2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
4 * This code is licenced under the GPL.
6 #include <linux/proc_fs.h>
8 #include <linux/init.h>
9 #include <linux/notifier.h>
10 #include <linux/sched/signal.h>
11 #include <linux/sched/hotplug.h>
12 #include <linux/sched/task.h>
13 #include <linux/sched/smt.h>
14 #include <linux/unistd.h>
15 #include <linux/cpu.h>
16 #include <linux/oom.h>
17 #include <linux/rcupdate.h>
18 #include <linux/export.h>
19 #include <linux/bug.h>
20 #include <linux/kthread.h>
21 #include <linux/stop_machine.h>
22 #include <linux/mutex.h>
23 #include <linux/gfp.h>
24 #include <linux/suspend.h>
25 #include <linux/lockdep.h>
26 #include <linux/tick.h>
27 #include <linux/irq.h>
28 #include <linux/nmi.h>
29 #include <linux/smpboot.h>
30 #include <linux/relay.h>
31 #include <linux/slab.h>
32 #include <linux/percpu-rwsem.h>
34 #include <trace/events/power.h>
35 #define CREATE_TRACE_POINTS
36 #include <trace/events/cpuhp.h>
41 * cpuhp_cpu_state - Per cpu hotplug state storage
42 * @state: The current cpu state
43 * @target: The target state
44 * @thread: Pointer to the hotplug thread
45 * @should_run: Thread should execute
46 * @rollback: Perform a rollback
47 * @single: Single callback invocation
48 * @bringup: Single callback bringup or teardown selector
49 * @cb_state: The state for a single callback (install/uninstall)
50 * @result: Result of the operation
51 * @done_up: Signal completion to the issuer of the task for cpu-up
52 * @done_down: Signal completion to the issuer of the task for cpu-down
54 struct cpuhp_cpu_state
{
55 enum cpuhp_state state
;
56 enum cpuhp_state target
;
57 enum cpuhp_state fail
;
59 struct task_struct
*thread
;
65 struct hlist_node
*node
;
66 struct hlist_node
*last
;
67 enum cpuhp_state cb_state
;
69 struct completion done_up
;
70 struct completion done_down
;
74 static DEFINE_PER_CPU(struct cpuhp_cpu_state
, cpuhp_state
) = {
75 .fail
= CPUHP_INVALID
,
78 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
79 static struct lockdep_map cpuhp_state_up_map
=
80 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map
);
81 static struct lockdep_map cpuhp_state_down_map
=
82 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map
);
85 static inline void cpuhp_lock_acquire(bool bringup
)
87 lock_map_acquire(bringup
? &cpuhp_state_up_map
: &cpuhp_state_down_map
);
90 static inline void cpuhp_lock_release(bool bringup
)
92 lock_map_release(bringup
? &cpuhp_state_up_map
: &cpuhp_state_down_map
);
96 static inline void cpuhp_lock_acquire(bool bringup
) { }
97 static inline void cpuhp_lock_release(bool bringup
) { }
102 * cpuhp_step - Hotplug state machine step
103 * @name: Name of the step
104 * @startup: Startup function of the step
105 * @teardown: Teardown function of the step
106 * @skip_onerr: Do not invoke the functions on error rollback
107 * Will go away once the notifiers are gone
108 * @cant_stop: Bringup/teardown can't be stopped at this step
113 int (*single
)(unsigned int cpu
);
114 int (*multi
)(unsigned int cpu
,
115 struct hlist_node
*node
);
118 int (*single
)(unsigned int cpu
);
119 int (*multi
)(unsigned int cpu
,
120 struct hlist_node
*node
);
122 struct hlist_head list
;
128 static DEFINE_MUTEX(cpuhp_state_mutex
);
129 static struct cpuhp_step cpuhp_bp_states
[];
130 static struct cpuhp_step cpuhp_ap_states
[];
132 static bool cpuhp_is_ap_state(enum cpuhp_state state
)
135 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
136 * purposes as that state is handled explicitly in cpu_down.
138 return state
> CPUHP_BRINGUP_CPU
&& state
!= CPUHP_TEARDOWN_CPU
;
141 static struct cpuhp_step
*cpuhp_get_step(enum cpuhp_state state
)
143 struct cpuhp_step
*sp
;
145 sp
= cpuhp_is_ap_state(state
) ? cpuhp_ap_states
: cpuhp_bp_states
;
150 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
151 * @cpu: The cpu for which the callback should be invoked
152 * @state: The state to do callbacks for
153 * @bringup: True if the bringup callback should be invoked
154 * @node: For multi-instance, do a single entry callback for install/remove
155 * @lastp: For multi-instance rollback, remember how far we got
157 * Called from cpu hotplug and from the state register machinery.
159 static int cpuhp_invoke_callback(unsigned int cpu
, enum cpuhp_state state
,
160 bool bringup
, struct hlist_node
*node
,
161 struct hlist_node
**lastp
)
163 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
164 struct cpuhp_step
*step
= cpuhp_get_step(state
);
165 int (*cbm
)(unsigned int cpu
, struct hlist_node
*node
);
166 int (*cb
)(unsigned int cpu
);
169 if (st
->fail
== state
) {
170 st
->fail
= CPUHP_INVALID
;
172 if (!(bringup
? step
->startup
.single
: step
->teardown
.single
))
178 if (!step
->multi_instance
) {
179 WARN_ON_ONCE(lastp
&& *lastp
);
180 cb
= bringup
? step
->startup
.single
: step
->teardown
.single
;
183 trace_cpuhp_enter(cpu
, st
->target
, state
, cb
);
185 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
188 cbm
= bringup
? step
->startup
.multi
: step
->teardown
.multi
;
192 /* Single invocation for instance add/remove */
194 WARN_ON_ONCE(lastp
&& *lastp
);
195 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
196 ret
= cbm(cpu
, node
);
197 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
201 /* State transition. Invoke on all instances */
203 hlist_for_each(node
, &step
->list
) {
204 if (lastp
&& node
== *lastp
)
207 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
208 ret
= cbm(cpu
, node
);
209 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
223 /* Rollback the instances if one failed */
224 cbm
= !bringup
? step
->startup
.multi
: step
->teardown
.multi
;
228 hlist_for_each(node
, &step
->list
) {
232 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
233 ret
= cbm(cpu
, node
);
234 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
236 * Rollback must not fail,
244 static inline void wait_for_ap_thread(struct cpuhp_cpu_state
*st
, bool bringup
)
246 struct completion
*done
= bringup
? &st
->done_up
: &st
->done_down
;
247 wait_for_completion(done
);
250 static inline void complete_ap_thread(struct cpuhp_cpu_state
*st
, bool bringup
)
252 struct completion
*done
= bringup
? &st
->done_up
: &st
->done_down
;
257 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
259 static bool cpuhp_is_atomic_state(enum cpuhp_state state
)
261 return CPUHP_AP_IDLE_DEAD
<= state
&& state
< CPUHP_AP_ONLINE
;
264 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
265 static DEFINE_MUTEX(cpu_add_remove_lock
);
266 bool cpuhp_tasks_frozen
;
267 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen
);
270 * The following two APIs (cpu_maps_update_begin/done) must be used when
271 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
273 void cpu_maps_update_begin(void)
275 mutex_lock(&cpu_add_remove_lock
);
278 void cpu_maps_update_done(void)
280 mutex_unlock(&cpu_add_remove_lock
);
284 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
285 * Should always be manipulated under cpu_add_remove_lock
287 static int cpu_hotplug_disabled
;
289 #ifdef CONFIG_HOTPLUG_CPU
291 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock
);
293 void cpus_read_lock(void)
295 percpu_down_read(&cpu_hotplug_lock
);
297 EXPORT_SYMBOL_GPL(cpus_read_lock
);
299 void cpus_read_unlock(void)
301 percpu_up_read(&cpu_hotplug_lock
);
303 EXPORT_SYMBOL_GPL(cpus_read_unlock
);
305 void cpus_write_lock(void)
307 percpu_down_write(&cpu_hotplug_lock
);
310 void cpus_write_unlock(void)
312 percpu_up_write(&cpu_hotplug_lock
);
315 void lockdep_assert_cpus_held(void)
318 * We can't have hotplug operations before userspace starts running,
319 * and some init codepaths will knowingly not take the hotplug lock.
320 * This is all valid, so mute lockdep until it makes sense to report
323 if (system_state
< SYSTEM_RUNNING
)
326 percpu_rwsem_assert_held(&cpu_hotplug_lock
);
330 * Wait for currently running CPU hotplug operations to complete (if any) and
331 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
332 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
333 * hotplug path before performing hotplug operations. So acquiring that lock
334 * guarantees mutual exclusion from any currently running hotplug operations.
336 void cpu_hotplug_disable(void)
338 cpu_maps_update_begin();
339 cpu_hotplug_disabled
++;
340 cpu_maps_update_done();
342 EXPORT_SYMBOL_GPL(cpu_hotplug_disable
);
344 static void __cpu_hotplug_enable(void)
346 if (WARN_ONCE(!cpu_hotplug_disabled
, "Unbalanced cpu hotplug enable\n"))
348 cpu_hotplug_disabled
--;
351 void cpu_hotplug_enable(void)
353 cpu_maps_update_begin();
354 __cpu_hotplug_enable();
355 cpu_maps_update_done();
357 EXPORT_SYMBOL_GPL(cpu_hotplug_enable
);
358 #endif /* CONFIG_HOTPLUG_CPU */
361 * Architectures that need SMT-specific errata handling during SMT hotplug
362 * should override this.
364 void __weak
arch_smt_update(void) { }
366 #ifdef CONFIG_HOTPLUG_SMT
367 enum cpuhp_smt_control cpu_smt_control __read_mostly
= CPU_SMT_ENABLED
;
369 void __init
cpu_smt_disable(bool force
)
371 if (cpu_smt_control
== CPU_SMT_FORCE_DISABLED
||
372 cpu_smt_control
== CPU_SMT_NOT_SUPPORTED
)
376 pr_info("SMT: Force disabled\n");
377 cpu_smt_control
= CPU_SMT_FORCE_DISABLED
;
379 cpu_smt_control
= CPU_SMT_DISABLED
;
384 * The decision whether SMT is supported can only be done after the full
385 * CPU identification. Called from architecture code.
387 void __init
cpu_smt_check_topology(void)
389 if (!topology_smt_supported())
390 cpu_smt_control
= CPU_SMT_NOT_SUPPORTED
;
393 static int __init
smt_cmdline_disable(char *str
)
395 cpu_smt_disable(str
&& !strcmp(str
, "force"));
398 early_param("nosmt", smt_cmdline_disable
);
400 static inline bool cpu_smt_allowed(unsigned int cpu
)
402 if (cpu_smt_control
== CPU_SMT_ENABLED
)
405 if (topology_is_primary_thread(cpu
))
409 * On x86 it's required to boot all logical CPUs at least once so
410 * that the init code can get a chance to set CR4.MCE on each
411 * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
412 * core will shutdown the machine.
414 return !per_cpu(cpuhp_state
, cpu
).booted_once
;
417 static inline bool cpu_smt_allowed(unsigned int cpu
) { return true; }
420 static inline enum cpuhp_state
421 cpuhp_set_state(struct cpuhp_cpu_state
*st
, enum cpuhp_state target
)
423 enum cpuhp_state prev_state
= st
->state
;
425 st
->rollback
= false;
430 st
->bringup
= st
->state
< target
;
436 cpuhp_reset_state(struct cpuhp_cpu_state
*st
, enum cpuhp_state prev_state
)
441 * If we have st->last we need to undo partial multi_instance of this
442 * state first. Otherwise start undo at the previous state.
451 st
->target
= prev_state
;
452 st
->bringup
= !st
->bringup
;
455 /* Regular hotplug invocation of the AP hotplug thread */
456 static void __cpuhp_kick_ap(struct cpuhp_cpu_state
*st
)
458 if (!st
->single
&& st
->state
== st
->target
)
463 * Make sure the above stores are visible before should_run becomes
464 * true. Paired with the mb() above in cpuhp_thread_fun()
467 st
->should_run
= true;
468 wake_up_process(st
->thread
);
469 wait_for_ap_thread(st
, st
->bringup
);
472 static int cpuhp_kick_ap(struct cpuhp_cpu_state
*st
, enum cpuhp_state target
)
474 enum cpuhp_state prev_state
;
477 prev_state
= cpuhp_set_state(st
, target
);
479 if ((ret
= st
->result
)) {
480 cpuhp_reset_state(st
, prev_state
);
487 static int bringup_wait_for_ap(unsigned int cpu
)
489 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
491 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
492 wait_for_ap_thread(st
, true);
493 if (WARN_ON_ONCE((!cpu_online(cpu
))))
496 /* Unpark the stopper thread and the hotplug thread of the target cpu */
497 stop_machine_unpark(cpu
);
498 kthread_unpark(st
->thread
);
501 * SMT soft disabling on X86 requires to bring the CPU out of the
502 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
503 * CPU marked itself as booted_once in cpu_notify_starting() so the
504 * cpu_smt_allowed() check will now return false if this is not the
507 if (!cpu_smt_allowed(cpu
))
510 if (st
->target
<= CPUHP_AP_ONLINE_IDLE
)
513 return cpuhp_kick_ap(st
, st
->target
);
516 static int bringup_cpu(unsigned int cpu
)
518 struct task_struct
*idle
= idle_thread_get(cpu
);
522 * Some architectures have to walk the irq descriptors to
523 * setup the vector space for the cpu which comes online.
524 * Prevent irq alloc/free across the bringup.
528 /* Arch-specific enabling code. */
529 ret
= __cpu_up(cpu
, idle
);
533 return bringup_wait_for_ap(cpu
);
537 * Hotplug state machine related functions
540 static void undo_cpu_up(unsigned int cpu
, struct cpuhp_cpu_state
*st
)
542 for (st
->state
--; st
->state
> st
->target
; st
->state
--) {
543 struct cpuhp_step
*step
= cpuhp_get_step(st
->state
);
545 if (!step
->skip_onerr
)
546 cpuhp_invoke_callback(cpu
, st
->state
, false, NULL
, NULL
);
550 static inline bool can_rollback_cpu(struct cpuhp_cpu_state
*st
)
552 if (IS_ENABLED(CONFIG_HOTPLUG_CPU
))
555 * When CPU hotplug is disabled, then taking the CPU down is not
556 * possible because takedown_cpu() and the architecture and
557 * subsystem specific mechanisms are not available. So the CPU
558 * which would be completely unplugged again needs to stay around
559 * in the current state.
561 return st
->state
<= CPUHP_BRINGUP_CPU
;
564 static int cpuhp_up_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
565 enum cpuhp_state target
)
567 enum cpuhp_state prev_state
= st
->state
;
570 while (st
->state
< target
) {
572 ret
= cpuhp_invoke_callback(cpu
, st
->state
, true, NULL
, NULL
);
574 if (can_rollback_cpu(st
)) {
575 st
->target
= prev_state
;
576 undo_cpu_up(cpu
, st
);
585 * The cpu hotplug threads manage the bringup and teardown of the cpus
587 static void cpuhp_create(unsigned int cpu
)
589 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
591 init_completion(&st
->done_up
);
592 init_completion(&st
->done_down
);
595 static int cpuhp_should_run(unsigned int cpu
)
597 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
599 return st
->should_run
;
603 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
604 * callbacks when a state gets [un]installed at runtime.
606 * Each invocation of this function by the smpboot thread does a single AP
609 * It has 3 modes of operation:
610 * - single: runs st->cb_state
611 * - up: runs ++st->state, while st->state < st->target
612 * - down: runs st->state--, while st->state > st->target
614 * When complete or on error, should_run is cleared and the completion is fired.
616 static void cpuhp_thread_fun(unsigned int cpu
)
618 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
619 bool bringup
= st
->bringup
;
620 enum cpuhp_state state
;
622 if (WARN_ON_ONCE(!st
->should_run
))
626 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
627 * that if we see ->should_run we also see the rest of the state.
631 cpuhp_lock_acquire(bringup
);
634 state
= st
->cb_state
;
635 st
->should_run
= false;
640 st
->should_run
= (st
->state
< st
->target
);
641 WARN_ON_ONCE(st
->state
> st
->target
);
645 st
->should_run
= (st
->state
> st
->target
);
646 WARN_ON_ONCE(st
->state
< st
->target
);
650 WARN_ON_ONCE(!cpuhp_is_ap_state(state
));
653 struct cpuhp_step
*step
= cpuhp_get_step(state
);
654 if (step
->skip_onerr
)
658 if (cpuhp_is_atomic_state(state
)) {
660 st
->result
= cpuhp_invoke_callback(cpu
, state
, bringup
, st
->node
, &st
->last
);
664 * STARTING/DYING must not fail!
666 WARN_ON_ONCE(st
->result
);
668 st
->result
= cpuhp_invoke_callback(cpu
, state
, bringup
, st
->node
, &st
->last
);
673 * If we fail on a rollback, we're up a creek without no
674 * paddle, no way forward, no way back. We loose, thanks for
677 WARN_ON_ONCE(st
->rollback
);
678 st
->should_run
= false;
682 cpuhp_lock_release(bringup
);
685 complete_ap_thread(st
, bringup
);
688 /* Invoke a single callback on a remote cpu */
690 cpuhp_invoke_ap_callback(int cpu
, enum cpuhp_state state
, bool bringup
,
691 struct hlist_node
*node
)
693 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
696 if (!cpu_online(cpu
))
699 cpuhp_lock_acquire(false);
700 cpuhp_lock_release(false);
702 cpuhp_lock_acquire(true);
703 cpuhp_lock_release(true);
706 * If we are up and running, use the hotplug thread. For early calls
707 * we invoke the thread function directly.
710 return cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
712 st
->rollback
= false;
716 st
->bringup
= bringup
;
717 st
->cb_state
= state
;
723 * If we failed and did a partial, do a rollback.
725 if ((ret
= st
->result
) && st
->last
) {
727 st
->bringup
= !bringup
;
733 * Clean up the leftovers so the next hotplug operation wont use stale
736 st
->node
= st
->last
= NULL
;
740 static int cpuhp_kick_ap_work(unsigned int cpu
)
742 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
743 enum cpuhp_state prev_state
= st
->state
;
746 cpuhp_lock_acquire(false);
747 cpuhp_lock_release(false);
749 cpuhp_lock_acquire(true);
750 cpuhp_lock_release(true);
752 trace_cpuhp_enter(cpu
, st
->target
, prev_state
, cpuhp_kick_ap_work
);
753 ret
= cpuhp_kick_ap(st
, st
->target
);
754 trace_cpuhp_exit(cpu
, st
->state
, prev_state
, ret
);
759 static struct smp_hotplug_thread cpuhp_threads
= {
760 .store
= &cpuhp_state
.thread
,
761 .create
= &cpuhp_create
,
762 .thread_should_run
= cpuhp_should_run
,
763 .thread_fn
= cpuhp_thread_fun
,
764 .thread_comm
= "cpuhp/%u",
768 void __init
cpuhp_threads_init(void)
770 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads
));
771 kthread_unpark(this_cpu_read(cpuhp_state
.thread
));
774 #ifdef CONFIG_HOTPLUG_CPU
776 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
779 * This function walks all processes, finds a valid mm struct for each one and
780 * then clears a corresponding bit in mm's cpumask. While this all sounds
781 * trivial, there are various non-obvious corner cases, which this function
782 * tries to solve in a safe manner.
784 * Also note that the function uses a somewhat relaxed locking scheme, so it may
785 * be called only for an already offlined CPU.
787 void clear_tasks_mm_cpumask(int cpu
)
789 struct task_struct
*p
;
792 * This function is called after the cpu is taken down and marked
793 * offline, so its not like new tasks will ever get this cpu set in
794 * their mm mask. -- Peter Zijlstra
795 * Thus, we may use rcu_read_lock() here, instead of grabbing
796 * full-fledged tasklist_lock.
798 WARN_ON(cpu_online(cpu
));
800 for_each_process(p
) {
801 struct task_struct
*t
;
804 * Main thread might exit, but other threads may still have
805 * a valid mm. Find one.
807 t
= find_lock_task_mm(p
);
810 cpumask_clear_cpu(cpu
, mm_cpumask(t
->mm
));
816 /* Take this CPU down. */
817 static int take_cpu_down(void *_param
)
819 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
820 enum cpuhp_state target
= max((int)st
->target
, CPUHP_AP_OFFLINE
);
821 int err
, cpu
= smp_processor_id();
824 /* Ensure this CPU doesn't handle any more interrupts. */
825 err
= __cpu_disable();
830 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
831 * do this step again.
833 WARN_ON(st
->state
!= CPUHP_TEARDOWN_CPU
);
835 /* Invoke the former CPU_DYING callbacks */
836 for (; st
->state
> target
; st
->state
--) {
837 ret
= cpuhp_invoke_callback(cpu
, st
->state
, false, NULL
, NULL
);
839 * DYING must not fail!
844 /* Give up timekeeping duties */
845 tick_handover_do_timer();
846 /* Park the stopper thread */
847 stop_machine_park(cpu
);
851 static int takedown_cpu(unsigned int cpu
)
853 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
856 /* Park the smpboot threads */
857 kthread_park(per_cpu_ptr(&cpuhp_state
, cpu
)->thread
);
860 * Prevent irq alloc/free while the dying cpu reorganizes the
861 * interrupt affinities.
866 * So now all preempt/rcu users must observe !cpu_active().
868 err
= stop_machine_cpuslocked(take_cpu_down
, NULL
, cpumask_of(cpu
));
870 /* CPU refused to die */
872 /* Unpark the hotplug thread so we can rollback there */
873 kthread_unpark(per_cpu_ptr(&cpuhp_state
, cpu
)->thread
);
876 BUG_ON(cpu_online(cpu
));
879 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
880 * all runnable tasks from the CPU, there's only the idle task left now
881 * that the migration thread is done doing the stop_machine thing.
883 * Wait for the stop thread to go away.
885 wait_for_ap_thread(st
, false);
886 BUG_ON(st
->state
!= CPUHP_AP_IDLE_DEAD
);
888 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
891 hotplug_cpu__broadcast_tick_pull(cpu
);
892 /* This actually kills the CPU. */
895 tick_cleanup_dead_cpu(cpu
);
896 rcutree_migrate_callbacks(cpu
);
900 static void cpuhp_complete_idle_dead(void *arg
)
902 struct cpuhp_cpu_state
*st
= arg
;
904 complete_ap_thread(st
, false);
907 void cpuhp_report_idle_dead(void)
909 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
911 BUG_ON(st
->state
!= CPUHP_AP_OFFLINE
);
912 rcu_report_dead(smp_processor_id());
913 st
->state
= CPUHP_AP_IDLE_DEAD
;
915 * We cannot call complete after rcu_report_dead() so we delegate it
918 smp_call_function_single(cpumask_first(cpu_online_mask
),
919 cpuhp_complete_idle_dead
, st
, 0);
922 static void undo_cpu_down(unsigned int cpu
, struct cpuhp_cpu_state
*st
)
924 for (st
->state
++; st
->state
< st
->target
; st
->state
++) {
925 struct cpuhp_step
*step
= cpuhp_get_step(st
->state
);
927 if (!step
->skip_onerr
)
928 cpuhp_invoke_callback(cpu
, st
->state
, true, NULL
, NULL
);
932 static int cpuhp_down_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
933 enum cpuhp_state target
)
935 enum cpuhp_state prev_state
= st
->state
;
938 for (; st
->state
> target
; st
->state
--) {
939 ret
= cpuhp_invoke_callback(cpu
, st
->state
, false, NULL
, NULL
);
941 st
->target
= prev_state
;
942 if (st
->state
< prev_state
)
943 undo_cpu_down(cpu
, st
);
950 /* Requires cpu_add_remove_lock to be held */
951 static int __ref
_cpu_down(unsigned int cpu
, int tasks_frozen
,
952 enum cpuhp_state target
)
954 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
955 int prev_state
, ret
= 0;
957 if (num_online_cpus() == 1)
960 if (!cpu_present(cpu
))
965 cpuhp_tasks_frozen
= tasks_frozen
;
967 prev_state
= cpuhp_set_state(st
, target
);
969 * If the current CPU state is in the range of the AP hotplug thread,
970 * then we need to kick the thread.
972 if (st
->state
> CPUHP_TEARDOWN_CPU
) {
973 st
->target
= max((int)target
, CPUHP_TEARDOWN_CPU
);
974 ret
= cpuhp_kick_ap_work(cpu
);
976 * The AP side has done the error rollback already. Just
977 * return the error code..
983 * We might have stopped still in the range of the AP hotplug
984 * thread. Nothing to do anymore.
986 if (st
->state
> CPUHP_TEARDOWN_CPU
)
992 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
993 * to do the further cleanups.
995 ret
= cpuhp_down_callbacks(cpu
, st
, target
);
996 if (ret
&& st
->state
== CPUHP_TEARDOWN_CPU
&& st
->state
< prev_state
) {
997 cpuhp_reset_state(st
, prev_state
);
1002 cpus_write_unlock();
1004 * Do post unplug cleanup. This is still protected against
1005 * concurrent CPU hotplug via cpu_add_remove_lock.
1007 lockup_detector_cleanup();
1012 static int cpu_down_maps_locked(unsigned int cpu
, enum cpuhp_state target
)
1014 if (cpu_hotplug_disabled
)
1016 return _cpu_down(cpu
, 0, target
);
1019 static int do_cpu_down(unsigned int cpu
, enum cpuhp_state target
)
1023 cpu_maps_update_begin();
1024 err
= cpu_down_maps_locked(cpu
, target
);
1025 cpu_maps_update_done();
1029 int cpu_down(unsigned int cpu
)
1031 return do_cpu_down(cpu
, CPUHP_OFFLINE
);
1033 EXPORT_SYMBOL(cpu_down
);
1036 #define takedown_cpu NULL
1037 #endif /*CONFIG_HOTPLUG_CPU*/
1040 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1041 * @cpu: cpu that just started
1043 * It must be called by the arch code on the new cpu, before the new cpu
1044 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1046 void notify_cpu_starting(unsigned int cpu
)
1048 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1049 enum cpuhp_state target
= min((int)st
->target
, CPUHP_AP_ONLINE
);
1052 rcu_cpu_starting(cpu
); /* Enables RCU usage on this CPU. */
1053 st
->booted_once
= true;
1054 while (st
->state
< target
) {
1056 ret
= cpuhp_invoke_callback(cpu
, st
->state
, true, NULL
, NULL
);
1058 * STARTING must not fail!
1065 * Called from the idle task. Wake up the controlling task which brings the
1066 * stopper and the hotplug thread of the upcoming CPU up and then delegates
1067 * the rest of the online bringup to the hotplug thread.
1069 void cpuhp_online_idle(enum cpuhp_state state
)
1071 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
1073 /* Happens for the boot cpu */
1074 if (state
!= CPUHP_AP_ONLINE_IDLE
)
1077 st
->state
= CPUHP_AP_ONLINE_IDLE
;
1078 complete_ap_thread(st
, true);
1081 /* Requires cpu_add_remove_lock to be held */
1082 static int _cpu_up(unsigned int cpu
, int tasks_frozen
, enum cpuhp_state target
)
1084 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1085 struct task_struct
*idle
;
1090 if (!cpu_present(cpu
)) {
1096 * The caller of do_cpu_up might have raced with another
1097 * caller. Ignore it for now.
1099 if (st
->state
>= target
)
1102 if (st
->state
== CPUHP_OFFLINE
) {
1103 /* Let it fail before we try to bring the cpu up */
1104 idle
= idle_thread_get(cpu
);
1106 ret
= PTR_ERR(idle
);
1111 cpuhp_tasks_frozen
= tasks_frozen
;
1113 cpuhp_set_state(st
, target
);
1115 * If the current CPU state is in the range of the AP hotplug thread,
1116 * then we need to kick the thread once more.
1118 if (st
->state
> CPUHP_BRINGUP_CPU
) {
1119 ret
= cpuhp_kick_ap_work(cpu
);
1121 * The AP side has done the error rollback already. Just
1122 * return the error code..
1129 * Try to reach the target state. We max out on the BP at
1130 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1131 * responsible for bringing it up to the target state.
1133 target
= min((int)target
, CPUHP_BRINGUP_CPU
);
1134 ret
= cpuhp_up_callbacks(cpu
, st
, target
);
1136 cpus_write_unlock();
1141 static int do_cpu_up(unsigned int cpu
, enum cpuhp_state target
)
1145 if (!cpu_possible(cpu
)) {
1146 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1148 #if defined(CONFIG_IA64)
1149 pr_err("please check additional_cpus= boot parameter\n");
1154 err
= try_online_node(cpu_to_node(cpu
));
1158 cpu_maps_update_begin();
1160 if (cpu_hotplug_disabled
) {
1164 if (!cpu_smt_allowed(cpu
)) {
1169 err
= _cpu_up(cpu
, 0, target
);
1171 cpu_maps_update_done();
1175 int cpu_up(unsigned int cpu
)
1177 return do_cpu_up(cpu
, CPUHP_ONLINE
);
1179 EXPORT_SYMBOL_GPL(cpu_up
);
1181 #ifdef CONFIG_PM_SLEEP_SMP
1182 static cpumask_var_t frozen_cpus
;
1184 int freeze_secondary_cpus(int primary
)
1188 cpu_maps_update_begin();
1189 if (!cpu_online(primary
))
1190 primary
= cpumask_first(cpu_online_mask
);
1192 * We take down all of the non-boot CPUs in one shot to avoid races
1193 * with the userspace trying to use the CPU hotplug at the same time
1195 cpumask_clear(frozen_cpus
);
1197 pr_info("Disabling non-boot CPUs ...\n");
1198 for_each_online_cpu(cpu
) {
1201 trace_suspend_resume(TPS("CPU_OFF"), cpu
, true);
1202 error
= _cpu_down(cpu
, 1, CPUHP_OFFLINE
);
1203 trace_suspend_resume(TPS("CPU_OFF"), cpu
, false);
1205 cpumask_set_cpu(cpu
, frozen_cpus
);
1207 pr_err("Error taking CPU%d down: %d\n", cpu
, error
);
1213 BUG_ON(num_online_cpus() > 1);
1215 pr_err("Non-boot CPUs are not disabled\n");
1218 * Make sure the CPUs won't be enabled by someone else. We need to do
1219 * this even in case of failure as all disable_nonboot_cpus() users are
1220 * supposed to do enable_nonboot_cpus() on the failure path.
1222 cpu_hotplug_disabled
++;
1224 cpu_maps_update_done();
1228 void __weak
arch_enable_nonboot_cpus_begin(void)
1232 void __weak
arch_enable_nonboot_cpus_end(void)
1236 void enable_nonboot_cpus(void)
1240 /* Allow everyone to use the CPU hotplug again */
1241 cpu_maps_update_begin();
1242 __cpu_hotplug_enable();
1243 if (cpumask_empty(frozen_cpus
))
1246 pr_info("Enabling non-boot CPUs ...\n");
1248 arch_enable_nonboot_cpus_begin();
1250 for_each_cpu(cpu
, frozen_cpus
) {
1251 trace_suspend_resume(TPS("CPU_ON"), cpu
, true);
1252 error
= _cpu_up(cpu
, 1, CPUHP_ONLINE
);
1253 trace_suspend_resume(TPS("CPU_ON"), cpu
, false);
1255 pr_info("CPU%d is up\n", cpu
);
1258 pr_warn("Error taking CPU%d up: %d\n", cpu
, error
);
1261 arch_enable_nonboot_cpus_end();
1263 cpumask_clear(frozen_cpus
);
1265 cpu_maps_update_done();
1268 static int __init
alloc_frozen_cpus(void)
1270 if (!alloc_cpumask_var(&frozen_cpus
, GFP_KERNEL
|__GFP_ZERO
))
1274 core_initcall(alloc_frozen_cpus
);
1277 * When callbacks for CPU hotplug notifications are being executed, we must
1278 * ensure that the state of the system with respect to the tasks being frozen
1279 * or not, as reported by the notification, remains unchanged *throughout the
1280 * duration* of the execution of the callbacks.
1281 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1283 * This synchronization is implemented by mutually excluding regular CPU
1284 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1285 * Hibernate notifications.
1288 cpu_hotplug_pm_callback(struct notifier_block
*nb
,
1289 unsigned long action
, void *ptr
)
1293 case PM_SUSPEND_PREPARE
:
1294 case PM_HIBERNATION_PREPARE
:
1295 cpu_hotplug_disable();
1298 case PM_POST_SUSPEND
:
1299 case PM_POST_HIBERNATION
:
1300 cpu_hotplug_enable();
1311 static int __init
cpu_hotplug_pm_sync_init(void)
1314 * cpu_hotplug_pm_callback has higher priority than x86
1315 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1316 * to disable cpu hotplug to avoid cpu hotplug race.
1318 pm_notifier(cpu_hotplug_pm_callback
, 0);
1321 core_initcall(cpu_hotplug_pm_sync_init
);
1323 #endif /* CONFIG_PM_SLEEP_SMP */
1327 #endif /* CONFIG_SMP */
1329 /* Boot processor state steps */
1330 static struct cpuhp_step cpuhp_bp_states
[] = {
1333 .startup
.single
= NULL
,
1334 .teardown
.single
= NULL
,
1337 [CPUHP_CREATE_THREADS
]= {
1338 .name
= "threads:prepare",
1339 .startup
.single
= smpboot_create_threads
,
1340 .teardown
.single
= NULL
,
1343 [CPUHP_PERF_PREPARE
] = {
1344 .name
= "perf:prepare",
1345 .startup
.single
= perf_event_init_cpu
,
1346 .teardown
.single
= perf_event_exit_cpu
,
1348 [CPUHP_WORKQUEUE_PREP
] = {
1349 .name
= "workqueue:prepare",
1350 .startup
.single
= workqueue_prepare_cpu
,
1351 .teardown
.single
= NULL
,
1353 [CPUHP_HRTIMERS_PREPARE
] = {
1354 .name
= "hrtimers:prepare",
1355 .startup
.single
= hrtimers_prepare_cpu
,
1356 .teardown
.single
= hrtimers_dead_cpu
,
1358 [CPUHP_SMPCFD_PREPARE
] = {
1359 .name
= "smpcfd:prepare",
1360 .startup
.single
= smpcfd_prepare_cpu
,
1361 .teardown
.single
= smpcfd_dead_cpu
,
1363 [CPUHP_RELAY_PREPARE
] = {
1364 .name
= "relay:prepare",
1365 .startup
.single
= relay_prepare_cpu
,
1366 .teardown
.single
= NULL
,
1368 [CPUHP_SLAB_PREPARE
] = {
1369 .name
= "slab:prepare",
1370 .startup
.single
= slab_prepare_cpu
,
1371 .teardown
.single
= slab_dead_cpu
,
1373 [CPUHP_RCUTREE_PREP
] = {
1374 .name
= "RCU/tree:prepare",
1375 .startup
.single
= rcutree_prepare_cpu
,
1376 .teardown
.single
= rcutree_dead_cpu
,
1379 * On the tear-down path, timers_dead_cpu() must be invoked
1380 * before blk_mq_queue_reinit_notify() from notify_dead(),
1381 * otherwise a RCU stall occurs.
1383 [CPUHP_TIMERS_PREPARE
] = {
1384 .name
= "timers:dead",
1385 .startup
.single
= timers_prepare_cpu
,
1386 .teardown
.single
= timers_dead_cpu
,
1388 /* Kicks the plugged cpu into life */
1389 [CPUHP_BRINGUP_CPU
] = {
1390 .name
= "cpu:bringup",
1391 .startup
.single
= bringup_cpu
,
1392 .teardown
.single
= NULL
,
1396 * Handled on controll processor until the plugged processor manages
1399 [CPUHP_TEARDOWN_CPU
] = {
1400 .name
= "cpu:teardown",
1401 .startup
.single
= NULL
,
1402 .teardown
.single
= takedown_cpu
,
1406 [CPUHP_BRINGUP_CPU
] = { },
1410 /* Application processor state steps */
1411 static struct cpuhp_step cpuhp_ap_states
[] = {
1413 /* Final state before CPU kills itself */
1414 [CPUHP_AP_IDLE_DEAD
] = {
1415 .name
= "idle:dead",
1418 * Last state before CPU enters the idle loop to die. Transient state
1419 * for synchronization.
1421 [CPUHP_AP_OFFLINE
] = {
1422 .name
= "ap:offline",
1425 /* First state is scheduler control. Interrupts are disabled */
1426 [CPUHP_AP_SCHED_STARTING
] = {
1427 .name
= "sched:starting",
1428 .startup
.single
= sched_cpu_starting
,
1429 .teardown
.single
= sched_cpu_dying
,
1431 [CPUHP_AP_RCUTREE_DYING
] = {
1432 .name
= "RCU/tree:dying",
1433 .startup
.single
= NULL
,
1434 .teardown
.single
= rcutree_dying_cpu
,
1436 [CPUHP_AP_SMPCFD_DYING
] = {
1437 .name
= "smpcfd:dying",
1438 .startup
.single
= NULL
,
1439 .teardown
.single
= smpcfd_dying_cpu
,
1441 /* Entry state on starting. Interrupts enabled from here on. Transient
1442 * state for synchronsization */
1443 [CPUHP_AP_ONLINE
] = {
1444 .name
= "ap:online",
1446 /* Handle smpboot threads park/unpark */
1447 [CPUHP_AP_SMPBOOT_THREADS
] = {
1448 .name
= "smpboot/threads:online",
1449 .startup
.single
= smpboot_unpark_threads
,
1450 .teardown
.single
= smpboot_park_threads
,
1452 [CPUHP_AP_IRQ_AFFINITY_ONLINE
] = {
1453 .name
= "irq/affinity:online",
1454 .startup
.single
= irq_affinity_online_cpu
,
1455 .teardown
.single
= NULL
,
1457 [CPUHP_AP_PERF_ONLINE
] = {
1458 .name
= "perf:online",
1459 .startup
.single
= perf_event_init_cpu
,
1460 .teardown
.single
= perf_event_exit_cpu
,
1462 [CPUHP_AP_WORKQUEUE_ONLINE
] = {
1463 .name
= "workqueue:online",
1464 .startup
.single
= workqueue_online_cpu
,
1465 .teardown
.single
= workqueue_offline_cpu
,
1467 [CPUHP_AP_RCUTREE_ONLINE
] = {
1468 .name
= "RCU/tree:online",
1469 .startup
.single
= rcutree_online_cpu
,
1470 .teardown
.single
= rcutree_offline_cpu
,
1474 * The dynamically registered state space is here
1478 /* Last state is scheduler control setting the cpu active */
1479 [CPUHP_AP_ACTIVE
] = {
1480 .name
= "sched:active",
1481 .startup
.single
= sched_cpu_activate
,
1482 .teardown
.single
= sched_cpu_deactivate
,
1486 /* CPU is fully up and running. */
1489 .startup
.single
= NULL
,
1490 .teardown
.single
= NULL
,
1494 /* Sanity check for callbacks */
1495 static int cpuhp_cb_check(enum cpuhp_state state
)
1497 if (state
<= CPUHP_OFFLINE
|| state
>= CPUHP_ONLINE
)
1503 * Returns a free for dynamic slot assignment of the Online state. The states
1504 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1505 * by having no name assigned.
1507 static int cpuhp_reserve_state(enum cpuhp_state state
)
1509 enum cpuhp_state i
, end
;
1510 struct cpuhp_step
*step
;
1513 case CPUHP_AP_ONLINE_DYN
:
1514 step
= cpuhp_ap_states
+ CPUHP_AP_ONLINE_DYN
;
1515 end
= CPUHP_AP_ONLINE_DYN_END
;
1517 case CPUHP_BP_PREPARE_DYN
:
1518 step
= cpuhp_bp_states
+ CPUHP_BP_PREPARE_DYN
;
1519 end
= CPUHP_BP_PREPARE_DYN_END
;
1525 for (i
= state
; i
<= end
; i
++, step
++) {
1529 WARN(1, "No more dynamic states available for CPU hotplug\n");
1533 static int cpuhp_store_callbacks(enum cpuhp_state state
, const char *name
,
1534 int (*startup
)(unsigned int cpu
),
1535 int (*teardown
)(unsigned int cpu
),
1536 bool multi_instance
)
1538 /* (Un)Install the callbacks for further cpu hotplug operations */
1539 struct cpuhp_step
*sp
;
1543 * If name is NULL, then the state gets removed.
1545 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1546 * the first allocation from these dynamic ranges, so the removal
1547 * would trigger a new allocation and clear the wrong (already
1548 * empty) state, leaving the callbacks of the to be cleared state
1549 * dangling, which causes wreckage on the next hotplug operation.
1551 if (name
&& (state
== CPUHP_AP_ONLINE_DYN
||
1552 state
== CPUHP_BP_PREPARE_DYN
)) {
1553 ret
= cpuhp_reserve_state(state
);
1558 sp
= cpuhp_get_step(state
);
1559 if (name
&& sp
->name
)
1562 sp
->startup
.single
= startup
;
1563 sp
->teardown
.single
= teardown
;
1565 sp
->multi_instance
= multi_instance
;
1566 INIT_HLIST_HEAD(&sp
->list
);
1570 static void *cpuhp_get_teardown_cb(enum cpuhp_state state
)
1572 return cpuhp_get_step(state
)->teardown
.single
;
1576 * Call the startup/teardown function for a step either on the AP or
1577 * on the current CPU.
1579 static int cpuhp_issue_call(int cpu
, enum cpuhp_state state
, bool bringup
,
1580 struct hlist_node
*node
)
1582 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
1586 * If there's nothing to do, we done.
1587 * Relies on the union for multi_instance.
1589 if ((bringup
&& !sp
->startup
.single
) ||
1590 (!bringup
&& !sp
->teardown
.single
))
1593 * The non AP bound callbacks can fail on bringup. On teardown
1594 * e.g. module removal we crash for now.
1597 if (cpuhp_is_ap_state(state
))
1598 ret
= cpuhp_invoke_ap_callback(cpu
, state
, bringup
, node
);
1600 ret
= cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
1602 ret
= cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
1604 BUG_ON(ret
&& !bringup
);
1609 * Called from __cpuhp_setup_state on a recoverable failure.
1611 * Note: The teardown callbacks for rollback are not allowed to fail!
1613 static void cpuhp_rollback_install(int failedcpu
, enum cpuhp_state state
,
1614 struct hlist_node
*node
)
1618 /* Roll back the already executed steps on the other cpus */
1619 for_each_present_cpu(cpu
) {
1620 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1621 int cpustate
= st
->state
;
1623 if (cpu
>= failedcpu
)
1626 /* Did we invoke the startup call on that cpu ? */
1627 if (cpustate
>= state
)
1628 cpuhp_issue_call(cpu
, state
, false, node
);
1632 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state
,
1633 struct hlist_node
*node
,
1636 struct cpuhp_step
*sp
;
1640 lockdep_assert_cpus_held();
1642 sp
= cpuhp_get_step(state
);
1643 if (sp
->multi_instance
== false)
1646 mutex_lock(&cpuhp_state_mutex
);
1648 if (!invoke
|| !sp
->startup
.multi
)
1652 * Try to call the startup callback for each present cpu
1653 * depending on the hotplug state of the cpu.
1655 for_each_present_cpu(cpu
) {
1656 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1657 int cpustate
= st
->state
;
1659 if (cpustate
< state
)
1662 ret
= cpuhp_issue_call(cpu
, state
, true, node
);
1664 if (sp
->teardown
.multi
)
1665 cpuhp_rollback_install(cpu
, state
, node
);
1671 hlist_add_head(node
, &sp
->list
);
1673 mutex_unlock(&cpuhp_state_mutex
);
1677 int __cpuhp_state_add_instance(enum cpuhp_state state
, struct hlist_node
*node
,
1683 ret
= __cpuhp_state_add_instance_cpuslocked(state
, node
, invoke
);
1687 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance
);
1690 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1691 * @state: The state to setup
1692 * @invoke: If true, the startup function is invoked for cpus where
1693 * cpu state >= @state
1694 * @startup: startup callback function
1695 * @teardown: teardown callback function
1696 * @multi_instance: State is set up for multiple instances which get
1699 * The caller needs to hold cpus read locked while calling this function.
1702 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1703 * 0 for all other states
1704 * On failure: proper (negative) error code
1706 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state
,
1707 const char *name
, bool invoke
,
1708 int (*startup
)(unsigned int cpu
),
1709 int (*teardown
)(unsigned int cpu
),
1710 bool multi_instance
)
1715 lockdep_assert_cpus_held();
1717 if (cpuhp_cb_check(state
) || !name
)
1720 mutex_lock(&cpuhp_state_mutex
);
1722 ret
= cpuhp_store_callbacks(state
, name
, startup
, teardown
,
1725 dynstate
= state
== CPUHP_AP_ONLINE_DYN
;
1726 if (ret
> 0 && dynstate
) {
1731 if (ret
|| !invoke
|| !startup
)
1735 * Try to call the startup callback for each present cpu
1736 * depending on the hotplug state of the cpu.
1738 for_each_present_cpu(cpu
) {
1739 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1740 int cpustate
= st
->state
;
1742 if (cpustate
< state
)
1745 ret
= cpuhp_issue_call(cpu
, state
, true, NULL
);
1748 cpuhp_rollback_install(cpu
, state
, NULL
);
1749 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
, false);
1754 mutex_unlock(&cpuhp_state_mutex
);
1756 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1757 * dynamically allocated state in case of success.
1759 if (!ret
&& dynstate
)
1763 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked
);
1765 int __cpuhp_setup_state(enum cpuhp_state state
,
1766 const char *name
, bool invoke
,
1767 int (*startup
)(unsigned int cpu
),
1768 int (*teardown
)(unsigned int cpu
),
1769 bool multi_instance
)
1774 ret
= __cpuhp_setup_state_cpuslocked(state
, name
, invoke
, startup
,
1775 teardown
, multi_instance
);
1779 EXPORT_SYMBOL(__cpuhp_setup_state
);
1781 int __cpuhp_state_remove_instance(enum cpuhp_state state
,
1782 struct hlist_node
*node
, bool invoke
)
1784 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
1787 BUG_ON(cpuhp_cb_check(state
));
1789 if (!sp
->multi_instance
)
1793 mutex_lock(&cpuhp_state_mutex
);
1795 if (!invoke
|| !cpuhp_get_teardown_cb(state
))
1798 * Call the teardown callback for each present cpu depending
1799 * on the hotplug state of the cpu. This function is not
1800 * allowed to fail currently!
1802 for_each_present_cpu(cpu
) {
1803 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1804 int cpustate
= st
->state
;
1806 if (cpustate
>= state
)
1807 cpuhp_issue_call(cpu
, state
, false, node
);
1812 mutex_unlock(&cpuhp_state_mutex
);
1817 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance
);
1820 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1821 * @state: The state to remove
1822 * @invoke: If true, the teardown function is invoked for cpus where
1823 * cpu state >= @state
1825 * The caller needs to hold cpus read locked while calling this function.
1826 * The teardown callback is currently not allowed to fail. Think
1827 * about module removal!
1829 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state
, bool invoke
)
1831 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
1834 BUG_ON(cpuhp_cb_check(state
));
1836 lockdep_assert_cpus_held();
1838 mutex_lock(&cpuhp_state_mutex
);
1839 if (sp
->multi_instance
) {
1840 WARN(!hlist_empty(&sp
->list
),
1841 "Error: Removing state %d which has instances left.\n",
1846 if (!invoke
|| !cpuhp_get_teardown_cb(state
))
1850 * Call the teardown callback for each present cpu depending
1851 * on the hotplug state of the cpu. This function is not
1852 * allowed to fail currently!
1854 for_each_present_cpu(cpu
) {
1855 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1856 int cpustate
= st
->state
;
1858 if (cpustate
>= state
)
1859 cpuhp_issue_call(cpu
, state
, false, NULL
);
1862 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
, false);
1863 mutex_unlock(&cpuhp_state_mutex
);
1865 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked
);
1867 void __cpuhp_remove_state(enum cpuhp_state state
, bool invoke
)
1870 __cpuhp_remove_state_cpuslocked(state
, invoke
);
1873 EXPORT_SYMBOL(__cpuhp_remove_state
);
1875 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1876 static ssize_t
show_cpuhp_state(struct device
*dev
,
1877 struct device_attribute
*attr
, char *buf
)
1879 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1881 return sprintf(buf
, "%d\n", st
->state
);
1883 static DEVICE_ATTR(state
, 0444, show_cpuhp_state
, NULL
);
1885 static ssize_t
write_cpuhp_target(struct device
*dev
,
1886 struct device_attribute
*attr
,
1887 const char *buf
, size_t count
)
1889 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1890 struct cpuhp_step
*sp
;
1893 ret
= kstrtoint(buf
, 10, &target
);
1897 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1898 if (target
< CPUHP_OFFLINE
|| target
> CPUHP_ONLINE
)
1901 if (target
!= CPUHP_OFFLINE
&& target
!= CPUHP_ONLINE
)
1905 ret
= lock_device_hotplug_sysfs();
1909 mutex_lock(&cpuhp_state_mutex
);
1910 sp
= cpuhp_get_step(target
);
1911 ret
= !sp
->name
|| sp
->cant_stop
? -EINVAL
: 0;
1912 mutex_unlock(&cpuhp_state_mutex
);
1916 if (st
->state
< target
)
1917 ret
= do_cpu_up(dev
->id
, target
);
1919 ret
= do_cpu_down(dev
->id
, target
);
1921 unlock_device_hotplug();
1922 return ret
? ret
: count
;
1925 static ssize_t
show_cpuhp_target(struct device
*dev
,
1926 struct device_attribute
*attr
, char *buf
)
1928 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1930 return sprintf(buf
, "%d\n", st
->target
);
1932 static DEVICE_ATTR(target
, 0644, show_cpuhp_target
, write_cpuhp_target
);
1935 static ssize_t
write_cpuhp_fail(struct device
*dev
,
1936 struct device_attribute
*attr
,
1937 const char *buf
, size_t count
)
1939 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1940 struct cpuhp_step
*sp
;
1943 ret
= kstrtoint(buf
, 10, &fail
);
1947 if (fail
< CPUHP_OFFLINE
|| fail
> CPUHP_ONLINE
)
1951 * Cannot fail STARTING/DYING callbacks.
1953 if (cpuhp_is_atomic_state(fail
))
1957 * Cannot fail anything that doesn't have callbacks.
1959 mutex_lock(&cpuhp_state_mutex
);
1960 sp
= cpuhp_get_step(fail
);
1961 if (!sp
->startup
.single
&& !sp
->teardown
.single
)
1963 mutex_unlock(&cpuhp_state_mutex
);
1972 static ssize_t
show_cpuhp_fail(struct device
*dev
,
1973 struct device_attribute
*attr
, char *buf
)
1975 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1977 return sprintf(buf
, "%d\n", st
->fail
);
1980 static DEVICE_ATTR(fail
, 0644, show_cpuhp_fail
, write_cpuhp_fail
);
1982 static struct attribute
*cpuhp_cpu_attrs
[] = {
1983 &dev_attr_state
.attr
,
1984 &dev_attr_target
.attr
,
1985 &dev_attr_fail
.attr
,
1989 static const struct attribute_group cpuhp_cpu_attr_group
= {
1990 .attrs
= cpuhp_cpu_attrs
,
1995 static ssize_t
show_cpuhp_states(struct device
*dev
,
1996 struct device_attribute
*attr
, char *buf
)
1998 ssize_t cur
, res
= 0;
2001 mutex_lock(&cpuhp_state_mutex
);
2002 for (i
= CPUHP_OFFLINE
; i
<= CPUHP_ONLINE
; i
++) {
2003 struct cpuhp_step
*sp
= cpuhp_get_step(i
);
2006 cur
= sprintf(buf
, "%3d: %s\n", i
, sp
->name
);
2011 mutex_unlock(&cpuhp_state_mutex
);
2014 static DEVICE_ATTR(states
, 0444, show_cpuhp_states
, NULL
);
2016 static struct attribute
*cpuhp_cpu_root_attrs
[] = {
2017 &dev_attr_states
.attr
,
2021 static const struct attribute_group cpuhp_cpu_root_attr_group
= {
2022 .attrs
= cpuhp_cpu_root_attrs
,
2027 #ifdef CONFIG_HOTPLUG_SMT
2029 static const char *smt_states
[] = {
2030 [CPU_SMT_ENABLED
] = "on",
2031 [CPU_SMT_DISABLED
] = "off",
2032 [CPU_SMT_FORCE_DISABLED
] = "forceoff",
2033 [CPU_SMT_NOT_SUPPORTED
] = "notsupported",
2037 show_smt_control(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
2039 return snprintf(buf
, PAGE_SIZE
- 2, "%s\n", smt_states
[cpu_smt_control
]);
2042 static void cpuhp_offline_cpu_device(unsigned int cpu
)
2044 struct device
*dev
= get_cpu_device(cpu
);
2046 dev
->offline
= true;
2047 /* Tell user space about the state change */
2048 kobject_uevent(&dev
->kobj
, KOBJ_OFFLINE
);
2051 static void cpuhp_online_cpu_device(unsigned int cpu
)
2053 struct device
*dev
= get_cpu_device(cpu
);
2055 dev
->offline
= false;
2056 /* Tell user space about the state change */
2057 kobject_uevent(&dev
->kobj
, KOBJ_ONLINE
);
2060 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval
)
2064 cpu_maps_update_begin();
2065 for_each_online_cpu(cpu
) {
2066 if (topology_is_primary_thread(cpu
))
2068 ret
= cpu_down_maps_locked(cpu
, CPUHP_OFFLINE
);
2072 * As this needs to hold the cpu maps lock it's impossible
2073 * to call device_offline() because that ends up calling
2074 * cpu_down() which takes cpu maps lock. cpu maps lock
2075 * needs to be held as this might race against in kernel
2076 * abusers of the hotplug machinery (thermal management).
2078 * So nothing would update device:offline state. That would
2079 * leave the sysfs entry stale and prevent onlining after
2080 * smt control has been changed to 'off' again. This is
2081 * called under the sysfs hotplug lock, so it is properly
2082 * serialized against the regular offline usage.
2084 cpuhp_offline_cpu_device(cpu
);
2087 cpu_smt_control
= ctrlval
;
2090 cpu_maps_update_done();
2094 int cpuhp_smt_enable(void)
2098 cpu_maps_update_begin();
2099 cpu_smt_control
= CPU_SMT_ENABLED
;
2101 for_each_present_cpu(cpu
) {
2102 /* Skip online CPUs and CPUs on offline nodes */
2103 if (cpu_online(cpu
) || !node_online(cpu_to_node(cpu
)))
2105 ret
= _cpu_up(cpu
, 0, CPUHP_ONLINE
);
2108 /* See comment in cpuhp_smt_disable() */
2109 cpuhp_online_cpu_device(cpu
);
2111 cpu_maps_update_done();
2116 store_smt_control(struct device
*dev
, struct device_attribute
*attr
,
2117 const char *buf
, size_t count
)
2121 if (sysfs_streq(buf
, "on"))
2122 ctrlval
= CPU_SMT_ENABLED
;
2123 else if (sysfs_streq(buf
, "off"))
2124 ctrlval
= CPU_SMT_DISABLED
;
2125 else if (sysfs_streq(buf
, "forceoff"))
2126 ctrlval
= CPU_SMT_FORCE_DISABLED
;
2130 if (cpu_smt_control
== CPU_SMT_FORCE_DISABLED
)
2133 if (cpu_smt_control
== CPU_SMT_NOT_SUPPORTED
)
2136 ret
= lock_device_hotplug_sysfs();
2140 if (ctrlval
!= cpu_smt_control
) {
2142 case CPU_SMT_ENABLED
:
2143 ret
= cpuhp_smt_enable();
2145 case CPU_SMT_DISABLED
:
2146 case CPU_SMT_FORCE_DISABLED
:
2147 ret
= cpuhp_smt_disable(ctrlval
);
2152 unlock_device_hotplug();
2153 return ret
? ret
: count
;
2155 static DEVICE_ATTR(control
, 0644, show_smt_control
, store_smt_control
);
2158 show_smt_active(struct device
*dev
, struct device_attribute
*attr
, char *buf
)
2160 bool active
= topology_max_smt_threads() > 1;
2162 return snprintf(buf
, PAGE_SIZE
- 2, "%d\n", active
);
2164 static DEVICE_ATTR(active
, 0444, show_smt_active
, NULL
);
2166 static struct attribute
*cpuhp_smt_attrs
[] = {
2167 &dev_attr_control
.attr
,
2168 &dev_attr_active
.attr
,
2172 static const struct attribute_group cpuhp_smt_attr_group
= {
2173 .attrs
= cpuhp_smt_attrs
,
2178 static int __init
cpu_smt_state_init(void)
2180 return sysfs_create_group(&cpu_subsys
.dev_root
->kobj
,
2181 &cpuhp_smt_attr_group
);
2185 static inline int cpu_smt_state_init(void) { return 0; }
2188 static int __init
cpuhp_sysfs_init(void)
2192 ret
= cpu_smt_state_init();
2196 ret
= sysfs_create_group(&cpu_subsys
.dev_root
->kobj
,
2197 &cpuhp_cpu_root_attr_group
);
2201 for_each_possible_cpu(cpu
) {
2202 struct device
*dev
= get_cpu_device(cpu
);
2206 ret
= sysfs_create_group(&dev
->kobj
, &cpuhp_cpu_attr_group
);
2212 device_initcall(cpuhp_sysfs_init
);
2216 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2217 * represents all NR_CPUS bits binary values of 1<<nr.
2219 * It is used by cpumask_of() to get a constant address to a CPU
2220 * mask value that has a single bit set only.
2223 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2224 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2225 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2226 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2227 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2229 const unsigned long cpu_bit_bitmap
[BITS_PER_LONG
+1][BITS_TO_LONGS(NR_CPUS
)] = {
2231 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2232 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2233 #if BITS_PER_LONG > 32
2234 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2235 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2238 EXPORT_SYMBOL_GPL(cpu_bit_bitmap
);
2240 const DECLARE_BITMAP(cpu_all_bits
, NR_CPUS
) = CPU_BITS_ALL
;
2241 EXPORT_SYMBOL(cpu_all_bits
);
2243 #ifdef CONFIG_INIT_ALL_POSSIBLE
2244 struct cpumask __cpu_possible_mask __read_mostly
2247 struct cpumask __cpu_possible_mask __read_mostly
;
2249 EXPORT_SYMBOL(__cpu_possible_mask
);
2251 struct cpumask __cpu_online_mask __read_mostly
;
2252 EXPORT_SYMBOL(__cpu_online_mask
);
2254 struct cpumask __cpu_present_mask __read_mostly
;
2255 EXPORT_SYMBOL(__cpu_present_mask
);
2257 struct cpumask __cpu_active_mask __read_mostly
;
2258 EXPORT_SYMBOL(__cpu_active_mask
);
2260 void init_cpu_present(const struct cpumask
*src
)
2262 cpumask_copy(&__cpu_present_mask
, src
);
2265 void init_cpu_possible(const struct cpumask
*src
)
2267 cpumask_copy(&__cpu_possible_mask
, src
);
2270 void init_cpu_online(const struct cpumask
*src
)
2272 cpumask_copy(&__cpu_online_mask
, src
);
2276 * Activate the first processor.
2278 void __init
boot_cpu_init(void)
2280 int cpu
= smp_processor_id();
2282 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2283 set_cpu_online(cpu
, true);
2284 set_cpu_active(cpu
, true);
2285 set_cpu_present(cpu
, true);
2286 set_cpu_possible(cpu
, true);
2289 __boot_cpu_id
= cpu
;
2294 * Must be called _AFTER_ setting up the per_cpu areas
2296 void __init
boot_cpu_hotplug_init(void)
2299 per_cpu_ptr(&cpuhp_state
, smp_processor_id())->booted_once
= true;
2301 per_cpu_ptr(&cpuhp_state
, smp_processor_id())->state
= CPUHP_ONLINE
;
2305 * These are used for a global "mitigations=" cmdline option for toggling
2306 * optional CPU mitigations.
2308 enum cpu_mitigations
{
2309 CPU_MITIGATIONS_OFF
,
2310 CPU_MITIGATIONS_AUTO
,
2311 CPU_MITIGATIONS_AUTO_NOSMT
,
2314 static enum cpu_mitigations cpu_mitigations __ro_after_init
=
2315 CPU_MITIGATIONS_AUTO
;
2317 static int __init
mitigations_parse_cmdline(char *arg
)
2319 if (!strcmp(arg
, "off"))
2320 cpu_mitigations
= CPU_MITIGATIONS_OFF
;
2321 else if (!strcmp(arg
, "auto"))
2322 cpu_mitigations
= CPU_MITIGATIONS_AUTO
;
2323 else if (!strcmp(arg
, "auto,nosmt"))
2324 cpu_mitigations
= CPU_MITIGATIONS_AUTO_NOSMT
;
2326 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2331 early_param("mitigations", mitigations_parse_cmdline
);
2333 /* mitigations=off */
2334 bool cpu_mitigations_off(void)
2336 return cpu_mitigations
== CPU_MITIGATIONS_OFF
;
2338 EXPORT_SYMBOL_GPL(cpu_mitigations_off
);
2340 /* mitigations=auto,nosmt */
2341 bool cpu_mitigations_auto_nosmt(void)
2343 return cpu_mitigations
== CPU_MITIGATIONS_AUTO_NOSMT
;
2345 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt
);