1240 &arg
->dst_task
->pi_lock
);
1241 double_rq_lock(src_rq
, dst_rq
);
1243 if (task_cpu(arg
->dst_task
) != arg
->dst_cpu
)
1246 if (task_cpu(arg
->src_task
) != arg
->src_cpu
)
1249 if (!cpumask_test_cpu(arg
->dst_cpu
, &arg
->src_task
->cpus_allowed
))
1252 if (!cpumask_test_cpu(arg
->src_cpu
, &arg
->dst_task
->cpus_allowed
))
1255 __migrate_swap_task(arg
->src_task
, arg
->dst_cpu
);
1256 __migrate_swap_task(arg
->dst_task
, arg
->src_cpu
);
1261 double_rq_unlock(src_rq
, dst_rq
);
1262 raw_spin_unlock(&arg
->dst_task
->pi_lock
);
1263 raw_spin_unlock(&arg
->src_task
->pi_lock
);
1269 * Cross migrate two tasks
1271 int migrate_swap(struct task_struct
*cur
, struct task_struct
*p
)
1273 struct migration_swap_arg arg
;
1276 arg
= (struct migration_swap_arg
){
1278 .src_cpu
= task_cpu(cur
),
1280 .dst_cpu
= task_cpu(p
),
1283 if (arg
.src_cpu
== arg
.dst_cpu
)
1287 * These three tests are all lockless; this is OK since all of them
1288 * will be re-checked with proper locks held further down the line.
1290 if (!cpu_active(arg
.src_cpu
) || !cpu_active(arg
.dst_cpu
))
1293 if (!cpumask_test_cpu(arg
.dst_cpu
, &arg
.src_task
->cpus_allowed
))
1296 if (!cpumask_test_cpu(arg
.src_cpu
, &arg
.dst_task
->cpus_allowed
))
1299 trace_sched_swap_numa(cur
, arg
.src_cpu
, p
, arg
.dst_cpu
);
1300 ret
= stop_two_cpus(arg
.dst_cpu
, arg
.src_cpu
, migrate_swap_stop
, &arg
);
1307 * wait_task_inactive - wait for a thread to unschedule.
1309 * If @match_state is nonzero, it's the @p->state value just checked and
1310 * not expected to change. If it changes, i.e. @p might have woken up,
1311 * then return zero. When we succeed in waiting for @p to be off its CPU,
1312 * we return a positive number (its total switch count). If a second call
1313 * a short while later returns the same number, the caller can be sure that
1314 * @p has remained unscheduled the whole time.
1316 * The caller must ensure that the task *will* unschedule sometime soon,
1317 * else this function might spin for a *long* time. This function can't
1318 * be called with interrupts off, or it may introduce deadlock with
1319 * smp_call_function() if an IPI is sent by the same process we are
1320 * waiting to become inactive.
1322 unsigned long wait_task_inactive(struct task_struct
*p
, long match_state
)
1324 int running
, queued
;
1331 * We do the initial early heuristics without holding
1332 * any task-queue locks at all. We'll only try to get
1333 * the runqueue lock when things look like they will
1339 * If the task is actively running on another CPU
1340 * still, just relax and busy-wait without holding
1343 * NOTE! Since we don't hold any locks, it's not
1344 * even sure that "rq" stays as the right runqueue!
1345 * But we don't care, since "task_running()" will
1346 * return false if the runqueue has changed and p
1347 * is actually now running somewhere else!
1349 while (task_running(rq
, p
)) {
1350 if (match_state
&& unlikely(p
->state
!= match_state
))
1356 * Ok, time to look more closely! We need the rq
1357 * lock now, to be *sure*. If we're wrong, we'll
1358 * just go back and repeat.
1360 rq
= task_rq_lock(p
, &rf
);
1361 trace_sched_wait_task(p
);
1362 running
= task_running(rq
, p
);
1363 queued
= task_on_rq_queued(p
);
1365 if (!match_state
|| p
->state
== match_state
)
1366 ncsw
= p
->nvcsw
| LONG_MIN
; /* sets MSB */
1367 task_rq_unlock(rq
, p
, &rf
);
1370 * If it changed from the expected state, bail out now.
1372 if (unlikely(!ncsw
))
1376 * Was it really running after all now that we
1377 * checked with the proper locks actually held?
1379 * Oops. Go back and try again..
1381 if (unlikely(running
)) {
1387 * It's not enough that it's not actively running,
1388 * it must be off the runqueue _entirely_, and not
1391 * So if it was still runnable (but just not actively
1392 * running right now), it's preempted, and we should
1393 * yield - it could be a while.
1395 if (unlikely(queued
)) {
1396 ktime_t to
= NSEC_PER_SEC
/ HZ
;
1398 set_current_state(TASK_UNINTERRUPTIBLE
);
1399 schedule_hrtimeout(&to
, HRTIMER_MODE_REL
);
1404 * Ahh, all good. It wasn't running, and it wasn't
1405 * runnable, which means that it will never become
1406 * running in the future either. We're all done!
1415 * kick_process - kick a running thread to enter/exit the kernel
1416 * @p: the to-be-kicked thread
1418 * Cause a process which is running on another CPU to enter
1419 * kernel-mode, without any delay. (to get signals handled.)
1421 * NOTE: this function doesn't have to take the runqueue lock,
1422 * because all it wants to ensure is that the remote task enters
1423 * the kernel. If the IPI races and the task has been migrated
1424 * to another CPU then no harm is done and the purpose has been
1427 void kick_process(struct task_struct
*p
)
1433 if ((cpu
!= smp_processor_id()) && task_curr(p
))
1434 smp_send_reschedule(cpu
);
1437 EXPORT_SYMBOL_GPL(kick_process
);
1440 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1442 * A few notes on cpu_active vs cpu_online:
1444 * - cpu_active must be a subset of cpu_online
1446 * - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
1447 * see __set_cpus_allowed_ptr(). At this point the newly online
1448 * CPU isn't yet part of the sched domains, and balancing will not
1451 * - on CPU-down we clear cpu_active() to mask the sched domains and
1452 * avoid the load balancer to place new tasks on the to be removed
1453 * CPU. Existing tasks will remain running there and will be taken
1456 * This means that fallback selection must not select !active CPUs.
1457 * And can assume that any active CPU must be online. Conversely
1458 * select_task_rq() below may allow selection of !active CPUs in order
1459 * to satisfy the above rules.
1461 static int select_fallback_rq(int cpu
, struct task_struct
*p
)
1463 int nid
= cpu_to_node(cpu
);
1464 const struct cpumask
*nodemask
= NULL
;
1465 enum { cpuset
, possible
, fail
} state
= cpuset
;
1469 * If the node that the CPU is on has been offlined, cpu_to_node()
1470 * will return -1. There is no CPU on the node, and we should
1471 * select the CPU on the other node.
1474 nodemask
= cpumask_of_node(nid
);
1476 /* Look for allowed, online CPU in same node. */
1477 for_each_cpu(dest_cpu
, nodemask
) {
1478 if (!cpu_active(dest_cpu
))
1480 if (cpumask_test_cpu(dest_cpu
, &p
->cpus_allowed
))
1486 /* Any allowed, online CPU? */
1487 for_each_cpu(dest_cpu
, &p
->cpus_allowed
) {
1488 if (!(p
->flags
& PF_KTHREAD
) && !cpu_active(dest_cpu
))
1490 if (!cpu_online(dest_cpu
))
1495 /* No more Mr. Nice Guy. */
1498 if (IS_ENABLED(CONFIG_CPUSETS
)) {
1499 cpuset_cpus_allowed_fallback(p
);
1505 do_set_cpus_allowed(p
, cpu_possible_mask
);
1516 if (state
!= cpuset
) {
1518 * Don't tell them about moving exiting tasks or
1519 * kernel threads (both mm NULL), since they never
1522 if (p
->mm
&& printk_ratelimit()) {
1523 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1524 task_pid_nr(p
), p
->comm
, cpu
);
1532 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1535 int select_task_rq(struct task_struct
*p
, int cpu
, int sd_flags
, int wake_flags
)
1537 lockdep_assert_held(&p
->pi_lock
);
1539 if (p
->nr_cpus_allowed
> 1)
1540 cpu
= p
->sched_class
->select_task_rq(p
, cpu
, sd_flags
, wake_flags
);
1542 cpu
= cpumask_any(&p
->cpus_allowed
);
1545 * In order not to call set_task_cpu() on a blocking task we need
1546 * to rely on ttwu() to place the task on a valid ->cpus_allowed
1549 * Since this is common to all placement strategies, this lives here.
1551 * [ this allows ->select_task() to simply return task_cpu(p) and
1552 * not worry about this generic constraint ]
1554 if (unlikely(!cpumask_test_cpu(cpu
, &p
->cpus_allowed
) ||
1556 cpu
= select_fallback_rq(task_cpu(p
), p
);
1561 static void update_avg(u64
*avg
, u64 sample
)
1563 s64 diff
= sample
- *avg
;
1567 void sched_set_stop_task(int cpu
, struct task_struct
*stop
)
1569 struct sched_param param
= { .sched_priority
= MAX_RT_PRIO
- 1 };
1570 struct task_struct
*old_stop
= cpu_rq(cpu
)->stop
;
1574 * Make it appear like a SCHED_FIFO task, its something
1575 * userspace knows about and won't get confused about.
1577 * Also, it will make PI more or less work without too
1578 * much confusion -- but then, stop work should not
1579 * rely on PI working anyway.
1581 sched_setscheduler_nocheck(stop
, SCHED_FIFO
, ¶m
);
1583 stop
->sched_class
= &stop_sched_class
;
1586 cpu_rq(cpu
)->stop
= stop
;
1590 * Reset it back to a normal scheduling class so that
1591 * it can die in pieces.
1593 old_stop
->sched_class
= &rt_sched_class
;
1599 static inline int __set_cpus_allowed_ptr(struct task_struct
*p
,
1600 const struct cpumask
*new_mask
, bool check
)
1602 return set_cpus_allowed_ptr(p
, new_mask
);
1605 #endif /* CONFIG_SMP */
1608 ttwu_stat(struct task_struct
*p
, int cpu
, int wake_flags
)
1612 if (!schedstat_enabled())
1618 if (cpu
== rq
->cpu
) {
1619 schedstat_inc(rq
->ttwu_local
);
1620 schedstat_inc(p
->se
.statistics
.nr_wakeups_local
);
1622 struct sched_domain
*sd
;
1624 schedstat_inc(p
->se
.statistics
.nr_wakeups_remote
);
1626 for_each_domain(rq
->cpu
, sd
) {
1627 if (cpumask_test_cpu(cpu
, sched_domain_span(sd
))) {
1628 schedstat_inc(sd
->ttwu_wake_remote
);
1635 if (wake_flags
& WF_MIGRATED
)
1636 schedstat_inc(p
->se
.statistics
.nr_wakeups_migrate
);
1637 #endif /* CONFIG_SMP */
1639 schedstat_inc(rq
->ttwu_count
);
1640 schedstat_inc(p
->se
.statistics
.nr_wakeups
);
1642 if (wake_flags
& WF_SYNC
)
1643 schedstat_inc(p
->se
.statistics
.nr_wakeups_sync
);
1646 static inline void ttwu_activate(struct rq
*rq
, struct task_struct
*p
, int en_flags
)
1648 activate_task(rq
, p
, en_flags
);
1649 p
->on_rq
= TASK_ON_RQ_QUEUED
;
1651 /* If a worker is waking up, notify the workqueue: */
1652 if (p
->flags
& PF_WQ_WORKER
)
1653 wq_worker_waking_up(p
, cpu_of(rq
));
1657 * Mark the task runnable and perform wakeup-preemption.
1659 static void ttwu_do_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
1660 struct rq_flags
*rf
)
1662 check_preempt_curr(rq
, p
, wake_flags
);
1663 p
->state
= TASK_RUNNING
;
1664 trace_sched_wakeup(p
);
1667 if (p
->sched_class
->task_woken
) {
1669 * Our task @p is fully woken up and running; so its safe to
1670 * drop the rq->lock, hereafter rq is only used for statistics.
1672 rq_unpin_lock(rq
, rf
);
1673 p
->sched_class
->task_woken(rq
, p
);
1674 rq_repin_lock(rq
, rf
);
1677 if (rq
->idle_stamp
) {
1678 u64 delta
= rq_clock(rq
) - rq
->idle_stamp
;
1679 u64 max
= 2*rq
->max_idle_balance_cost
;
1681 update_avg(&rq
->avg_idle
, delta
);
1683 if (rq
->avg_idle
> max
)
1692 ttwu_do_activate(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
1693 struct rq_flags
*rf
)
1695 int en_flags
= ENQUEUE_WAKEUP
| ENQUEUE_NOCLOCK
;
1697 lockdep_assert_held(&rq
->lock
);
1700 if (p
->sched_contributes_to_load
)
1701 rq
->nr_uninterruptible
--;
1703 if (wake_flags
& WF_MIGRATED
)
1704 en_flags
|= ENQUEUE_MIGRATED
;
1707 ttwu_activate(rq
, p
, en_flags
);
1708 ttwu_do_wakeup(rq
, p
, wake_flags
, rf
);
1712 * Called in case the task @p isn't fully descheduled from its runqueue,
1713 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1714 * since all we need to do is flip p->state to TASK_RUNNING, since
1715 * the task is still ->on_rq.
1717 static int ttwu_remote(struct task_struct
*p
, int wake_flags
)
1723 rq
= __task_rq_lock(p
, &rf
);
1724 if (task_on_rq_queued(p
)) {
1725 /* check_preempt_curr() may use rq clock */
1726 update_rq_clock(rq
);
1727 ttwu_do_wakeup(rq
, p
, wake_flags
, &rf
);
1730 __task_rq_unlock(rq
, &rf
);
1736 void sched_ttwu_pending(void)
1738 struct rq
*rq
= this_rq();
1739 struct llist_node
*llist
= llist_del_all(&rq
->wake_list
);
1740 struct task_struct
*p
, *t
;
1746 rq_lock_irqsave(rq
, &rf
);
1747 update_rq_clock(rq
);
1749 llist_for_each_entry_safe(p
, t
, llist
, wake_entry
)
1750 ttwu_do_activate(rq
, p
, p
->sched_remote_wakeup
? WF_MIGRATED
: 0, &rf
);
1752 rq_unlock_irqrestore(rq
, &rf
);
1755 void scheduler_ipi(void)
1758 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1759 * TIF_NEED_RESCHED remotely (for the first time) will also send
1762 preempt_fold_need_resched();
1764 if (llist_empty(&this_rq()->wake_list
) && !got_nohz_idle_kick())
1768 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1769 * traditionally all their work was done from the interrupt return
1770 * path. Now that we actually do some work, we need to make sure
1773 * Some archs already do call them, luckily irq_enter/exit nest
1776 * Arguably we should visit all archs and update all handlers,
1777 * however a fair share of IPIs are still resched only so this would
1778 * somewhat pessimize the simple resched case.
1781 sched_ttwu_pending();
1784 * Check if someone kicked us for doing the nohz idle load balance.
1786 if (unlikely(got_nohz_idle_kick())) {
1787 this_rq()->idle_balance
= 1;
1788 raise_softirq_irqoff(SCHED_SOFTIRQ
);
1793 static void ttwu_queue_remote(struct task_struct
*p
, int cpu
, int wake_flags
)
1795 struct rq
*rq
= cpu_rq(cpu
);
1797 p
->sched_remote_wakeup
= !!(wake_flags
& WF_MIGRATED
);
1799 if (llist_add(&p
->wake_entry
, &cpu_rq(cpu
)->wake_list
)) {
1800 if (!set_nr_if_polling(rq
->idle
))
1801 smp_send_reschedule(cpu
);
1803 trace_sched_wake_idle_without_ipi(cpu
);
1807 void wake_up_if_idle(int cpu
)
1809 struct rq
*rq
= cpu_rq(cpu
);
1814 if (!is_idle_task(rcu_dereference(rq
->curr
)))
1817 if (set_nr_if_polling(rq
->idle
)) {
1818 trace_sched_wake_idle_without_ipi(cpu
);
1820 rq_lock_irqsave(rq
, &rf
);
1821 if (is_idle_task(rq
->curr
))
1822 smp_send_reschedule(cpu
);
1823 /* Else CPU is not idle, do nothing here: */
1824 rq_unlock_irqrestore(rq
, &rf
);
1831 bool cpus_share_cache(int this_cpu
, int that_cpu
)
1833 return per_cpu(sd_llc_id
, this_cpu
) == per_cpu(sd_llc_id
, that_cpu
);
1835 #endif /* CONFIG_SMP */
1837 static void ttwu_queue(struct task_struct
*p
, int cpu
, int wake_flags
)
1839 struct rq
*rq
= cpu_rq(cpu
);
1842 #if defined(CONFIG_SMP)
1843 if (sched_feat(TTWU_QUEUE
) && !cpus_share_cache(smp_processor_id(), cpu
)) {
1844 sched_clock_cpu(cpu
); /* Sync clocks across CPUs */
1845 ttwu_queue_remote(p
, cpu
, wake_flags
);
1851 update_rq_clock(rq
);
1852 ttwu_do_activate(rq
, p
, wake_flags
, &rf
);
1857 * Notes on Program-Order guarantees on SMP systems.
1861 * The basic program-order guarantee on SMP systems is that when a task [t]
1862 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
1863 * execution on its new CPU [c1].
1865 * For migration (of runnable tasks) this is provided by the following means:
1867 * A) UNLOCK of the rq(c0)->lock scheduling out task t
1868 * B) migration for t is required to synchronize *both* rq(c0)->lock and
1869 * rq(c1)->lock (if not at the same time, then in that order).
1870 * C) LOCK of the rq(c1)->lock scheduling in task
1872 * Transitivity guarantees that B happens after A and C after B.
1873 * Note: we only require RCpc transitivity.
1874 * Note: the CPU doing B need not be c0 or c1
1883 * UNLOCK rq(0)->lock
1885 * LOCK rq(0)->lock // orders against CPU0
1887 * UNLOCK rq(0)->lock
1891 * UNLOCK rq(1)->lock
1893 * LOCK rq(1)->lock // orders against CPU2
1896 * UNLOCK rq(1)->lock
1899 * BLOCKING -- aka. SLEEP + WAKEUP
1901 * For blocking we (obviously) need to provide the same guarantee as for
1902 * migration. However the means are completely different as there is no lock
1903 * chain to provide order. Instead we do:
1905 * 1) smp_store_release(X->on_cpu, 0)
1906 * 2) smp_cond_load_acquire(!X->on_cpu)
1910 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
1912 * LOCK rq(0)->lock LOCK X->pi_lock
1915 * smp_store_release(X->on_cpu, 0);
1917 * smp_cond_load_acquire(&X->on_cpu, !VAL);
1923 * X->state = RUNNING
1924 * UNLOCK rq(2)->lock
1926 * LOCK rq(2)->lock // orders against CPU1
1929 * UNLOCK rq(2)->lock
1932 * UNLOCK rq(0)->lock
1935 * However; for wakeups there is a second guarantee we must provide, namely we
1936 * must observe the state that lead to our wakeup. That is, not only must our
1937 * task observe its own prior state, it must also observe the stores prior to
1940 * This means that any means of doing remote wakeups must order the CPU doing
1941 * the wakeup against the CPU the task is going to end up running on. This,
1942 * however, is already required for the regular Program-Order guarantee above,
1943 * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1948 * try_to_wake_up - wake up a thread
1949 * @p: the thread to be awakened
1950 * @state: the mask of task states that can be woken
1951 * @wake_flags: wake modifier flags (WF_*)
1953 * If (@state & @p->state) @p->state = TASK_RUNNING.
1955 * If the task was not queued/runnable, also place it back on a runqueue.
1957 * Atomic against schedule() which would dequeue a task, also see
1958 * set_current_state().
1960 * Return: %true if @p->state changes (an actual wakeup was done),
1964 try_to_wake_up(struct task_struct
*p
, unsigned int state
, int wake_flags
)
1966 unsigned long flags
;
1967 int cpu
, success
= 0;
1970 * If we are going to wake up a thread waiting for CONDITION we
1971 * need to ensure that CONDITION=1 done by the caller can not be
1972 * reordered with p->state check below. This pairs with mb() in
1973 * set_current_state() the waiting thread does.
1975 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
1976 smp_mb__after_spinlock();
1977 if (!(p
->state
& state
))
1980 trace_sched_waking(p
);
1982 /* We're going to change ->state: */
1987 * Ensure we load p->on_rq _after_ p->state, otherwise it would
1988 * be possible to, falsely, observe p->on_rq == 0 and get stuck
1989 * in smp_cond_load_acquire() below.
1991 * sched_ttwu_pending() try_to_wake_up()
1992 * [S] p->on_rq = 1; [L] P->state
1993 * UNLOCK rq->lock -----.
1997 * LOCK rq->lock -----'
2001 * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq
2003 * Pairs with the UNLOCK+LOCK on rq->lock from the
2004 * last wakeup of our task and the schedule that got our task
2008 if (p
->on_rq
&& ttwu_remote(p
, wake_flags
))
2013 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2014 * possible to, falsely, observe p->on_cpu == 0.
2016 * One must be running (->on_cpu == 1) in order to remove oneself
2017 * from the runqueue.
2019 * [S] ->on_cpu = 1; [L] ->on_rq
2023 * [S] ->on_rq = 0; [L] ->on_cpu
2025 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2026 * from the consecutive calls to schedule(); the first switching to our
2027 * task, the second putting it to sleep.
2032 * If the owning (remote) CPU is still in the middle of schedule() with
2033 * this task as prev, wait until its done referencing the task.
2035 * Pairs with the smp_store_release() in finish_lock_switch().
2037 * This ensures that tasks getting woken will be fully ordered against
2038 * their previous state and preserve Program Order.
2040 smp_cond_load_acquire(&p
->on_cpu
, !VAL
);
2042 p
->sched_contributes_to_load
= !!task_contributes_to_load(p
);
2043 p
->state
= TASK_WAKING
;
2046 delayacct_blkio_end();
2047 atomic_dec(&task_rq(p
)->nr_iowait
);
2050 cpu
= select_task_rq(p
, p
->wake_cpu
, SD_BALANCE_WAKE
, wake_flags
);
2051 if (task_cpu(p
) != cpu
) {
2052 wake_flags
|= WF_MIGRATED
;
2053 set_task_cpu(p
, cpu
);
2056 #else /* CONFIG_SMP */
2059 delayacct_blkio_end();
2060 atomic_dec(&task_rq(p
)->nr_iowait
);
2063 #endif /* CONFIG_SMP */
2065 ttwu_queue(p
, cpu
, wake_flags
);
2067 ttwu_stat(p
, cpu
, wake_flags
);
2069 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2075 * try_to_wake_up_local - try to wake up a local task with rq lock held
2076 * @p: the thread to be awakened
2077 * @rf: request-queue flags for pinning
2079 * Put @p on the run-queue if it's not already there. The caller must
2080 * ensure that this_rq() is locked, @p is bound to this_rq() and not
2083 static void try_to_wake_up_local(struct task_struct
*p
, struct rq_flags
*rf
)
2085 struct rq
*rq
= task_rq(p
);
2087 if (WARN_ON_ONCE(rq
!= this_rq()) ||
2088 WARN_ON_ONCE(p
== current
))
2091 lockdep_assert_held(&rq
->lock
);
2093 if (!raw_spin_trylock(&p
->pi_lock
)) {
2095 * This is OK, because current is on_cpu, which avoids it being
2096 * picked for load-balance and preemption/IRQs are still
2097 * disabled avoiding further scheduler activity on it and we've
2098 * not yet picked a replacement task.
2101 raw_spin_lock(&p
->pi_lock
);
2105 if (!(p
->state
& TASK_NORMAL
))
2108 trace_sched_waking(p
);
2110 if (!task_on_rq_queued(p
)) {
2112 delayacct_blkio_end();
2113 atomic_dec(&rq
->nr_iowait
);
2115 ttwu_activate(rq
, p
, ENQUEUE_WAKEUP
| ENQUEUE_NOCLOCK
);
2118 ttwu_do_wakeup(rq
, p
, 0, rf
);
2119 ttwu_stat(p
, smp_processor_id(), 0);
2121 raw_spin_unlock(&p
->pi_lock
);
2125 * wake_up_process - Wake up a specific process
2126 * @p: The process to be woken up.
2128 * Attempt to wake up the nominated process and move it to the set of runnable
2131 * Return: 1 if the process was woken up, 0 if it was already running.
2133 * It may be assumed that this function implies a write memory barrier before
2134 * changing the task state if and only if any tasks are woken up.
2136 int wake_up_process(struct task_struct
*p
)
2138 return try_to_wake_up(p
, TASK_NORMAL
, 0);
2140 EXPORT_SYMBOL(wake_up_process
);
2142 int wake_up_state(struct task_struct
*p
, unsigned int state
)
2144 return try_to_wake_up(p
, state
, 0);
2148 * Perform scheduler related setup for a newly forked process p.
2149 * p is forked by current.
2151 * __sched_fork() is basic setup used by init_idle() too:
2153 static void __sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
2158 p
->se
.exec_start
= 0;
2159 p
->se
.sum_exec_runtime
= 0;
2160 p
->se
.prev_sum_exec_runtime
= 0;
2161 p
->se
.nr_migrations
= 0;
2163 INIT_LIST_HEAD(&p
->se
.group_node
);
2165 #ifdef CONFIG_FAIR_GROUP_SCHED
2166 p
->se
.cfs_rq
= NULL
;
2169 #ifdef CONFIG_SCHEDSTATS
2170 /* Even if schedstat is disabled, there should not be garbage */
2171 memset(&p
->se
.statistics
, 0, sizeof(p
->se
.statistics
));
2174 RB_CLEAR_NODE(&p
->dl
.rb_node
);
2175 init_dl_task_timer(&p
->dl
);
2176 init_dl_inactive_task_timer(&p
->dl
);
2177 __dl_clear_params(p
);
2179 INIT_LIST_HEAD(&p
->rt
.run_list
);
2181 p
->rt
.time_slice
= sched_rr_timeslice
;
2185 #ifdef CONFIG_PREEMPT_NOTIFIERS
2186 INIT_HLIST_HEAD(&p
->preempt_notifiers
);
2189 #ifdef CONFIG_NUMA_BALANCING
2190 if (p
->mm
&& atomic_read(&p
->mm
->mm_users
) == 1) {
2191 p
->mm
->numa_next_scan
= jiffies
+ msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2192 p
->mm
->numa_scan_seq
= 0;
2195 if (clone_flags
& CLONE_VM
)
2196 p
->numa_preferred_nid
= current
->numa_preferred_nid
;
2198 p
->numa_preferred_nid
= -1;
2200 p
->node_stamp
= 0ULL;
2201 p
->numa_scan_seq
= p
->mm
? p
->mm
->numa_scan_seq
: 0;
2202 p
->numa_scan_period
= sysctl_numa_balancing_scan_delay
;
2203 p
->numa_work
.next
= &p
->numa_work
;
2204 p
->numa_faults
= NULL
;
2205 p
->last_task_numa_placement
= 0;
2206 p
->last_sum_exec_runtime
= 0;
2208 p
->numa_group
= NULL
;
2209 #endif /* CONFIG_NUMA_BALANCING */
2212 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing
);
2214 #ifdef CONFIG_NUMA_BALANCING
2216 void set_numabalancing_state(bool enabled
)
2219 static_branch_enable(&sched_numa_balancing
);
2221 static_branch_disable(&sched_numa_balancing
);
2224 #ifdef CONFIG_PROC_SYSCTL
2225 int sysctl_numa_balancing(struct ctl_table
*table
, int write
,
2226 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2230 int state
= static_branch_likely(&sched_numa_balancing
);
2232 if (write
&& !capable(CAP_SYS_ADMIN
))
2237 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2241 set_numabalancing_state(state
);
2247 #ifdef CONFIG_SCHEDSTATS
2249 DEFINE_STATIC_KEY_FALSE(sched_schedstats
);
2250 static bool __initdata __sched_schedstats
= false;
2252 static void set_schedstats(bool enabled
)
2255 static_branch_enable(&sched_schedstats
);
2257 static_branch_disable(&sched_schedstats
);
2260 void force_schedstat_enabled(void)
2262 if (!schedstat_enabled()) {
2263 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2264 static_branch_enable(&sched_schedstats
);
2268 static int __init
setup_schedstats(char *str
)
2275 * This code is called before jump labels have been set up, so we can't
2276 * change the static branch directly just yet. Instead set a temporary
2277 * variable so init_schedstats() can do it later.
2279 if (!strcmp(str
, "enable")) {
2280 __sched_schedstats
= true;
2282 } else if (!strcmp(str
, "disable")) {
2283 __sched_schedstats
= false;
2288 pr_warn("Unable to parse schedstats=\n");
2292 __setup("schedstats=", setup_schedstats
);
2294 static void __init
init_schedstats(void)
2296 set_schedstats(__sched_schedstats
);
2299 #ifdef CONFIG_PROC_SYSCTL
2300 int sysctl_schedstats(struct ctl_table
*table
, int write
,
2301 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2305 int state
= static_branch_likely(&sched_schedstats
);
2307 if (write
&& !capable(CAP_SYS_ADMIN
))
2312 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2316 set_schedstats(state
);
2319 #endif /* CONFIG_PROC_SYSCTL */
2320 #else /* !CONFIG_SCHEDSTATS */
2321 static inline void init_schedstats(void) {}
2322 #endif /* CONFIG_SCHEDSTATS */
2325 * fork()/clone()-time setup:
2327 int sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
2329 unsigned long flags
;
2330 int cpu
= get_cpu();
2332 __sched_fork(clone_flags
, p
);
2334 * We mark the process as NEW here. This guarantees that
2335 * nobody will actually run it, and a signal or other external
2336 * event cannot wake it up and insert it on the runqueue either.
2338 p
->state
= TASK_NEW
;
2341 * Make sure we do not leak PI boosting priority to the child.
2343 p
->prio
= current
->normal_prio
;
2346 * Revert to default priority/policy on fork if requested.
2348 if (unlikely(p
->sched_reset_on_fork
)) {
2349 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
2350 p
->policy
= SCHED_NORMAL
;
2351 p
->static_prio
= NICE_TO_PRIO(0);
2353 } else if (PRIO_TO_NICE(p
->static_prio
) < 0)
2354 p
->static_prio
= NICE_TO_PRIO(0);
2356 p
->prio
= p
->normal_prio
= __normal_prio(p
);
2360 * We don't need the reset flag anymore after the fork. It has
2361 * fulfilled its duty:
2363 p
->sched_reset_on_fork
= 0;
2366 if (dl_prio(p
->prio
)) {
2369 } else if (rt_prio(p
->prio
)) {
2370 p
->sched_class
= &rt_sched_class
;
2372 p
->sched_class
= &fair_sched_class
;
2375 init_entity_runnable_average(&p
->se
);
2378 * The child is not yet in the pid-hash so no cgroup attach races,
2379 * and the cgroup is pinned to this child due to cgroup_fork()
2380 * is ran before sched_fork().
2382 * Silence PROVE_RCU.
2384 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
2386 * We're setting the CPU for the first time, we don't migrate,
2387 * so use __set_task_cpu().
2389 __set_task_cpu(p
, cpu
);
2390 if (p
->sched_class
->task_fork
)
2391 p
->sched_class
->task_fork(p
);
2392 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2394 #ifdef CONFIG_SCHED_INFO
2395 if (likely(sched_info_on()))
2396 memset(&p
->sched_info
, 0, sizeof(p
->sched_info
));
2398 #if defined(CONFIG_SMP)
2401 init_task_preempt_count(p
);
2403 plist_node_init(&p
->pushable_tasks
, MAX_PRIO
);
2404 RB_CLEAR_NODE(&p
->pushable_dl_tasks
);
2411 unsigned long to_ratio(u64 period
, u64 runtime
)
2413 if (runtime
== RUNTIME_INF
)
2417 * Doing this here saves a lot of checks in all
2418 * the calling paths, and returning zero seems
2419 * safe for them anyway.
2424 return div64_u64(runtime
<< BW_SHIFT
, period
);
2428 * wake_up_new_task - wake up a newly created task for the first time.
2430 * This function will do some initial scheduler statistics housekeeping
2431 * that must be done for every newly created context, then puts the task
2432 * on the runqueue and wakes it.
2434 void wake_up_new_task(struct task_struct
*p
)
2439 raw_spin_lock_irqsave(&p
->pi_lock
, rf
.flags
);
2440 p
->state
= TASK_RUNNING
;
2443 * Fork balancing, do it here and not earlier because:
2444 * - cpus_allowed can change in the fork path
2445 * - any previously selected CPU might disappear through hotplug
2447 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2448 * as we're not fully set-up yet.
2450 __set_task_cpu(p
, select_task_rq(p
, task_cpu(p
), SD_BALANCE_FORK
, 0));
2452 rq
= __task_rq_lock(p
, &rf
);
2453 update_rq_clock(rq
);
2454 post_init_entity_util_avg(&p
->se
);
2456 activate_task(rq
, p
, ENQUEUE_NOCLOCK
);
2457 p
->on_rq
= TASK_ON_RQ_QUEUED
;
2458 trace_sched_wakeup_new(p
);
2459 check_preempt_curr(rq
, p
, WF_FORK
);
2461 if (p
->sched_class
->task_woken
) {
2463 * Nothing relies on rq->lock after this, so its fine to
2466 rq_unpin_lock(rq
, &rf
);
2467 p
->sched_class
->task_woken(rq
, p
);
2468 rq_repin_lock(rq
, &rf
);
2471 task_rq_unlock(rq
, p
, &rf
);
2474 #ifdef CONFIG_PREEMPT_NOTIFIERS
2476 static struct static_key preempt_notifier_key
= STATIC_KEY_INIT_FALSE
;
2478 void preempt_notifier_inc(void)
2480 static_key_slow_inc(&preempt_notifier_key
);
2482 EXPORT_SYMBOL_GPL(preempt_notifier_inc
);
2484 void preempt_notifier_dec(void)
2486 static_key_slow_dec(&preempt_notifier_key
);
2488 EXPORT_SYMBOL_GPL(preempt_notifier_dec
);
2491 * preempt_notifier_register - tell me when current is being preempted & rescheduled
2492 * @notifier: notifier struct to register
2494 void preempt_notifier_register(struct preempt_notifier
*notifier
)
2496 if (!static_key_false(&preempt_notifier_key
))
2497 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2499 hlist_add_head(¬ifier
->link
, ¤t
->preempt_notifiers
);
2501 EXPORT_SYMBOL_GPL(preempt_notifier_register
);
2504 * preempt_notifier_unregister - no longer interested in preemption notifications
2505 * @notifier: notifier struct to unregister
2507 * This is *not* safe to call from within a preemption notifier.
2509 void preempt_notifier_unregister(struct preempt_notifier
*notifier
)
2511 hlist_del(¬ifier
->link
);
2513 EXPORT_SYMBOL_GPL(preempt_notifier_unregister
);
2515 static void __fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2517 struct preempt_notifier
*notifier
;
2519 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
2520 notifier
->ops
->sched_in(notifier
, raw_smp_processor_id());
2523 static __always_inline
void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2525 if (static_key_false(&preempt_notifier_key
))
2526 __fire_sched_in_preempt_notifiers(curr
);
2530 __fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2531 struct task_struct
*next
)
2533 struct preempt_notifier
*notifier
;
2535 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
2536 notifier
->ops
->sched_out(notifier
, next
);
2539 static __always_inline
void
2540 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2541 struct task_struct
*next
)
2543 if (static_key_false(&preempt_notifier_key
))
2544 __fire_sched_out_preempt_notifiers(curr
, next
);
2547 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2549 static inline void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2554 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2555 struct task_struct
*next
)
2559 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2562 * prepare_task_switch - prepare to switch tasks
2563 * @rq: the runqueue preparing to switch
2564 * @prev: the current task that is being switched out
2565 * @next: the task we are going to switch to.
2567 * This is called with the rq lock held and interrupts off. It must
2568 * be paired with a subsequent finish_task_switch after the context
2571 * prepare_task_switch sets up locking and calls architecture specific
2575 prepare_task_switch(struct rq
*rq
, struct task_struct
*prev
,
2576 struct task_struct
*next
)
2578 sched_info_switch(rq
, prev
, next
);
2579 perf_event_task_sched_out(prev
, next
);
2580 fire_sched_out_preempt_notifiers(prev
, next
);
2581 prepare_lock_switch(rq
, next
);
2582 prepare_arch_switch(next
);
2586 * finish_task_switch - clean up after a task-switch
2587 * @prev: the thread we just switched away from.
2589 * finish_task_switch must be called after the context switch, paired
2590 * with a prepare_task_switch call before the context switch.
2591 * finish_task_switch will reconcile locking set up by prepare_task_switch,
2592 * and do any other architecture-specific cleanup actions.
2594 * Note that we may have delayed dropping an mm in context_switch(). If
2595 * so, we finish that here outside of the runqueue lock. (Doing it
2596 * with the lock held can cause deadlocks; see schedule() for
2599 * The context switch have flipped the stack from under us and restored the
2600 * local variables which were saved when this task called schedule() in the
2601 * past. prev == current is still correct but we need to recalculate this_rq
2602 * because prev may have moved to another CPU.
2604 static struct rq
*finish_task_switch(struct task_struct
*prev
)
2605 __releases(rq
->lock
)
2607 struct rq
*rq
= this_rq();
2608 struct mm_struct
*mm
= rq
->prev_mm
;
2612 * The previous task will have left us with a preempt_count of 2
2613 * because it left us after:
2616 * preempt_disable(); // 1
2618 * raw_spin_lock_irq(&rq->lock) // 2
2620 * Also, see FORK_PREEMPT_COUNT.
2622 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET
,
2623 "corrupted preempt_count: %s/%d/0x%x\n",
2624 current
->comm
, current
->pid
, preempt_count()))
2625 preempt_count_set(FORK_PREEMPT_COUNT
);
2630 * A task struct has one reference for the use as "current".
2631 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2632 * schedule one last time. The schedule call will never return, and
2633 * the scheduled task must drop that reference.
2635 * We must observe prev->state before clearing prev->on_cpu (in
2636 * finish_lock_switch), otherwise a concurrent wakeup can get prev
2637 * running on another CPU and we could rave with its RUNNING -> DEAD
2638 * transition, resulting in a double drop.
2640 prev_state
= prev
->state
;
2641 vtime_task_switch(prev
);
2642 perf_event_task_sched_in(prev
, current
);
2644 * The membarrier system call requires a full memory barrier
2645 * after storing to rq->curr, before going back to user-space.
2647 * TODO: This smp_mb__after_unlock_lock can go away if PPC end
2648 * up adding a full barrier to switch_mm(), or we should figure
2649 * out if a smp_mb__after_unlock_lock is really the proper API
2652 smp_mb__after_unlock_lock();
2653 finish_lock_switch(rq
, prev
);
2654 finish_arch_post_lock_switch();
2656 fire_sched_in_preempt_notifiers(current
);
2659 if (unlikely(prev_state
== TASK_DEAD
)) {
2660 if (prev
->sched_class
->task_dead
)
2661 prev
->sched_class
->task_dead(prev
);
2664 * Remove function-return probe instances associated with this
2665 * task and put them back on the free list.
2667 kprobe_flush_task(prev
);
2669 /* Task is done with its stack. */
2670 put_task_stack(prev
);
2672 put_task_struct(prev
);
2675 tick_nohz_task_switch();
2681 /* rq->lock is NOT held, but preemption is disabled */
2682 static void __balance_callback(struct rq
*rq
)
2684 struct callback_head
*head
, *next
;
2685 void (*func
)(struct rq
*rq
);
2686 unsigned long flags
;
2688 raw_spin_lock_irqsave(&rq
->lock
, flags
);
2689 head
= rq
->balance_callback
;
2690 rq
->balance_callback
= NULL
;
2692 func
= (void (*)(struct rq
*))head
->func
;
2699 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
2702 static inline void balance_callback(struct rq
*rq
)
2704 if (unlikely(rq
->balance_callback
))
2705 __balance_callback(rq
);
2710 static inline void balance_callback(struct rq
*rq
)
2717 * schedule_tail - first thing a freshly forked thread must call.
2718 * @prev: the thread we just switched away from.
2720 asmlinkage __visible
void schedule_tail(struct task_struct
*prev
)
2721 __releases(rq
->lock
)
2726 * New tasks start with FORK_PREEMPT_COUNT, see there and
2727 * finish_task_switch() for details.
2729 * finish_task_switch() will drop rq->lock() and lower preempt_count
2730 * and the preempt_enable() will end up enabling preemption (on
2731 * PREEMPT_COUNT kernels).
2734 rq
= finish_task_switch(prev
);
2735 balance_callback(rq
);
2738 if (current
->set_child_tid
)
2739 put_user(task_pid_vnr(current
), current
->set_child_tid
);
2743 * context_switch - switch to the new MM and the new thread's register state.
2745 static __always_inline
struct rq
*
2746 context_switch(struct rq
*rq
, struct task_struct
*prev
,
2747 struct task_struct
*next
, struct rq_flags
*rf
)
2749 struct mm_struct
*mm
, *oldmm
;
2751 prepare_task_switch(rq
, prev
, next
);
2754 oldmm
= prev
->active_mm
;
2756 * For paravirt, this is coupled with an exit in switch_to to
2757 * combine the page table reload and the switch backend into
2760 arch_start_context_switch(prev
);
2763 next
->active_mm
= oldmm
;
2765 enter_lazy_tlb(oldmm
, next
);
2767 switch_mm_irqs_off(oldmm
, mm
, next
);
2770 prev
->active_mm
= NULL
;
2771 rq
->prev_mm
= oldmm
;
2774 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
2777 * Since the runqueue lock will be released by the next
2778 * task (which is an invalid locking op but in the case
2779 * of the scheduler it's an obvious special-case), so we
2780 * do an early lockdep release here:
2782 rq_unpin_lock(rq
, rf
);
2783 spin_release(&rq
->lock
.dep_map
, 1, _THIS_IP_
);
2785 /* Here we just switch the register state and the stack. */
2786 switch_to(prev
, next
, prev
);
2789 return finish_task_switch(prev
);
2793 * nr_running and nr_context_switches:
2795 * externally visible scheduler statistics: current number of runnable
2796 * threads, total number of context switches performed since bootup.
2798 unsigned long nr_running(void)
2800 unsigned long i
, sum
= 0;
2802 for_each_online_cpu(i
)
2803 sum
+= cpu_rq(i
)->nr_running
;
2809 * Check if only the current task is running on the CPU.
2811 * Caution: this function does not check that the caller has disabled
2812 * preemption, thus the result might have a time-of-check-to-time-of-use
2813 * race. The caller is responsible to use it correctly, for example:
2815 * - from a non-preemptable section (of course)
2817 * - from a thread that is bound to a single CPU
2819 * - in a loop with very short iterations (e.g. a polling loop)
2821 bool single_task_running(void)
2823 return raw_rq()->nr_running
== 1;
2825 EXPORT_SYMBOL(single_task_running
);
2827 unsigned long long nr_context_switches(void)
2830 unsigned long long sum
= 0;
2832 for_each_possible_cpu(i
)
2833 sum
+= cpu_rq(i
)->nr_switches
;
2839 * IO-wait accounting, and how its mostly bollocks (on SMP).
2841 * The idea behind IO-wait account is to account the idle time that we could
2842 * have spend running if it were not for IO. That is, if we were to improve the
2843 * storage performance, we'd have a proportional reduction in IO-wait time.
2845 * This all works nicely on UP, where, when a task blocks on IO, we account
2846 * idle time as IO-wait, because if the storage were faster, it could've been
2847 * running and we'd not be idle.
2849 * This has been extended to SMP, by doing the same for each CPU. This however
2852 * Imagine for instance the case where two tasks block on one CPU, only the one
2853 * CPU will have IO-wait accounted, while the other has regular idle. Even
2854 * though, if the storage were faster, both could've ran at the same time,
2855 * utilising both CPUs.
2857 * This means, that when looking globally, the current IO-wait accounting on
2858 * SMP is a lower bound, by reason of under accounting.
2860 * Worse, since the numbers are provided per CPU, they are sometimes
2861 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
2862 * associated with any one particular CPU, it can wake to another CPU than it
2863 * blocked on. This means the per CPU IO-wait number is meaningless.
2865 * Task CPU affinities can make all that even more 'interesting'.
2868 unsigned long nr_iowait(void)
2870 unsigned long i
, sum
= 0;
2872 for_each_possible_cpu(i
)
2873 sum
+= atomic_read(&cpu_rq(i
)->nr_iowait
);
2879 * Consumers of these two interfaces, like for example the cpufreq menu
2880 * governor are using nonsensical data. Boosting frequency for a CPU that has
2881 * IO-wait which might not even end up running the task when it does become
2885 unsigned long nr_iowait_cpu(int cpu
)
2887 struct rq
*this = cpu_rq(cpu
);
2888 return atomic_read(&this->nr_iowait
);
2891 void get_iowait_load(unsigned long *nr_waiters
, unsigned long *load
)
2893 struct rq
*rq
= this_rq();
2894 *nr_waiters
= atomic_read(&rq
->nr_iowait
);
2895 *load
= rq
->load
.weight
;
2901 * sched_exec - execve() is a valuable balancing opportunity, because at
2902 * this point the task has the smallest effective memory and cache footprint.
2904 void sched_exec(void)
2906 struct task_struct
*p
= current
;
2907 unsigned long flags
;
2910 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
2911 dest_cpu
= p
->sched_class
->select_task_rq(p
, task_cpu(p
), SD_BALANCE_EXEC
, 0);
2912 if (dest_cpu
== smp_processor_id())
2915 if (likely(cpu_active(dest_cpu
))) {
2916 struct migration_arg arg
= { p
, dest_cpu
};
2918 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2919 stop_one_cpu(task_cpu(p
), migration_cpu_stop
, &arg
);
2923 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2928 DEFINE_PER_CPU(struct kernel_stat
, kstat
);
2929 DEFINE_PER_CPU(struct kernel_cpustat
, kernel_cpustat
);
2931 EXPORT_PER_CPU_SYMBOL(kstat
);
2932 EXPORT_PER_CPU_SYMBOL(kernel_cpustat
);
2935 * The function fair_sched_class.update_curr accesses the struct curr
2936 * and its field curr->exec_start; when called from task_sched_runtime(),
2937 * we observe a high rate of cache misses in practice.
2938 * Prefetching this data results in improved performance.
2940 static inline void prefetch_curr_exec_start(struct task_struct
*p
)
2942 #ifdef CONFIG_FAIR_GROUP_SCHED
2943 struct sched_entity
*curr
= (&p
->se
)->cfs_rq
->curr
;
2945 struct sched_entity
*curr
= (&task_rq(p
)->cfs
)->curr
;
2948 prefetch(&curr
->exec_start
);
2952 * Return accounted runtime for the task.
2953 * In case the task is currently running, return the runtime plus current's
2954 * pending runtime that have not been accounted yet.
2956 unsigned long long task_sched_runtime(struct task_struct
*p
)
2962 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
2964 * 64-bit doesn't need locks to atomically read a 64bit value.
2965 * So we have a optimization chance when the task's delta_exec is 0.
2966 * Reading ->on_cpu is racy, but this is ok.
2968 * If we race with it leaving CPU, we'll take a lock. So we're correct.
2969 * If we race with it entering CPU, unaccounted time is 0. This is
2970 * indistinguishable from the read occurring a few cycles earlier.
2971 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
2972 * been accounted, so we're correct here as well.
2974 if (!p
->on_cpu
|| !task_on_rq_queued(p
))
2975 return p
->se
.sum_exec_runtime
;
2978 rq
= task_rq_lock(p
, &rf
);
2980 * Must be ->curr _and_ ->on_rq. If dequeued, we would
2981 * project cycles that may never be accounted to this
2982 * thread, breaking clock_gettime().
2984 if (task_current(rq
, p
) && task_on_rq_queued(p
)) {
2985 prefetch_curr_exec_start(p
);
2986 update_rq_clock(rq
);
2987 p
->sched_class
->update_curr(rq
);
2989 ns
= p
->se
.sum_exec_runtime
;
2990 task_rq_unlock(rq
, p
, &rf
);
2996 * This function gets called by the timer code, with HZ frequency.
2997 * We call it with interrupts disabled.
2999 void scheduler_tick(void)
3001 int cpu
= smp_processor_id();
3002 struct rq
*rq
= cpu_rq(cpu
);
3003 struct task_struct
*curr
= rq
->curr
;
3010 update_rq_clock(rq
);
3011 curr
->sched_class
->task_tick(rq
, curr
, 0);
3012 cpu_load_update_active(rq
);
3013 calc_global_load_tick(rq
);
3017 perf_event_task_tick();
3020 rq
->idle_balance
= idle_cpu(cpu
);
3021 trigger_load_balance(rq
);
3023 rq_last_tick_reset(rq
);
3026 #ifdef CONFIG_NO_HZ_FULL
3028 * scheduler_tick_max_deferment
3030 * Keep at least one tick per second when a single
3031 * active task is running because the scheduler doesn't
3032 * yet completely support full dynticks environment.
3034 * This makes sure that uptime, CFS vruntime, load
3035 * balancing, etc... continue to move forward, even
3036 * with a very low granularity.
3038 * Return: Maximum deferment in nanoseconds.
3040 u64
scheduler_tick_max_deferment(void)
3042 struct rq
*rq
= this_rq();
3043 unsigned long next
, now
= READ_ONCE(jiffies
);
3045 next
= rq
->last_sched_tick
+ HZ
;
3047 if (time_before_eq(next
, now
))
3050 return jiffies_to_nsecs(next
- now
);
3054 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3055 defined(CONFIG_PREEMPT_TRACER))
3057 * If the value passed in is equal to the current preempt count
3058 * then we just disabled preemption. Start timing the latency.
3060 static inline void preempt_latency_start(int val
)
3062 if (preempt_count() == val
) {
3063 unsigned long ip
= get_lock_parent_ip();
3064 #ifdef CONFIG_DEBUG_PREEMPT
3065 current
->preempt_disable_ip
= ip
;
3067 trace_preempt_off(CALLER_ADDR0
, ip
);
3071 void preempt_count_add(int val
)
3073 #ifdef CONFIG_DEBUG_PREEMPT
3077 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3080 __preempt_count_add(val
);
3081 #ifdef CONFIG_DEBUG_PREEMPT
3083 * Spinlock count overflowing soon?
3085 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK
) >=
3088 preempt_latency_start(val
);
3090 EXPORT_SYMBOL(preempt_count_add
);
3091 NOKPROBE_SYMBOL(preempt_count_add
);
3094 * If the value passed in equals to the current preempt count
3095 * then we just enabled preemption. Stop timing the latency.
3097 static inline void preempt_latency_stop(int val
)
3099 if (preempt_count() == val
)
3100 trace_preempt_on(CALLER_ADDR0
, get_lock_parent_ip());
3103 void preempt_count_sub(int val
)
3105 #ifdef CONFIG_DEBUG_PREEMPT
3109 if (DEBUG_LOCKS_WARN_ON(val
> preempt_count()))
3112 * Is the spinlock portion underflowing?
3114 if (DEBUG_LOCKS_WARN_ON((val
< PREEMPT_MASK
) &&
3115 !(preempt_count() & PREEMPT_MASK
)))
3119 preempt_latency_stop(val
);
3120 __preempt_count_sub(val
);
3122 EXPORT_SYMBOL(preempt_count_sub
);
3123 NOKPROBE_SYMBOL(preempt_count_sub
);
3126 static inline void preempt_latency_start(int val
) { }
3127 static inline void preempt_latency_stop(int val
) { }
3130 static inline unsigned long get_preempt_disable_ip(struct task_struct
*p
)
3132 #ifdef CONFIG_DEBUG_PREEMPT
3133 return p
->preempt_disable_ip
;
3140 * Print scheduling while atomic bug:
3142 static noinline
void __schedule_bug(struct task_struct
*prev
)
3144 /* Save this before calling printk(), since that will clobber it */
3145 unsigned long preempt_disable_ip
= get_preempt_disable_ip(current
);
3147 if (oops_in_progress
)
3150 printk(KERN_ERR
"BUG: scheduling while atomic: %s/%d/0x%08x\n",
3151 prev
->comm
, prev
->pid
, preempt_count());
3153 debug_show_held_locks(prev
);
3155 if (irqs_disabled())
3156 print_irqtrace_events(prev
);
3157 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
3158 && in_atomic_preempt_off()) {
3159 pr_err("Preemption disabled at:");
3160 print_ip_sym(preempt_disable_ip
);
3164 panic("scheduling while atomic\n");
3167 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
3171 * Various schedule()-time debugging checks and statistics:
3173 static inline void schedule_debug(struct task_struct
*prev
)
3175 #ifdef CONFIG_SCHED_STACK_END_CHECK
3176 if (task_stack_end_corrupted(prev
))
3177 panic("corrupted stack end detected inside scheduler\n");
3180 if (unlikely(in_atomic_preempt_off())) {
3181 __schedule_bug(prev
);
3182 preempt_count_set(PREEMPT_DISABLED
);
3186 profile_hit(SCHED_PROFILING
, __builtin_return_address(0));
3188 schedstat_inc(this_rq()->sched_count
);
3192 * Pick up the highest-prio task:
3194 static inline struct task_struct
*
3195 pick_next_task(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
3197 const struct sched_class
*class;
3198 struct task_struct
*p
;
3201 * Optimization: we know that if all tasks are in the fair class we can
3202 * call that function directly, but only if the @prev task wasn't of a
3203 * higher scheduling class, because otherwise those loose the
3204 * opportunity to pull in more work from other CPUs.
3206 if (likely((prev
->sched_class
== &idle_sched_class
||
3207 prev
->sched_class
== &fair_sched_class
) &&
3208 rq
->nr_running
== rq
->cfs
.h_nr_running
)) {
3210 p
= fair_sched_class
.pick_next_task(rq
, prev
, rf
);
3211 if (unlikely(p
== RETRY_TASK
))
3214 /* Assumes fair_sched_class->next == idle_sched_class */
3216 p
= idle_sched_class
.pick_next_task(rq
, prev
, rf
);
3222 for_each_class(class) {
3223 p
= class->pick_next_task(rq
, prev
, rf
);
3225 if (unlikely(p
== RETRY_TASK
))
3231 /* The idle class should always have a runnable task: */
3236 * __schedule() is the main scheduler function.
3238 * The main means of driving the scheduler and thus entering this function are:
3240 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3242 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3243 * paths. For example, see arch/x86/entry_64.S.
3245 * To drive preemption between tasks, the scheduler sets the flag in timer
3246 * interrupt handler scheduler_tick().
3248 * 3. Wakeups don't really cause entry into schedule(). They add a
3249 * task to the run-queue and that's it.
3251 * Now, if the new task added to the run-queue preempts the current
3252 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3253 * called on the nearest possible occasion:
3255 * - If the kernel is preemptible (CONFIG_PREEMPT=y):
3257 * - in syscall or exception context, at the next outmost
3258 * preempt_enable(). (this might be as soon as the wake_up()'s
3261 * - in IRQ context, return from interrupt-handler to
3262 * preemptible context
3264 * - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3267 * - cond_resched() call
3268 * - explicit schedule() call
3269 * - return from syscall or exception to user-space
3270 * - return from interrupt-handler to user-space
3272 * WARNING: must be called with preemption disabled!
3274 static void __sched notrace
__schedule(bool preempt
)
3276 struct task_struct
*prev
, *next
;
3277 unsigned long *switch_count
;
3282 cpu
= smp_processor_id();
3286 schedule_debug(prev
);
3288 if (sched_feat(HRTICK
))
3291 local_irq_disable();
3292 rcu_note_context_switch(preempt
);
3295 * Make sure that signal_pending_state()->signal_pending() below
3296 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3297 * done by the caller to avoid the race with signal_wake_up().
3300 smp_mb__after_spinlock();
3302 /* Promote REQ to ACT */
3303 rq
->clock_update_flags
<<= 1;
3304 update_rq_clock(rq
);
3306 switch_count
= &prev
->nivcsw
;
3307 if (!preempt
&& prev
->state
) {
3308 if (unlikely(signal_pending_state(prev
->state
, prev
))) {
3309 prev
->state
= TASK_RUNNING
;
3311 deactivate_task(rq
, prev
, DEQUEUE_SLEEP
| DEQUEUE_NOCLOCK
);
3314 if (prev
->in_iowait
) {
3315 atomic_inc(&rq
->nr_iowait
);
3316 delayacct_blkio_start();
3320 * If a worker went to sleep, notify and ask workqueue
3321 * whether it wants to wake up a task to maintain
3324 if (prev
->flags
& PF_WQ_WORKER
) {
3325 struct task_struct
*to_wakeup
;
3327 to_wakeup
= wq_worker_sleeping(prev
);
3329 try_to_wake_up_local(to_wakeup
, &rf
);
3332 switch_count
= &prev
->nvcsw
;
3335 next
= pick_next_task(rq
, prev
, &rf
);
3336 clear_tsk_need_resched(prev
);
3337 clear_preempt_need_resched();
3339 if (likely(prev
!= next
)) {
3343 * The membarrier system call requires each architecture
3344 * to have a full memory barrier after updating
3345 * rq->curr, before returning to user-space. For TSO
3346 * (e.g. x86), the architecture must provide its own
3347 * barrier in switch_mm(). For weakly ordered machines
3348 * for which spin_unlock() acts as a full memory
3349 * barrier, finish_lock_switch() in common code takes
3350 * care of this barrier. For weakly ordered machines for
3351 * which spin_unlock() acts as a RELEASE barrier (only
3352 * arm64 and PowerPC), arm64 has a full barrier in
3353 * switch_to(), and PowerPC has
3354 * smp_mb__after_unlock_lock() before
3355 * finish_lock_switch().
3359 trace_sched_switch(preempt
, prev
, next
);
3361 /* Also unlocks the rq: */
3362 rq
= context_switch(rq
, prev
, next
, &rf
);
3364 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
3365 rq_unlock_irq(rq
, &rf
);
3368 balance_callback(rq
);
3371 void __noreturn
do_task_dead(void)
3374 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
3375 * when the following two conditions become true.
3376 * - There is race condition of mmap_sem (It is acquired by
3378 * - SMI occurs before setting TASK_RUNINNG.
3379 * (or hypervisor of virtual machine switches to other guest)
3380 * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
3382 * To avoid it, we have to wait for releasing tsk->pi_lock which
3383 * is held by try_to_wake_up()
3385 raw_spin_lock_irq(¤t
->pi_lock
);
3386 raw_spin_unlock_irq(¤t
->pi_lock
);
3388 /* Causes final put_task_struct in finish_task_switch(): */
3389 __set_current_state(TASK_DEAD
);
3391 /* Tell freezer to ignore us: */
3392 current
->flags
|= PF_NOFREEZE
;
3397 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
3402 static inline void sched_submit_work(struct task_struct
*tsk
)
3404 if (!tsk
->state
|| tsk_is_pi_blocked(tsk
))
3407 * If we are going to sleep and we have plugged IO queued,
3408 * make sure to submit it to avoid deadlocks.
3410 if (blk_needs_flush_plug(tsk
))
3411 blk_schedule_flush_plug(tsk
);
3414 asmlinkage __visible
void __sched
schedule(void)
3416 struct task_struct
*tsk
= current
;
3418 sched_submit_work(tsk
);
3422 sched_preempt_enable_no_resched();
3423 } while (need_resched());
3425 EXPORT_SYMBOL(schedule
);
3428 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
3429 * state (have scheduled out non-voluntarily) by making sure that all
3430 * tasks have either left the run queue or have gone into user space.
3431 * As idle tasks do not do either, they must not ever be preempted
3432 * (schedule out non-voluntarily).
3434 * schedule_idle() is similar to schedule_preempt_disable() except that it
3435 * never enables preemption because it does not call sched_submit_work().
3437 void __sched
schedule_idle(void)
3440 * As this skips calling sched_submit_work(), which the idle task does
3441 * regardless because that function is a nop when the task is in a
3442 * TASK_RUNNING state, make sure this isn't used someplace that the
3443 * current task can be in any other state. Note, idle is always in the
3444 * TASK_RUNNING state.
3446 WARN_ON_ONCE(current
->state
);
3449 } while (need_resched());
3452 #ifdef CONFIG_CONTEXT_TRACKING
3453 asmlinkage __visible
void __sched
schedule_user(void)
3456 * If we come here after a random call to set_need_resched(),
3457 * or we have been woken up remotely but the IPI has not yet arrived,
3458 * we haven't yet exited the RCU idle mode. Do it here manually until
3459 * we find a better solution.
3461 * NB: There are buggy callers of this function. Ideally we
3462 * should warn if prev_state != CONTEXT_USER, but that will trigger
3463 * too frequently to make sense yet.
3465 enum ctx_state prev_state
= exception_enter();
3467 exception_exit(prev_state
);
3472 * schedule_preempt_disabled - called with preemption disabled
3474 * Returns with preemption disabled. Note: preempt_count must be 1
3476 void __sched
schedule_preempt_disabled(void)
3478 sched_preempt_enable_no_resched();
3483 static void __sched notrace
preempt_schedule_common(void)
3487 * Because the function tracer can trace preempt_count_sub()
3488 * and it also uses preempt_enable/disable_notrace(), if
3489 * NEED_RESCHED is set, the preempt_enable_notrace() called
3490 * by the function tracer will call this function again and
3491 * cause infinite recursion.
3493 * Preemption must be disabled here before the function
3494 * tracer can trace. Break up preempt_disable() into two
3495 * calls. One to disable preemption without fear of being
3496 * traced. The other to still record the preemption latency,
3497 * which can also be traced by the function tracer.
3499 preempt_disable_notrace();
3500 preempt_latency_start(1);
3502 preempt_latency_stop(1);
3503 preempt_enable_no_resched_notrace();
3506 * Check again in case we missed a preemption opportunity
3507 * between schedule and now.
3509 } while (need_resched());
3512 #ifdef CONFIG_PREEMPT
3514 * this is the entry point to schedule() from in-kernel preemption
3515 * off of preempt_enable. Kernel preemptions off return from interrupt
3516 * occur there and call schedule directly.
3518 asmlinkage __visible
void __sched notrace
preempt_schedule(void)
3521 * If there is a non-zero preempt_count or interrupts are disabled,
3522 * we do not want to preempt the current task. Just return..
3524 if (likely(!preemptible()))
3527 preempt_schedule_common();
3529 NOKPROBE_SYMBOL(preempt_schedule
);
3530 EXPORT_SYMBOL(preempt_schedule
);
3533 * preempt_schedule_notrace - preempt_schedule called by tracing
3535 * The tracing infrastructure uses preempt_enable_notrace to prevent
3536 * recursion and tracing preempt enabling caused by the tracing
3537 * infrastructure itself. But as tracing can happen in areas coming
3538 * from userspace or just about to enter userspace, a preempt enable
3539 * can occur before user_exit() is called. This will cause the scheduler
3540 * to be called when the system is still in usermode.
3542 * To prevent this, the preempt_enable_notrace will use this function
3543 * instead of preempt_schedule() to exit user context if needed before
3544 * calling the scheduler.
3546 asmlinkage __visible
void __sched notrace
preempt_schedule_notrace(void)
3548 enum ctx_state prev_ctx
;
3550 if (likely(!preemptible()))
3555 * Because the function tracer can trace preempt_count_sub()
3556 * and it also uses preempt_enable/disable_notrace(), if
3557 * NEED_RESCHED is set, the preempt_enable_notrace() called
3558 * by the function tracer will call this function again and
3559 * cause infinite recursion.
3561 * Preemption must be disabled here before the function
3562 * tracer can trace. Break up preempt_disable() into two
3563 * calls. One to disable preemption without fear of being
3564 * traced. The other to still record the preemption latency,
3565 * which can also be traced by the function tracer.
3567 preempt_disable_notrace();
3568 preempt_latency_start(1);
3570 * Needs preempt disabled in case user_exit() is traced
3571 * and the tracer calls preempt_enable_notrace() causing
3572 * an infinite recursion.
3574 prev_ctx
= exception_enter();
3576 exception_exit(prev_ctx
);
3578 preempt_latency_stop(1);
3579 preempt_enable_no_resched_notrace();
3580 } while (need_resched());
3582 EXPORT_SYMBOL_GPL(preempt_schedule_notrace
);
3584 #endif /* CONFIG_PREEMPT */
3587 * this is the entry point to schedule() from kernel preemption
3588 * off of irq context.
3589 * Note, that this is called and return with irqs disabled. This will
3590 * protect us against recursive calling from irq.
3592 asmlinkage __visible
void __sched
preempt_schedule_irq(void)
3594 enum ctx_state prev_state
;
3596 /* Catch callers which need to be fixed */
3597 BUG_ON(preempt_count() || !irqs_disabled());
3599 prev_state
= exception_enter();
3605 local_irq_disable();
3606 sched_preempt_enable_no_resched();
3607 } while (need_resched());
3609 exception_exit(prev_state
);
3612 int default_wake_function(wait_queue_entry_t
*curr
, unsigned mode
, int wake_flags
,
3615 return try_to_wake_up(curr
->private, mode
, wake_flags
);
3617 EXPORT_SYMBOL(default_wake_function
);
3619 #ifdef CONFIG_RT_MUTEXES
3621 static inline int __rt_effective_prio(struct task_struct
*pi_task
, int prio
)
3624 prio
= min(prio
, pi_task
->prio
);
3629 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
3631 struct task_struct
*pi_task
= rt_mutex_get_top_task(p
);
3633 return __rt_effective_prio(pi_task
, prio
);
3637 * rt_mutex_setprio - set the current priority of a task
3639 * @pi_task: donor task
3641 * This function changes the 'effective' priority of a task. It does
3642 * not touch ->normal_prio like __setscheduler().
3644 * Used by the rt_mutex code to implement priority inheritance
3645 * logic. Call site only calls if the priority of the task changed.
3647 void rt_mutex_setprio(struct task_struct
*p
, struct task_struct
*pi_task
)
3649 int prio
, oldprio
, queued
, running
, queue_flag
=
3650 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
3651 const struct sched_class
*prev_class
;
3655 /* XXX used to be waiter->prio, not waiter->task->prio */
3656 prio
= __rt_effective_prio(pi_task
, p
->normal_prio
);
3659 * If nothing changed; bail early.
3661 if (p
->pi_top_task
== pi_task
&& prio
== p
->prio
&& !dl_prio(prio
))
3664 rq
= __task_rq_lock(p
, &rf
);
3665 update_rq_clock(rq
);
3667 * Set under pi_lock && rq->lock, such that the value can be used under
3670 * Note that there is loads of tricky to make this pointer cache work
3671 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
3672 * ensure a task is de-boosted (pi_task is set to NULL) before the
3673 * task is allowed to run again (and can exit). This ensures the pointer
3674 * points to a blocked task -- which guaratees the task is present.
3676 p
->pi_top_task
= pi_task
;
3679 * For FIFO/RR we only need to set prio, if that matches we're done.
3681 if (prio
== p
->prio
&& !dl_prio(prio
))
3685 * Idle task boosting is a nono in general. There is one
3686 * exception, when PREEMPT_RT and NOHZ is active:
3688 * The idle task calls get_next_timer_interrupt() and holds
3689 * the timer wheel base->lock on the CPU and another CPU wants
3690 * to access the timer (probably to cancel it). We can safely
3691 * ignore the boosting request, as the idle CPU runs this code
3692 * with interrupts disabled and will complete the lock
3693 * protected section without being interrupted. So there is no
3694 * real need to boost.
3696 if (unlikely(p
== rq
->idle
)) {
3697 WARN_ON(p
!= rq
->curr
);
3698 WARN_ON(p
->pi_blocked_on
);
3702 trace_sched_pi_setprio(p
, pi_task
);
3705 if (oldprio
== prio
)
3706 queue_flag
&= ~DEQUEUE_MOVE
;
3708 prev_class
= p
->sched_class
;
3709 queued
= task_on_rq_queued(p
);
3710 running
= task_current(rq
, p
);
3712 dequeue_task(rq
, p
, queue_flag
);
3714 put_prev_task(rq
, p
);
3717 * Boosting condition are:
3718 * 1. -rt task is running and holds mutex A
3719 * --> -dl task blocks on mutex A
3721 * 2. -dl task is running and holds mutex A
3722 * --> -dl task blocks on mutex A and could preempt the
3725 if (dl_prio(prio
)) {
3726 if (!dl_prio(p
->normal_prio
) ||
3727 (pi_task
&& dl_entity_preempt(&pi_task
->dl
, &p
->dl
))) {
3728 p
->dl
.dl_boosted
= 1;
3729 queue_flag
|= ENQUEUE_REPLENISH
;
3731 p
->dl
.dl_boosted
= 0;
3732 p
->sched_class
= &dl_sched_class
;
3733 } else if (rt_prio(prio
)) {
3734 if (dl_prio(oldprio
))
3735 p
->dl
.dl_boosted
= 0;
3737 queue_flag
|= ENQUEUE_HEAD
;
3738 p
->sched_class
= &rt_sched_class
;
3740 if (dl_prio(oldprio
))
3741 p
->dl
.dl_boosted
= 0;
3742 if (rt_prio(oldprio
))
3744 p
->sched_class
= &fair_sched_class
;
3750 enqueue_task(rq
, p
, queue_flag
);
3752 set_curr_task(rq
, p
);
3754 check_class_changed(rq
, p
, prev_class
, oldprio
);
3756 /* Avoid rq from going away on us: */
3758 __task_rq_unlock(rq
, &rf
);
3760 balance_callback(rq
);
3764 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
3770 void set_user_nice(struct task_struct
*p
, long nice
)
3772 bool queued
, running
;
3773 int old_prio
, delta
;
3777 if (task_nice(p
) == nice
|| nice
< MIN_NICE
|| nice
> MAX_NICE
)
3780 * We have to be careful, if called from sys_setpriority(),
3781 * the task might be in the middle of scheduling on another CPU.
3783 rq
= task_rq_lock(p
, &rf
);
3784 update_rq_clock(rq
);
3787 * The RT priorities are set via sched_setscheduler(), but we still
3788 * allow the 'normal' nice value to be set - but as expected
3789 * it wont have any effect on scheduling until the task is
3790 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3792 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
3793 p
->static_prio
= NICE_TO_PRIO(nice
);
3796 queued
= task_on_rq_queued(p
);
3797 running
= task_current(rq
, p
);
3799 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
3801 put_prev_task(rq
, p
);
3803 p
->static_prio
= NICE_TO_PRIO(nice
);
3806 p
->prio
= effective_prio(p
);
3807 delta
= p
->prio
- old_prio
;
3810 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
3812 * If the task increased its priority or is running and
3813 * lowered its priority, then reschedule its CPU:
3815 if (delta
< 0 || (delta
> 0 && task_running(rq
, p
)))
3819 set_curr_task(rq
, p
);
3821 task_rq_unlock(rq
, p
, &rf
);
3823 EXPORT_SYMBOL(set_user_nice
);
3826 * can_nice - check if a task can reduce its nice value
3830 int can_nice(const struct task_struct
*p
, const int nice
)
3832 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
3833 int nice_rlim
= nice_to_rlimit(nice
);
3835 return (nice_rlim
<= task_rlimit(p
, RLIMIT_NICE
) ||
3836 capable(CAP_SYS_NICE
));
3839 #ifdef __ARCH_WANT_SYS_NICE
3842 * sys_nice - change the priority of the current process.
3843 * @increment: priority increment
3845 * sys_setpriority is a more generic, but much slower function that
3846 * does similar things.
3848 SYSCALL_DEFINE1(nice
, int, increment
)
3853 * Setpriority might change our priority at the same moment.
3854 * We don't have to worry. Conceptually one call occurs first
3855 * and we have a single winner.
3857 increment
= clamp(increment
, -NICE_WIDTH
, NICE_WIDTH
);
3858 nice
= task_nice(current
) + increment
;
3860 nice
= clamp_val(nice
, MIN_NICE
, MAX_NICE
);
3861 if (increment
< 0 && !can_nice(current
, nice
))
3864 retval
= security_task_setnice(current
, nice
);
3868 set_user_nice(current
, nice
);
3875 * task_prio - return the priority value of a given task.
3876 * @p: the task in question.
3878 * Return: The priority value as seen by users in /proc.
3879 * RT tasks are offset by -200. Normal tasks are centered
3880 * around 0, value goes from -16 to +15.
3882 int task_prio(const struct task_struct
*p
)
3884 return p
->prio
- MAX_RT_PRIO
;
3888 * idle_cpu - is a given CPU idle currently?
3889 * @cpu: the processor in question.
3891 * Return: 1 if the CPU is currently idle. 0 otherwise.
3893 int idle_cpu(int cpu
)
3895 struct rq
*rq
= cpu_rq(cpu
);
3897 if (rq
->curr
!= rq
->idle
)
3904 if (!llist_empty(&rq
->wake_list
))
3912 * idle_task - return the idle task for a given CPU.
3913 * @cpu: the processor in question.
3915 * Return: The idle task for the CPU @cpu.
3917 struct task_struct
*idle_task(int cpu
)
3919 return cpu_rq(cpu
)->idle
;
3923 * find_process_by_pid - find a process with a matching PID value.
3924 * @pid: the pid in question.
3926 * The task of @pid, if found. %NULL otherwise.
3928 static struct task_struct
*find_process_by_pid(pid_t pid
)
3930 return pid
? find_task_by_vpid(pid
) : current
;
3934 * sched_setparam() passes in -1 for its policy, to let the functions
3935 * it calls know not to change it.
3937 #define SETPARAM_POLICY -1
3939 static void __setscheduler_params(struct task_struct
*p
,
3940 const struct sched_attr
*attr
)
3942 int policy
= attr
->sched_policy
;
3944 if (policy
== SETPARAM_POLICY
)
3949 if (dl_policy(policy
))
3950 __setparam_dl(p
, attr
);
3951 else if (fair_policy(policy
))
3952 p
->static_prio
= NICE_TO_PRIO(attr
->sched_nice
);
3955 * __sched_setscheduler() ensures attr->sched_priority == 0 when
3956 * !rt_policy. Always setting this ensures that things like
3957 * getparam()/getattr() don't report silly values for !rt tasks.
3959 p
->rt_priority
= attr
->sched_priority
;
3960 p
->normal_prio
= normal_prio(p
);
3964 /* Actually do priority change: must hold pi & rq lock. */
3965 static void __setscheduler(struct rq
*rq
, struct task_struct
*p
,
3966 const struct sched_attr
*attr
, bool keep_boost
)
3968 __setscheduler_params(p
, attr
);
3971 * Keep a potential priority boosting if called from
3972 * sched_setscheduler().
3974 p
->prio
= normal_prio(p
);
3976 p
->prio
= rt_effective_prio(p
, p
->prio
);
3978 if (dl_prio(p
->prio
))
3979 p
->sched_class
= &dl_sched_class
;
3980 else if (rt_prio(p
->prio
))
3981 p
->sched_class
= &rt_sched_class
;
3983 p
->sched_class
= &fair_sched_class
;
3987 * Check the target process has a UID that matches the current process's:
3989 static bool check_same_owner(struct task_struct
*p
)
3991 const struct cred
*cred
= current_cred(), *pcred
;
3995 pcred
= __task_cred(p
);
3996 match
= (uid_eq(cred
->euid
, pcred
->euid
) ||
3997 uid_eq(cred
->euid
, pcred
->uid
));
4002 static int __sched_setscheduler(struct task_struct
*p
,
4003 const struct sched_attr
*attr
,
4006 int newprio
= dl_policy(attr
->sched_policy
) ? MAX_DL_PRIO
- 1 :
4007 MAX_RT_PRIO
- 1 - attr
->sched_priority
;
4008 int retval
, oldprio
, oldpolicy
= -1, queued
, running
;
4009 int new_effective_prio
, policy
= attr
->sched_policy
;
4010 const struct sched_class
*prev_class
;
4013 int queue_flags
= DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
4016 /* The pi code expects interrupts enabled */
4017 BUG_ON(pi
&& in_interrupt());
4019 /* Double check policy once rq lock held: */
4021 reset_on_fork
= p
->sched_reset_on_fork
;
4022 policy
= oldpolicy
= p
->policy
;
4024 reset_on_fork
= !!(attr
->sched_flags
& SCHED_FLAG_RESET_ON_FORK
);
4026 if (!valid_policy(policy
))
4030 if (attr
->sched_flags
&
4031 ~(SCHED_FLAG_RESET_ON_FORK
| SCHED_FLAG_RECLAIM
))
4035 * Valid priorities for SCHED_FIFO and SCHED_RR are
4036 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4037 * SCHED_BATCH and SCHED_IDLE is 0.
4039 if ((p
->mm
&& attr
->sched_priority
> MAX_USER_RT_PRIO
-1) ||
4040 (!p
->mm
&& attr
->sched_priority
> MAX_RT_PRIO
-1))
4042 if ((dl_policy(policy
) && !__checkparam_dl(attr
)) ||
4043 (rt_policy(policy
) != (attr
->sched_priority
!= 0)))
4047 * Allow unprivileged RT tasks to decrease priority:
4049 if (user
&& !capable(CAP_SYS_NICE
)) {
4050 if (fair_policy(policy
)) {
4051 if (attr
->sched_nice
< task_nice(p
) &&
4052 !can_nice(p
, attr
->sched_nice
))
4056 if (rt_policy(policy
)) {
4057 unsigned long rlim_rtprio
=
4058 task_rlimit(p
, RLIMIT_RTPRIO
);
4060 /* Can't set/change the rt policy: */
4061 if (policy
!= p
->policy
&& !rlim_rtprio
)
4064 /* Can't increase priority: */
4065 if (attr
->sched_priority
> p
->rt_priority
&&
4066 attr
->sched_priority
> rlim_rtprio
)
4071 * Can't set/change SCHED_DEADLINE policy at all for now
4072 * (safest behavior); in the future we would like to allow
4073 * unprivileged DL tasks to increase their relative deadline
4074 * or reduce their runtime (both ways reducing utilization)
4076 if (dl_policy(policy
))
4080 * Treat SCHED_IDLE as nice 20. Only allow a switch to
4081 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4083 if (idle_policy(p
->policy
) && !idle_policy(policy
)) {
4084 if (!can_nice(p
, task_nice(p
)))
4088 /* Can't change other user's priorities: */
4089 if (!check_same_owner(p
))
4092 /* Normal users shall not reset the sched_reset_on_fork flag: */
4093 if (p
->sched_reset_on_fork
&& !reset_on_fork
)
4098 retval
= security_task_setscheduler(p
);
4104 * Make sure no PI-waiters arrive (or leave) while we are
4105 * changing the priority of the task:
4107 * To be able to change p->policy safely, the appropriate
4108 * runqueue lock must be held.
4110 rq
= task_rq_lock(p
, &rf
);
4111 update_rq_clock(rq
);
4114 * Changing the policy of the stop threads its a very bad idea:
4116 if (p
== rq
->stop
) {
4117 task_rq_unlock(rq
, p
, &rf
);
4122 * If not changing anything there's no need to proceed further,
4123 * but store a possible modification of reset_on_fork.
4125 if (unlikely(policy
== p
->policy
)) {
4126 if (fair_policy(policy
) && attr
->sched_nice
!= task_nice(p
))
4128 if (rt_policy(policy
) && attr
->sched_priority
!= p
->rt_priority
)
4130 if (dl_policy(policy
) && dl_param_changed(p
, attr
))
4133 p
->sched_reset_on_fork
= reset_on_fork
;
4134 task_rq_unlock(rq
, p
, &rf
);
4140 #ifdef CONFIG_RT_GROUP_SCHED
4142 * Do not allow realtime tasks into groups that have no runtime
4145 if (rt_bandwidth_enabled() && rt_policy(policy
) &&
4146 task_group(p
)->rt_bandwidth
.rt_runtime
== 0 &&
4147 !task_group_is_autogroup(task_group(p
))) {
4148 task_rq_unlock(rq
, p
, &rf
);
4153 if (dl_bandwidth_enabled() && dl_policy(policy
)) {
4154 cpumask_t
*span
= rq
->rd
->span
;
4157 * Don't allow tasks with an affinity mask smaller than
4158 * the entire root_domain to become SCHED_DEADLINE. We
4159 * will also fail if there's no bandwidth available.
4161 if (!cpumask_subset(span
, &p
->cpus_allowed
) ||
4162 rq
->rd
->dl_bw
.bw
== 0) {
4163 task_rq_unlock(rq
, p
, &rf
);
4170 /* Re-check policy now with rq lock held: */
4171 if (unlikely(oldpolicy
!= -1 && oldpolicy
!= p
->policy
)) {
4172 policy
= oldpolicy
= -1;
4173 task_rq_unlock(rq
, p
, &rf
);
4178 * If setscheduling to SCHED_DEADLINE (or changing the parameters
4179 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4182 if ((dl_policy(policy
) || dl_task(p
)) && sched_dl_overflow(p
, policy
, attr
)) {
4183 task_rq_unlock(rq
, p
, &rf
);
4187 p
->sched_reset_on_fork
= reset_on_fork
;
4192 * Take priority boosted tasks into account. If the new
4193 * effective priority is unchanged, we just store the new
4194 * normal parameters and do not touch the scheduler class and
4195 * the runqueue. This will be done when the task deboost
4198 new_effective_prio
= rt_effective_prio(p
, newprio
);
4199 if (new_effective_prio
== oldprio
)
4200 queue_flags
&= ~DEQUEUE_MOVE
;
4203 queued
= task_on_rq_queued(p
);
4204 running
= task_current(rq
, p
);
4206 dequeue_task(rq
, p
, queue_flags
);
4208 put_prev_task(rq
, p
);
4210 prev_class
= p
->sched_class
;
4211 __setscheduler(rq
, p
, attr
, pi
);
4215 * We enqueue to tail when the priority of a task is
4216 * increased (user space view).
4218 if (oldprio
< p
->prio
)
4219 queue_flags
|= ENQUEUE_HEAD
;
4221 enqueue_task(rq
, p
, queue_flags
);
4224 set_curr_task(rq
, p
);
4226 check_class_changed(rq
, p
, prev_class
, oldprio
);
4228 /* Avoid rq from going away on us: */
4230 task_rq_unlock(rq
, p
, &rf
);
4233 rt_mutex_adjust_pi(p
);
4235 /* Run balance callbacks after we've adjusted the PI chain: */
4236 balance_callback(rq
);
4242 static int _sched_setscheduler(struct task_struct
*p
, int policy
,
4243 const struct sched_param
*param
, bool check
)
4245 struct sched_attr attr
= {
4246 .sched_policy
= policy
,
4247 .sched_priority
= param
->sched_priority
,
4248 .sched_nice
= PRIO_TO_NICE(p
->static_prio
),
4251 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4252 if ((policy
!= SETPARAM_POLICY
) && (policy
& SCHED_RESET_ON_FORK
)) {
4253 attr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
4254 policy
&= ~SCHED_RESET_ON_FORK
;
4255 attr
.sched_policy
= policy
;
4258 return __sched_setscheduler(p
, &attr
, check
, true);
4261 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4262 * @p: the task in question.
4263 * @policy: new policy.
4264 * @param: structure containing the new RT priority.
4266 * Return: 0 on success. An error code otherwise.
4268 * NOTE that the task may be already dead.
4270 int sched_setscheduler(struct task_struct
*p
, int policy
,
4271 const struct sched_param
*param
)
4273 return _sched_setscheduler(p
, policy
, param
, true);
4275 EXPORT_SYMBOL_GPL(sched_setscheduler
);
4277 int sched_setattr(struct task_struct
*p
, const struct sched_attr
*attr
)
4279 return __sched_setscheduler(p
, attr
, true, true);
4281 EXPORT_SYMBOL_GPL(sched_setattr
);
4284 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4285 * @p: the task in question.
4286 * @policy: new policy.
4287 * @param: structure containing the new RT priority.
4289 * Just like sched_setscheduler, only don't bother checking if the
4290 * current context has permission. For example, this is needed in
4291 * stop_machine(): we create temporary high priority worker threads,
4292 * but our caller might not have that capability.
4294 * Return: 0 on success. An error code otherwise.
4296 int sched_setscheduler_nocheck(struct task_struct
*p
, int policy
,
4297 const struct sched_param
*param
)
4299 return _sched_setscheduler(p
, policy
, param
, false);
4301 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck
);
4304 do_sched_setscheduler(pid_t pid
, int policy
, struct sched_param __user
*param
)
4306 struct sched_param lparam
;
4307 struct task_struct
*p
;
4310 if (!param
|| pid
< 0)
4312 if (copy_from_user(&lparam
, param
, sizeof(struct sched_param
)))
4317 p
= find_process_by_pid(pid
);
4319 retval
= sched_setscheduler(p
, policy
, &lparam
);
4326 * Mimics kernel/events/core.c perf_copy_attr().
4328 static int sched_copy_attr(struct sched_attr __user
*uattr
, struct sched_attr
*attr
)
4333 if (!access_ok(VERIFY_WRITE
, uattr
, SCHED_ATTR_SIZE_VER0
))
4336 /* Zero the full structure, so that a short copy will be nice: */
4337 memset(attr
, 0, sizeof(*attr
));
4339 ret
= get_user(size
, &uattr
->size
);
4343 /* Bail out on silly large: */
4344 if (size
> PAGE_SIZE
)
4347 /* ABI compatibility quirk: */
4349 size
= SCHED_ATTR_SIZE_VER0
;
4351 if (size
< SCHED_ATTR_SIZE_VER0
)
4355 * If we're handed a bigger struct than we know of,
4356 * ensure all the unknown bits are 0 - i.e. new
4357 * user-space does not rely on any kernel feature
4358 * extensions we dont know about yet.
4360 if (size
> sizeof(*attr
)) {
4361 unsigned char __user
*addr
;
4362 unsigned char __user
*end
;
4365 addr
= (void __user
*)uattr
+ sizeof(*attr
);
4366 end
= (void __user
*)uattr
+ size
;
4368 for (; addr
< end
; addr
++) {
4369 ret
= get_user(val
, addr
);
4375 size
= sizeof(*attr
);
4378 ret
= copy_from_user(attr
, uattr
, size
);
4383 * XXX: Do we want to be lenient like existing syscalls; or do we want
4384 * to be strict and return an error on out-of-bounds values?
4386 attr
->sched_nice
= clamp(attr
->sched_nice
, MIN_NICE
, MAX_NICE
);
4391 put_user(sizeof(*attr
), &uattr
->size
);
4396 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4397 * @pid: the pid in question.
4398 * @policy: new policy.
4399 * @param: structure containing the new RT priority.
4401 * Return: 0 on success. An error code otherwise.
4403 SYSCALL_DEFINE3(sched_setscheduler
, pid_t
, pid
, int, policy
, struct sched_param __user
*, param
)
4408 return do_sched_setscheduler(pid
, policy
, param
);
4412 * sys_sched_setparam - set/change the RT priority of a thread
4413 * @pid: the pid in question.
4414 * @param: structure containing the new RT priority.
4416 * Return: 0 on success. An error code otherwise.
4418 SYSCALL_DEFINE2(sched_setparam
, pid_t
, pid
, struct sched_param __user
*, param
)
4420 return do_sched_setscheduler(pid
, SETPARAM_POLICY
, param
);
4424 * sys_sched_setattr - same as above, but with extended sched_attr
4425 * @pid: the pid in question.
4426 * @uattr: structure containing the extended parameters.
4427 * @flags: for future extension.
4429 SYSCALL_DEFINE3(sched_setattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
4430 unsigned int, flags
)
4432 struct sched_attr attr
;
4433 struct task_struct
*p
;
4436 if (!uattr
|| pid
< 0 || flags
)
4439 retval
= sched_copy_attr(uattr
, &attr
);
4443 if ((int)attr
.sched_policy
< 0)
4448 p
= find_process_by_pid(pid
);
4450 retval
= sched_setattr(p
, &attr
);
4457 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4458 * @pid: the pid in question.
4460 * Return: On success, the policy of the thread. Otherwise, a negative error
4463 SYSCALL_DEFINE1(sched_getscheduler
, pid_t
, pid
)
4465 struct task_struct
*p
;
4473 p
= find_process_by_pid(pid
);
4475 retval
= security_task_getscheduler(p
);
4478 | (p
->sched_reset_on_fork
? SCHED_RESET_ON_FORK
: 0);
4485 * sys_sched_getparam - get the RT priority of a thread
4486 * @pid: the pid in question.
4487 * @param: structure containing the RT priority.
4489 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4492 SYSCALL_DEFINE2(sched_getparam
, pid_t
, pid
, struct sched_param __user
*, param
)
4494 struct sched_param lp
= { .sched_priority
= 0 };
4495 struct task_struct
*p
;
4498 if (!param
|| pid
< 0)
4502 p
= find_process_by_pid(pid
);
4507 retval
= security_task_getscheduler(p
);
4511 if (task_has_rt_policy(p
))
4512 lp
.sched_priority
= p
->rt_priority
;
4516 * This one might sleep, we cannot do it with a spinlock held ...
4518 retval
= copy_to_user(param
, &lp
, sizeof(*param
)) ? -EFAULT
: 0;
4527 static int sched_read_attr(struct sched_attr __user
*uattr
,
4528 struct sched_attr
*attr
,
4533 if (!access_ok(VERIFY_WRITE
, uattr
, usize
))
4537 * If we're handed a smaller struct than we know of,
4538 * ensure all the unknown bits are 0 - i.e. old
4539 * user-space does not get uncomplete information.
4541 if (usize
< sizeof(*attr
)) {
4542 unsigned char *addr
;
4545 addr
= (void *)attr
+ usize
;
4546 end
= (void *)attr
+ sizeof(*attr
);
4548 for (; addr
< end
; addr
++) {
4556 ret
= copy_to_user(uattr
, attr
, attr
->size
);
4564 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4565 * @pid: the pid in question.
4566 * @uattr: structure containing the extended parameters.
4567 * @size: sizeof(attr) for fwd/bwd comp.
4568 * @flags: for future extension.
4570 SYSCALL_DEFINE4(sched_getattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
4571 unsigned int, size
, unsigned int, flags
)
4573 struct sched_attr attr
= {
4574 .size
= sizeof(struct sched_attr
),
4576 struct task_struct
*p
;
4579 if (!uattr
|| pid
< 0 || size
> PAGE_SIZE
||
4580 size
< SCHED_ATTR_SIZE_VER0
|| flags
)
4584 p
= find_process_by_pid(pid
);
4589 retval
= security_task_getscheduler(p
);
4593 attr
.sched_policy
= p
->policy
;
4594 if (p
->sched_reset_on_fork
)
4595 attr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
4596 if (task_has_dl_policy(p
))
4597 __getparam_dl(p
, &attr
);
4598 else if (task_has_rt_policy(p
))
4599 attr
.sched_priority
= p
->rt_priority
;
4601 attr
.sched_nice
= task_nice(p
);
4605 retval
= sched_read_attr(uattr
, &attr
, size
);
4613 long sched_setaffinity(pid_t pid
, const struct cpumask
*in_mask
)
4615 cpumask_var_t cpus_allowed
, new_mask
;
4616 struct task_struct
*p
;
4621 p
= find_process_by_pid(pid
);
4627 /* Prevent p going away */
4631 if (p
->flags
& PF_NO_SETAFFINITY
) {
4635 if (!alloc_cpumask_var(&cpus_allowed
, GFP_KERNEL
)) {
4639 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
)) {
4641 goto out_free_cpus_allowed
;
4644 if (!check_same_owner(p
)) {
4646 if (!ns_capable(__task_cred(p
)->user_ns
, CAP_SYS_NICE
)) {
4648 goto out_free_new_mask
;
4653 retval
= security_task_setscheduler(p
);
4655 goto out_free_new_mask
;
4658 cpuset_cpus_allowed(p
, cpus_allowed
);
4659 cpumask_and(new_mask
, in_mask
, cpus_allowed
);
4662 * Since bandwidth control happens on root_domain basis,
4663 * if admission test is enabled, we only admit -deadline
4664 * tasks allowed to run on all the CPUs in the task's
4668 if (task_has_dl_policy(p
) && dl_bandwidth_enabled()) {
4670 if (!cpumask_subset(task_rq(p
)->rd
->span
, new_mask
)) {
4673 goto out_free_new_mask
;
4679 retval
= __set_cpus_allowed_ptr(p
, new_mask
, true);
4682 cpuset_cpus_allowed(p
, cpus_allowed
);
4683 if (!cpumask_subset(new_mask
, cpus_allowed
)) {
4685 * We must have raced with a concurrent cpuset
4686 * update. Just reset the cpus_allowed to the
4687 * cpuset's cpus_allowed
4689 cpumask_copy(new_mask
, cpus_allowed
);
4694 free_cpumask_var(new_mask
);
4695 out_free_cpus_allowed
:
4696 free_cpumask_var(cpus_allowed
);
4702 static int get_user_cpu_mask(unsigned long __user
*user_mask_ptr
, unsigned len
,
4703 struct cpumask
*new_mask
)
4705 if (len
< cpumask_size())
4706 cpumask_clear(new_mask
);
4707 else if (len
> cpumask_size())
4708 len
= cpumask_size();
4710 return copy_from_user(new_mask
, user_mask_ptr
, len
) ? -EFAULT
: 0;
4714 * sys_sched_setaffinity - set the CPU affinity of a process
4715 * @pid: pid of the process
4716 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4717 * @user_mask_ptr: user-space pointer to the new CPU mask
4719 * Return: 0 on success. An error code otherwise.
4721 SYSCALL_DEFINE3(sched_setaffinity
, pid_t
, pid
, unsigned int, len
,
4722 unsigned long __user
*, user_mask_ptr
)
4724 cpumask_var_t new_mask
;
4727 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
))
4730 retval
= get_user_cpu_mask(user_mask_ptr
, len
, new_mask
);
4732 retval
= sched_setaffinity(pid
, new_mask
);
4733 free_cpumask_var(new_mask
);
4737 long sched_getaffinity(pid_t pid
, struct cpumask
*mask
)
4739 struct task_struct
*p
;
4740 unsigned long flags
;
4746 p
= find_process_by_pid(pid
);
4750 retval
= security_task_getscheduler(p
);
4754 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
4755 cpumask_and(mask
, &p
->cpus_allowed
, cpu_active_mask
);
4756 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
4765 * sys_sched_getaffinity - get the CPU affinity of a process
4766 * @pid: pid of the process
4767 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4768 * @user_mask_ptr: user-space pointer to hold the current CPU mask
4770 * Return: size of CPU mask copied to user_mask_ptr on success. An
4771 * error code otherwise.
4773 SYSCALL_DEFINE3(sched_getaffinity
, pid_t
, pid
, unsigned int, len
,
4774 unsigned long __user
*, user_mask_ptr
)
4779 if ((len
* BITS_PER_BYTE
) < nr_cpu_ids
)
4781 if (len
& (sizeof(unsigned long)-1))
4784 if (!alloc_cpumask_var(&mask
, GFP_KERNEL
))
4787 ret
= sched_getaffinity(pid
, mask
);
4789 size_t retlen
= min_t(size_t, len
, cpumask_size());
4791 if (copy_to_user(user_mask_ptr
, mask
, retlen
))
4796 free_cpumask_var(mask
);
4802 * sys_sched_yield - yield the current processor to other threads.
4804 * This function yields the current CPU to other tasks. If there are no
4805 * other threads running on this CPU then this function will return.
4809 SYSCALL_DEFINE0(sched_yield
)
4814 local_irq_disable();
4818 schedstat_inc(rq
->yld_count
);
4819 current
->sched_class
->yield_task(rq
);
4822 * Since we are going to call schedule() anyway, there's
4823 * no need to preempt or enable interrupts:
4827 sched_preempt_enable_no_resched();
4834 #ifndef CONFIG_PREEMPT
4835 int __sched
_cond_resched(void)
4837 if (should_resched(0)) {
4838 preempt_schedule_common();
4843 EXPORT_SYMBOL(_cond_resched
);
4847 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4848 * call schedule, and on return reacquire the lock.
4850 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4851 * operations here to prevent schedule() from being called twice (once via
4852 * spin_unlock(), once by hand).
4854 int __cond_resched_lock(spinlock_t
*lock
)
4856 int resched
= should_resched(PREEMPT_LOCK_OFFSET
);
4859 lockdep_assert_held(lock
);
4861 if (spin_needbreak(lock
) || resched
) {
4864 preempt_schedule_common();
4872 EXPORT_SYMBOL(__cond_resched_lock
);
4874 int __sched
__cond_resched_softirq(void)
4876 BUG_ON(!in_softirq());
4878 if (should_resched(SOFTIRQ_DISABLE_OFFSET
)) {
4880 preempt_schedule_common();
4886 EXPORT_SYMBOL(__cond_resched_softirq
);
4889 * yield - yield the current processor to other threads.
4891 * Do not ever use this function, there's a 99% chance you're doing it wrong.
4893 * The scheduler is at all times free to pick the calling task as the most
4894 * eligible task to run, if removing the yield() call from your code breaks
4895 * it, its already broken.
4897 * Typical broken usage is:
4902 * where one assumes that yield() will let 'the other' process run that will
4903 * make event true. If the current task is a SCHED_FIFO task that will never
4904 * happen. Never use yield() as a progress guarantee!!
4906 * If you want to use yield() to wait for something, use wait_event().
4907 * If you want to use yield() to be 'nice' for others, use cond_resched().
4908 * If you still want to use yield(), do not!
4910 void __sched
yield(void)
4912 set_current_state(TASK_RUNNING
);
4915 EXPORT_SYMBOL(yield
);
4918 * yield_to - yield the current processor to another thread in
4919 * your thread group, or accelerate that thread toward the
4920 * processor it's on.
4922 * @preempt: whether task preemption is allowed or not
4924 * It's the caller's job to ensure that the target task struct
4925 * can't go away on us before we can do any checks.
4928 * true (>0) if we indeed boosted the target task.
4929 * false (0) if we failed to boost the target.
4930 * -ESRCH if there's no task to yield to.
4932 int __sched
yield_to(struct task_struct
*p
, bool preempt
)
4934 struct task_struct
*curr
= current
;
4935 struct rq
*rq
, *p_rq
;
4936 unsigned long flags
;
4939 local_irq_save(flags
);
4945 * If we're the only runnable task on the rq and target rq also
4946 * has only one task, there's absolutely no point in yielding.
4948 if (rq
->nr_running
== 1 && p_rq
->nr_running
== 1) {
4953 double_rq_lock(rq
, p_rq
);
4954 if (task_rq(p
) != p_rq
) {
4955 double_rq_unlock(rq
, p_rq
);
4959 if (!curr
->sched_class
->yield_to_task
)
4962 if (curr
->sched_class
!= p
->sched_class
)
4965 if (task_running(p_rq
, p
) || p
->state
)
4968 yielded
= curr
->sched_class
->yield_to_task(rq
, p
, preempt
);
4970 schedstat_inc(rq
->yld_count
);
4972 * Make p's CPU reschedule; pick_next_entity takes care of
4975 if (preempt
&& rq
!= p_rq
)
4980 double_rq_unlock(rq
, p_rq
);
4982 local_irq_restore(flags
);
4989 EXPORT_SYMBOL_GPL(yield_to
);
4991 int io_schedule_prepare(void)
4993 int old_iowait
= current
->in_iowait
;
4995 current
->in_iowait
= 1;
4996 blk_schedule_flush_plug(current
);
5001 void io_schedule_finish(int token
)
5003 current
->in_iowait
= token
;
5007 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5008 * that process accounting knows that this is a task in IO wait state.
5010 long __sched
io_schedule_timeout(long timeout
)
5015 token
= io_schedule_prepare();
5016 ret
= schedule_timeout(timeout
);
5017 io_schedule_finish(token
);
5021 EXPORT_SYMBOL(io_schedule_timeout
);
5023 void io_schedule(void)
5027 token
= io_schedule_prepare();
5029 io_schedule_finish(token
);
5031 EXPORT_SYMBOL(io_schedule
);
5034 * sys_sched_get_priority_max - return maximum RT priority.
5035 * @policy: scheduling class.
5037 * Return: On success, this syscall returns the maximum
5038 * rt_priority that can be used by a given scheduling class.
5039 * On failure, a negative error code is returned.
5041 SYSCALL_DEFINE1(sched_get_priority_max
, int, policy
)
5048 ret
= MAX_USER_RT_PRIO
-1;
5050 case SCHED_DEADLINE
:
5061 * sys_sched_get_priority_min - return minimum RT priority.
5062 * @policy: scheduling class.
5064 * Return: On success, this syscall returns the minimum
5065 * rt_priority that can be used by a given scheduling class.
5066 * On failure, a negative error code is returned.
5068 SYSCALL_DEFINE1(sched_get_priority_min
, int, policy
)
5077 case SCHED_DEADLINE
:
5087 * sys_sched_rr_get_interval - return the default timeslice of a process.
5088 * @pid: pid of the process.
5089 * @interval: userspace pointer to the timeslice value.
5091 * this syscall writes the default timeslice value of a given process
5092 * into the user-space timespec buffer. A value of '0' means infinity.
5094 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5097 SYSCALL_DEFINE2(sched_rr_get_interval
, pid_t
, pid
,
5098 struct timespec __user
*, interval
)
5100 struct task_struct
*p
;
5101 unsigned int time_slice
;
5112 p
= find_process_by_pid(pid
);
5116 retval
= security_task_getscheduler(p
);
5120 rq
= task_rq_lock(p
, &rf
);
5122 if (p
->sched_class
->get_rr_interval
)
5123 time_slice
= p
->sched_class
->get_rr_interval(rq
, p
);
5124 task_rq_unlock(rq
, p
, &rf
);
5127 jiffies_to_timespec(time_slice
, &t
);
5128 retval
= copy_to_user(interval
, &t
, sizeof(t
)) ? -EFAULT
: 0;
5136 void sched_show_task(struct task_struct
*p
)
5138 unsigned long free
= 0;
5141 if (!try_get_task_stack(p
))
5144 printk(KERN_INFO
"%-15.15s %c", p
->comm
, task_state_to_char(p
));
5146 if (p
->state
== TASK_RUNNING
)
5147 printk(KERN_CONT
" running task ");
5148 #ifdef CONFIG_DEBUG_STACK_USAGE
5149 free
= stack_not_used(p
);
5154 ppid
= task_pid_nr(rcu_dereference(p
->real_parent
));
5156 printk(KERN_CONT
"%5lu %5d %6d 0x%08lx\n", free
,
5157 task_pid_nr(p
), ppid
,
5158 (unsigned long)task_thread_info(p
)->flags
);
5160 print_worker_info(KERN_INFO
, p
);
5161 show_stack(p
, NULL
);
5165 void show_state_filter(unsigned long state_filter
)
5167 struct task_struct
*g
, *p
;
5169 #if BITS_PER_LONG == 32
5171 " task PC stack pid father\n");
5174 " task PC stack pid father\n");
5177 for_each_process_thread(g
, p
) {
5179 * reset the NMI-timeout, listing all files on a slow
5180 * console might take a lot of time:
5181 * Also, reset softlockup watchdogs on all CPUs, because
5182 * another CPU might be blocked waiting for us to process
5185 touch_nmi_watchdog();
5186 touch_all_softlockup_watchdogs();
5187 if (!state_filter
|| (p
->state
& state_filter
))
5191 #ifdef CONFIG_SCHED_DEBUG
5193 sysrq_sched_debug_show();
5197 * Only show locks if all tasks are dumped:
5200 debug_show_all_locks();
5204 * init_idle - set up an idle thread for a given CPU
5205 * @idle: task in question
5206 * @cpu: CPU the idle task belongs to
5208 * NOTE: this function does not set the idle thread's NEED_RESCHED
5209 * flag, to make booting more robust.
5211 void init_idle(struct task_struct
*idle
, int cpu
)
5213 struct rq
*rq
= cpu_rq(cpu
);
5214 unsigned long flags
;
5216 raw_spin_lock_irqsave(&idle
->pi_lock
, flags
);
5217 raw_spin_lock(&rq
->lock
);
5219 __sched_fork(0, idle
);
5220 idle
->state
= TASK_RUNNING
;
5221 idle
->se
.exec_start
= sched_clock();
5222 idle
->flags
|= PF_IDLE
;
5224 kasan_unpoison_task_stack(idle
);
5228 * Its possible that init_idle() gets called multiple times on a task,
5229 * in that case do_set_cpus_allowed() will not do the right thing.
5231 * And since this is boot we can forgo the serialization.
5233 set_cpus_allowed_common(idle
, cpumask_of(cpu
));
5236 * We're having a chicken and egg problem, even though we are
5237 * holding rq->lock, the CPU isn't yet set to this CPU so the
5238 * lockdep check in task_group() will fail.
5240 * Similar case to sched_fork(). / Alternatively we could
5241 * use task_rq_lock() here and obtain the other rq->lock.
5246 __set_task_cpu(idle
, cpu
);
5249 rq
->curr
= rq
->idle
= idle
;
5250 idle
->on_rq
= TASK_ON_RQ_QUEUED
;
5254 raw_spin_unlock(&rq
->lock
);
5255 raw_spin_unlock_irqrestore(&idle
->pi_lock
, flags
);
5257 /* Set the preempt count _outside_ the spinlocks! */
5258 init_idle_preempt_count(idle
, cpu
);
5261 * The idle tasks have their own, simple scheduling class:
5263 idle
->sched_class
= &idle_sched_class
;
5264 ftrace_graph_init_idle_task(idle
, cpu
);
5265 vtime_init_idle(idle
, cpu
);
5267 sprintf(idle
->comm
, "%s/%d", INIT_TASK_COMM
, cpu
);
5273 int cpuset_cpumask_can_shrink(const struct cpumask
*cur
,
5274 const struct cpumask
*trial
)
5278 if (!cpumask_weight(cur
))
5281 ret
= dl_cpuset_cpumask_can_shrink(cur
, trial
);
5286 int task_can_attach(struct task_struct
*p
,
5287 const struct cpumask
*cs_cpus_allowed
)
5292 * Kthreads which disallow setaffinity shouldn't be moved
5293 * to a new cpuset; we don't want to change their CPU
5294 * affinity and isolating such threads by their set of
5295 * allowed nodes is unnecessary. Thus, cpusets are not
5296 * applicable for such threads. This prevents checking for
5297 * success of set_cpus_allowed_ptr() on all attached tasks
5298 * before cpus_allowed may be changed.
5300 if (p
->flags
& PF_NO_SETAFFINITY
) {
5305 if (dl_task(p
) && !cpumask_intersects(task_rq(p
)->rd
->span
,
5307 ret
= dl_task_can_attach(p
, cs_cpus_allowed
);
5313 bool sched_smp_initialized __read_mostly
;
5315 #ifdef CONFIG_NUMA_BALANCING
5316 /* Migrate current task p to target_cpu */
5317 int migrate_task_to(struct task_struct
*p
, int target_cpu
)
5319 struct migration_arg arg
= { p
, target_cpu
};
5320 int curr_cpu
= task_cpu(p
);
5322 if (curr_cpu
== target_cpu
)
5325 if (!cpumask_test_cpu(target_cpu
, &p
->cpus_allowed
))
5328 /* TODO: This is not properly updating schedstats */
5330 trace_sched_move_numa(p
, curr_cpu
, target_cpu
);
5331 return stop_one_cpu(curr_cpu
, migration_cpu_stop
, &arg
);
5335 * Requeue a task on a given node and accurately track the number of NUMA
5336 * tasks on the runqueues
5338 void sched_setnuma(struct task_struct
*p
, int nid
)
5340 bool queued
, running
;
5344 rq
= task_rq_lock(p
, &rf
);
5345 queued
= task_on_rq_queued(p
);
5346 running
= task_current(rq
, p
);
5349 dequeue_task(rq
, p
, DEQUEUE_SAVE
);
5351 put_prev_task(rq
, p
);
5353 p
->numa_preferred_nid
= nid
;
5356 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
5358 set_curr_task(rq
, p
);
5359 task_rq_unlock(rq
, p
, &rf
);
5361 #endif /* CONFIG_NUMA_BALANCING */
5363 #ifdef CONFIG_HOTPLUG_CPU
5365 * Ensure that the idle task is using init_mm right before its CPU goes
5368 void idle_task_exit(void)
5370 struct mm_struct
*mm
= current
->active_mm
;
5372 BUG_ON(cpu_online(smp_processor_id()));
5374 if (mm
!= &init_mm
) {
5375 switch_mm(mm
, &init_mm
, current
);
5376 finish_arch_post_lock_switch();
5382 * Since this CPU is going 'away' for a while, fold any nr_active delta
5383 * we might have. Assumes we're called after migrate_tasks() so that the
5384 * nr_active count is stable. We need to take the teardown thread which
5385 * is calling this into account, so we hand in adjust = 1 to the load
5388 * Also see the comment "Global load-average calculations".
5390 static void calc_load_migrate(struct rq
*rq
)
5392 long delta
= calc_load_fold_active(rq
, 1);
5394 atomic_long_add(delta
, &calc_load_tasks
);
5397 static void put_prev_task_fake(struct rq
*rq
, struct task_struct
*prev
)
5401 static const struct sched_class fake_sched_class
= {
5402 .put_prev_task
= put_prev_task_fake
,
5405 static struct task_struct fake_task
= {
5407 * Avoid pull_{rt,dl}_task()
5409 .prio
= MAX_PRIO
+ 1,
5410 .sched_class
= &fake_sched_class
,
5414 * Migrate all tasks from the rq, sleeping tasks will be migrated by
5415 * try_to_wake_up()->select_task_rq().
5417 * Called with rq->lock held even though we'er in stop_machine() and
5418 * there's no concurrency possible, we hold the required locks anyway
5419 * because of lock validation efforts.
5421 static void migrate_tasks(struct rq
*dead_rq
, struct rq_flags
*rf
)
5423 struct rq
*rq
= dead_rq
;
5424 struct task_struct
*next
, *stop
= rq
->stop
;
5425 struct rq_flags orf
= *rf
;
5429 * Fudge the rq selection such that the below task selection loop
5430 * doesn't get stuck on the currently eligible stop task.
5432 * We're currently inside stop_machine() and the rq is either stuck
5433 * in the stop_machine_cpu_stop() loop, or we're executing this code,
5434 * either way we should never end up calling schedule() until we're
5440 * put_prev_task() and pick_next_task() sched
5441 * class method both need to have an up-to-date
5442 * value of rq->clock[_task]
5444 update_rq_clock(rq
);
5448 * There's this thread running, bail when that's the only
5451 if (rq
->nr_running
== 1)
5455 * pick_next_task() assumes pinned rq->lock:
5457 next
= pick_next_task(rq
, &fake_task
, rf
);
5459 put_prev_task(rq
, next
);
5462 * Rules for changing task_struct::cpus_allowed are holding
5463 * both pi_lock and rq->lock, such that holding either
5464 * stabilizes the mask.
5466 * Drop rq->lock is not quite as disastrous as it usually is
5467 * because !cpu_active at this point, which means load-balance
5468 * will not interfere. Also, stop-machine.
5471 raw_spin_lock(&next
->pi_lock
);
5475 * Since we're inside stop-machine, _nothing_ should have
5476 * changed the task, WARN if weird stuff happened, because in
5477 * that case the above rq->lock drop is a fail too.
5479 if (WARN_ON(task_rq(next
) != rq
|| !task_on_rq_queued(next
))) {
5480 raw_spin_unlock(&next
->pi_lock
);
5484 /* Find suitable destination for @next, with force if needed. */
5485 dest_cpu
= select_fallback_rq(dead_rq
->cpu
, next
);
5486 rq
= __migrate_task(rq
, rf
, next
, dest_cpu
);
5487 if (rq
!= dead_rq
) {
5493 raw_spin_unlock(&next
->pi_lock
);
5498 #endif /* CONFIG_HOTPLUG_CPU */
5500 void set_rq_online(struct rq
*rq
)
5503 const struct sched_class
*class;
5505 cpumask_set_cpu(rq
->cpu
, rq
->rd
->online
);
5508 for_each_class(class) {
5509 if (class->rq_online
)
5510 class->rq_online(rq
);
5515 void set_rq_offline(struct rq
*rq
)
5518 const struct sched_class
*class;
5520 for_each_class(class) {
5521 if (class->rq_offline
)
5522 class->rq_offline(rq
);
5525 cpumask_clear_cpu(rq
->cpu
, rq
->rd
->online
);
5530 static void set_cpu_rq_start_time(unsigned int cpu
)
5532 struct rq
*rq
= cpu_rq(cpu
);
5534 rq
->age_stamp
= sched_clock_cpu(cpu
);
5538 * used to mark begin/end of suspend/resume:
5540 static int num_cpus_frozen
;
5543 * Update cpusets according to cpu_active mask. If cpusets are
5544 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
5545 * around partition_sched_domains().
5547 * If we come here as part of a suspend/resume, don't touch cpusets because we
5548 * want to restore it back to its original state upon resume anyway.
5550 static void cpuset_cpu_active(void)
5552 if (cpuhp_tasks_frozen
) {
5554 * num_cpus_frozen tracks how many CPUs are involved in suspend
5555 * resume sequence. As long as this is not the last online
5556 * operation in the resume sequence, just build a single sched
5557 * domain, ignoring cpusets.
5560 if (likely(num_cpus_frozen
)) {
5561 partition_sched_domains(1, NULL
, NULL
);
5565 * This is the last CPU online operation. So fall through and
5566 * restore the original sched domains by considering the
5567 * cpuset configurations.
5570 cpuset_update_active_cpus();
5573 static int cpuset_cpu_inactive(unsigned int cpu
)
5575 if (!cpuhp_tasks_frozen
) {
5576 if (dl_cpu_busy(cpu
))
5578 cpuset_update_active_cpus();
5581 partition_sched_domains(1, NULL
, NULL
);
5586 int sched_cpu_activate(unsigned int cpu
)
5588 struct rq
*rq
= cpu_rq(cpu
);
5591 set_cpu_active(cpu
, true);
5593 if (sched_smp_initialized
) {
5594 sched_domains_numa_masks_set(cpu
);
5595 cpuset_cpu_active();
5599 * Put the rq online, if not already. This happens:
5601 * 1) In the early boot process, because we build the real domains
5602 * after all CPUs have been brought up.
5604 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
5607 rq_lock_irqsave(rq
, &rf
);
5609 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
5612 rq_unlock_irqrestore(rq
, &rf
);
5614 update_max_interval();
5619 int sched_cpu_deactivate(unsigned int cpu
)
5623 set_cpu_active(cpu
, false);
5625 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
5626 * users of this state to go away such that all new such users will
5629 * Do sync before park smpboot threads to take care the rcu boost case.
5631 synchronize_rcu_mult(call_rcu
, call_rcu_sched
);
5633 if (!sched_smp_initialized
)
5636 ret
= cpuset_cpu_inactive(cpu
);
5638 set_cpu_active(cpu
, true);
5641 sched_domains_numa_masks_clear(cpu
);
5645 static void sched_rq_cpu_starting(unsigned int cpu
)
5647 struct rq
*rq
= cpu_rq(cpu
);
5649 rq
->calc_load_update
= calc_load_update
;
5650 update_max_interval();
5653 int sched_cpu_starting(unsigned int cpu
)
5655 set_cpu_rq_start_time(cpu
);
5656 sched_rq_cpu_starting(cpu
);
5660 #ifdef CONFIG_HOTPLUG_CPU
5661 int sched_cpu_dying(unsigned int cpu
)
5663 struct rq
*rq
= cpu_rq(cpu
);
5666 /* Handle pending wakeups and then migrate everything off */
5667 sched_ttwu_pending();
5669 rq_lock_irqsave(rq
, &rf
);
5671 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
5674 migrate_tasks(rq
, &rf
);
5675 BUG_ON(rq
->nr_running
!= 1);
5676 rq_unlock_irqrestore(rq
, &rf
);
5678 calc_load_migrate(rq
);
5679 update_max_interval();
5680 nohz_balance_exit_idle(cpu
);
5686 #ifdef CONFIG_SCHED_SMT
5687 DEFINE_STATIC_KEY_FALSE(sched_smt_present
);
5689 static void sched_init_smt(void)
5692 * We've enumerated all CPUs and will assume that if any CPU
5693 * has SMT siblings, CPU0 will too.
5695 if (cpumask_weight(cpu_smt_mask(0)) > 1)
5696 static_branch_enable(&sched_smt_present
);
5699 static inline void sched_init_smt(void) { }
5702 void __init
sched_init_smp(void)
5704 cpumask_var_t non_isolated_cpus
;
5706 alloc_cpumask_var(&non_isolated_cpus
, GFP_KERNEL
);
5711 * There's no userspace yet to cause hotplug operations; hence all the
5712 * CPU masks are stable and all blatant races in the below code cannot
5715 mutex_lock(&sched_domains_mutex
);
5716 sched_init_domains(cpu_active_mask
);
5717 cpumask_andnot(non_isolated_cpus
, cpu_possible_mask
, cpu_isolated_map
);
5718 if (cpumask_empty(non_isolated_cpus
))
5719 cpumask_set_cpu(smp_processor_id(), non_isolated_cpus
);
5720 mutex_unlock(&sched_domains_mutex
);
5722 /* Move init over to a non-isolated CPU */
5723 if (set_cpus_allowed_ptr(current
, non_isolated_cpus
) < 0)
5725 sched_init_granularity();
5726 free_cpumask_var(non_isolated_cpus
);
5728 init_sched_rt_class();
5729 init_sched_dl_class();
5733 sched_smp_initialized
= true;
5736 static int __init
migration_init(void)
5738 sched_rq_cpu_starting(smp_processor_id());
5741 early_initcall(migration_init
);
5744 void __init
sched_init_smp(void)
5746 sched_init_granularity();
5748 #endif /* CONFIG_SMP */
5750 int in_sched_functions(unsigned long addr
)
5752 return in_lock_functions(addr
) ||
5753 (addr
>= (unsigned long)__sched_text_start
5754 && addr
< (unsigned long)__sched_text_end
);
5757 #ifdef CONFIG_CGROUP_SCHED
5759 * Default task group.
5760 * Every task in system belongs to this group at bootup.
5762 struct task_group root_task_group
;
5763 LIST_HEAD(task_groups
);
5765 /* Cacheline aligned slab cache for task_group */
5766 static struct kmem_cache
*task_group_cache __read_mostly
;
5769 DECLARE_PER_CPU(cpumask_var_t
, load_balance_mask
);
5770 DECLARE_PER_CPU(cpumask_var_t
, select_idle_mask
);
5772 void __init
sched_init(void)
5775 unsigned long alloc_size
= 0, ptr
;
5780 #ifdef CONFIG_FAIR_GROUP_SCHED
5781 alloc_size
+= 2 * nr_cpu_ids
* sizeof(void **);
5783 #ifdef CONFIG_RT_GROUP_SCHED
5784 alloc_size
+= 2 * nr_cpu_ids
* sizeof(void **);
5787 ptr
= (unsigned long)kzalloc(alloc_size
, GFP_NOWAIT
);
5789 #ifdef CONFIG_FAIR_GROUP_SCHED
5790 root_task_group
.se
= (struct sched_entity
**)ptr
;
5791 ptr
+= nr_cpu_ids
* sizeof(void **);
5793 root_task_group
.cfs_rq
= (struct cfs_rq
**)ptr
;
5794 ptr
+= nr_cpu_ids
* sizeof(void **);
5796 #endif /* CONFIG_FAIR_GROUP_SCHED */
5797 #ifdef CONFIG_RT_GROUP_SCHED
5798 root_task_group
.rt_se
= (struct sched_rt_entity
**)ptr
;
5799 ptr
+= nr_cpu_ids
* sizeof(void **);
5801 root_task_group
.rt_rq
= (struct rt_rq
**)ptr
;
5802 ptr
+= nr_cpu_ids
* sizeof(void **);
5804 #endif /* CONFIG_RT_GROUP_SCHED */
5806 #ifdef CONFIG_CPUMASK_OFFSTACK
5807 for_each_possible_cpu(i
) {
5808 per_cpu(load_balance_mask
, i
) = (cpumask_var_t
)kzalloc_node(
5809 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
5810 per_cpu(select_idle_mask
, i
) = (cpumask_var_t
)kzalloc_node(
5811 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
5813 #endif /* CONFIG_CPUMASK_OFFSTACK */
5815 init_rt_bandwidth(&def_rt_bandwidth
, global_rt_period(), global_rt_runtime());
5816 init_dl_bandwidth(&def_dl_bandwidth
, global_rt_period(), global_rt_runtime());
5819 init_defrootdomain();
5822 #ifdef CONFIG_RT_GROUP_SCHED
5823 init_rt_bandwidth(&root_task_group
.rt_bandwidth
,
5824 global_rt_period(), global_rt_runtime());
5825 #endif /* CONFIG_RT_GROUP_SCHED */
5827 #ifdef CONFIG_CGROUP_SCHED
5828 task_group_cache
= KMEM_CACHE(task_group
, 0);
5830 list_add(&root_task_group
.list
, &task_groups
);
5831 INIT_LIST_HEAD(&root_task_group
.children
);
5832 INIT_LIST_HEAD(&root_task_group
.siblings
);
5833 autogroup_init(&init_task
);
5834 #endif /* CONFIG_CGROUP_SCHED */
5836 for_each_possible_cpu(i
) {
5840 raw_spin_lock_init(&rq
->lock
);
5842 rq
->calc_load_active
= 0;
5843 rq
->calc_load_update
= jiffies
+ LOAD_FREQ
;
5844 init_cfs_rq(&rq
->cfs
);
5845 init_rt_rq(&rq
->rt
);
5846 init_dl_rq(&rq
->dl
);
5847 #ifdef CONFIG_FAIR_GROUP_SCHED
5848 root_task_group
.shares
= ROOT_TASK_GROUP_LOAD
;
5849 INIT_LIST_HEAD(&rq
->leaf_cfs_rq_list
);
5850 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
5852 * How much CPU bandwidth does root_task_group get?
5854 * In case of task-groups formed thr' the cgroup filesystem, it
5855 * gets 100% of the CPU resources in the system. This overall
5856 * system CPU resource is divided among the tasks of
5857 * root_task_group and its child task-groups in a fair manner,
5858 * based on each entity's (task or task-group's) weight
5859 * (se->load.weight).
5861 * In other words, if root_task_group has 10 tasks of weight
5862 * 1024) and two child groups A0 and A1 (of weight 1024 each),
5863 * then A0's share of the CPU resource is:
5865 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
5867 * We achieve this by letting root_task_group's tasks sit
5868 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
5870 init_cfs_bandwidth(&root_task_group
.cfs_bandwidth
);
5871 init_tg_cfs_entry(&root_task_group
, &rq
->cfs
, NULL
, i
, NULL
);
5872 #endif /* CONFIG_FAIR_GROUP_SCHED */
5874 rq
->rt
.rt_runtime
= def_rt_bandwidth
.rt_runtime
;
5875 #ifdef CONFIG_RT_GROUP_SCHED
5876 init_tg_rt_entry(&root_task_group
, &rq
->rt
, NULL
, i
, NULL
);
5879 for (j
= 0; j
< CPU_LOAD_IDX_MAX
; j
++)
5880 rq
->cpu_load
[j
] = 0;
5885 rq
->cpu_capacity
= rq
->cpu_capacity_orig
= SCHED_CAPACITY_SCALE
;
5886 rq
->balance_callback
= NULL
;
5887 rq
->active_balance
= 0;
5888 rq
->next_balance
= jiffies
;
5893 rq
->avg_idle
= 2*sysctl_sched_migration_cost
;
5894 rq
->max_idle_balance_cost
= sysctl_sched_migration_cost
;
5896 INIT_LIST_HEAD(&rq
->cfs_tasks
);
5898 rq_attach_root(rq
, &def_root_domain
);
5899 #ifdef CONFIG_NO_HZ_COMMON
5900 rq
->last_load_update_tick
= jiffies
;
5903 #ifdef CONFIG_NO_HZ_FULL
5904 rq
->last_sched_tick
= 0;
5906 #endif /* CONFIG_SMP */
5908 atomic_set(&rq
->nr_iowait
, 0);
5911 set_load_weight(&init_task
);
5914 * The boot idle thread does lazy MMU switching as well:
5917 enter_lazy_tlb(&init_mm
, current
);
5920 * Make us the idle thread. Technically, schedule() should not be
5921 * called from this thread, however somewhere below it might be,
5922 * but because we are the idle thread, we just pick up running again
5923 * when this runqueue becomes "idle".
5925 init_idle(current
, smp_processor_id());
5927 calc_load_update
= jiffies
+ LOAD_FREQ
;
5930 /* May be allocated at isolcpus cmdline parse time */
5931 if (cpu_isolated_map
== NULL
)
5932 zalloc_cpumask_var(&cpu_isolated_map
, GFP_NOWAIT
);
5933 idle_thread_set_boot_cpu();
5934 set_cpu_rq_start_time(smp_processor_id());
5936 init_sched_fair_class();
5940 scheduler_running
= 1;
5943 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5944 static inline int preempt_count_equals(int preempt_offset
)
5946 int nested
= preempt_count() + rcu_preempt_depth();
5948 return (nested
== preempt_offset
);
5951 void __might_sleep(const char *file
, int line
, int preempt_offset
)
5954 * Blocking primitives will set (and therefore destroy) current->state,
5955 * since we will exit with TASK_RUNNING make sure we enter with it,
5956 * otherwise we will destroy state.
5958 WARN_ONCE(current
->state
!= TASK_RUNNING
&& current
->task_state_change
,
5959 "do not call blocking ops when !TASK_RUNNING; "
5960 "state=%lx set at [<%p>] %pS\n",
5962 (void *)current
->task_state_change
,
5963 (void *)current
->task_state_change
);
5965 ___might_sleep(file
, line
, preempt_offset
);
5967 EXPORT_SYMBOL(__might_sleep
);
5969 void ___might_sleep(const char *file
, int line
, int preempt_offset
)
5971 /* Ratelimiting timestamp: */
5972 static unsigned long prev_jiffy
;
5974 unsigned long preempt_disable_ip
;
5976 /* WARN_ON_ONCE() by default, no rate limit required: */
5979 if ((preempt_count_equals(preempt_offset
) && !irqs_disabled() &&
5980 !is_idle_task(current
)) ||
5981 system_state
== SYSTEM_BOOTING
|| system_state
> SYSTEM_RUNNING
||
5985 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
5987 prev_jiffy
= jiffies
;
5989 /* Save this before calling printk(), since that will clobber it: */
5990 preempt_disable_ip
= get_preempt_disable_ip(current
);
5993 "BUG: sleeping function called from invalid context at %s:%d\n",
5996 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
5997 in_atomic(), irqs_disabled(),
5998 current
->pid
, current
->comm
);
6000 if (task_stack_end_corrupted(current
))
6001 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
6003 debug_show_held_locks(current
);
6004 if (irqs_disabled())
6005 print_irqtrace_events(current
);
6006 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
6007 && !preempt_count_equals(preempt_offset
)) {
6008 pr_err("Preemption disabled at:");
6009 print_ip_sym(preempt_disable_ip
);
6013 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
6015 EXPORT_SYMBOL(___might_sleep
);
6018 #ifdef CONFIG_MAGIC_SYSRQ
6019 void normalize_rt_tasks(void)
6021 struct task_struct
*g
, *p
;
6022 struct sched_attr attr
= {
6023 .sched_policy
= SCHED_NORMAL
,
6026 read_lock(&tasklist_lock
);
6027 for_each_process_thread(g
, p
) {
6029 * Only normalize user tasks:
6031 if (p
->flags
& PF_KTHREAD
)
6034 p
->se
.exec_start
= 0;
6035 schedstat_set(p
->se
.statistics
.wait_start
, 0);
6036 schedstat_set(p
->se
.statistics
.sleep_start
, 0);
6037 schedstat_set(p
->se
.statistics
.block_start
, 0);
6039 if (!dl_task(p
) && !rt_task(p
)) {
6041 * Renice negative nice level userspace
6044 if (task_nice(p
) < 0)
6045 set_user_nice(p
, 0);
6049 __sched_setscheduler(p
, &attr
, false, false);
6051 read_unlock(&tasklist_lock
);
6054 #endif /* CONFIG_MAGIC_SYSRQ */
6056 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
6058 * These functions are only useful for the IA64 MCA handling, or kdb.
6060 * They can only be called when the whole system has been
6061 * stopped - every CPU needs to be quiescent, and no scheduling
6062 * activity can take place. Using them for anything else would
6063 * be a serious bug, and as a result, they aren't even visible
6064 * under any other configuration.
6068 * curr_task - return the current task for a given CPU.
6069 * @cpu: the processor in question.
6071 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6073 * Return: The current task for @cpu.
6075 struct task_struct
*curr_task(int cpu
)
6077 return cpu_curr(cpu
);
6080 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
6084 * set_curr_task - set the current task for a given CPU.
6085 * @cpu: the processor in question.
6086 * @p: the task pointer to set.
6088 * Description: This function must only be used when non-maskable interrupts
6089 * are serviced on a separate stack. It allows the architecture to switch the
6090 * notion of the current task on a CPU in a non-blocking manner. This function
6091 * must be called with all CPU's synchronized, and interrupts disabled, the
6092 * and caller must save the original value of the current task (see
6093 * curr_task() above) and restore that value before reenabling interrupts and
6094 * re-starting the system.
6096 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6098 void ia64_set_curr_task(int cpu
, struct task_struct
*p
)
6105 #ifdef CONFIG_CGROUP_SCHED
6106 /* task_group_lock serializes the addition/removal of task groups */
6107 static DEFINE_SPINLOCK(task_group_lock
);
6109 static void sched_free_group(struct task_group
*tg
)
6111 free_fair_sched_group(tg
);
6112 free_rt_sched_group(tg
);
6114 kmem_cache_free(task_group_cache
, tg
);
6117 /* allocate runqueue etc for a new task group */
6118 struct task_group
*sched_create_group(struct task_group
*parent
)
6120 struct task_group
*tg
;
6122 tg
= kmem_cache_alloc(task_group_cache
, GFP_KERNEL
| __GFP_ZERO
);
6124 return ERR_PTR(-ENOMEM
);
6126 if (!alloc_fair_sched_group(tg
, parent
))
6129 if (!alloc_rt_sched_group(tg
, parent
))
6135 sched_free_group(tg
);
6136 return ERR_PTR(-ENOMEM
);
6139 void sched_online_group(struct task_group
*tg
, struct task_group
*parent
)
6141 unsigned long flags
;
6143 spin_lock_irqsave(&task_group_lock
, flags
);
6144 list_add_rcu(&tg
->list
, &task_groups
);
6146 /* Root should already exist: */
6149 tg
->parent
= parent
;
6150 INIT_LIST_HEAD(&tg
->children
);
6151 list_add_rcu(&tg
->siblings
, &parent
->children
);
6152 spin_unlock_irqrestore(&task_group_lock
, flags
);
6154 online_fair_sched_group(tg
);
6157 /* rcu callback to free various structures associated with a task group */
6158 static void sched_free_group_rcu(struct rcu_head
*rhp
)
6160 /* Now it should be safe to free those cfs_rqs: */
6161 sched_free_group(container_of(rhp
, struct task_group
, rcu
));
6164 void sched_destroy_group(struct task_group
*tg
)
6166 /* Wait for possible concurrent references to cfs_rqs complete: */
6167 call_rcu(&tg
->rcu
, sched_free_group_rcu
);
6170 void sched_offline_group(struct task_group
*tg
)
6172 unsigned long flags
;
6174 /* End participation in shares distribution: */
6175 unregister_fair_sched_group(tg
);
6177 spin_lock_irqsave(&task_group_lock
, flags
);
6178 list_del_rcu(&tg
->list
);
6179 list_del_rcu(&tg
->siblings
);
6180 spin_unlock_irqrestore(&task_group_lock
, flags
);
6183 static void sched_change_group(struct task_struct
*tsk
, int type
)
6185 struct task_group
*tg
;
6188 * All callers are synchronized by task_rq_lock(); we do not use RCU
6189 * which is pointless here. Thus, we pass "true" to task_css_check()
6190 * to prevent lockdep warnings.
6192 tg
= container_of(task_css_check(tsk
, cpu_cgrp_id
, true),
6193 struct task_group
, css
);
6194 tg
= autogroup_task_group(tsk
, tg
);
6195 tsk
->sched_task_group
= tg
;
6197 #ifdef CONFIG_FAIR_GROUP_SCHED
6198 if (tsk
->sched_class
->task_change_group
)
6199 tsk
->sched_class
->task_change_group(tsk
, type
);
6202 set_task_rq(tsk
, task_cpu(tsk
));
6206 * Change task's runqueue when it moves between groups.
6208 * The caller of this function should have put the task in its new group by
6209 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
6212 void sched_move_task(struct task_struct
*tsk
)
6214 int queued
, running
, queue_flags
=
6215 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
6219 rq
= task_rq_lock(tsk
, &rf
);
6220 update_rq_clock(rq
);
6222 running
= task_current(rq
, tsk
);
6223 queued
= task_on_rq_queued(tsk
);
6226 dequeue_task(rq
, tsk
, queue_flags
);
6228 put_prev_task(rq
, tsk
);
6230 sched_change_group(tsk
, TASK_MOVE_GROUP
);
6233 enqueue_task(rq
, tsk
, queue_flags
);
6235 set_curr_task(rq
, tsk
);
6237 task_rq_unlock(rq
, tsk
, &rf
);
6240 static inline struct task_group
*css_tg(struct cgroup_subsys_state
*css
)
6242 return css
? container_of(css
, struct task_group
, css
) : NULL
;
6245 static struct cgroup_subsys_state
*
6246 cpu_cgroup_css_alloc(struct cgroup_subsys_state
*parent_css
)
6248 struct task_group
*parent
= css_tg(parent_css
);
6249 struct task_group
*tg
;
6252 /* This is early initialization for the top cgroup */
6253 return &root_task_group
.css
;
6256 tg
= sched_create_group(parent
);
6258 return ERR_PTR(-ENOMEM
);
6263 /* Expose task group only after completing cgroup initialization */
6264 static int cpu_cgroup_css_online(struct cgroup_subsys_state
*css
)
6266 struct task_group
*tg
= css_tg(css
);
6267 struct task_group
*parent
= css_tg(css
->parent
);
6270 sched_online_group(tg
, parent
);
6274 static void cpu_cgroup_css_released(struct cgroup_subsys_state
*css
)
6276 struct task_group
*tg
= css_tg(css
);
6278 sched_offline_group(tg
);
6281 static void cpu_cgroup_css_free(struct cgroup_subsys_state
*css
)
6283 struct task_group
*tg
= css_tg(css
);
6286 * Relies on the RCU grace period between css_released() and this.
6288 sched_free_group(tg
);
6292 * This is called before wake_up_new_task(), therefore we really only
6293 * have to set its group bits, all the other stuff does not apply.
6295 static void cpu_cgroup_fork(struct task_struct
*task
)
6300 rq
= task_rq_lock(task
, &rf
);
6302 update_rq_clock(rq
);
6303 sched_change_group(task
, TASK_SET_GROUP
);
6305 task_rq_unlock(rq
, task
, &rf
);
6308 static int cpu_cgroup_can_attach(struct cgroup_taskset
*tset
)
6310 struct task_struct
*task
;
6311 struct cgroup_subsys_state
*css
;
6314 cgroup_taskset_for_each(task
, css
, tset
) {
6315 #ifdef CONFIG_RT_GROUP_SCHED
6316 if (!sched_rt_can_attach(css_tg(css
), task
))
6319 /* We don't support RT-tasks being in separate groups */
6320 if (task
->sched_class
!= &fair_sched_class
)
6324 * Serialize against wake_up_new_task() such that if its
6325 * running, we're sure to observe its full state.
6327 raw_spin_lock_irq(&task
->pi_lock
);
6329 * Avoid calling sched_move_task() before wake_up_new_task()
6330 * has happened. This would lead to problems with PELT, due to
6331 * move wanting to detach+attach while we're not attached yet.
6333 if (task
->state
== TASK_NEW
)
6335 raw_spin_unlock_irq(&task
->pi_lock
);
6343 static void cpu_cgroup_attach(struct cgroup_taskset
*tset
)
6345 struct task_struct
*task
;
6346 struct cgroup_subsys_state
*css
;
6348 cgroup_taskset_for_each(task
, css
, tset
)
6349 sched_move_task(task
);
6352 #ifdef CONFIG_FAIR_GROUP_SCHED
6353 static int cpu_shares_write_u64(struct cgroup_subsys_state
*css
,
6354 struct cftype
*cftype
, u64 shareval
)
6356 return sched_group_set_shares(css_tg(css
), scale_load(shareval
));
6359 static u64
cpu_shares_read_u64(struct cgroup_subsys_state
*css
,
6362 struct task_group
*tg
= css_tg(css
);
6364 return (u64
) scale_load_down(tg
->shares
);
6367 #ifdef CONFIG_CFS_BANDWIDTH
6368 static DEFINE_MUTEX(cfs_constraints_mutex
);
6370 const u64 max_cfs_quota_period
= 1 * NSEC_PER_SEC
; /* 1s */
6371 const u64 min_cfs_quota_period
= 1 * NSEC_PER_MSEC
; /* 1ms */
6373 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 runtime
);
6375 static int tg_set_cfs_bandwidth(struct task_group
*tg
, u64 period
, u64 quota
)
6377 int i
, ret
= 0, runtime_enabled
, runtime_was_enabled
;
6378 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6380 if (tg
== &root_task_group
)
6384 * Ensure we have at some amount of bandwidth every period. This is
6385 * to prevent reaching a state of large arrears when throttled via
6386 * entity_tick() resulting in prolonged exit starvation.
6388 if (quota
< min_cfs_quota_period
|| period
< min_cfs_quota_period
)
6392 * Likewise, bound things on the otherside by preventing insane quota
6393 * periods. This also allows us to normalize in computing quota
6396 if (period
> max_cfs_quota_period
)
6400 * Prevent race between setting of cfs_rq->runtime_enabled and
6401 * unthrottle_offline_cfs_rqs().
6404 mutex_lock(&cfs_constraints_mutex
);
6405 ret
= __cfs_schedulable(tg
, period
, quota
);
6409 runtime_enabled
= quota
!= RUNTIME_INF
;
6410 runtime_was_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
6412 * If we need to toggle cfs_bandwidth_used, off->on must occur
6413 * before making related changes, and on->off must occur afterwards
6415 if (runtime_enabled
&& !runtime_was_enabled
)
6416 cfs_bandwidth_usage_inc();
6417 raw_spin_lock_irq(&cfs_b
->lock
);
6418 cfs_b
->period
= ns_to_ktime(period
);
6419 cfs_b
->quota
= quota
;
6421 __refill_cfs_bandwidth_runtime(cfs_b
);
6423 /* Restart the period timer (if active) to handle new period expiry: */
6424 if (runtime_enabled
)
6425 start_cfs_bandwidth(cfs_b
);
6427 raw_spin_unlock_irq(&cfs_b
->lock
);
6429 for_each_online_cpu(i
) {
6430 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[i
];
6431 struct rq
*rq
= cfs_rq
->rq
;
6434 rq_lock_irq(rq
, &rf
);
6435 cfs_rq
->runtime_enabled
= runtime_enabled
;
6436 cfs_rq
->runtime_remaining
= 0;
6438 if (cfs_rq
->throttled
)
6439 unthrottle_cfs_rq(cfs_rq
);
6440 rq_unlock_irq(rq
, &rf
);
6442 if (runtime_was_enabled
&& !runtime_enabled
)
6443 cfs_bandwidth_usage_dec();
6445 mutex_unlock(&cfs_constraints_mutex
);
6451 int tg_set_cfs_quota(struct task_group
*tg
, long cfs_quota_us
)
6455 period
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
6456 if (cfs_quota_us
< 0)
6457 quota
= RUNTIME_INF
;
6459 quota
= (u64
)cfs_quota_us
* NSEC_PER_USEC
;
6461 return tg_set_cfs_bandwidth(tg
, period
, quota
);
6464 long tg_get_cfs_quota(struct task_group
*tg
)
6468 if (tg
->cfs_bandwidth
.quota
== RUNTIME_INF
)
6471 quota_us
= tg
->cfs_bandwidth
.quota
;
6472 do_div(quota_us
, NSEC_PER_USEC
);
6477 int tg_set_cfs_period(struct task_group
*tg
, long cfs_period_us
)
6481 period
= (u64
)cfs_period_us
* NSEC_PER_USEC
;
6482 quota
= tg
->cfs_bandwidth
.quota
;
6484 return tg_set_cfs_bandwidth(tg
, period
, quota
);
6487 long tg_get_cfs_period(struct task_group
*tg
)
6491 cfs_period_us
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
6492 do_div(cfs_period_us
, NSEC_PER_USEC
);
6494 return cfs_period_us
;
6497 static s64
cpu_cfs_quota_read_s64(struct cgroup_subsys_state
*css
,
6500 return tg_get_cfs_quota(css_tg(css
));
6503 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state
*css
,
6504 struct cftype
*cftype
, s64 cfs_quota_us
)
6506 return tg_set_cfs_quota(css_tg(css
), cfs_quota_us
);
6509 static u64
cpu_cfs_period_read_u64(struct cgroup_subsys_state
*css
,
6512 return tg_get_cfs_period(css_tg(css
));
6515 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state
*css
,
6516 struct cftype
*cftype
, u64 cfs_period_us
)
6518 return tg_set_cfs_period(css_tg(css
), cfs_period_us
);
6521 struct cfs_schedulable_data
{
6522 struct task_group
*tg
;
6527 * normalize group quota/period to be quota/max_period
6528 * note: units are usecs
6530 static u64
normalize_cfs_quota(struct task_group
*tg
,
6531 struct cfs_schedulable_data
*d
)
6539 period
= tg_get_cfs_period(tg
);
6540 quota
= tg_get_cfs_quota(tg
);
6543 /* note: these should typically be equivalent */
6544 if (quota
== RUNTIME_INF
|| quota
== -1)
6547 return to_ratio(period
, quota
);
6550 static int tg_cfs_schedulable_down(struct task_group
*tg
, void *data
)
6552 struct cfs_schedulable_data
*d
= data
;
6553 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6554 s64 quota
= 0, parent_quota
= -1;
6557 quota
= RUNTIME_INF
;
6559 struct cfs_bandwidth
*parent_b
= &tg
->parent
->cfs_bandwidth
;
6561 quota
= normalize_cfs_quota(tg
, d
);
6562 parent_quota
= parent_b
->hierarchical_quota
;
6565 * Ensure max(child_quota) <= parent_quota, inherit when no
6568 if (quota
== RUNTIME_INF
)
6569 quota
= parent_quota
;
6570 else if (parent_quota
!= RUNTIME_INF
&& quota
> parent_quota
)
6573 cfs_b
->hierarchical_quota
= quota
;
6578 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 quota
)
6581 struct cfs_schedulable_data data
= {
6587 if (quota
!= RUNTIME_INF
) {
6588 do_div(data
.period
, NSEC_PER_USEC
);
6589 do_div(data
.quota
, NSEC_PER_USEC
);
6593 ret
= walk_tg_tree(tg_cfs_schedulable_down
, tg_nop
, &data
);
6599 static int cpu_stats_show(struct seq_file
*sf
, void *v
)
6601 struct task_group
*tg
= css_tg(seq_css(sf
));
6602 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6604 seq_printf(sf
, "nr_periods %d\n", cfs_b
->nr_periods
);
6605 seq_printf(sf
, "nr_throttled %d\n", cfs_b
->nr_throttled
);
6606 seq_printf(sf
, "throttled_time %llu\n", cfs_b
->throttled_time
);
6610 #endif /* CONFIG_CFS_BANDWIDTH */
6611 #endif /* CONFIG_FAIR_GROUP_SCHED */
6613 #ifdef CONFIG_RT_GROUP_SCHED
6614 static int cpu_rt_runtime_write(struct cgroup_subsys_state
*css
,
6615 struct cftype
*cft
, s64 val
)
6617 return sched_group_set_rt_runtime(css_tg(css
), val
);
6620 static s64
cpu_rt_runtime_read(struct cgroup_subsys_state
*css
,
6623 return sched_group_rt_runtime(css_tg(css
));
6626 static int cpu_rt_period_write_uint(struct cgroup_subsys_state
*css
,
6627 struct cftype
*cftype
, u64 rt_period_us
)
6629 return sched_group_set_rt_period(css_tg(css
), rt_period_us
);
6632 static u64
cpu_rt_period_read_uint(struct cgroup_subsys_state
*css
,
6635 return sched_group_rt_period(css_tg(css
));
6637 #endif /* CONFIG_RT_GROUP_SCHED */
6639 static struct cftype cpu_files
[] = {
6640 #ifdef CONFIG_FAIR_GROUP_SCHED
6643 .read_u64
= cpu_shares_read_u64
,
6644 .write_u64
= cpu_shares_write_u64
,
6647 #ifdef CONFIG_CFS_BANDWIDTH
6649 .name
= "cfs_quota_us",
6650 .read_s64
= cpu_cfs_quota_read_s64
,
6651 .write_s64
= cpu_cfs_quota_write_s64
,
6654 .name
= "cfs_period_us",
6655 .read_u64
= cpu_cfs_period_read_u64
,
6656 .write_u64
= cpu_cfs_period_write_u64
,
6660 .seq_show
= cpu_stats_show
,
6663 #ifdef CONFIG_RT_GROUP_SCHED
6665 .name
= "rt_runtime_us",
6666 .read_s64
= cpu_rt_runtime_read
,
6667 .write_s64
= cpu_rt_runtime_write
,
6670 .name
= "rt_period_us",
6671 .read_u64
= cpu_rt_period_read_uint
,
6672 .write_u64
= cpu_rt_period_write_uint
,
6678 struct cgroup_subsys cpu_cgrp_subsys
= {
6679 .css_alloc
= cpu_cgroup_css_alloc
,
6680 .css_online
= cpu_cgroup_css_online
,
6681 .css_released
= cpu_cgroup_css_released
,
6682 .css_free
= cpu_cgroup_css_free
,
6683 .fork
= cpu_cgroup_fork
,
6684 .can_attach
= cpu_cgroup_can_attach
,
6685 .attach
= cpu_cgroup_attach
,
6686 .legacy_cftypes
= cpu_files
,
6690 #endif /* CONFIG_CGROUP_SCHED */
6692 void dump_cpu_task(int cpu
)
6694 pr_info("Task dump for CPU %d:\n", cpu
);
6695 sched_show_task(cpu_curr(cpu
));
6699 * Nice levels are multiplicative, with a gentle 10% change for every
6700 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
6701 * nice 1, it will get ~10% less CPU time than another CPU-bound task
6702 * that remained on nice 0.
6704 * The "10% effect" is relative and cumulative: from _any_ nice level,
6705 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
6706 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
6707 * If a task goes up by ~10% and another task goes down by ~10% then
6708 * the relative distance between them is ~25%.)
6710 const int sched_prio_to_weight
[40] = {
6711 /* -20 */ 88761, 71755, 56483, 46273, 36291,
6712 /* -15 */ 29154, 23254, 18705, 14949, 11916,
6713 /* -10 */ 9548, 7620, 6100, 4904, 3906,
6714 /* -5 */ 3121, 2501, 1991, 1586, 1277,
6715 /* 0 */ 1024, 820, 655, 526, 423,
6716 /* 5 */ 335, 272, 215, 172, 137,
6717 /* 10 */ 110, 87, 70, 56, 45,
6718 /* 15 */ 36, 29, 23, 18, 15,
6722 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
6724 * In cases where the weight does not change often, we can use the
6725 * precalculated inverse to speed up arithmetics by turning divisions
6726 * into multiplications:
6728 const u32 sched_prio_to_wmult
[40] = {
6729 /* -20 */ 48388, 59856, 76040, 92818, 118348,
6730 /* -15 */ 147320, 184698, 229616, 287308, 360437,
6731 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
6732 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
6733 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
6734 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
6735 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
6736 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,