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>
19 #include <linux/compat.h>
21 #include <linux/blkdev.h>
22 #include <linux/kprobes.h>
23 #include <linux/mmu_context.h>
24 #include <linux/module.h>
25 #include <linux/nmi.h>
26 #include <linux/prefetch.h>
27 #include <linux/profile.h>
28 #include <linux/security.h>
29 #include <linux/syscalls.h>
30 #include <linux/sched/isolation.h>
32 #include <asm/switch_to.h>
34 #ifdef CONFIG_PARAVIRT
35 #include <asm/paravirt.h>
39 #include "../workqueue_internal.h"
40 #include "../smpboot.h"
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/sched.h>
45 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq
, runqueues
);
47 #if defined(CONFIG_SCHED_DEBUG) && defined(HAVE_JUMP_LABEL)
49 * Debugging: various feature bits
51 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
52 * sysctl_sched_features, defined in sched.h, to allow constants propagation
53 * at compile time and compiler optimization based on features default.
55 #define SCHED_FEAT(name, enabled) \
56 (1UL << __SCHED_FEAT_##name) * enabled |
57 const_debug
unsigned int sysctl_sched_features
=
64 * Number of tasks to iterate in a single balance run.
65 * Limited because this is done with IRQs disabled.
67 const_debug
unsigned int sysctl_sched_nr_migrate
= 32;
70 * period over which we average the RT time consumption, measured
75 const_debug
unsigned int sysctl_sched_time_avg
= MSEC_PER_SEC
;
78 * period over which we measure -rt task CPU usage in us.
81 unsigned int sysctl_sched_rt_period
= 1000000;
83 __read_mostly
int scheduler_running
;
86 * part of the period that we allow rt tasks to run in us.
89 int sysctl_sched_rt_runtime
= 950000;
92 * __task_rq_lock - lock the rq @p resides on.
94 struct rq
*__task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
99 lockdep_assert_held(&p
->pi_lock
);
103 raw_spin_lock(&rq
->lock
);
104 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
108 raw_spin_unlock(&rq
->lock
);
110 while (unlikely(task_on_rq_migrating(p
)))
116 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
118 struct rq
*task_rq_lock(struct task_struct
*p
, struct rq_flags
*rf
)
119 __acquires(p
->pi_lock
)
125 raw_spin_lock_irqsave(&p
->pi_lock
, rf
->flags
);
127 raw_spin_lock(&rq
->lock
);
129 * move_queued_task() task_rq_lock()
132 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
133 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
134 * [S] ->cpu = new_cpu [L] task_rq()
138 * If we observe the old cpu in task_rq_lock, the acquire of
139 * the old rq->lock will fully serialize against the stores.
141 * If we observe the new CPU in task_rq_lock, the acquire will
142 * pair with the WMB to ensure we must then also see migrating.
144 if (likely(rq
== task_rq(p
) && !task_on_rq_migrating(p
))) {
148 raw_spin_unlock(&rq
->lock
);
149 raw_spin_unlock_irqrestore(&p
->pi_lock
, rf
->flags
);
151 while (unlikely(task_on_rq_migrating(p
)))
157 * RQ-clock updating methods:
160 static void update_rq_clock_task(struct rq
*rq
, s64 delta
)
163 * In theory, the compile should just see 0 here, and optimize out the call
164 * to sched_rt_avg_update. But I don't trust it...
166 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
167 s64 steal
= 0, irq_delta
= 0;
169 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
170 irq_delta
= irq_time_read(cpu_of(rq
)) - rq
->prev_irq_time
;
173 * Since irq_time is only updated on {soft,}irq_exit, we might run into
174 * this case when a previous update_rq_clock() happened inside a
177 * When this happens, we stop ->clock_task and only update the
178 * prev_irq_time stamp to account for the part that fit, so that a next
179 * update will consume the rest. This ensures ->clock_task is
182 * It does however cause some slight miss-attribution of {soft,}irq
183 * time, a more accurate solution would be to update the irq_time using
184 * the current rq->clock timestamp, except that would require using
187 if (irq_delta
> delta
)
190 rq
->prev_irq_time
+= irq_delta
;
193 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
194 if (static_key_false((¶virt_steal_rq_enabled
))) {
195 steal
= paravirt_steal_clock(cpu_of(rq
));
196 steal
-= rq
->prev_steal_time_rq
;
198 if (unlikely(steal
> delta
))
201 rq
->prev_steal_time_rq
+= steal
;
206 rq
->clock_task
+= delta
;
208 #if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
209 if ((irq_delta
+ steal
) && sched_feat(NONTASK_CAPACITY
))
210 sched_rt_avg_update(rq
, irq_delta
+ steal
);
214 void update_rq_clock(struct rq
*rq
)
218 lockdep_assert_held(&rq
->lock
);
220 if (rq
->clock_update_flags
& RQCF_ACT_SKIP
)
223 #ifdef CONFIG_SCHED_DEBUG
224 if (sched_feat(WARN_DOUBLE_CLOCK
))
225 SCHED_WARN_ON(rq
->clock_update_flags
& RQCF_UPDATED
);
226 rq
->clock_update_flags
|= RQCF_UPDATED
;
229 delta
= sched_clock_cpu(cpu_of(rq
)) - rq
->clock
;
233 update_rq_clock_task(rq
, delta
);
237 #ifdef CONFIG_SCHED_HRTICK
239 * Use HR-timers to deliver accurate preemption points.
242 static void hrtick_clear(struct rq
*rq
)
244 if (hrtimer_active(&rq
->hrtick_timer
))
245 hrtimer_cancel(&rq
->hrtick_timer
);
249 * High-resolution timer tick.
250 * Runs from hardirq context with interrupts disabled.
252 static enum hrtimer_restart
hrtick(struct hrtimer
*timer
)
254 struct rq
*rq
= container_of(timer
, struct rq
, hrtick_timer
);
257 WARN_ON_ONCE(cpu_of(rq
) != smp_processor_id());
261 rq
->curr
->sched_class
->task_tick(rq
, rq
->curr
, 1);
264 return HRTIMER_NORESTART
;
269 static void __hrtick_restart(struct rq
*rq
)
271 struct hrtimer
*timer
= &rq
->hrtick_timer
;
273 hrtimer_start_expires(timer
, HRTIMER_MODE_ABS_PINNED
);
277 * called from hardirq (IPI) context
279 static void __hrtick_start(void *arg
)
285 __hrtick_restart(rq
);
286 rq
->hrtick_csd_pending
= 0;
291 * Called to set the hrtick timer state.
293 * called with rq->lock held and irqs disabled
295 void hrtick_start(struct rq
*rq
, u64 delay
)
297 struct hrtimer
*timer
= &rq
->hrtick_timer
;
302 * Don't schedule slices shorter than 10000ns, that just
303 * doesn't make sense and can cause timer DoS.
305 delta
= max_t(s64
, delay
, 10000LL);
306 time
= ktime_add_ns(timer
->base
->get_time(), delta
);
308 hrtimer_set_expires(timer
, time
);
310 if (rq
== this_rq()) {
311 __hrtick_restart(rq
);
312 } else if (!rq
->hrtick_csd_pending
) {
313 smp_call_function_single_async(cpu_of(rq
), &rq
->hrtick_csd
);
314 rq
->hrtick_csd_pending
= 1;
320 * Called to set the hrtick timer state.
322 * called with rq->lock held and irqs disabled
324 void hrtick_start(struct rq
*rq
, u64 delay
)
327 * Don't schedule slices shorter than 10000ns, that just
328 * doesn't make sense. Rely on vruntime for fairness.
330 delay
= max_t(u64
, delay
, 10000LL);
331 hrtimer_start(&rq
->hrtick_timer
, ns_to_ktime(delay
),
332 HRTIMER_MODE_REL_PINNED
);
334 #endif /* CONFIG_SMP */
336 static void init_rq_hrtick(struct rq
*rq
)
339 rq
->hrtick_csd_pending
= 0;
341 rq
->hrtick_csd
.flags
= 0;
342 rq
->hrtick_csd
.func
= __hrtick_start
;
343 rq
->hrtick_csd
.info
= rq
;
346 hrtimer_init(&rq
->hrtick_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
347 rq
->hrtick_timer
.function
= hrtick
;
349 #else /* CONFIG_SCHED_HRTICK */
350 static inline void hrtick_clear(struct rq
*rq
)
354 static inline void init_rq_hrtick(struct rq
*rq
)
357 #endif /* CONFIG_SCHED_HRTICK */
360 * cmpxchg based fetch_or, macro so it works for different integer types
362 #define fetch_or(ptr, mask) \
364 typeof(ptr) _ptr = (ptr); \
365 typeof(mask) _mask = (mask); \
366 typeof(*_ptr) _old, _val = *_ptr; \
369 _old = cmpxchg(_ptr, _val, _val | _mask); \
377 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
379 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
380 * this avoids any races wrt polling state changes and thereby avoids
383 static bool set_nr_and_not_polling(struct task_struct
*p
)
385 struct thread_info
*ti
= task_thread_info(p
);
386 return !(fetch_or(&ti
->flags
, _TIF_NEED_RESCHED
) & _TIF_POLLING_NRFLAG
);
390 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
392 * If this returns true, then the idle task promises to call
393 * sched_ttwu_pending() and reschedule soon.
395 static bool set_nr_if_polling(struct task_struct
*p
)
397 struct thread_info
*ti
= task_thread_info(p
);
398 typeof(ti
->flags
) old
, val
= READ_ONCE(ti
->flags
);
401 if (!(val
& _TIF_POLLING_NRFLAG
))
403 if (val
& _TIF_NEED_RESCHED
)
405 old
= cmpxchg(&ti
->flags
, val
, val
| _TIF_NEED_RESCHED
);
414 static bool set_nr_and_not_polling(struct task_struct
*p
)
416 set_tsk_need_resched(p
);
421 static bool set_nr_if_polling(struct task_struct
*p
)
428 void wake_q_add(struct wake_q_head
*head
, struct task_struct
*task
)
430 struct wake_q_node
*node
= &task
->wake_q
;
433 * Atomically grab the task, if ->wake_q is !nil already it means
434 * its already queued (either by us or someone else) and will get the
435 * wakeup due to that.
437 * This cmpxchg() implies a full barrier, which pairs with the write
438 * barrier implied by the wakeup in wake_up_q().
440 if (cmpxchg(&node
->next
, NULL
, WAKE_Q_TAIL
))
443 get_task_struct(task
);
446 * The head is context local, there can be no concurrency.
449 head
->lastp
= &node
->next
;
452 void wake_up_q(struct wake_q_head
*head
)
454 struct wake_q_node
*node
= head
->first
;
456 while (node
!= WAKE_Q_TAIL
) {
457 struct task_struct
*task
;
459 task
= container_of(node
, struct task_struct
, wake_q
);
461 /* Task can safely be re-inserted now: */
463 task
->wake_q
.next
= NULL
;
466 * wake_up_process() implies a wmb() to pair with the queueing
467 * in wake_q_add() so as not to miss wakeups.
469 wake_up_process(task
);
470 put_task_struct(task
);
475 * resched_curr - mark rq's current task 'to be rescheduled now'.
477 * On UP this means the setting of the need_resched flag, on SMP it
478 * might also involve a cross-CPU call to trigger the scheduler on
481 void resched_curr(struct rq
*rq
)
483 struct task_struct
*curr
= rq
->curr
;
486 lockdep_assert_held(&rq
->lock
);
488 if (test_tsk_need_resched(curr
))
493 if (cpu
== smp_processor_id()) {
494 set_tsk_need_resched(curr
);
495 set_preempt_need_resched();
499 if (set_nr_and_not_polling(curr
))
500 smp_send_reschedule(cpu
);
502 trace_sched_wake_idle_without_ipi(cpu
);
505 void resched_cpu(int cpu
)
507 struct rq
*rq
= cpu_rq(cpu
);
510 raw_spin_lock_irqsave(&rq
->lock
, flags
);
512 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
516 #ifdef CONFIG_NO_HZ_COMMON
518 * In the semi idle case, use the nearest busy CPU for migrating timers
519 * from an idle CPU. This is good for power-savings.
521 * We don't do similar optimization for completely idle system, as
522 * selecting an idle CPU will add more delays to the timers than intended
523 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
525 int get_nohz_timer_target(void)
527 int i
, cpu
= smp_processor_id();
528 struct sched_domain
*sd
;
530 if (!idle_cpu(cpu
) && housekeeping_cpu(cpu
, HK_FLAG_TIMER
))
534 for_each_domain(cpu
, sd
) {
535 for_each_cpu(i
, sched_domain_span(sd
)) {
539 if (!idle_cpu(i
) && housekeeping_cpu(i
, HK_FLAG_TIMER
)) {
546 if (!housekeeping_cpu(cpu
, HK_FLAG_TIMER
))
547 cpu
= housekeeping_any_cpu(HK_FLAG_TIMER
);
554 * When add_timer_on() enqueues a timer into the timer wheel of an
555 * idle CPU then this timer might expire before the next timer event
556 * which is scheduled to wake up that CPU. In case of a completely
557 * idle system the next event might even be infinite time into the
558 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
559 * leaves the inner idle loop so the newly added timer is taken into
560 * account when the CPU goes back to idle and evaluates the timer
561 * wheel for the next timer event.
563 static void wake_up_idle_cpu(int cpu
)
565 struct rq
*rq
= cpu_rq(cpu
);
567 if (cpu
== smp_processor_id())
570 if (set_nr_and_not_polling(rq
->idle
))
571 smp_send_reschedule(cpu
);
573 trace_sched_wake_idle_without_ipi(cpu
);
576 static bool wake_up_full_nohz_cpu(int cpu
)
579 * We just need the target to call irq_exit() and re-evaluate
580 * the next tick. The nohz full kick at least implies that.
581 * If needed we can still optimize that later with an
584 if (cpu_is_offline(cpu
))
585 return true; /* Don't try to wake offline CPUs. */
586 if (tick_nohz_full_cpu(cpu
)) {
587 if (cpu
!= smp_processor_id() ||
588 tick_nohz_tick_stopped())
589 tick_nohz_full_kick_cpu(cpu
);
597 * Wake up the specified CPU. If the CPU is going offline, it is the
598 * caller's responsibility to deal with the lost wakeup, for example,
599 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
601 void wake_up_nohz_cpu(int cpu
)
603 if (!wake_up_full_nohz_cpu(cpu
))
604 wake_up_idle_cpu(cpu
);
607 static inline bool got_nohz_idle_kick(void)
609 int cpu
= smp_processor_id();
611 if (!test_bit(NOHZ_BALANCE_KICK
, nohz_flags(cpu
)))
614 if (idle_cpu(cpu
) && !need_resched())
618 * We can't run Idle Load Balance on this CPU for this time so we
619 * cancel it and clear NOHZ_BALANCE_KICK
621 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(cpu
));
625 #else /* CONFIG_NO_HZ_COMMON */
627 static inline bool got_nohz_idle_kick(void)
632 #endif /* CONFIG_NO_HZ_COMMON */
634 #ifdef CONFIG_NO_HZ_FULL
635 bool sched_can_stop_tick(struct rq
*rq
)
639 /* Deadline tasks, even if single, need the tick */
640 if (rq
->dl
.dl_nr_running
)
644 * If there are more than one RR tasks, we need the tick to effect the
645 * actual RR behaviour.
647 if (rq
->rt
.rr_nr_running
) {
648 if (rq
->rt
.rr_nr_running
== 1)
655 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
656 * forced preemption between FIFO tasks.
658 fifo_nr_running
= rq
->rt
.rt_nr_running
- rq
->rt
.rr_nr_running
;
663 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
664 * if there's more than one we need the tick for involuntary
667 if (rq
->nr_running
> 1)
672 #endif /* CONFIG_NO_HZ_FULL */
674 void sched_avg_update(struct rq
*rq
)
676 s64 period
= sched_avg_period();
678 while ((s64
)(rq_clock(rq
) - rq
->age_stamp
) > period
) {
680 * Inline assembly required to prevent the compiler
681 * optimising this loop into a divmod call.
682 * See __iter_div_u64_rem() for another example of this.
684 asm("" : "+rm" (rq
->age_stamp
));
685 rq
->age_stamp
+= period
;
690 #endif /* CONFIG_SMP */
692 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
693 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
695 * Iterate task_group tree rooted at *from, calling @down when first entering a
696 * node and @up when leaving it for the final time.
698 * Caller must hold rcu_lock or sufficient equivalent.
700 int walk_tg_tree_from(struct task_group
*from
,
701 tg_visitor down
, tg_visitor up
, void *data
)
703 struct task_group
*parent
, *child
;
709 ret
= (*down
)(parent
, data
);
712 list_for_each_entry_rcu(child
, &parent
->children
, siblings
) {
719 ret
= (*up
)(parent
, data
);
720 if (ret
|| parent
== from
)
724 parent
= parent
->parent
;
731 int tg_nop(struct task_group
*tg
, void *data
)
737 static void set_load_weight(struct task_struct
*p
, bool update_load
)
739 int prio
= p
->static_prio
- MAX_RT_PRIO
;
740 struct load_weight
*load
= &p
->se
.load
;
743 * SCHED_IDLE tasks get minimal weight:
745 if (idle_policy(p
->policy
)) {
746 load
->weight
= scale_load(WEIGHT_IDLEPRIO
);
747 load
->inv_weight
= WMULT_IDLEPRIO
;
752 * SCHED_OTHER tasks have to update their load when changing their
755 if (update_load
&& p
->sched_class
== &fair_sched_class
) {
756 reweight_task(p
, prio
);
758 load
->weight
= scale_load(sched_prio_to_weight
[prio
]);
759 load
->inv_weight
= sched_prio_to_wmult
[prio
];
763 static inline void enqueue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
765 if (!(flags
& ENQUEUE_NOCLOCK
))
768 if (!(flags
& ENQUEUE_RESTORE
))
769 sched_info_queued(rq
, p
);
771 p
->sched_class
->enqueue_task(rq
, p
, flags
);
774 static inline void dequeue_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
776 if (!(flags
& DEQUEUE_NOCLOCK
))
779 if (!(flags
& DEQUEUE_SAVE
))
780 sched_info_dequeued(rq
, p
);
782 p
->sched_class
->dequeue_task(rq
, p
, flags
);
785 void activate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
787 if (task_contributes_to_load(p
))
788 rq
->nr_uninterruptible
--;
790 enqueue_task(rq
, p
, flags
);
793 void deactivate_task(struct rq
*rq
, struct task_struct
*p
, int flags
)
795 if (task_contributes_to_load(p
))
796 rq
->nr_uninterruptible
++;
798 dequeue_task(rq
, p
, flags
);
802 * __normal_prio - return the priority that is based on the static prio
804 static inline int __normal_prio(struct task_struct
*p
)
806 return p
->static_prio
;
810 * Calculate the expected normal priority: i.e. priority
811 * without taking RT-inheritance into account. Might be
812 * boosted by interactivity modifiers. Changes upon fork,
813 * setprio syscalls, and whenever the interactivity
814 * estimator recalculates.
816 static inline int normal_prio(struct task_struct
*p
)
820 if (task_has_dl_policy(p
))
821 prio
= MAX_DL_PRIO
-1;
822 else if (task_has_rt_policy(p
))
823 prio
= MAX_RT_PRIO
-1 - p
->rt_priority
;
825 prio
= __normal_prio(p
);
830 * Calculate the current priority, i.e. the priority
831 * taken into account by the scheduler. This value might
832 * be boosted by RT tasks, or might be boosted by
833 * interactivity modifiers. Will be RT if the task got
834 * RT-boosted. If not then it returns p->normal_prio.
836 static int effective_prio(struct task_struct
*p
)
838 p
->normal_prio
= normal_prio(p
);
840 * If we are RT tasks or we were boosted to RT priority,
841 * keep the priority unchanged. Otherwise, update priority
842 * to the normal priority:
844 if (!rt_prio(p
->prio
))
845 return p
->normal_prio
;
850 * task_curr - is this task currently executing on a CPU?
851 * @p: the task in question.
853 * Return: 1 if the task is currently executing. 0 otherwise.
855 inline int task_curr(const struct task_struct
*p
)
857 return cpu_curr(task_cpu(p
)) == p
;
861 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
862 * use the balance_callback list if you want balancing.
864 * this means any call to check_class_changed() must be followed by a call to
865 * balance_callback().
867 static inline void check_class_changed(struct rq
*rq
, struct task_struct
*p
,
868 const struct sched_class
*prev_class
,
871 if (prev_class
!= p
->sched_class
) {
872 if (prev_class
->switched_from
)
873 prev_class
->switched_from(rq
, p
);
875 p
->sched_class
->switched_to(rq
, p
);
876 } else if (oldprio
!= p
->prio
|| dl_task(p
))
877 p
->sched_class
->prio_changed(rq
, p
, oldprio
);
880 void check_preempt_curr(struct rq
*rq
, struct task_struct
*p
, int flags
)
882 const struct sched_class
*class;
884 if (p
->sched_class
== rq
->curr
->sched_class
) {
885 rq
->curr
->sched_class
->check_preempt_curr(rq
, p
, flags
);
887 for_each_class(class) {
888 if (class == rq
->curr
->sched_class
)
890 if (class == p
->sched_class
) {
898 * A queue event has occurred, and we're going to schedule. In
899 * this case, we can save a useless back to back clock update.
901 if (task_on_rq_queued(rq
->curr
) && test_tsk_need_resched(rq
->curr
))
902 rq_clock_skip_update(rq
, true);
907 * This is how migration works:
909 * 1) we invoke migration_cpu_stop() on the target CPU using
911 * 2) stopper starts to run (implicitly forcing the migrated thread
913 * 3) it checks whether the migrated task is still in the wrong runqueue.
914 * 4) if it's in the wrong runqueue then the migration thread removes
915 * it and puts it into the right queue.
916 * 5) stopper completes and stop_one_cpu() returns and the migration
921 * move_queued_task - move a queued task to new rq.
923 * Returns (locked) new rq. Old rq's lock is released.
925 static struct rq
*move_queued_task(struct rq
*rq
, struct rq_flags
*rf
,
926 struct task_struct
*p
, int new_cpu
)
928 lockdep_assert_held(&rq
->lock
);
930 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
931 dequeue_task(rq
, p
, DEQUEUE_NOCLOCK
);
932 set_task_cpu(p
, new_cpu
);
935 rq
= cpu_rq(new_cpu
);
938 BUG_ON(task_cpu(p
) != new_cpu
);
939 enqueue_task(rq
, p
, 0);
940 p
->on_rq
= TASK_ON_RQ_QUEUED
;
941 check_preempt_curr(rq
, p
, 0);
946 struct migration_arg
{
947 struct task_struct
*task
;
952 * Move (not current) task off this CPU, onto the destination CPU. We're doing
953 * this because either it can't run here any more (set_cpus_allowed()
954 * away from this CPU, or CPU going down), or because we're
955 * attempting to rebalance this task on exec (sched_exec).
957 * So we race with normal scheduler movements, but that's OK, as long
958 * as the task is no longer on this CPU.
960 static struct rq
*__migrate_task(struct rq
*rq
, struct rq_flags
*rf
,
961 struct task_struct
*p
, int dest_cpu
)
963 if (p
->flags
& PF_KTHREAD
) {
964 if (unlikely(!cpu_online(dest_cpu
)))
967 if (unlikely(!cpu_active(dest_cpu
)))
971 /* Affinity changed (again). */
972 if (!cpumask_test_cpu(dest_cpu
, &p
->cpus_allowed
))
976 rq
= move_queued_task(rq
, rf
, p
, dest_cpu
);
982 * migration_cpu_stop - this will be executed by a highprio stopper thread
983 * and performs thread migration by bumping thread off CPU then
984 * 'pushing' onto another runqueue.
986 static int migration_cpu_stop(void *data
)
988 struct migration_arg
*arg
= data
;
989 struct task_struct
*p
= arg
->task
;
990 struct rq
*rq
= this_rq();
994 * The original target CPU might have gone down and we might
995 * be on another CPU but it doesn't matter.
999 * We need to explicitly wake pending tasks before running
1000 * __migrate_task() such that we will not miss enforcing cpus_allowed
1001 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1003 sched_ttwu_pending();
1005 raw_spin_lock(&p
->pi_lock
);
1008 * If task_rq(p) != rq, it cannot be migrated here, because we're
1009 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1010 * we're holding p->pi_lock.
1012 if (task_rq(p
) == rq
) {
1013 if (task_on_rq_queued(p
))
1014 rq
= __migrate_task(rq
, &rf
, p
, arg
->dest_cpu
);
1016 p
->wake_cpu
= arg
->dest_cpu
;
1019 raw_spin_unlock(&p
->pi_lock
);
1026 * sched_class::set_cpus_allowed must do the below, but is not required to
1027 * actually call this function.
1029 void set_cpus_allowed_common(struct task_struct
*p
, const struct cpumask
*new_mask
)
1031 cpumask_copy(&p
->cpus_allowed
, new_mask
);
1032 p
->nr_cpus_allowed
= cpumask_weight(new_mask
);
1035 void do_set_cpus_allowed(struct task_struct
*p
, const struct cpumask
*new_mask
)
1037 struct rq
*rq
= task_rq(p
);
1038 bool queued
, running
;
1040 lockdep_assert_held(&p
->pi_lock
);
1042 queued
= task_on_rq_queued(p
);
1043 running
= task_current(rq
, p
);
1047 * Because __kthread_bind() calls this on blocked tasks without
1050 lockdep_assert_held(&rq
->lock
);
1051 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
1054 put_prev_task(rq
, p
);
1056 p
->sched_class
->set_cpus_allowed(p
, new_mask
);
1059 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
1061 set_curr_task(rq
, p
);
1065 * Change a given task's CPU affinity. Migrate the thread to a
1066 * proper CPU and schedule it away if the CPU it's executing on
1067 * is removed from the allowed bitmask.
1069 * NOTE: the caller must have a valid reference to the task, the
1070 * task must not exit() & deallocate itself prematurely. The
1071 * call is not atomic; no spinlocks may be held.
1073 static int __set_cpus_allowed_ptr(struct task_struct
*p
,
1074 const struct cpumask
*new_mask
, bool check
)
1076 const struct cpumask
*cpu_valid_mask
= cpu_active_mask
;
1077 unsigned int dest_cpu
;
1082 rq
= task_rq_lock(p
, &rf
);
1083 update_rq_clock(rq
);
1085 if (p
->flags
& PF_KTHREAD
) {
1087 * Kernel threads are allowed on online && !active CPUs
1089 cpu_valid_mask
= cpu_online_mask
;
1093 * Must re-check here, to close a race against __kthread_bind(),
1094 * sched_setaffinity() is not guaranteed to observe the flag.
1096 if (check
&& (p
->flags
& PF_NO_SETAFFINITY
)) {
1101 if (cpumask_equal(&p
->cpus_allowed
, new_mask
))
1104 if (!cpumask_intersects(new_mask
, cpu_valid_mask
)) {
1109 do_set_cpus_allowed(p
, new_mask
);
1111 if (p
->flags
& PF_KTHREAD
) {
1113 * For kernel threads that do indeed end up on online &&
1114 * !active we want to ensure they are strict per-CPU threads.
1116 WARN_ON(cpumask_intersects(new_mask
, cpu_online_mask
) &&
1117 !cpumask_intersects(new_mask
, cpu_active_mask
) &&
1118 p
->nr_cpus_allowed
!= 1);
1121 /* Can the task run on the task's current CPU? If so, we're done */
1122 if (cpumask_test_cpu(task_cpu(p
), new_mask
))
1125 dest_cpu
= cpumask_any_and(cpu_valid_mask
, new_mask
);
1126 if (task_running(rq
, p
) || p
->state
== TASK_WAKING
) {
1127 struct migration_arg arg
= { p
, dest_cpu
};
1128 /* Need help from migration thread: drop lock and wait. */
1129 task_rq_unlock(rq
, p
, &rf
);
1130 stop_one_cpu(cpu_of(rq
), migration_cpu_stop
, &arg
);
1131 tlb_migrate_finish(p
->mm
);
1133 } else if (task_on_rq_queued(p
)) {
1135 * OK, since we're going to drop the lock immediately
1136 * afterwards anyway.
1138 rq
= move_queued_task(rq
, &rf
, p
, dest_cpu
);
1141 task_rq_unlock(rq
, p
, &rf
);
1146 int set_cpus_allowed_ptr(struct task_struct
*p
, const struct cpumask
*new_mask
)
1148 return __set_cpus_allowed_ptr(p
, new_mask
, false);
1150 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr
);
1152 void set_task_cpu(struct task_struct
*p
, unsigned int new_cpu
)
1154 #ifdef CONFIG_SCHED_DEBUG
1156 * We should never call set_task_cpu() on a blocked task,
1157 * ttwu() will sort out the placement.
1159 WARN_ON_ONCE(p
->state
!= TASK_RUNNING
&& p
->state
!= TASK_WAKING
&&
1163 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1164 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1165 * time relying on p->on_rq.
1167 WARN_ON_ONCE(p
->state
== TASK_RUNNING
&&
1168 p
->sched_class
== &fair_sched_class
&&
1169 (p
->on_rq
&& !task_on_rq_migrating(p
)));
1171 #ifdef CONFIG_LOCKDEP
1173 * The caller should hold either p->pi_lock or rq->lock, when changing
1174 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1176 * sched_move_task() holds both and thus holding either pins the cgroup,
1179 * Furthermore, all task_rq users should acquire both locks, see
1182 WARN_ON_ONCE(debug_locks
&& !(lockdep_is_held(&p
->pi_lock
) ||
1183 lockdep_is_held(&task_rq(p
)->lock
)));
1186 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
1188 WARN_ON_ONCE(!cpu_online(new_cpu
));
1191 trace_sched_migrate_task(p
, new_cpu
);
1193 if (task_cpu(p
) != new_cpu
) {
1194 if (p
->sched_class
->migrate_task_rq
)
1195 p
->sched_class
->migrate_task_rq(p
);
1196 p
->se
.nr_migrations
++;
1197 perf_event_task_migrate(p
);
1200 __set_task_cpu(p
, new_cpu
);
1203 static void __migrate_swap_task(struct task_struct
*p
, int cpu
)
1205 if (task_on_rq_queued(p
)) {
1206 struct rq
*src_rq
, *dst_rq
;
1207 struct rq_flags srf
, drf
;
1209 src_rq
= task_rq(p
);
1210 dst_rq
= cpu_rq(cpu
);
1212 rq_pin_lock(src_rq
, &srf
);
1213 rq_pin_lock(dst_rq
, &drf
);
1215 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
1216 deactivate_task(src_rq
, p
, 0);
1217 set_task_cpu(p
, cpu
);
1218 activate_task(dst_rq
, p
, 0);
1219 p
->on_rq
= TASK_ON_RQ_QUEUED
;
1220 check_preempt_curr(dst_rq
, p
, 0);
1222 rq_unpin_lock(dst_rq
, &drf
);
1223 rq_unpin_lock(src_rq
, &srf
);
1227 * Task isn't running anymore; make it appear like we migrated
1228 * it before it went to sleep. This means on wakeup we make the
1229 * previous CPU our target instead of where it really is.
1235 struct migration_swap_arg
{
1236 struct task_struct
*src_task
, *dst_task
;
1237 int src_cpu
, dst_cpu
;
1240 static int migrate_swap_stop(void *data
)
1242 struct migration_swap_arg
*arg
= data
;
1243 struct rq
*src_rq
, *dst_rq
;
1246 if (!cpu_active(arg
->src_cpu
) || !cpu_active(arg
->dst_cpu
))
1249 src_rq
= cpu_rq(arg
->src_cpu
);
1250 dst_rq
= cpu_rq(arg
->dst_cpu
);
1252 double_raw_lock(&arg
->src_task
->pi_lock
,
1253 &arg
->dst_task
->pi_lock
);
1254 double_rq_lock(src_rq
, dst_rq
);
1256 if (task_cpu(arg
->dst_task
) != arg
->dst_cpu
)
1259 if (task_cpu(arg
->src_task
) != arg
->src_cpu
)
1262 if (!cpumask_test_cpu(arg
->dst_cpu
, &arg
->src_task
->cpus_allowed
))
1265 if (!cpumask_test_cpu(arg
->src_cpu
, &arg
->dst_task
->cpus_allowed
))
1268 __migrate_swap_task(arg
->src_task
, arg
->dst_cpu
);
1269 __migrate_swap_task(arg
->dst_task
, arg
->src_cpu
);
1274 double_rq_unlock(src_rq
, dst_rq
);
1275 raw_spin_unlock(&arg
->dst_task
->pi_lock
);
1276 raw_spin_unlock(&arg
->src_task
->pi_lock
);
1282 * Cross migrate two tasks
1284 int migrate_swap(struct task_struct
*cur
, struct task_struct
*p
)
1286 struct migration_swap_arg arg
;
1289 arg
= (struct migration_swap_arg
){
1291 .src_cpu
= task_cpu(cur
),
1293 .dst_cpu
= task_cpu(p
),
1296 if (arg
.src_cpu
== arg
.dst_cpu
)
1300 * These three tests are all lockless; this is OK since all of them
1301 * will be re-checked with proper locks held further down the line.
1303 if (!cpu_active(arg
.src_cpu
) || !cpu_active(arg
.dst_cpu
))
1306 if (!cpumask_test_cpu(arg
.dst_cpu
, &arg
.src_task
->cpus_allowed
))
1309 if (!cpumask_test_cpu(arg
.src_cpu
, &arg
.dst_task
->cpus_allowed
))
1312 trace_sched_swap_numa(cur
, arg
.src_cpu
, p
, arg
.dst_cpu
);
1313 ret
= stop_two_cpus(arg
.dst_cpu
, arg
.src_cpu
, migrate_swap_stop
, &arg
);
1320 * wait_task_inactive - wait for a thread to unschedule.
1322 * If @match_state is nonzero, it's the @p->state value just checked and
1323 * not expected to change. If it changes, i.e. @p might have woken up,
1324 * then return zero. When we succeed in waiting for @p to be off its CPU,
1325 * we return a positive number (its total switch count). If a second call
1326 * a short while later returns the same number, the caller can be sure that
1327 * @p has remained unscheduled the whole time.
1329 * The caller must ensure that the task *will* unschedule sometime soon,
1330 * else this function might spin for a *long* time. This function can't
1331 * be called with interrupts off, or it may introduce deadlock with
1332 * smp_call_function() if an IPI is sent by the same process we are
1333 * waiting to become inactive.
1335 unsigned long wait_task_inactive(struct task_struct
*p
, long match_state
)
1337 int running
, queued
;
1344 * We do the initial early heuristics without holding
1345 * any task-queue locks at all. We'll only try to get
1346 * the runqueue lock when things look like they will
1352 * If the task is actively running on another CPU
1353 * still, just relax and busy-wait without holding
1356 * NOTE! Since we don't hold any locks, it's not
1357 * even sure that "rq" stays as the right runqueue!
1358 * But we don't care, since "task_running()" will
1359 * return false if the runqueue has changed and p
1360 * is actually now running somewhere else!
1362 while (task_running(rq
, p
)) {
1363 if (match_state
&& unlikely(p
->state
!= match_state
))
1369 * Ok, time to look more closely! We need the rq
1370 * lock now, to be *sure*. If we're wrong, we'll
1371 * just go back and repeat.
1373 rq
= task_rq_lock(p
, &rf
);
1374 trace_sched_wait_task(p
);
1375 running
= task_running(rq
, p
);
1376 queued
= task_on_rq_queued(p
);
1378 if (!match_state
|| p
->state
== match_state
)
1379 ncsw
= p
->nvcsw
| LONG_MIN
; /* sets MSB */
1380 task_rq_unlock(rq
, p
, &rf
);
1383 * If it changed from the expected state, bail out now.
1385 if (unlikely(!ncsw
))
1389 * Was it really running after all now that we
1390 * checked with the proper locks actually held?
1392 * Oops. Go back and try again..
1394 if (unlikely(running
)) {
1400 * It's not enough that it's not actively running,
1401 * it must be off the runqueue _entirely_, and not
1404 * So if it was still runnable (but just not actively
1405 * running right now), it's preempted, and we should
1406 * yield - it could be a while.
1408 if (unlikely(queued
)) {
1409 ktime_t to
= NSEC_PER_SEC
/ HZ
;
1411 set_current_state(TASK_UNINTERRUPTIBLE
);
1412 schedule_hrtimeout(&to
, HRTIMER_MODE_REL
);
1417 * Ahh, all good. It wasn't running, and it wasn't
1418 * runnable, which means that it will never become
1419 * running in the future either. We're all done!
1428 * kick_process - kick a running thread to enter/exit the kernel
1429 * @p: the to-be-kicked thread
1431 * Cause a process which is running on another CPU to enter
1432 * kernel-mode, without any delay. (to get signals handled.)
1434 * NOTE: this function doesn't have to take the runqueue lock,
1435 * because all it wants to ensure is that the remote task enters
1436 * the kernel. If the IPI races and the task has been migrated
1437 * to another CPU then no harm is done and the purpose has been
1440 void kick_process(struct task_struct
*p
)
1446 if ((cpu
!= smp_processor_id()) && task_curr(p
))
1447 smp_send_reschedule(cpu
);
1450 EXPORT_SYMBOL_GPL(kick_process
);
1453 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1455 * A few notes on cpu_active vs cpu_online:
1457 * - cpu_active must be a subset of cpu_online
1459 * - on cpu-up we allow per-cpu kthreads on the online && !active cpu,
1460 * see __set_cpus_allowed_ptr(). At this point the newly online
1461 * CPU isn't yet part of the sched domains, and balancing will not
1464 * - on CPU-down we clear cpu_active() to mask the sched domains and
1465 * avoid the load balancer to place new tasks on the to be removed
1466 * CPU. Existing tasks will remain running there and will be taken
1469 * This means that fallback selection must not select !active CPUs.
1470 * And can assume that any active CPU must be online. Conversely
1471 * select_task_rq() below may allow selection of !active CPUs in order
1472 * to satisfy the above rules.
1474 static int select_fallback_rq(int cpu
, struct task_struct
*p
)
1476 int nid
= cpu_to_node(cpu
);
1477 const struct cpumask
*nodemask
= NULL
;
1478 enum { cpuset
, possible
, fail
} state
= cpuset
;
1482 * If the node that the CPU is on has been offlined, cpu_to_node()
1483 * will return -1. There is no CPU on the node, and we should
1484 * select the CPU on the other node.
1487 nodemask
= cpumask_of_node(nid
);
1489 /* Look for allowed, online CPU in same node. */
1490 for_each_cpu(dest_cpu
, nodemask
) {
1491 if (!cpu_active(dest_cpu
))
1493 if (cpumask_test_cpu(dest_cpu
, &p
->cpus_allowed
))
1499 /* Any allowed, online CPU? */
1500 for_each_cpu(dest_cpu
, &p
->cpus_allowed
) {
1501 if (!(p
->flags
& PF_KTHREAD
) && !cpu_active(dest_cpu
))
1503 if (!cpu_online(dest_cpu
))
1508 /* No more Mr. Nice Guy. */
1511 if (IS_ENABLED(CONFIG_CPUSETS
)) {
1512 cpuset_cpus_allowed_fallback(p
);
1518 do_set_cpus_allowed(p
, cpu_possible_mask
);
1529 if (state
!= cpuset
) {
1531 * Don't tell them about moving exiting tasks or
1532 * kernel threads (both mm NULL), since they never
1535 if (p
->mm
&& printk_ratelimit()) {
1536 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1537 task_pid_nr(p
), p
->comm
, cpu
);
1545 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1548 int select_task_rq(struct task_struct
*p
, int cpu
, int sd_flags
, int wake_flags
)
1550 lockdep_assert_held(&p
->pi_lock
);
1552 if (p
->nr_cpus_allowed
> 1)
1553 cpu
= p
->sched_class
->select_task_rq(p
, cpu
, sd_flags
, wake_flags
);
1555 cpu
= cpumask_any(&p
->cpus_allowed
);
1558 * In order not to call set_task_cpu() on a blocking task we need
1559 * to rely on ttwu() to place the task on a valid ->cpus_allowed
1562 * Since this is common to all placement strategies, this lives here.
1564 * [ this allows ->select_task() to simply return task_cpu(p) and
1565 * not worry about this generic constraint ]
1567 if (unlikely(!cpumask_test_cpu(cpu
, &p
->cpus_allowed
) ||
1569 cpu
= select_fallback_rq(task_cpu(p
), p
);
1574 static void update_avg(u64
*avg
, u64 sample
)
1576 s64 diff
= sample
- *avg
;
1580 void sched_set_stop_task(int cpu
, struct task_struct
*stop
)
1582 struct sched_param param
= { .sched_priority
= MAX_RT_PRIO
- 1 };
1583 struct task_struct
*old_stop
= cpu_rq(cpu
)->stop
;
1587 * Make it appear like a SCHED_FIFO task, its something
1588 * userspace knows about and won't get confused about.
1590 * Also, it will make PI more or less work without too
1591 * much confusion -- but then, stop work should not
1592 * rely on PI working anyway.
1594 sched_setscheduler_nocheck(stop
, SCHED_FIFO
, ¶m
);
1596 stop
->sched_class
= &stop_sched_class
;
1599 cpu_rq(cpu
)->stop
= stop
;
1603 * Reset it back to a normal scheduling class so that
1604 * it can die in pieces.
1606 old_stop
->sched_class
= &rt_sched_class
;
1612 static inline int __set_cpus_allowed_ptr(struct task_struct
*p
,
1613 const struct cpumask
*new_mask
, bool check
)
1615 return set_cpus_allowed_ptr(p
, new_mask
);
1618 #endif /* CONFIG_SMP */
1621 ttwu_stat(struct task_struct
*p
, int cpu
, int wake_flags
)
1625 if (!schedstat_enabled())
1631 if (cpu
== rq
->cpu
) {
1632 schedstat_inc(rq
->ttwu_local
);
1633 schedstat_inc(p
->se
.statistics
.nr_wakeups_local
);
1635 struct sched_domain
*sd
;
1637 schedstat_inc(p
->se
.statistics
.nr_wakeups_remote
);
1639 for_each_domain(rq
->cpu
, sd
) {
1640 if (cpumask_test_cpu(cpu
, sched_domain_span(sd
))) {
1641 schedstat_inc(sd
->ttwu_wake_remote
);
1648 if (wake_flags
& WF_MIGRATED
)
1649 schedstat_inc(p
->se
.statistics
.nr_wakeups_migrate
);
1650 #endif /* CONFIG_SMP */
1652 schedstat_inc(rq
->ttwu_count
);
1653 schedstat_inc(p
->se
.statistics
.nr_wakeups
);
1655 if (wake_flags
& WF_SYNC
)
1656 schedstat_inc(p
->se
.statistics
.nr_wakeups_sync
);
1659 static inline void ttwu_activate(struct rq
*rq
, struct task_struct
*p
, int en_flags
)
1661 activate_task(rq
, p
, en_flags
);
1662 p
->on_rq
= TASK_ON_RQ_QUEUED
;
1664 /* If a worker is waking up, notify the workqueue: */
1665 if (p
->flags
& PF_WQ_WORKER
)
1666 wq_worker_waking_up(p
, cpu_of(rq
));
1670 * Mark the task runnable and perform wakeup-preemption.
1672 static void ttwu_do_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
1673 struct rq_flags
*rf
)
1675 check_preempt_curr(rq
, p
, wake_flags
);
1676 p
->state
= TASK_RUNNING
;
1677 trace_sched_wakeup(p
);
1680 if (p
->sched_class
->task_woken
) {
1682 * Our task @p is fully woken up and running; so its safe to
1683 * drop the rq->lock, hereafter rq is only used for statistics.
1685 rq_unpin_lock(rq
, rf
);
1686 p
->sched_class
->task_woken(rq
, p
);
1687 rq_repin_lock(rq
, rf
);
1690 if (rq
->idle_stamp
) {
1691 u64 delta
= rq_clock(rq
) - rq
->idle_stamp
;
1692 u64 max
= 2*rq
->max_idle_balance_cost
;
1694 update_avg(&rq
->avg_idle
, delta
);
1696 if (rq
->avg_idle
> max
)
1705 ttwu_do_activate(struct rq
*rq
, struct task_struct
*p
, int wake_flags
,
1706 struct rq_flags
*rf
)
1708 int en_flags
= ENQUEUE_WAKEUP
| ENQUEUE_NOCLOCK
;
1710 lockdep_assert_held(&rq
->lock
);
1713 if (p
->sched_contributes_to_load
)
1714 rq
->nr_uninterruptible
--;
1716 if (wake_flags
& WF_MIGRATED
)
1717 en_flags
|= ENQUEUE_MIGRATED
;
1720 ttwu_activate(rq
, p
, en_flags
);
1721 ttwu_do_wakeup(rq
, p
, wake_flags
, rf
);
1725 * Called in case the task @p isn't fully descheduled from its runqueue,
1726 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1727 * since all we need to do is flip p->state to TASK_RUNNING, since
1728 * the task is still ->on_rq.
1730 static int ttwu_remote(struct task_struct
*p
, int wake_flags
)
1736 rq
= __task_rq_lock(p
, &rf
);
1737 if (task_on_rq_queued(p
)) {
1738 /* check_preempt_curr() may use rq clock */
1739 update_rq_clock(rq
);
1740 ttwu_do_wakeup(rq
, p
, wake_flags
, &rf
);
1743 __task_rq_unlock(rq
, &rf
);
1749 void sched_ttwu_pending(void)
1751 struct rq
*rq
= this_rq();
1752 struct llist_node
*llist
= llist_del_all(&rq
->wake_list
);
1753 struct task_struct
*p
, *t
;
1759 rq_lock_irqsave(rq
, &rf
);
1760 update_rq_clock(rq
);
1762 llist_for_each_entry_safe(p
, t
, llist
, wake_entry
)
1763 ttwu_do_activate(rq
, p
, p
->sched_remote_wakeup
? WF_MIGRATED
: 0, &rf
);
1765 rq_unlock_irqrestore(rq
, &rf
);
1768 void scheduler_ipi(void)
1771 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1772 * TIF_NEED_RESCHED remotely (for the first time) will also send
1775 preempt_fold_need_resched();
1777 if (llist_empty(&this_rq()->wake_list
) && !got_nohz_idle_kick())
1781 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1782 * traditionally all their work was done from the interrupt return
1783 * path. Now that we actually do some work, we need to make sure
1786 * Some archs already do call them, luckily irq_enter/exit nest
1789 * Arguably we should visit all archs and update all handlers,
1790 * however a fair share of IPIs are still resched only so this would
1791 * somewhat pessimize the simple resched case.
1794 sched_ttwu_pending();
1797 * Check if someone kicked us for doing the nohz idle load balance.
1799 if (unlikely(got_nohz_idle_kick())) {
1800 this_rq()->idle_balance
= 1;
1801 raise_softirq_irqoff(SCHED_SOFTIRQ
);
1806 static void ttwu_queue_remote(struct task_struct
*p
, int cpu
, int wake_flags
)
1808 struct rq
*rq
= cpu_rq(cpu
);
1810 p
->sched_remote_wakeup
= !!(wake_flags
& WF_MIGRATED
);
1812 if (llist_add(&p
->wake_entry
, &cpu_rq(cpu
)->wake_list
)) {
1813 if (!set_nr_if_polling(rq
->idle
))
1814 smp_send_reschedule(cpu
);
1816 trace_sched_wake_idle_without_ipi(cpu
);
1820 void wake_up_if_idle(int cpu
)
1822 struct rq
*rq
= cpu_rq(cpu
);
1827 if (!is_idle_task(rcu_dereference(rq
->curr
)))
1830 if (set_nr_if_polling(rq
->idle
)) {
1831 trace_sched_wake_idle_without_ipi(cpu
);
1833 rq_lock_irqsave(rq
, &rf
);
1834 if (is_idle_task(rq
->curr
))
1835 smp_send_reschedule(cpu
);
1836 /* Else CPU is not idle, do nothing here: */
1837 rq_unlock_irqrestore(rq
, &rf
);
1844 bool cpus_share_cache(int this_cpu
, int that_cpu
)
1846 return per_cpu(sd_llc_id
, this_cpu
) == per_cpu(sd_llc_id
, that_cpu
);
1848 #endif /* CONFIG_SMP */
1850 static void ttwu_queue(struct task_struct
*p
, int cpu
, int wake_flags
)
1852 struct rq
*rq
= cpu_rq(cpu
);
1855 #if defined(CONFIG_SMP)
1856 if (sched_feat(TTWU_QUEUE
) && !cpus_share_cache(smp_processor_id(), cpu
)) {
1857 sched_clock_cpu(cpu
); /* Sync clocks across CPUs */
1858 ttwu_queue_remote(p
, cpu
, wake_flags
);
1864 update_rq_clock(rq
);
1865 ttwu_do_activate(rq
, p
, wake_flags
, &rf
);
1870 * Notes on Program-Order guarantees on SMP systems.
1874 * The basic program-order guarantee on SMP systems is that when a task [t]
1875 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
1876 * execution on its new CPU [c1].
1878 * For migration (of runnable tasks) this is provided by the following means:
1880 * A) UNLOCK of the rq(c0)->lock scheduling out task t
1881 * B) migration for t is required to synchronize *both* rq(c0)->lock and
1882 * rq(c1)->lock (if not at the same time, then in that order).
1883 * C) LOCK of the rq(c1)->lock scheduling in task
1885 * Transitivity guarantees that B happens after A and C after B.
1886 * Note: we only require RCpc transitivity.
1887 * Note: the CPU doing B need not be c0 or c1
1896 * UNLOCK rq(0)->lock
1898 * LOCK rq(0)->lock // orders against CPU0
1900 * UNLOCK rq(0)->lock
1904 * UNLOCK rq(1)->lock
1906 * LOCK rq(1)->lock // orders against CPU2
1909 * UNLOCK rq(1)->lock
1912 * BLOCKING -- aka. SLEEP + WAKEUP
1914 * For blocking we (obviously) need to provide the same guarantee as for
1915 * migration. However the means are completely different as there is no lock
1916 * chain to provide order. Instead we do:
1918 * 1) smp_store_release(X->on_cpu, 0)
1919 * 2) smp_cond_load_acquire(!X->on_cpu)
1923 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
1925 * LOCK rq(0)->lock LOCK X->pi_lock
1928 * smp_store_release(X->on_cpu, 0);
1930 * smp_cond_load_acquire(&X->on_cpu, !VAL);
1936 * X->state = RUNNING
1937 * UNLOCK rq(2)->lock
1939 * LOCK rq(2)->lock // orders against CPU1
1942 * UNLOCK rq(2)->lock
1945 * UNLOCK rq(0)->lock
1948 * However; for wakeups there is a second guarantee we must provide, namely we
1949 * must observe the state that lead to our wakeup. That is, not only must our
1950 * task observe its own prior state, it must also observe the stores prior to
1953 * This means that any means of doing remote wakeups must order the CPU doing
1954 * the wakeup against the CPU the task is going to end up running on. This,
1955 * however, is already required for the regular Program-Order guarantee above,
1956 * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1961 * try_to_wake_up - wake up a thread
1962 * @p: the thread to be awakened
1963 * @state: the mask of task states that can be woken
1964 * @wake_flags: wake modifier flags (WF_*)
1966 * If (@state & @p->state) @p->state = TASK_RUNNING.
1968 * If the task was not queued/runnable, also place it back on a runqueue.
1970 * Atomic against schedule() which would dequeue a task, also see
1971 * set_current_state().
1973 * Return: %true if @p->state changes (an actual wakeup was done),
1977 try_to_wake_up(struct task_struct
*p
, unsigned int state
, int wake_flags
)
1979 unsigned long flags
;
1980 int cpu
, success
= 0;
1983 * If we are going to wake up a thread waiting for CONDITION we
1984 * need to ensure that CONDITION=1 done by the caller can not be
1985 * reordered with p->state check below. This pairs with mb() in
1986 * set_current_state() the waiting thread does.
1988 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
1989 smp_mb__after_spinlock();
1990 if (!(p
->state
& state
))
1993 trace_sched_waking(p
);
1995 /* We're going to change ->state: */
2000 * Ensure we load p->on_rq _after_ p->state, otherwise it would
2001 * be possible to, falsely, observe p->on_rq == 0 and get stuck
2002 * in smp_cond_load_acquire() below.
2004 * sched_ttwu_pending() try_to_wake_up()
2005 * [S] p->on_rq = 1; [L] P->state
2006 * UNLOCK rq->lock -----.
2010 * LOCK rq->lock -----'
2014 * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq
2016 * Pairs with the UNLOCK+LOCK on rq->lock from the
2017 * last wakeup of our task and the schedule that got our task
2021 if (p
->on_rq
&& ttwu_remote(p
, wake_flags
))
2026 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2027 * possible to, falsely, observe p->on_cpu == 0.
2029 * One must be running (->on_cpu == 1) in order to remove oneself
2030 * from the runqueue.
2032 * [S] ->on_cpu = 1; [L] ->on_rq
2036 * [S] ->on_rq = 0; [L] ->on_cpu
2038 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2039 * from the consecutive calls to schedule(); the first switching to our
2040 * task, the second putting it to sleep.
2045 * If the owning (remote) CPU is still in the middle of schedule() with
2046 * this task as prev, wait until its done referencing the task.
2048 * Pairs with the smp_store_release() in finish_lock_switch().
2050 * This ensures that tasks getting woken will be fully ordered against
2051 * their previous state and preserve Program Order.
2053 smp_cond_load_acquire(&p
->on_cpu
, !VAL
);
2055 p
->sched_contributes_to_load
= !!task_contributes_to_load(p
);
2056 p
->state
= TASK_WAKING
;
2059 delayacct_blkio_end(p
);
2060 atomic_dec(&task_rq(p
)->nr_iowait
);
2063 cpu
= select_task_rq(p
, p
->wake_cpu
, SD_BALANCE_WAKE
, wake_flags
);
2064 if (task_cpu(p
) != cpu
) {
2065 wake_flags
|= WF_MIGRATED
;
2066 set_task_cpu(p
, cpu
);
2069 #else /* CONFIG_SMP */
2072 delayacct_blkio_end(p
);
2073 atomic_dec(&task_rq(p
)->nr_iowait
);
2076 #endif /* CONFIG_SMP */
2078 ttwu_queue(p
, cpu
, wake_flags
);
2080 ttwu_stat(p
, cpu
, wake_flags
);
2082 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2088 * try_to_wake_up_local - try to wake up a local task with rq lock held
2089 * @p: the thread to be awakened
2090 * @rf: request-queue flags for pinning
2092 * Put @p on the run-queue if it's not already there. The caller must
2093 * ensure that this_rq() is locked, @p is bound to this_rq() and not
2096 static void try_to_wake_up_local(struct task_struct
*p
, struct rq_flags
*rf
)
2098 struct rq
*rq
= task_rq(p
);
2100 if (WARN_ON_ONCE(rq
!= this_rq()) ||
2101 WARN_ON_ONCE(p
== current
))
2104 lockdep_assert_held(&rq
->lock
);
2106 if (!raw_spin_trylock(&p
->pi_lock
)) {
2108 * This is OK, because current is on_cpu, which avoids it being
2109 * picked for load-balance and preemption/IRQs are still
2110 * disabled avoiding further scheduler activity on it and we've
2111 * not yet picked a replacement task.
2114 raw_spin_lock(&p
->pi_lock
);
2118 if (!(p
->state
& TASK_NORMAL
))
2121 trace_sched_waking(p
);
2123 if (!task_on_rq_queued(p
)) {
2125 delayacct_blkio_end(p
);
2126 atomic_dec(&rq
->nr_iowait
);
2128 ttwu_activate(rq
, p
, ENQUEUE_WAKEUP
| ENQUEUE_NOCLOCK
);
2131 ttwu_do_wakeup(rq
, p
, 0, rf
);
2132 ttwu_stat(p
, smp_processor_id(), 0);
2134 raw_spin_unlock(&p
->pi_lock
);
2138 * wake_up_process - Wake up a specific process
2139 * @p: The process to be woken up.
2141 * Attempt to wake up the nominated process and move it to the set of runnable
2144 * Return: 1 if the process was woken up, 0 if it was already running.
2146 * It may be assumed that this function implies a write memory barrier before
2147 * changing the task state if and only if any tasks are woken up.
2149 int wake_up_process(struct task_struct
*p
)
2151 return try_to_wake_up(p
, TASK_NORMAL
, 0);
2153 EXPORT_SYMBOL(wake_up_process
);
2155 int wake_up_state(struct task_struct
*p
, unsigned int state
)
2157 return try_to_wake_up(p
, state
, 0);
2161 * Perform scheduler related setup for a newly forked process p.
2162 * p is forked by current.
2164 * __sched_fork() is basic setup used by init_idle() too:
2166 static void __sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
2171 p
->se
.exec_start
= 0;
2172 p
->se
.sum_exec_runtime
= 0;
2173 p
->se
.prev_sum_exec_runtime
= 0;
2174 p
->se
.nr_migrations
= 0;
2176 INIT_LIST_HEAD(&p
->se
.group_node
);
2178 #ifdef CONFIG_FAIR_GROUP_SCHED
2179 p
->se
.cfs_rq
= NULL
;
2182 #ifdef CONFIG_SCHEDSTATS
2183 /* Even if schedstat is disabled, there should not be garbage */
2184 memset(&p
->se
.statistics
, 0, sizeof(p
->se
.statistics
));
2187 RB_CLEAR_NODE(&p
->dl
.rb_node
);
2188 init_dl_task_timer(&p
->dl
);
2189 init_dl_inactive_task_timer(&p
->dl
);
2190 __dl_clear_params(p
);
2192 INIT_LIST_HEAD(&p
->rt
.run_list
);
2194 p
->rt
.time_slice
= sched_rr_timeslice
;
2198 #ifdef CONFIG_PREEMPT_NOTIFIERS
2199 INIT_HLIST_HEAD(&p
->preempt_notifiers
);
2202 #ifdef CONFIG_NUMA_BALANCING
2203 if (p
->mm
&& atomic_read(&p
->mm
->mm_users
) == 1) {
2204 p
->mm
->numa_next_scan
= jiffies
+ msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2205 p
->mm
->numa_scan_seq
= 0;
2208 if (clone_flags
& CLONE_VM
)
2209 p
->numa_preferred_nid
= current
->numa_preferred_nid
;
2211 p
->numa_preferred_nid
= -1;
2213 p
->node_stamp
= 0ULL;
2214 p
->numa_scan_seq
= p
->mm
? p
->mm
->numa_scan_seq
: 0;
2215 p
->numa_scan_period
= sysctl_numa_balancing_scan_delay
;
2216 p
->numa_work
.next
= &p
->numa_work
;
2217 p
->numa_faults
= NULL
;
2218 p
->last_task_numa_placement
= 0;
2219 p
->last_sum_exec_runtime
= 0;
2221 p
->numa_group
= NULL
;
2222 #endif /* CONFIG_NUMA_BALANCING */
2225 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing
);
2227 #ifdef CONFIG_NUMA_BALANCING
2229 void set_numabalancing_state(bool enabled
)
2232 static_branch_enable(&sched_numa_balancing
);
2234 static_branch_disable(&sched_numa_balancing
);
2237 #ifdef CONFIG_PROC_SYSCTL
2238 int sysctl_numa_balancing(struct ctl_table
*table
, int write
,
2239 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2243 int state
= static_branch_likely(&sched_numa_balancing
);
2245 if (write
&& !capable(CAP_SYS_ADMIN
))
2250 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2254 set_numabalancing_state(state
);
2260 #ifdef CONFIG_SCHEDSTATS
2262 DEFINE_STATIC_KEY_FALSE(sched_schedstats
);
2263 static bool __initdata __sched_schedstats
= false;
2265 static void set_schedstats(bool enabled
)
2268 static_branch_enable(&sched_schedstats
);
2270 static_branch_disable(&sched_schedstats
);
2273 void force_schedstat_enabled(void)
2275 if (!schedstat_enabled()) {
2276 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2277 static_branch_enable(&sched_schedstats
);
2281 static int __init
setup_schedstats(char *str
)
2288 * This code is called before jump labels have been set up, so we can't
2289 * change the static branch directly just yet. Instead set a temporary
2290 * variable so init_schedstats() can do it later.
2292 if (!strcmp(str
, "enable")) {
2293 __sched_schedstats
= true;
2295 } else if (!strcmp(str
, "disable")) {
2296 __sched_schedstats
= false;
2301 pr_warn("Unable to parse schedstats=\n");
2305 __setup("schedstats=", setup_schedstats
);
2307 static void __init
init_schedstats(void)
2309 set_schedstats(__sched_schedstats
);
2312 #ifdef CONFIG_PROC_SYSCTL
2313 int sysctl_schedstats(struct ctl_table
*table
, int write
,
2314 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
2318 int state
= static_branch_likely(&sched_schedstats
);
2320 if (write
&& !capable(CAP_SYS_ADMIN
))
2325 err
= proc_dointvec_minmax(&t
, write
, buffer
, lenp
, ppos
);
2329 set_schedstats(state
);
2332 #endif /* CONFIG_PROC_SYSCTL */
2333 #else /* !CONFIG_SCHEDSTATS */
2334 static inline void init_schedstats(void) {}
2335 #endif /* CONFIG_SCHEDSTATS */
2338 * fork()/clone()-time setup:
2340 int sched_fork(unsigned long clone_flags
, struct task_struct
*p
)
2342 unsigned long flags
;
2343 int cpu
= get_cpu();
2345 __sched_fork(clone_flags
, p
);
2347 * We mark the process as NEW here. This guarantees that
2348 * nobody will actually run it, and a signal or other external
2349 * event cannot wake it up and insert it on the runqueue either.
2351 p
->state
= TASK_NEW
;
2354 * Make sure we do not leak PI boosting priority to the child.
2356 p
->prio
= current
->normal_prio
;
2359 * Revert to default priority/policy on fork if requested.
2361 if (unlikely(p
->sched_reset_on_fork
)) {
2362 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
2363 p
->policy
= SCHED_NORMAL
;
2364 p
->static_prio
= NICE_TO_PRIO(0);
2366 } else if (PRIO_TO_NICE(p
->static_prio
) < 0)
2367 p
->static_prio
= NICE_TO_PRIO(0);
2369 p
->prio
= p
->normal_prio
= __normal_prio(p
);
2370 set_load_weight(p
, false);
2373 * We don't need the reset flag anymore after the fork. It has
2374 * fulfilled its duty:
2376 p
->sched_reset_on_fork
= 0;
2379 if (dl_prio(p
->prio
)) {
2382 } else if (rt_prio(p
->prio
)) {
2383 p
->sched_class
= &rt_sched_class
;
2385 p
->sched_class
= &fair_sched_class
;
2388 init_entity_runnable_average(&p
->se
);
2391 * The child is not yet in the pid-hash so no cgroup attach races,
2392 * and the cgroup is pinned to this child due to cgroup_fork()
2393 * is ran before sched_fork().
2395 * Silence PROVE_RCU.
2397 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
2399 * We're setting the CPU for the first time, we don't migrate,
2400 * so use __set_task_cpu().
2402 __set_task_cpu(p
, cpu
);
2403 if (p
->sched_class
->task_fork
)
2404 p
->sched_class
->task_fork(p
);
2405 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2407 #ifdef CONFIG_SCHED_INFO
2408 if (likely(sched_info_on()))
2409 memset(&p
->sched_info
, 0, sizeof(p
->sched_info
));
2411 #if defined(CONFIG_SMP)
2414 init_task_preempt_count(p
);
2416 plist_node_init(&p
->pushable_tasks
, MAX_PRIO
);
2417 RB_CLEAR_NODE(&p
->pushable_dl_tasks
);
2424 unsigned long to_ratio(u64 period
, u64 runtime
)
2426 if (runtime
== RUNTIME_INF
)
2430 * Doing this here saves a lot of checks in all
2431 * the calling paths, and returning zero seems
2432 * safe for them anyway.
2437 return div64_u64(runtime
<< BW_SHIFT
, period
);
2441 * wake_up_new_task - wake up a newly created task for the first time.
2443 * This function will do some initial scheduler statistics housekeeping
2444 * that must be done for every newly created context, then puts the task
2445 * on the runqueue and wakes it.
2447 void wake_up_new_task(struct task_struct
*p
)
2452 raw_spin_lock_irqsave(&p
->pi_lock
, rf
.flags
);
2453 p
->state
= TASK_RUNNING
;
2456 * Fork balancing, do it here and not earlier because:
2457 * - cpus_allowed can change in the fork path
2458 * - any previously selected CPU might disappear through hotplug
2460 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2461 * as we're not fully set-up yet.
2463 __set_task_cpu(p
, select_task_rq(p
, task_cpu(p
), SD_BALANCE_FORK
, 0));
2465 rq
= __task_rq_lock(p
, &rf
);
2466 update_rq_clock(rq
);
2467 post_init_entity_util_avg(&p
->se
);
2469 activate_task(rq
, p
, ENQUEUE_NOCLOCK
);
2470 p
->on_rq
= TASK_ON_RQ_QUEUED
;
2471 trace_sched_wakeup_new(p
);
2472 check_preempt_curr(rq
, p
, WF_FORK
);
2474 if (p
->sched_class
->task_woken
) {
2476 * Nothing relies on rq->lock after this, so its fine to
2479 rq_unpin_lock(rq
, &rf
);
2480 p
->sched_class
->task_woken(rq
, p
);
2481 rq_repin_lock(rq
, &rf
);
2484 task_rq_unlock(rq
, p
, &rf
);
2487 #ifdef CONFIG_PREEMPT_NOTIFIERS
2489 static struct static_key preempt_notifier_key
= STATIC_KEY_INIT_FALSE
;
2491 void preempt_notifier_inc(void)
2493 static_key_slow_inc(&preempt_notifier_key
);
2495 EXPORT_SYMBOL_GPL(preempt_notifier_inc
);
2497 void preempt_notifier_dec(void)
2499 static_key_slow_dec(&preempt_notifier_key
);
2501 EXPORT_SYMBOL_GPL(preempt_notifier_dec
);
2504 * preempt_notifier_register - tell me when current is being preempted & rescheduled
2505 * @notifier: notifier struct to register
2507 void preempt_notifier_register(struct preempt_notifier
*notifier
)
2509 if (!static_key_false(&preempt_notifier_key
))
2510 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2512 hlist_add_head(¬ifier
->link
, ¤t
->preempt_notifiers
);
2514 EXPORT_SYMBOL_GPL(preempt_notifier_register
);
2517 * preempt_notifier_unregister - no longer interested in preemption notifications
2518 * @notifier: notifier struct to unregister
2520 * This is *not* safe to call from within a preemption notifier.
2522 void preempt_notifier_unregister(struct preempt_notifier
*notifier
)
2524 hlist_del(¬ifier
->link
);
2526 EXPORT_SYMBOL_GPL(preempt_notifier_unregister
);
2528 static void __fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2530 struct preempt_notifier
*notifier
;
2532 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
2533 notifier
->ops
->sched_in(notifier
, raw_smp_processor_id());
2536 static __always_inline
void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2538 if (static_key_false(&preempt_notifier_key
))
2539 __fire_sched_in_preempt_notifiers(curr
);
2543 __fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2544 struct task_struct
*next
)
2546 struct preempt_notifier
*notifier
;
2548 hlist_for_each_entry(notifier
, &curr
->preempt_notifiers
, link
)
2549 notifier
->ops
->sched_out(notifier
, next
);
2552 static __always_inline
void
2553 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2554 struct task_struct
*next
)
2556 if (static_key_false(&preempt_notifier_key
))
2557 __fire_sched_out_preempt_notifiers(curr
, next
);
2560 #else /* !CONFIG_PREEMPT_NOTIFIERS */
2562 static inline void fire_sched_in_preempt_notifiers(struct task_struct
*curr
)
2567 fire_sched_out_preempt_notifiers(struct task_struct
*curr
,
2568 struct task_struct
*next
)
2572 #endif /* CONFIG_PREEMPT_NOTIFIERS */
2575 * prepare_task_switch - prepare to switch tasks
2576 * @rq: the runqueue preparing to switch
2577 * @prev: the current task that is being switched out
2578 * @next: the task we are going to switch to.
2580 * This is called with the rq lock held and interrupts off. It must
2581 * be paired with a subsequent finish_task_switch after the context
2584 * prepare_task_switch sets up locking and calls architecture specific
2588 prepare_task_switch(struct rq
*rq
, struct task_struct
*prev
,
2589 struct task_struct
*next
)
2591 sched_info_switch(rq
, prev
, next
);
2592 perf_event_task_sched_out(prev
, next
);
2593 fire_sched_out_preempt_notifiers(prev
, next
);
2594 prepare_lock_switch(rq
, next
);
2595 prepare_arch_switch(next
);
2599 * finish_task_switch - clean up after a task-switch
2600 * @prev: the thread we just switched away from.
2602 * finish_task_switch must be called after the context switch, paired
2603 * with a prepare_task_switch call before the context switch.
2604 * finish_task_switch will reconcile locking set up by prepare_task_switch,
2605 * and do any other architecture-specific cleanup actions.
2607 * Note that we may have delayed dropping an mm in context_switch(). If
2608 * so, we finish that here outside of the runqueue lock. (Doing it
2609 * with the lock held can cause deadlocks; see schedule() for
2612 * The context switch have flipped the stack from under us and restored the
2613 * local variables which were saved when this task called schedule() in the
2614 * past. prev == current is still correct but we need to recalculate this_rq
2615 * because prev may have moved to another CPU.
2617 static struct rq
*finish_task_switch(struct task_struct
*prev
)
2618 __releases(rq
->lock
)
2620 struct rq
*rq
= this_rq();
2621 struct mm_struct
*mm
= rq
->prev_mm
;
2625 * The previous task will have left us with a preempt_count of 2
2626 * because it left us after:
2629 * preempt_disable(); // 1
2631 * raw_spin_lock_irq(&rq->lock) // 2
2633 * Also, see FORK_PREEMPT_COUNT.
2635 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET
,
2636 "corrupted preempt_count: %s/%d/0x%x\n",
2637 current
->comm
, current
->pid
, preempt_count()))
2638 preempt_count_set(FORK_PREEMPT_COUNT
);
2643 * A task struct has one reference for the use as "current".
2644 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2645 * schedule one last time. The schedule call will never return, and
2646 * the scheduled task must drop that reference.
2648 * We must observe prev->state before clearing prev->on_cpu (in
2649 * finish_lock_switch), otherwise a concurrent wakeup can get prev
2650 * running on another CPU and we could rave with its RUNNING -> DEAD
2651 * transition, resulting in a double drop.
2653 prev_state
= prev
->state
;
2654 vtime_task_switch(prev
);
2655 perf_event_task_sched_in(prev
, current
);
2657 * The membarrier system call requires a full memory barrier
2658 * after storing to rq->curr, before going back to user-space.
2660 * TODO: This smp_mb__after_unlock_lock can go away if PPC end
2661 * up adding a full barrier to switch_mm(), or we should figure
2662 * out if a smp_mb__after_unlock_lock is really the proper API
2665 smp_mb__after_unlock_lock();
2666 finish_lock_switch(rq
, prev
);
2667 finish_arch_post_lock_switch();
2669 fire_sched_in_preempt_notifiers(current
);
2672 if (unlikely(prev_state
== TASK_DEAD
)) {
2673 if (prev
->sched_class
->task_dead
)
2674 prev
->sched_class
->task_dead(prev
);
2677 * Remove function-return probe instances associated with this
2678 * task and put them back on the free list.
2680 kprobe_flush_task(prev
);
2682 /* Task is done with its stack. */
2683 put_task_stack(prev
);
2685 put_task_struct(prev
);
2688 tick_nohz_task_switch();
2694 /* rq->lock is NOT held, but preemption is disabled */
2695 static void __balance_callback(struct rq
*rq
)
2697 struct callback_head
*head
, *next
;
2698 void (*func
)(struct rq
*rq
);
2699 unsigned long flags
;
2701 raw_spin_lock_irqsave(&rq
->lock
, flags
);
2702 head
= rq
->balance_callback
;
2703 rq
->balance_callback
= NULL
;
2705 func
= (void (*)(struct rq
*))head
->func
;
2712 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
2715 static inline void balance_callback(struct rq
*rq
)
2717 if (unlikely(rq
->balance_callback
))
2718 __balance_callback(rq
);
2723 static inline void balance_callback(struct rq
*rq
)
2730 * schedule_tail - first thing a freshly forked thread must call.
2731 * @prev: the thread we just switched away from.
2733 asmlinkage __visible
void schedule_tail(struct task_struct
*prev
)
2734 __releases(rq
->lock
)
2739 * New tasks start with FORK_PREEMPT_COUNT, see there and
2740 * finish_task_switch() for details.
2742 * finish_task_switch() will drop rq->lock() and lower preempt_count
2743 * and the preempt_enable() will end up enabling preemption (on
2744 * PREEMPT_COUNT kernels).
2747 rq
= finish_task_switch(prev
);
2748 balance_callback(rq
);
2751 if (current
->set_child_tid
)
2752 put_user(task_pid_vnr(current
), current
->set_child_tid
);
2756 * context_switch - switch to the new MM and the new thread's register state.
2758 static __always_inline
struct rq
*
2759 context_switch(struct rq
*rq
, struct task_struct
*prev
,
2760 struct task_struct
*next
, struct rq_flags
*rf
)
2762 struct mm_struct
*mm
, *oldmm
;
2764 prepare_task_switch(rq
, prev
, next
);
2767 oldmm
= prev
->active_mm
;
2769 * For paravirt, this is coupled with an exit in switch_to to
2770 * combine the page table reload and the switch backend into
2773 arch_start_context_switch(prev
);
2776 next
->active_mm
= oldmm
;
2778 enter_lazy_tlb(oldmm
, next
);
2780 switch_mm_irqs_off(oldmm
, mm
, next
);
2783 prev
->active_mm
= NULL
;
2784 rq
->prev_mm
= oldmm
;
2787 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
2790 * Since the runqueue lock will be released by the next
2791 * task (which is an invalid locking op but in the case
2792 * of the scheduler it's an obvious special-case), so we
2793 * do an early lockdep release here:
2795 rq_unpin_lock(rq
, rf
);
2796 spin_release(&rq
->lock
.dep_map
, 1, _THIS_IP_
);
2798 /* Here we just switch the register state and the stack. */
2799 switch_to(prev
, next
, prev
);
2802 return finish_task_switch(prev
);
2806 * nr_running and nr_context_switches:
2808 * externally visible scheduler statistics: current number of runnable
2809 * threads, total number of context switches performed since bootup.
2811 unsigned long nr_running(void)
2813 unsigned long i
, sum
= 0;
2815 for_each_online_cpu(i
)
2816 sum
+= cpu_rq(i
)->nr_running
;
2822 * Check if only the current task is running on the CPU.
2824 * Caution: this function does not check that the caller has disabled
2825 * preemption, thus the result might have a time-of-check-to-time-of-use
2826 * race. The caller is responsible to use it correctly, for example:
2828 * - from a non-preemptable section (of course)
2830 * - from a thread that is bound to a single CPU
2832 * - in a loop with very short iterations (e.g. a polling loop)
2834 bool single_task_running(void)
2836 return raw_rq()->nr_running
== 1;
2838 EXPORT_SYMBOL(single_task_running
);
2840 unsigned long long nr_context_switches(void)
2843 unsigned long long sum
= 0;
2845 for_each_possible_cpu(i
)
2846 sum
+= cpu_rq(i
)->nr_switches
;
2852 * IO-wait accounting, and how its mostly bollocks (on SMP).
2854 * The idea behind IO-wait account is to account the idle time that we could
2855 * have spend running if it were not for IO. That is, if we were to improve the
2856 * storage performance, we'd have a proportional reduction in IO-wait time.
2858 * This all works nicely on UP, where, when a task blocks on IO, we account
2859 * idle time as IO-wait, because if the storage were faster, it could've been
2860 * running and we'd not be idle.
2862 * This has been extended to SMP, by doing the same for each CPU. This however
2865 * Imagine for instance the case where two tasks block on one CPU, only the one
2866 * CPU will have IO-wait accounted, while the other has regular idle. Even
2867 * though, if the storage were faster, both could've ran at the same time,
2868 * utilising both CPUs.
2870 * This means, that when looking globally, the current IO-wait accounting on
2871 * SMP is a lower bound, by reason of under accounting.
2873 * Worse, since the numbers are provided per CPU, they are sometimes
2874 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
2875 * associated with any one particular CPU, it can wake to another CPU than it
2876 * blocked on. This means the per CPU IO-wait number is meaningless.
2878 * Task CPU affinities can make all that even more 'interesting'.
2881 unsigned long nr_iowait(void)
2883 unsigned long i
, sum
= 0;
2885 for_each_possible_cpu(i
)
2886 sum
+= atomic_read(&cpu_rq(i
)->nr_iowait
);
2892 * Consumers of these two interfaces, like for example the cpufreq menu
2893 * governor are using nonsensical data. Boosting frequency for a CPU that has
2894 * IO-wait which might not even end up running the task when it does become
2898 unsigned long nr_iowait_cpu(int cpu
)
2900 struct rq
*this = cpu_rq(cpu
);
2901 return atomic_read(&this->nr_iowait
);
2904 void get_iowait_load(unsigned long *nr_waiters
, unsigned long *load
)
2906 struct rq
*rq
= this_rq();
2907 *nr_waiters
= atomic_read(&rq
->nr_iowait
);
2908 *load
= rq
->load
.weight
;
2914 * sched_exec - execve() is a valuable balancing opportunity, because at
2915 * this point the task has the smallest effective memory and cache footprint.
2917 void sched_exec(void)
2919 struct task_struct
*p
= current
;
2920 unsigned long flags
;
2923 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
2924 dest_cpu
= p
->sched_class
->select_task_rq(p
, task_cpu(p
), SD_BALANCE_EXEC
, 0);
2925 if (dest_cpu
== smp_processor_id())
2928 if (likely(cpu_active(dest_cpu
))) {
2929 struct migration_arg arg
= { p
, dest_cpu
};
2931 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2932 stop_one_cpu(task_cpu(p
), migration_cpu_stop
, &arg
);
2936 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
2941 DEFINE_PER_CPU(struct kernel_stat
, kstat
);
2942 DEFINE_PER_CPU(struct kernel_cpustat
, kernel_cpustat
);
2944 EXPORT_PER_CPU_SYMBOL(kstat
);
2945 EXPORT_PER_CPU_SYMBOL(kernel_cpustat
);
2948 * The function fair_sched_class.update_curr accesses the struct curr
2949 * and its field curr->exec_start; when called from task_sched_runtime(),
2950 * we observe a high rate of cache misses in practice.
2951 * Prefetching this data results in improved performance.
2953 static inline void prefetch_curr_exec_start(struct task_struct
*p
)
2955 #ifdef CONFIG_FAIR_GROUP_SCHED
2956 struct sched_entity
*curr
= (&p
->se
)->cfs_rq
->curr
;
2958 struct sched_entity
*curr
= (&task_rq(p
)->cfs
)->curr
;
2961 prefetch(&curr
->exec_start
);
2965 * Return accounted runtime for the task.
2966 * In case the task is currently running, return the runtime plus current's
2967 * pending runtime that have not been accounted yet.
2969 unsigned long long task_sched_runtime(struct task_struct
*p
)
2975 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
2977 * 64-bit doesn't need locks to atomically read a 64bit value.
2978 * So we have a optimization chance when the task's delta_exec is 0.
2979 * Reading ->on_cpu is racy, but this is ok.
2981 * If we race with it leaving CPU, we'll take a lock. So we're correct.
2982 * If we race with it entering CPU, unaccounted time is 0. This is
2983 * indistinguishable from the read occurring a few cycles earlier.
2984 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
2985 * been accounted, so we're correct here as well.
2987 if (!p
->on_cpu
|| !task_on_rq_queued(p
))
2988 return p
->se
.sum_exec_runtime
;
2991 rq
= task_rq_lock(p
, &rf
);
2993 * Must be ->curr _and_ ->on_rq. If dequeued, we would
2994 * project cycles that may never be accounted to this
2995 * thread, breaking clock_gettime().
2997 if (task_current(rq
, p
) && task_on_rq_queued(p
)) {
2998 prefetch_curr_exec_start(p
);
2999 update_rq_clock(rq
);
3000 p
->sched_class
->update_curr(rq
);
3002 ns
= p
->se
.sum_exec_runtime
;
3003 task_rq_unlock(rq
, p
, &rf
);
3009 * This function gets called by the timer code, with HZ frequency.
3010 * We call it with interrupts disabled.
3012 void scheduler_tick(void)
3014 int cpu
= smp_processor_id();
3015 struct rq
*rq
= cpu_rq(cpu
);
3016 struct task_struct
*curr
= rq
->curr
;
3023 update_rq_clock(rq
);
3024 curr
->sched_class
->task_tick(rq
, curr
, 0);
3025 cpu_load_update_active(rq
);
3026 calc_global_load_tick(rq
);
3030 perf_event_task_tick();
3033 rq
->idle_balance
= idle_cpu(cpu
);
3034 trigger_load_balance(rq
);
3036 rq_last_tick_reset(rq
);
3039 #ifdef CONFIG_NO_HZ_FULL
3041 * scheduler_tick_max_deferment
3043 * Keep at least one tick per second when a single
3044 * active task is running because the scheduler doesn't
3045 * yet completely support full dynticks environment.
3047 * This makes sure that uptime, CFS vruntime, load
3048 * balancing, etc... continue to move forward, even
3049 * with a very low granularity.
3051 * Return: Maximum deferment in nanoseconds.
3053 u64
scheduler_tick_max_deferment(void)
3055 struct rq
*rq
= this_rq();
3056 unsigned long next
, now
= READ_ONCE(jiffies
);
3058 next
= rq
->last_sched_tick
+ HZ
;
3060 if (time_before_eq(next
, now
))
3063 return jiffies_to_nsecs(next
- now
);
3067 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3068 defined(CONFIG_PREEMPT_TRACER))
3070 * If the value passed in is equal to the current preempt count
3071 * then we just disabled preemption. Start timing the latency.
3073 static inline void preempt_latency_start(int val
)
3075 if (preempt_count() == val
) {
3076 unsigned long ip
= get_lock_parent_ip();
3077 #ifdef CONFIG_DEBUG_PREEMPT
3078 current
->preempt_disable_ip
= ip
;
3080 trace_preempt_off(CALLER_ADDR0
, ip
);
3084 void preempt_count_add(int val
)
3086 #ifdef CONFIG_DEBUG_PREEMPT
3090 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3093 __preempt_count_add(val
);
3094 #ifdef CONFIG_DEBUG_PREEMPT
3096 * Spinlock count overflowing soon?
3098 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK
) >=
3101 preempt_latency_start(val
);
3103 EXPORT_SYMBOL(preempt_count_add
);
3104 NOKPROBE_SYMBOL(preempt_count_add
);
3107 * If the value passed in equals to the current preempt count
3108 * then we just enabled preemption. Stop timing the latency.
3110 static inline void preempt_latency_stop(int val
)
3112 if (preempt_count() == val
)
3113 trace_preempt_on(CALLER_ADDR0
, get_lock_parent_ip());
3116 void preempt_count_sub(int val
)
3118 #ifdef CONFIG_DEBUG_PREEMPT
3122 if (DEBUG_LOCKS_WARN_ON(val
> preempt_count()))
3125 * Is the spinlock portion underflowing?
3127 if (DEBUG_LOCKS_WARN_ON((val
< PREEMPT_MASK
) &&
3128 !(preempt_count() & PREEMPT_MASK
)))
3132 preempt_latency_stop(val
);
3133 __preempt_count_sub(val
);
3135 EXPORT_SYMBOL(preempt_count_sub
);
3136 NOKPROBE_SYMBOL(preempt_count_sub
);
3139 static inline void preempt_latency_start(int val
) { }
3140 static inline void preempt_latency_stop(int val
) { }
3143 static inline unsigned long get_preempt_disable_ip(struct task_struct
*p
)
3145 #ifdef CONFIG_DEBUG_PREEMPT
3146 return p
->preempt_disable_ip
;
3153 * Print scheduling while atomic bug:
3155 static noinline
void __schedule_bug(struct task_struct
*prev
)
3157 /* Save this before calling printk(), since that will clobber it */
3158 unsigned long preempt_disable_ip
= get_preempt_disable_ip(current
);
3160 if (oops_in_progress
)
3163 printk(KERN_ERR
"BUG: scheduling while atomic: %s/%d/0x%08x\n",
3164 prev
->comm
, prev
->pid
, preempt_count());
3166 debug_show_held_locks(prev
);
3168 if (irqs_disabled())
3169 print_irqtrace_events(prev
);
3170 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
3171 && in_atomic_preempt_off()) {
3172 pr_err("Preemption disabled at:");
3173 print_ip_sym(preempt_disable_ip
);
3177 panic("scheduling while atomic\n");
3180 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
3184 * Various schedule()-time debugging checks and statistics:
3186 static inline void schedule_debug(struct task_struct
*prev
)
3188 #ifdef CONFIG_SCHED_STACK_END_CHECK
3189 if (task_stack_end_corrupted(prev
))
3190 panic("corrupted stack end detected inside scheduler\n");
3193 if (unlikely(in_atomic_preempt_off())) {
3194 __schedule_bug(prev
);
3195 preempt_count_set(PREEMPT_DISABLED
);
3199 profile_hit(SCHED_PROFILING
, __builtin_return_address(0));
3201 schedstat_inc(this_rq()->sched_count
);
3205 * Pick up the highest-prio task:
3207 static inline struct task_struct
*
3208 pick_next_task(struct rq
*rq
, struct task_struct
*prev
, struct rq_flags
*rf
)
3210 const struct sched_class
*class;
3211 struct task_struct
*p
;
3214 * Optimization: we know that if all tasks are in the fair class we can
3215 * call that function directly, but only if the @prev task wasn't of a
3216 * higher scheduling class, because otherwise those loose the
3217 * opportunity to pull in more work from other CPUs.
3219 if (likely((prev
->sched_class
== &idle_sched_class
||
3220 prev
->sched_class
== &fair_sched_class
) &&
3221 rq
->nr_running
== rq
->cfs
.h_nr_running
)) {
3223 p
= fair_sched_class
.pick_next_task(rq
, prev
, rf
);
3224 if (unlikely(p
== RETRY_TASK
))
3227 /* Assumes fair_sched_class->next == idle_sched_class */
3229 p
= idle_sched_class
.pick_next_task(rq
, prev
, rf
);
3235 for_each_class(class) {
3236 p
= class->pick_next_task(rq
, prev
, rf
);
3238 if (unlikely(p
== RETRY_TASK
))
3244 /* The idle class should always have a runnable task: */
3249 * __schedule() is the main scheduler function.
3251 * The main means of driving the scheduler and thus entering this function are:
3253 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3255 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3256 * paths. For example, see arch/x86/entry_64.S.
3258 * To drive preemption between tasks, the scheduler sets the flag in timer
3259 * interrupt handler scheduler_tick().
3261 * 3. Wakeups don't really cause entry into schedule(). They add a
3262 * task to the run-queue and that's it.
3264 * Now, if the new task added to the run-queue preempts the current
3265 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3266 * called on the nearest possible occasion:
3268 * - If the kernel is preemptible (CONFIG_PREEMPT=y):
3270 * - in syscall or exception context, at the next outmost
3271 * preempt_enable(). (this might be as soon as the wake_up()'s
3274 * - in IRQ context, return from interrupt-handler to
3275 * preemptible context
3277 * - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3280 * - cond_resched() call
3281 * - explicit schedule() call
3282 * - return from syscall or exception to user-space
3283 * - return from interrupt-handler to user-space
3285 * WARNING: must be called with preemption disabled!
3287 static void __sched notrace
__schedule(bool preempt
)
3289 struct task_struct
*prev
, *next
;
3290 unsigned long *switch_count
;
3295 cpu
= smp_processor_id();
3299 schedule_debug(prev
);
3301 if (sched_feat(HRTICK
))
3304 local_irq_disable();
3305 rcu_note_context_switch(preempt
);
3308 * Make sure that signal_pending_state()->signal_pending() below
3309 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3310 * done by the caller to avoid the race with signal_wake_up().
3313 smp_mb__after_spinlock();
3315 /* Promote REQ to ACT */
3316 rq
->clock_update_flags
<<= 1;
3317 update_rq_clock(rq
);
3319 switch_count
= &prev
->nivcsw
;
3320 if (!preempt
&& prev
->state
) {
3321 if (unlikely(signal_pending_state(prev
->state
, prev
))) {
3322 prev
->state
= TASK_RUNNING
;
3324 deactivate_task(rq
, prev
, DEQUEUE_SLEEP
| DEQUEUE_NOCLOCK
);
3327 if (prev
->in_iowait
) {
3328 atomic_inc(&rq
->nr_iowait
);
3329 delayacct_blkio_start();
3333 * If a worker went to sleep, notify and ask workqueue
3334 * whether it wants to wake up a task to maintain
3337 if (prev
->flags
& PF_WQ_WORKER
) {
3338 struct task_struct
*to_wakeup
;
3340 to_wakeup
= wq_worker_sleeping(prev
);
3342 try_to_wake_up_local(to_wakeup
, &rf
);
3345 switch_count
= &prev
->nvcsw
;
3348 next
= pick_next_task(rq
, prev
, &rf
);
3349 clear_tsk_need_resched(prev
);
3350 clear_preempt_need_resched();
3352 if (likely(prev
!= next
)) {
3356 * The membarrier system call requires each architecture
3357 * to have a full memory barrier after updating
3358 * rq->curr, before returning to user-space. For TSO
3359 * (e.g. x86), the architecture must provide its own
3360 * barrier in switch_mm(). For weakly ordered machines
3361 * for which spin_unlock() acts as a full memory
3362 * barrier, finish_lock_switch() in common code takes
3363 * care of this barrier. For weakly ordered machines for
3364 * which spin_unlock() acts as a RELEASE barrier (only
3365 * arm64 and PowerPC), arm64 has a full barrier in
3366 * switch_to(), and PowerPC has
3367 * smp_mb__after_unlock_lock() before
3368 * finish_lock_switch().
3372 trace_sched_switch(preempt
, prev
, next
);
3374 /* Also unlocks the rq: */
3375 rq
= context_switch(rq
, prev
, next
, &rf
);
3377 rq
->clock_update_flags
&= ~(RQCF_ACT_SKIP
|RQCF_REQ_SKIP
);
3378 rq_unlock_irq(rq
, &rf
);
3381 balance_callback(rq
);
3384 void __noreturn
do_task_dead(void)
3387 * The setting of TASK_RUNNING by try_to_wake_up() may be delayed
3388 * when the following two conditions become true.
3389 * - There is race condition of mmap_sem (It is acquired by
3391 * - SMI occurs before setting TASK_RUNINNG.
3392 * (or hypervisor of virtual machine switches to other guest)
3393 * As a result, we may become TASK_RUNNING after becoming TASK_DEAD
3395 * To avoid it, we have to wait for releasing tsk->pi_lock which
3396 * is held by try_to_wake_up()
3398 raw_spin_lock_irq(¤t
->pi_lock
);
3399 raw_spin_unlock_irq(¤t
->pi_lock
);
3401 /* Causes final put_task_struct in finish_task_switch(): */
3402 __set_current_state(TASK_DEAD
);
3404 /* Tell freezer to ignore us: */
3405 current
->flags
|= PF_NOFREEZE
;
3410 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
3415 static inline void sched_submit_work(struct task_struct
*tsk
)
3417 if (!tsk
->state
|| tsk_is_pi_blocked(tsk
))
3420 * If we are going to sleep and we have plugged IO queued,
3421 * make sure to submit it to avoid deadlocks.
3423 if (blk_needs_flush_plug(tsk
))
3424 blk_schedule_flush_plug(tsk
);
3427 asmlinkage __visible
void __sched
schedule(void)
3429 struct task_struct
*tsk
= current
;
3431 sched_submit_work(tsk
);
3435 sched_preempt_enable_no_resched();
3436 } while (need_resched());
3438 EXPORT_SYMBOL(schedule
);
3441 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
3442 * state (have scheduled out non-voluntarily) by making sure that all
3443 * tasks have either left the run queue or have gone into user space.
3444 * As idle tasks do not do either, they must not ever be preempted
3445 * (schedule out non-voluntarily).
3447 * schedule_idle() is similar to schedule_preempt_disable() except that it
3448 * never enables preemption because it does not call sched_submit_work().
3450 void __sched
schedule_idle(void)
3453 * As this skips calling sched_submit_work(), which the idle task does
3454 * regardless because that function is a nop when the task is in a
3455 * TASK_RUNNING state, make sure this isn't used someplace that the
3456 * current task can be in any other state. Note, idle is always in the
3457 * TASK_RUNNING state.
3459 WARN_ON_ONCE(current
->state
);
3462 } while (need_resched());
3465 #ifdef CONFIG_CONTEXT_TRACKING
3466 asmlinkage __visible
void __sched
schedule_user(void)
3469 * If we come here after a random call to set_need_resched(),
3470 * or we have been woken up remotely but the IPI has not yet arrived,
3471 * we haven't yet exited the RCU idle mode. Do it here manually until
3472 * we find a better solution.
3474 * NB: There are buggy callers of this function. Ideally we
3475 * should warn if prev_state != CONTEXT_USER, but that will trigger
3476 * too frequently to make sense yet.
3478 enum ctx_state prev_state
= exception_enter();
3480 exception_exit(prev_state
);
3485 * schedule_preempt_disabled - called with preemption disabled
3487 * Returns with preemption disabled. Note: preempt_count must be 1
3489 void __sched
schedule_preempt_disabled(void)
3491 sched_preempt_enable_no_resched();
3496 static void __sched notrace
preempt_schedule_common(void)
3500 * Because the function tracer can trace preempt_count_sub()
3501 * and it also uses preempt_enable/disable_notrace(), if
3502 * NEED_RESCHED is set, the preempt_enable_notrace() called
3503 * by the function tracer will call this function again and
3504 * cause infinite recursion.
3506 * Preemption must be disabled here before the function
3507 * tracer can trace. Break up preempt_disable() into two
3508 * calls. One to disable preemption without fear of being
3509 * traced. The other to still record the preemption latency,
3510 * which can also be traced by the function tracer.
3512 preempt_disable_notrace();
3513 preempt_latency_start(1);
3515 preempt_latency_stop(1);
3516 preempt_enable_no_resched_notrace();
3519 * Check again in case we missed a preemption opportunity
3520 * between schedule and now.
3522 } while (need_resched());
3525 #ifdef CONFIG_PREEMPT
3527 * this is the entry point to schedule() from in-kernel preemption
3528 * off of preempt_enable. Kernel preemptions off return from interrupt
3529 * occur there and call schedule directly.
3531 asmlinkage __visible
void __sched notrace
preempt_schedule(void)
3534 * If there is a non-zero preempt_count or interrupts are disabled,
3535 * we do not want to preempt the current task. Just return..
3537 if (likely(!preemptible()))
3540 preempt_schedule_common();
3542 NOKPROBE_SYMBOL(preempt_schedule
);
3543 EXPORT_SYMBOL(preempt_schedule
);
3546 * preempt_schedule_notrace - preempt_schedule called by tracing
3548 * The tracing infrastructure uses preempt_enable_notrace to prevent
3549 * recursion and tracing preempt enabling caused by the tracing
3550 * infrastructure itself. But as tracing can happen in areas coming
3551 * from userspace or just about to enter userspace, a preempt enable
3552 * can occur before user_exit() is called. This will cause the scheduler
3553 * to be called when the system is still in usermode.
3555 * To prevent this, the preempt_enable_notrace will use this function
3556 * instead of preempt_schedule() to exit user context if needed before
3557 * calling the scheduler.
3559 asmlinkage __visible
void __sched notrace
preempt_schedule_notrace(void)
3561 enum ctx_state prev_ctx
;
3563 if (likely(!preemptible()))
3568 * Because the function tracer can trace preempt_count_sub()
3569 * and it also uses preempt_enable/disable_notrace(), if
3570 * NEED_RESCHED is set, the preempt_enable_notrace() called
3571 * by the function tracer will call this function again and
3572 * cause infinite recursion.
3574 * Preemption must be disabled here before the function
3575 * tracer can trace. Break up preempt_disable() into two
3576 * calls. One to disable preemption without fear of being
3577 * traced. The other to still record the preemption latency,
3578 * which can also be traced by the function tracer.
3580 preempt_disable_notrace();
3581 preempt_latency_start(1);
3583 * Needs preempt disabled in case user_exit() is traced
3584 * and the tracer calls preempt_enable_notrace() causing
3585 * an infinite recursion.
3587 prev_ctx
= exception_enter();
3589 exception_exit(prev_ctx
);
3591 preempt_latency_stop(1);
3592 preempt_enable_no_resched_notrace();
3593 } while (need_resched());
3595 EXPORT_SYMBOL_GPL(preempt_schedule_notrace
);
3597 #endif /* CONFIG_PREEMPT */
3600 * this is the entry point to schedule() from kernel preemption
3601 * off of irq context.
3602 * Note, that this is called and return with irqs disabled. This will
3603 * protect us against recursive calling from irq.
3605 asmlinkage __visible
void __sched
preempt_schedule_irq(void)
3607 enum ctx_state prev_state
;
3609 /* Catch callers which need to be fixed */
3610 BUG_ON(preempt_count() || !irqs_disabled());
3612 prev_state
= exception_enter();
3618 local_irq_disable();
3619 sched_preempt_enable_no_resched();
3620 } while (need_resched());
3622 exception_exit(prev_state
);
3625 int default_wake_function(wait_queue_entry_t
*curr
, unsigned mode
, int wake_flags
,
3628 return try_to_wake_up(curr
->private, mode
, wake_flags
);
3630 EXPORT_SYMBOL(default_wake_function
);
3632 #ifdef CONFIG_RT_MUTEXES
3634 static inline int __rt_effective_prio(struct task_struct
*pi_task
, int prio
)
3637 prio
= min(prio
, pi_task
->prio
);
3642 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
3644 struct task_struct
*pi_task
= rt_mutex_get_top_task(p
);
3646 return __rt_effective_prio(pi_task
, prio
);
3650 * rt_mutex_setprio - set the current priority of a task
3652 * @pi_task: donor task
3654 * This function changes the 'effective' priority of a task. It does
3655 * not touch ->normal_prio like __setscheduler().
3657 * Used by the rt_mutex code to implement priority inheritance
3658 * logic. Call site only calls if the priority of the task changed.
3660 void rt_mutex_setprio(struct task_struct
*p
, struct task_struct
*pi_task
)
3662 int prio
, oldprio
, queued
, running
, queue_flag
=
3663 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
3664 const struct sched_class
*prev_class
;
3668 /* XXX used to be waiter->prio, not waiter->task->prio */
3669 prio
= __rt_effective_prio(pi_task
, p
->normal_prio
);
3672 * If nothing changed; bail early.
3674 if (p
->pi_top_task
== pi_task
&& prio
== p
->prio
&& !dl_prio(prio
))
3677 rq
= __task_rq_lock(p
, &rf
);
3678 update_rq_clock(rq
);
3680 * Set under pi_lock && rq->lock, such that the value can be used under
3683 * Note that there is loads of tricky to make this pointer cache work
3684 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
3685 * ensure a task is de-boosted (pi_task is set to NULL) before the
3686 * task is allowed to run again (and can exit). This ensures the pointer
3687 * points to a blocked task -- which guaratees the task is present.
3689 p
->pi_top_task
= pi_task
;
3692 * For FIFO/RR we only need to set prio, if that matches we're done.
3694 if (prio
== p
->prio
&& !dl_prio(prio
))
3698 * Idle task boosting is a nono in general. There is one
3699 * exception, when PREEMPT_RT and NOHZ is active:
3701 * The idle task calls get_next_timer_interrupt() and holds
3702 * the timer wheel base->lock on the CPU and another CPU wants
3703 * to access the timer (probably to cancel it). We can safely
3704 * ignore the boosting request, as the idle CPU runs this code
3705 * with interrupts disabled and will complete the lock
3706 * protected section without being interrupted. So there is no
3707 * real need to boost.
3709 if (unlikely(p
== rq
->idle
)) {
3710 WARN_ON(p
!= rq
->curr
);
3711 WARN_ON(p
->pi_blocked_on
);
3715 trace_sched_pi_setprio(p
, pi_task
);
3718 if (oldprio
== prio
)
3719 queue_flag
&= ~DEQUEUE_MOVE
;
3721 prev_class
= p
->sched_class
;
3722 queued
= task_on_rq_queued(p
);
3723 running
= task_current(rq
, p
);
3725 dequeue_task(rq
, p
, queue_flag
);
3727 put_prev_task(rq
, p
);
3730 * Boosting condition are:
3731 * 1. -rt task is running and holds mutex A
3732 * --> -dl task blocks on mutex A
3734 * 2. -dl task is running and holds mutex A
3735 * --> -dl task blocks on mutex A and could preempt the
3738 if (dl_prio(prio
)) {
3739 if (!dl_prio(p
->normal_prio
) ||
3740 (pi_task
&& dl_entity_preempt(&pi_task
->dl
, &p
->dl
))) {
3741 p
->dl
.dl_boosted
= 1;
3742 queue_flag
|= ENQUEUE_REPLENISH
;
3744 p
->dl
.dl_boosted
= 0;
3745 p
->sched_class
= &dl_sched_class
;
3746 } else if (rt_prio(prio
)) {
3747 if (dl_prio(oldprio
))
3748 p
->dl
.dl_boosted
= 0;
3750 queue_flag
|= ENQUEUE_HEAD
;
3751 p
->sched_class
= &rt_sched_class
;
3753 if (dl_prio(oldprio
))
3754 p
->dl
.dl_boosted
= 0;
3755 if (rt_prio(oldprio
))
3757 p
->sched_class
= &fair_sched_class
;
3763 enqueue_task(rq
, p
, queue_flag
);
3765 set_curr_task(rq
, p
);
3767 check_class_changed(rq
, p
, prev_class
, oldprio
);
3769 /* Avoid rq from going away on us: */
3771 __task_rq_unlock(rq
, &rf
);
3773 balance_callback(rq
);
3777 static inline int rt_effective_prio(struct task_struct
*p
, int prio
)
3783 void set_user_nice(struct task_struct
*p
, long nice
)
3785 bool queued
, running
;
3786 int old_prio
, delta
;
3790 if (task_nice(p
) == nice
|| nice
< MIN_NICE
|| nice
> MAX_NICE
)
3793 * We have to be careful, if called from sys_setpriority(),
3794 * the task might be in the middle of scheduling on another CPU.
3796 rq
= task_rq_lock(p
, &rf
);
3797 update_rq_clock(rq
);
3800 * The RT priorities are set via sched_setscheduler(), but we still
3801 * allow the 'normal' nice value to be set - but as expected
3802 * it wont have any effect on scheduling until the task is
3803 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3805 if (task_has_dl_policy(p
) || task_has_rt_policy(p
)) {
3806 p
->static_prio
= NICE_TO_PRIO(nice
);
3809 queued
= task_on_rq_queued(p
);
3810 running
= task_current(rq
, p
);
3812 dequeue_task(rq
, p
, DEQUEUE_SAVE
| DEQUEUE_NOCLOCK
);
3814 put_prev_task(rq
, p
);
3816 p
->static_prio
= NICE_TO_PRIO(nice
);
3817 set_load_weight(p
, true);
3819 p
->prio
= effective_prio(p
);
3820 delta
= p
->prio
- old_prio
;
3823 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
3825 * If the task increased its priority or is running and
3826 * lowered its priority, then reschedule its CPU:
3828 if (delta
< 0 || (delta
> 0 && task_running(rq
, p
)))
3832 set_curr_task(rq
, p
);
3834 task_rq_unlock(rq
, p
, &rf
);
3836 EXPORT_SYMBOL(set_user_nice
);
3839 * can_nice - check if a task can reduce its nice value
3843 int can_nice(const struct task_struct
*p
, const int nice
)
3845 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
3846 int nice_rlim
= nice_to_rlimit(nice
);
3848 return (nice_rlim
<= task_rlimit(p
, RLIMIT_NICE
) ||
3849 capable(CAP_SYS_NICE
));
3852 #ifdef __ARCH_WANT_SYS_NICE
3855 * sys_nice - change the priority of the current process.
3856 * @increment: priority increment
3858 * sys_setpriority is a more generic, but much slower function that
3859 * does similar things.
3861 SYSCALL_DEFINE1(nice
, int, increment
)
3866 * Setpriority might change our priority at the same moment.
3867 * We don't have to worry. Conceptually one call occurs first
3868 * and we have a single winner.
3870 increment
= clamp(increment
, -NICE_WIDTH
, NICE_WIDTH
);
3871 nice
= task_nice(current
) + increment
;
3873 nice
= clamp_val(nice
, MIN_NICE
, MAX_NICE
);
3874 if (increment
< 0 && !can_nice(current
, nice
))
3877 retval
= security_task_setnice(current
, nice
);
3881 set_user_nice(current
, nice
);
3888 * task_prio - return the priority value of a given task.
3889 * @p: the task in question.
3891 * Return: The priority value as seen by users in /proc.
3892 * RT tasks are offset by -200. Normal tasks are centered
3893 * around 0, value goes from -16 to +15.
3895 int task_prio(const struct task_struct
*p
)
3897 return p
->prio
- MAX_RT_PRIO
;
3901 * idle_cpu - is a given CPU idle currently?
3902 * @cpu: the processor in question.
3904 * Return: 1 if the CPU is currently idle. 0 otherwise.
3906 int idle_cpu(int cpu
)
3908 struct rq
*rq
= cpu_rq(cpu
);
3910 if (rq
->curr
!= rq
->idle
)
3917 if (!llist_empty(&rq
->wake_list
))
3925 * idle_task - return the idle task for a given CPU.
3926 * @cpu: the processor in question.
3928 * Return: The idle task for the CPU @cpu.
3930 struct task_struct
*idle_task(int cpu
)
3932 return cpu_rq(cpu
)->idle
;
3936 * find_process_by_pid - find a process with a matching PID value.
3937 * @pid: the pid in question.
3939 * The task of @pid, if found. %NULL otherwise.
3941 static struct task_struct
*find_process_by_pid(pid_t pid
)
3943 return pid
? find_task_by_vpid(pid
) : current
;
3947 * sched_setparam() passes in -1 for its policy, to let the functions
3948 * it calls know not to change it.
3950 #define SETPARAM_POLICY -1
3952 static void __setscheduler_params(struct task_struct
*p
,
3953 const struct sched_attr
*attr
)
3955 int policy
= attr
->sched_policy
;
3957 if (policy
== SETPARAM_POLICY
)
3962 if (dl_policy(policy
))
3963 __setparam_dl(p
, attr
);
3964 else if (fair_policy(policy
))
3965 p
->static_prio
= NICE_TO_PRIO(attr
->sched_nice
);
3968 * __sched_setscheduler() ensures attr->sched_priority == 0 when
3969 * !rt_policy. Always setting this ensures that things like
3970 * getparam()/getattr() don't report silly values for !rt tasks.
3972 p
->rt_priority
= attr
->sched_priority
;
3973 p
->normal_prio
= normal_prio(p
);
3974 set_load_weight(p
, true);
3977 /* Actually do priority change: must hold pi & rq lock. */
3978 static void __setscheduler(struct rq
*rq
, struct task_struct
*p
,
3979 const struct sched_attr
*attr
, bool keep_boost
)
3981 __setscheduler_params(p
, attr
);
3984 * Keep a potential priority boosting if called from
3985 * sched_setscheduler().
3987 p
->prio
= normal_prio(p
);
3989 p
->prio
= rt_effective_prio(p
, p
->prio
);
3991 if (dl_prio(p
->prio
))
3992 p
->sched_class
= &dl_sched_class
;
3993 else if (rt_prio(p
->prio
))
3994 p
->sched_class
= &rt_sched_class
;
3996 p
->sched_class
= &fair_sched_class
;
4000 * Check the target process has a UID that matches the current process's:
4002 static bool check_same_owner(struct task_struct
*p
)
4004 const struct cred
*cred
= current_cred(), *pcred
;
4008 pcred
= __task_cred(p
);
4009 match
= (uid_eq(cred
->euid
, pcred
->euid
) ||
4010 uid_eq(cred
->euid
, pcred
->uid
));
4015 static int __sched_setscheduler(struct task_struct
*p
,
4016 const struct sched_attr
*attr
,
4019 int newprio
= dl_policy(attr
->sched_policy
) ? MAX_DL_PRIO
- 1 :
4020 MAX_RT_PRIO
- 1 - attr
->sched_priority
;
4021 int retval
, oldprio
, oldpolicy
= -1, queued
, running
;
4022 int new_effective_prio
, policy
= attr
->sched_policy
;
4023 const struct sched_class
*prev_class
;
4026 int queue_flags
= DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
4029 /* The pi code expects interrupts enabled */
4030 BUG_ON(pi
&& in_interrupt());
4032 /* Double check policy once rq lock held: */
4034 reset_on_fork
= p
->sched_reset_on_fork
;
4035 policy
= oldpolicy
= p
->policy
;
4037 reset_on_fork
= !!(attr
->sched_flags
& SCHED_FLAG_RESET_ON_FORK
);
4039 if (!valid_policy(policy
))
4043 if (attr
->sched_flags
&
4044 ~(SCHED_FLAG_RESET_ON_FORK
| SCHED_FLAG_RECLAIM
))
4048 * Valid priorities for SCHED_FIFO and SCHED_RR are
4049 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4050 * SCHED_BATCH and SCHED_IDLE is 0.
4052 if ((p
->mm
&& attr
->sched_priority
> MAX_USER_RT_PRIO
-1) ||
4053 (!p
->mm
&& attr
->sched_priority
> MAX_RT_PRIO
-1))
4055 if ((dl_policy(policy
) && !__checkparam_dl(attr
)) ||
4056 (rt_policy(policy
) != (attr
->sched_priority
!= 0)))
4060 * Allow unprivileged RT tasks to decrease priority:
4062 if (user
&& !capable(CAP_SYS_NICE
)) {
4063 if (fair_policy(policy
)) {
4064 if (attr
->sched_nice
< task_nice(p
) &&
4065 !can_nice(p
, attr
->sched_nice
))
4069 if (rt_policy(policy
)) {
4070 unsigned long rlim_rtprio
=
4071 task_rlimit(p
, RLIMIT_RTPRIO
);
4073 /* Can't set/change the rt policy: */
4074 if (policy
!= p
->policy
&& !rlim_rtprio
)
4077 /* Can't increase priority: */
4078 if (attr
->sched_priority
> p
->rt_priority
&&
4079 attr
->sched_priority
> rlim_rtprio
)
4084 * Can't set/change SCHED_DEADLINE policy at all for now
4085 * (safest behavior); in the future we would like to allow
4086 * unprivileged DL tasks to increase their relative deadline
4087 * or reduce their runtime (both ways reducing utilization)
4089 if (dl_policy(policy
))
4093 * Treat SCHED_IDLE as nice 20. Only allow a switch to
4094 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4096 if (idle_policy(p
->policy
) && !idle_policy(policy
)) {
4097 if (!can_nice(p
, task_nice(p
)))
4101 /* Can't change other user's priorities: */
4102 if (!check_same_owner(p
))
4105 /* Normal users shall not reset the sched_reset_on_fork flag: */
4106 if (p
->sched_reset_on_fork
&& !reset_on_fork
)
4111 retval
= security_task_setscheduler(p
);
4117 * Make sure no PI-waiters arrive (or leave) while we are
4118 * changing the priority of the task:
4120 * To be able to change p->policy safely, the appropriate
4121 * runqueue lock must be held.
4123 rq
= task_rq_lock(p
, &rf
);
4124 update_rq_clock(rq
);
4127 * Changing the policy of the stop threads its a very bad idea:
4129 if (p
== rq
->stop
) {
4130 task_rq_unlock(rq
, p
, &rf
);
4135 * If not changing anything there's no need to proceed further,
4136 * but store a possible modification of reset_on_fork.
4138 if (unlikely(policy
== p
->policy
)) {
4139 if (fair_policy(policy
) && attr
->sched_nice
!= task_nice(p
))
4141 if (rt_policy(policy
) && attr
->sched_priority
!= p
->rt_priority
)
4143 if (dl_policy(policy
) && dl_param_changed(p
, attr
))
4146 p
->sched_reset_on_fork
= reset_on_fork
;
4147 task_rq_unlock(rq
, p
, &rf
);
4153 #ifdef CONFIG_RT_GROUP_SCHED
4155 * Do not allow realtime tasks into groups that have no runtime
4158 if (rt_bandwidth_enabled() && rt_policy(policy
) &&
4159 task_group(p
)->rt_bandwidth
.rt_runtime
== 0 &&
4160 !task_group_is_autogroup(task_group(p
))) {
4161 task_rq_unlock(rq
, p
, &rf
);
4166 if (dl_bandwidth_enabled() && dl_policy(policy
)) {
4167 cpumask_t
*span
= rq
->rd
->span
;
4170 * Don't allow tasks with an affinity mask smaller than
4171 * the entire root_domain to become SCHED_DEADLINE. We
4172 * will also fail if there's no bandwidth available.
4174 if (!cpumask_subset(span
, &p
->cpus_allowed
) ||
4175 rq
->rd
->dl_bw
.bw
== 0) {
4176 task_rq_unlock(rq
, p
, &rf
);
4183 /* Re-check policy now with rq lock held: */
4184 if (unlikely(oldpolicy
!= -1 && oldpolicy
!= p
->policy
)) {
4185 policy
= oldpolicy
= -1;
4186 task_rq_unlock(rq
, p
, &rf
);
4191 * If setscheduling to SCHED_DEADLINE (or changing the parameters
4192 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4195 if ((dl_policy(policy
) || dl_task(p
)) && sched_dl_overflow(p
, policy
, attr
)) {
4196 task_rq_unlock(rq
, p
, &rf
);
4200 p
->sched_reset_on_fork
= reset_on_fork
;
4205 * Take priority boosted tasks into account. If the new
4206 * effective priority is unchanged, we just store the new
4207 * normal parameters and do not touch the scheduler class and
4208 * the runqueue. This will be done when the task deboost
4211 new_effective_prio
= rt_effective_prio(p
, newprio
);
4212 if (new_effective_prio
== oldprio
)
4213 queue_flags
&= ~DEQUEUE_MOVE
;
4216 queued
= task_on_rq_queued(p
);
4217 running
= task_current(rq
, p
);
4219 dequeue_task(rq
, p
, queue_flags
);
4221 put_prev_task(rq
, p
);
4223 prev_class
= p
->sched_class
;
4224 __setscheduler(rq
, p
, attr
, pi
);
4228 * We enqueue to tail when the priority of a task is
4229 * increased (user space view).
4231 if (oldprio
< p
->prio
)
4232 queue_flags
|= ENQUEUE_HEAD
;
4234 enqueue_task(rq
, p
, queue_flags
);
4237 set_curr_task(rq
, p
);
4239 check_class_changed(rq
, p
, prev_class
, oldprio
);
4241 /* Avoid rq from going away on us: */
4243 task_rq_unlock(rq
, p
, &rf
);
4246 rt_mutex_adjust_pi(p
);
4248 /* Run balance callbacks after we've adjusted the PI chain: */
4249 balance_callback(rq
);
4255 static int _sched_setscheduler(struct task_struct
*p
, int policy
,
4256 const struct sched_param
*param
, bool check
)
4258 struct sched_attr attr
= {
4259 .sched_policy
= policy
,
4260 .sched_priority
= param
->sched_priority
,
4261 .sched_nice
= PRIO_TO_NICE(p
->static_prio
),
4264 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4265 if ((policy
!= SETPARAM_POLICY
) && (policy
& SCHED_RESET_ON_FORK
)) {
4266 attr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
4267 policy
&= ~SCHED_RESET_ON_FORK
;
4268 attr
.sched_policy
= policy
;
4271 return __sched_setscheduler(p
, &attr
, check
, true);
4274 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4275 * @p: the task in question.
4276 * @policy: new policy.
4277 * @param: structure containing the new RT priority.
4279 * Return: 0 on success. An error code otherwise.
4281 * NOTE that the task may be already dead.
4283 int sched_setscheduler(struct task_struct
*p
, int policy
,
4284 const struct sched_param
*param
)
4286 return _sched_setscheduler(p
, policy
, param
, true);
4288 EXPORT_SYMBOL_GPL(sched_setscheduler
);
4290 int sched_setattr(struct task_struct
*p
, const struct sched_attr
*attr
)
4292 return __sched_setscheduler(p
, attr
, true, true);
4294 EXPORT_SYMBOL_GPL(sched_setattr
);
4297 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4298 * @p: the task in question.
4299 * @policy: new policy.
4300 * @param: structure containing the new RT priority.
4302 * Just like sched_setscheduler, only don't bother checking if the
4303 * current context has permission. For example, this is needed in
4304 * stop_machine(): we create temporary high priority worker threads,
4305 * but our caller might not have that capability.
4307 * Return: 0 on success. An error code otherwise.
4309 int sched_setscheduler_nocheck(struct task_struct
*p
, int policy
,
4310 const struct sched_param
*param
)
4312 return _sched_setscheduler(p
, policy
, param
, false);
4314 EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck
);
4317 do_sched_setscheduler(pid_t pid
, int policy
, struct sched_param __user
*param
)
4319 struct sched_param lparam
;
4320 struct task_struct
*p
;
4323 if (!param
|| pid
< 0)
4325 if (copy_from_user(&lparam
, param
, sizeof(struct sched_param
)))
4330 p
= find_process_by_pid(pid
);
4332 retval
= sched_setscheduler(p
, policy
, &lparam
);
4339 * Mimics kernel/events/core.c perf_copy_attr().
4341 static int sched_copy_attr(struct sched_attr __user
*uattr
, struct sched_attr
*attr
)
4346 if (!access_ok(VERIFY_WRITE
, uattr
, SCHED_ATTR_SIZE_VER0
))
4349 /* Zero the full structure, so that a short copy will be nice: */
4350 memset(attr
, 0, sizeof(*attr
));
4352 ret
= get_user(size
, &uattr
->size
);
4356 /* Bail out on silly large: */
4357 if (size
> PAGE_SIZE
)
4360 /* ABI compatibility quirk: */
4362 size
= SCHED_ATTR_SIZE_VER0
;
4364 if (size
< SCHED_ATTR_SIZE_VER0
)
4368 * If we're handed a bigger struct than we know of,
4369 * ensure all the unknown bits are 0 - i.e. new
4370 * user-space does not rely on any kernel feature
4371 * extensions we dont know about yet.
4373 if (size
> sizeof(*attr
)) {
4374 unsigned char __user
*addr
;
4375 unsigned char __user
*end
;
4378 addr
= (void __user
*)uattr
+ sizeof(*attr
);
4379 end
= (void __user
*)uattr
+ size
;
4381 for (; addr
< end
; addr
++) {
4382 ret
= get_user(val
, addr
);
4388 size
= sizeof(*attr
);
4391 ret
= copy_from_user(attr
, uattr
, size
);
4396 * XXX: Do we want to be lenient like existing syscalls; or do we want
4397 * to be strict and return an error on out-of-bounds values?
4399 attr
->sched_nice
= clamp(attr
->sched_nice
, MIN_NICE
, MAX_NICE
);
4404 put_user(sizeof(*attr
), &uattr
->size
);
4409 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4410 * @pid: the pid in question.
4411 * @policy: new policy.
4412 * @param: structure containing the new RT priority.
4414 * Return: 0 on success. An error code otherwise.
4416 SYSCALL_DEFINE3(sched_setscheduler
, pid_t
, pid
, int, policy
, struct sched_param __user
*, param
)
4421 return do_sched_setscheduler(pid
, policy
, param
);
4425 * sys_sched_setparam - set/change the RT priority of a thread
4426 * @pid: the pid in question.
4427 * @param: structure containing the new RT priority.
4429 * Return: 0 on success. An error code otherwise.
4431 SYSCALL_DEFINE2(sched_setparam
, pid_t
, pid
, struct sched_param __user
*, param
)
4433 return do_sched_setscheduler(pid
, SETPARAM_POLICY
, param
);
4437 * sys_sched_setattr - same as above, but with extended sched_attr
4438 * @pid: the pid in question.
4439 * @uattr: structure containing the extended parameters.
4440 * @flags: for future extension.
4442 SYSCALL_DEFINE3(sched_setattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
4443 unsigned int, flags
)
4445 struct sched_attr attr
;
4446 struct task_struct
*p
;
4449 if (!uattr
|| pid
< 0 || flags
)
4452 retval
= sched_copy_attr(uattr
, &attr
);
4456 if ((int)attr
.sched_policy
< 0)
4461 p
= find_process_by_pid(pid
);
4463 retval
= sched_setattr(p
, &attr
);
4470 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4471 * @pid: the pid in question.
4473 * Return: On success, the policy of the thread. Otherwise, a negative error
4476 SYSCALL_DEFINE1(sched_getscheduler
, pid_t
, pid
)
4478 struct task_struct
*p
;
4486 p
= find_process_by_pid(pid
);
4488 retval
= security_task_getscheduler(p
);
4491 | (p
->sched_reset_on_fork
? SCHED_RESET_ON_FORK
: 0);
4498 * sys_sched_getparam - get the RT priority of a thread
4499 * @pid: the pid in question.
4500 * @param: structure containing the RT priority.
4502 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4505 SYSCALL_DEFINE2(sched_getparam
, pid_t
, pid
, struct sched_param __user
*, param
)
4507 struct sched_param lp
= { .sched_priority
= 0 };
4508 struct task_struct
*p
;
4511 if (!param
|| pid
< 0)
4515 p
= find_process_by_pid(pid
);
4520 retval
= security_task_getscheduler(p
);
4524 if (task_has_rt_policy(p
))
4525 lp
.sched_priority
= p
->rt_priority
;
4529 * This one might sleep, we cannot do it with a spinlock held ...
4531 retval
= copy_to_user(param
, &lp
, sizeof(*param
)) ? -EFAULT
: 0;
4540 static int sched_read_attr(struct sched_attr __user
*uattr
,
4541 struct sched_attr
*attr
,
4546 if (!access_ok(VERIFY_WRITE
, uattr
, usize
))
4550 * If we're handed a smaller struct than we know of,
4551 * ensure all the unknown bits are 0 - i.e. old
4552 * user-space does not get uncomplete information.
4554 if (usize
< sizeof(*attr
)) {
4555 unsigned char *addr
;
4558 addr
= (void *)attr
+ usize
;
4559 end
= (void *)attr
+ sizeof(*attr
);
4561 for (; addr
< end
; addr
++) {
4569 ret
= copy_to_user(uattr
, attr
, attr
->size
);
4577 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4578 * @pid: the pid in question.
4579 * @uattr: structure containing the extended parameters.
4580 * @size: sizeof(attr) for fwd/bwd comp.
4581 * @flags: for future extension.
4583 SYSCALL_DEFINE4(sched_getattr
, pid_t
, pid
, struct sched_attr __user
*, uattr
,
4584 unsigned int, size
, unsigned int, flags
)
4586 struct sched_attr attr
= {
4587 .size
= sizeof(struct sched_attr
),
4589 struct task_struct
*p
;
4592 if (!uattr
|| pid
< 0 || size
> PAGE_SIZE
||
4593 size
< SCHED_ATTR_SIZE_VER0
|| flags
)
4597 p
= find_process_by_pid(pid
);
4602 retval
= security_task_getscheduler(p
);
4606 attr
.sched_policy
= p
->policy
;
4607 if (p
->sched_reset_on_fork
)
4608 attr
.sched_flags
|= SCHED_FLAG_RESET_ON_FORK
;
4609 if (task_has_dl_policy(p
))
4610 __getparam_dl(p
, &attr
);
4611 else if (task_has_rt_policy(p
))
4612 attr
.sched_priority
= p
->rt_priority
;
4614 attr
.sched_nice
= task_nice(p
);
4618 retval
= sched_read_attr(uattr
, &attr
, size
);
4626 long sched_setaffinity(pid_t pid
, const struct cpumask
*in_mask
)
4628 cpumask_var_t cpus_allowed
, new_mask
;
4629 struct task_struct
*p
;
4634 p
= find_process_by_pid(pid
);
4640 /* Prevent p going away */
4644 if (p
->flags
& PF_NO_SETAFFINITY
) {
4648 if (!alloc_cpumask_var(&cpus_allowed
, GFP_KERNEL
)) {
4652 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
)) {
4654 goto out_free_cpus_allowed
;
4657 if (!check_same_owner(p
)) {
4659 if (!ns_capable(__task_cred(p
)->user_ns
, CAP_SYS_NICE
)) {
4661 goto out_free_new_mask
;
4666 retval
= security_task_setscheduler(p
);
4668 goto out_free_new_mask
;
4671 cpuset_cpus_allowed(p
, cpus_allowed
);
4672 cpumask_and(new_mask
, in_mask
, cpus_allowed
);
4675 * Since bandwidth control happens on root_domain basis,
4676 * if admission test is enabled, we only admit -deadline
4677 * tasks allowed to run on all the CPUs in the task's
4681 if (task_has_dl_policy(p
) && dl_bandwidth_enabled()) {
4683 if (!cpumask_subset(task_rq(p
)->rd
->span
, new_mask
)) {
4686 goto out_free_new_mask
;
4692 retval
= __set_cpus_allowed_ptr(p
, new_mask
, true);
4695 cpuset_cpus_allowed(p
, cpus_allowed
);
4696 if (!cpumask_subset(new_mask
, cpus_allowed
)) {
4698 * We must have raced with a concurrent cpuset
4699 * update. Just reset the cpus_allowed to the
4700 * cpuset's cpus_allowed
4702 cpumask_copy(new_mask
, cpus_allowed
);
4707 free_cpumask_var(new_mask
);
4708 out_free_cpus_allowed
:
4709 free_cpumask_var(cpus_allowed
);
4715 static int get_user_cpu_mask(unsigned long __user
*user_mask_ptr
, unsigned len
,
4716 struct cpumask
*new_mask
)
4718 if (len
< cpumask_size())
4719 cpumask_clear(new_mask
);
4720 else if (len
> cpumask_size())
4721 len
= cpumask_size();
4723 return copy_from_user(new_mask
, user_mask_ptr
, len
) ? -EFAULT
: 0;
4727 * sys_sched_setaffinity - set the CPU affinity of a process
4728 * @pid: pid of the process
4729 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4730 * @user_mask_ptr: user-space pointer to the new CPU mask
4732 * Return: 0 on success. An error code otherwise.
4734 SYSCALL_DEFINE3(sched_setaffinity
, pid_t
, pid
, unsigned int, len
,
4735 unsigned long __user
*, user_mask_ptr
)
4737 cpumask_var_t new_mask
;
4740 if (!alloc_cpumask_var(&new_mask
, GFP_KERNEL
))
4743 retval
= get_user_cpu_mask(user_mask_ptr
, len
, new_mask
);
4745 retval
= sched_setaffinity(pid
, new_mask
);
4746 free_cpumask_var(new_mask
);
4750 long sched_getaffinity(pid_t pid
, struct cpumask
*mask
)
4752 struct task_struct
*p
;
4753 unsigned long flags
;
4759 p
= find_process_by_pid(pid
);
4763 retval
= security_task_getscheduler(p
);
4767 raw_spin_lock_irqsave(&p
->pi_lock
, flags
);
4768 cpumask_and(mask
, &p
->cpus_allowed
, cpu_active_mask
);
4769 raw_spin_unlock_irqrestore(&p
->pi_lock
, flags
);
4778 * sys_sched_getaffinity - get the CPU affinity of a process
4779 * @pid: pid of the process
4780 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4781 * @user_mask_ptr: user-space pointer to hold the current CPU mask
4783 * Return: size of CPU mask copied to user_mask_ptr on success. An
4784 * error code otherwise.
4786 SYSCALL_DEFINE3(sched_getaffinity
, pid_t
, pid
, unsigned int, len
,
4787 unsigned long __user
*, user_mask_ptr
)
4792 if ((len
* BITS_PER_BYTE
) < nr_cpu_ids
)
4794 if (len
& (sizeof(unsigned long)-1))
4797 if (!alloc_cpumask_var(&mask
, GFP_KERNEL
))
4800 ret
= sched_getaffinity(pid
, mask
);
4802 size_t retlen
= min_t(size_t, len
, cpumask_size());
4804 if (copy_to_user(user_mask_ptr
, mask
, retlen
))
4809 free_cpumask_var(mask
);
4815 * sys_sched_yield - yield the current processor to other threads.
4817 * This function yields the current CPU to other tasks. If there are no
4818 * other threads running on this CPU then this function will return.
4822 SYSCALL_DEFINE0(sched_yield
)
4827 local_irq_disable();
4831 schedstat_inc(rq
->yld_count
);
4832 current
->sched_class
->yield_task(rq
);
4835 * Since we are going to call schedule() anyway, there's
4836 * no need to preempt or enable interrupts:
4840 sched_preempt_enable_no_resched();
4847 #ifndef CONFIG_PREEMPT
4848 int __sched
_cond_resched(void)
4850 if (should_resched(0)) {
4851 preempt_schedule_common();
4857 EXPORT_SYMBOL(_cond_resched
);
4861 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
4862 * call schedule, and on return reacquire the lock.
4864 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
4865 * operations here to prevent schedule() from being called twice (once via
4866 * spin_unlock(), once by hand).
4868 int __cond_resched_lock(spinlock_t
*lock
)
4870 int resched
= should_resched(PREEMPT_LOCK_OFFSET
);
4873 lockdep_assert_held(lock
);
4875 if (spin_needbreak(lock
) || resched
) {
4878 preempt_schedule_common();
4886 EXPORT_SYMBOL(__cond_resched_lock
);
4888 int __sched
__cond_resched_softirq(void)
4890 BUG_ON(!in_softirq());
4892 if (should_resched(SOFTIRQ_DISABLE_OFFSET
)) {
4894 preempt_schedule_common();
4900 EXPORT_SYMBOL(__cond_resched_softirq
);
4903 * yield - yield the current processor to other threads.
4905 * Do not ever use this function, there's a 99% chance you're doing it wrong.
4907 * The scheduler is at all times free to pick the calling task as the most
4908 * eligible task to run, if removing the yield() call from your code breaks
4909 * it, its already broken.
4911 * Typical broken usage is:
4916 * where one assumes that yield() will let 'the other' process run that will
4917 * make event true. If the current task is a SCHED_FIFO task that will never
4918 * happen. Never use yield() as a progress guarantee!!
4920 * If you want to use yield() to wait for something, use wait_event().
4921 * If you want to use yield() to be 'nice' for others, use cond_resched().
4922 * If you still want to use yield(), do not!
4924 void __sched
yield(void)
4926 set_current_state(TASK_RUNNING
);
4929 EXPORT_SYMBOL(yield
);
4932 * yield_to - yield the current processor to another thread in
4933 * your thread group, or accelerate that thread toward the
4934 * processor it's on.
4936 * @preempt: whether task preemption is allowed or not
4938 * It's the caller's job to ensure that the target task struct
4939 * can't go away on us before we can do any checks.
4942 * true (>0) if we indeed boosted the target task.
4943 * false (0) if we failed to boost the target.
4944 * -ESRCH if there's no task to yield to.
4946 int __sched
yield_to(struct task_struct
*p
, bool preempt
)
4948 struct task_struct
*curr
= current
;
4949 struct rq
*rq
, *p_rq
;
4950 unsigned long flags
;
4953 local_irq_save(flags
);
4959 * If we're the only runnable task on the rq and target rq also
4960 * has only one task, there's absolutely no point in yielding.
4962 if (rq
->nr_running
== 1 && p_rq
->nr_running
== 1) {
4967 double_rq_lock(rq
, p_rq
);
4968 if (task_rq(p
) != p_rq
) {
4969 double_rq_unlock(rq
, p_rq
);
4973 if (!curr
->sched_class
->yield_to_task
)
4976 if (curr
->sched_class
!= p
->sched_class
)
4979 if (task_running(p_rq
, p
) || p
->state
)
4982 yielded
= curr
->sched_class
->yield_to_task(rq
, p
, preempt
);
4984 schedstat_inc(rq
->yld_count
);
4986 * Make p's CPU reschedule; pick_next_entity takes care of
4989 if (preempt
&& rq
!= p_rq
)
4994 double_rq_unlock(rq
, p_rq
);
4996 local_irq_restore(flags
);
5003 EXPORT_SYMBOL_GPL(yield_to
);
5005 int io_schedule_prepare(void)
5007 int old_iowait
= current
->in_iowait
;
5009 current
->in_iowait
= 1;
5010 blk_schedule_flush_plug(current
);
5015 void io_schedule_finish(int token
)
5017 current
->in_iowait
= token
;
5021 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5022 * that process accounting knows that this is a task in IO wait state.
5024 long __sched
io_schedule_timeout(long timeout
)
5029 token
= io_schedule_prepare();
5030 ret
= schedule_timeout(timeout
);
5031 io_schedule_finish(token
);
5035 EXPORT_SYMBOL(io_schedule_timeout
);
5037 void io_schedule(void)
5041 token
= io_schedule_prepare();
5043 io_schedule_finish(token
);
5045 EXPORT_SYMBOL(io_schedule
);
5048 * sys_sched_get_priority_max - return maximum RT priority.
5049 * @policy: scheduling class.
5051 * Return: On success, this syscall returns the maximum
5052 * rt_priority that can be used by a given scheduling class.
5053 * On failure, a negative error code is returned.
5055 SYSCALL_DEFINE1(sched_get_priority_max
, int, policy
)
5062 ret
= MAX_USER_RT_PRIO
-1;
5064 case SCHED_DEADLINE
:
5075 * sys_sched_get_priority_min - return minimum RT priority.
5076 * @policy: scheduling class.
5078 * Return: On success, this syscall returns the minimum
5079 * rt_priority that can be used by a given scheduling class.
5080 * On failure, a negative error code is returned.
5082 SYSCALL_DEFINE1(sched_get_priority_min
, int, policy
)
5091 case SCHED_DEADLINE
:
5100 static int sched_rr_get_interval(pid_t pid
, struct timespec64
*t
)
5102 struct task_struct
*p
;
5103 unsigned int time_slice
;
5113 p
= find_process_by_pid(pid
);
5117 retval
= security_task_getscheduler(p
);
5121 rq
= task_rq_lock(p
, &rf
);
5123 if (p
->sched_class
->get_rr_interval
)
5124 time_slice
= p
->sched_class
->get_rr_interval(rq
, p
);
5125 task_rq_unlock(rq
, p
, &rf
);
5128 jiffies_to_timespec64(time_slice
, t
);
5137 * sys_sched_rr_get_interval - return the default timeslice of a process.
5138 * @pid: pid of the process.
5139 * @interval: userspace pointer to the timeslice value.
5141 * this syscall writes the default timeslice value of a given process
5142 * into the user-space timespec buffer. A value of '0' means infinity.
5144 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5147 SYSCALL_DEFINE2(sched_rr_get_interval
, pid_t
, pid
,
5148 struct timespec __user
*, interval
)
5150 struct timespec64 t
;
5151 int retval
= sched_rr_get_interval(pid
, &t
);
5154 retval
= put_timespec64(&t
, interval
);
5159 #ifdef CONFIG_COMPAT
5160 COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval
,
5162 struct compat_timespec __user
*, interval
)
5164 struct timespec64 t
;
5165 int retval
= sched_rr_get_interval(pid
, &t
);
5168 retval
= compat_put_timespec64(&t
, interval
);
5173 void sched_show_task(struct task_struct
*p
)
5175 unsigned long free
= 0;
5178 if (!try_get_task_stack(p
))
5181 printk(KERN_INFO
"%-15.15s %c", p
->comm
, task_state_to_char(p
));
5183 if (p
->state
== TASK_RUNNING
)
5184 printk(KERN_CONT
" running task ");
5185 #ifdef CONFIG_DEBUG_STACK_USAGE
5186 free
= stack_not_used(p
);
5191 ppid
= task_pid_nr(rcu_dereference(p
->real_parent
));
5193 printk(KERN_CONT
"%5lu %5d %6d 0x%08lx\n", free
,
5194 task_pid_nr(p
), ppid
,
5195 (unsigned long)task_thread_info(p
)->flags
);
5197 print_worker_info(KERN_INFO
, p
);
5198 show_stack(p
, NULL
);
5201 EXPORT_SYMBOL_GPL(sched_show_task
);
5204 state_filter_match(unsigned long state_filter
, struct task_struct
*p
)
5206 /* no filter, everything matches */
5210 /* filter, but doesn't match */
5211 if (!(p
->state
& state_filter
))
5215 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
5218 if (state_filter
== TASK_UNINTERRUPTIBLE
&& p
->state
== TASK_IDLE
)
5225 void show_state_filter(unsigned long state_filter
)
5227 struct task_struct
*g
, *p
;
5229 #if BITS_PER_LONG == 32
5231 " task PC stack pid father\n");
5234 " task PC stack pid father\n");
5237 for_each_process_thread(g
, p
) {
5239 * reset the NMI-timeout, listing all files on a slow
5240 * console might take a lot of time:
5241 * Also, reset softlockup watchdogs on all CPUs, because
5242 * another CPU might be blocked waiting for us to process
5245 touch_nmi_watchdog();
5246 touch_all_softlockup_watchdogs();
5247 if (state_filter_match(state_filter
, p
))
5251 #ifdef CONFIG_SCHED_DEBUG
5253 sysrq_sched_debug_show();
5257 * Only show locks if all tasks are dumped:
5260 debug_show_all_locks();
5264 * init_idle - set up an idle thread for a given CPU
5265 * @idle: task in question
5266 * @cpu: CPU the idle task belongs to
5268 * NOTE: this function does not set the idle thread's NEED_RESCHED
5269 * flag, to make booting more robust.
5271 void init_idle(struct task_struct
*idle
, int cpu
)
5273 struct rq
*rq
= cpu_rq(cpu
);
5274 unsigned long flags
;
5276 raw_spin_lock_irqsave(&idle
->pi_lock
, flags
);
5277 raw_spin_lock(&rq
->lock
);
5279 __sched_fork(0, idle
);
5280 idle
->state
= TASK_RUNNING
;
5281 idle
->se
.exec_start
= sched_clock();
5282 idle
->flags
|= PF_IDLE
;
5284 kasan_unpoison_task_stack(idle
);
5288 * Its possible that init_idle() gets called multiple times on a task,
5289 * in that case do_set_cpus_allowed() will not do the right thing.
5291 * And since this is boot we can forgo the serialization.
5293 set_cpus_allowed_common(idle
, cpumask_of(cpu
));
5296 * We're having a chicken and egg problem, even though we are
5297 * holding rq->lock, the CPU isn't yet set to this CPU so the
5298 * lockdep check in task_group() will fail.
5300 * Similar case to sched_fork(). / Alternatively we could
5301 * use task_rq_lock() here and obtain the other rq->lock.
5306 __set_task_cpu(idle
, cpu
);
5309 rq
->curr
= rq
->idle
= idle
;
5310 idle
->on_rq
= TASK_ON_RQ_QUEUED
;
5314 raw_spin_unlock(&rq
->lock
);
5315 raw_spin_unlock_irqrestore(&idle
->pi_lock
, flags
);
5317 /* Set the preempt count _outside_ the spinlocks! */
5318 init_idle_preempt_count(idle
, cpu
);
5321 * The idle tasks have their own, simple scheduling class:
5323 idle
->sched_class
= &idle_sched_class
;
5324 ftrace_graph_init_idle_task(idle
, cpu
);
5325 vtime_init_idle(idle
, cpu
);
5327 sprintf(idle
->comm
, "%s/%d", INIT_TASK_COMM
, cpu
);
5333 int cpuset_cpumask_can_shrink(const struct cpumask
*cur
,
5334 const struct cpumask
*trial
)
5338 if (!cpumask_weight(cur
))
5341 ret
= dl_cpuset_cpumask_can_shrink(cur
, trial
);
5346 int task_can_attach(struct task_struct
*p
,
5347 const struct cpumask
*cs_cpus_allowed
)
5352 * Kthreads which disallow setaffinity shouldn't be moved
5353 * to a new cpuset; we don't want to change their CPU
5354 * affinity and isolating such threads by their set of
5355 * allowed nodes is unnecessary. Thus, cpusets are not
5356 * applicable for such threads. This prevents checking for
5357 * success of set_cpus_allowed_ptr() on all attached tasks
5358 * before cpus_allowed may be changed.
5360 if (p
->flags
& PF_NO_SETAFFINITY
) {
5365 if (dl_task(p
) && !cpumask_intersects(task_rq(p
)->rd
->span
,
5367 ret
= dl_task_can_attach(p
, cs_cpus_allowed
);
5373 bool sched_smp_initialized __read_mostly
;
5375 #ifdef CONFIG_NUMA_BALANCING
5376 /* Migrate current task p to target_cpu */
5377 int migrate_task_to(struct task_struct
*p
, int target_cpu
)
5379 struct migration_arg arg
= { p
, target_cpu
};
5380 int curr_cpu
= task_cpu(p
);
5382 if (curr_cpu
== target_cpu
)
5385 if (!cpumask_test_cpu(target_cpu
, &p
->cpus_allowed
))
5388 /* TODO: This is not properly updating schedstats */
5390 trace_sched_move_numa(p
, curr_cpu
, target_cpu
);
5391 return stop_one_cpu(curr_cpu
, migration_cpu_stop
, &arg
);
5395 * Requeue a task on a given node and accurately track the number of NUMA
5396 * tasks on the runqueues
5398 void sched_setnuma(struct task_struct
*p
, int nid
)
5400 bool queued
, running
;
5404 rq
= task_rq_lock(p
, &rf
);
5405 queued
= task_on_rq_queued(p
);
5406 running
= task_current(rq
, p
);
5409 dequeue_task(rq
, p
, DEQUEUE_SAVE
);
5411 put_prev_task(rq
, p
);
5413 p
->numa_preferred_nid
= nid
;
5416 enqueue_task(rq
, p
, ENQUEUE_RESTORE
| ENQUEUE_NOCLOCK
);
5418 set_curr_task(rq
, p
);
5419 task_rq_unlock(rq
, p
, &rf
);
5421 #endif /* CONFIG_NUMA_BALANCING */
5423 #ifdef CONFIG_HOTPLUG_CPU
5425 * Ensure that the idle task is using init_mm right before its CPU goes
5428 void idle_task_exit(void)
5430 struct mm_struct
*mm
= current
->active_mm
;
5432 BUG_ON(cpu_online(smp_processor_id()));
5434 if (mm
!= &init_mm
) {
5435 switch_mm(mm
, &init_mm
, current
);
5436 finish_arch_post_lock_switch();
5442 * Since this CPU is going 'away' for a while, fold any nr_active delta
5443 * we might have. Assumes we're called after migrate_tasks() so that the
5444 * nr_active count is stable. We need to take the teardown thread which
5445 * is calling this into account, so we hand in adjust = 1 to the load
5448 * Also see the comment "Global load-average calculations".
5450 static void calc_load_migrate(struct rq
*rq
)
5452 long delta
= calc_load_fold_active(rq
, 1);
5454 atomic_long_add(delta
, &calc_load_tasks
);
5457 static void put_prev_task_fake(struct rq
*rq
, struct task_struct
*prev
)
5461 static const struct sched_class fake_sched_class
= {
5462 .put_prev_task
= put_prev_task_fake
,
5465 static struct task_struct fake_task
= {
5467 * Avoid pull_{rt,dl}_task()
5469 .prio
= MAX_PRIO
+ 1,
5470 .sched_class
= &fake_sched_class
,
5474 * Migrate all tasks from the rq, sleeping tasks will be migrated by
5475 * try_to_wake_up()->select_task_rq().
5477 * Called with rq->lock held even though we'er in stop_machine() and
5478 * there's no concurrency possible, we hold the required locks anyway
5479 * because of lock validation efforts.
5481 static void migrate_tasks(struct rq
*dead_rq
, struct rq_flags
*rf
)
5483 struct rq
*rq
= dead_rq
;
5484 struct task_struct
*next
, *stop
= rq
->stop
;
5485 struct rq_flags orf
= *rf
;
5489 * Fudge the rq selection such that the below task selection loop
5490 * doesn't get stuck on the currently eligible stop task.
5492 * We're currently inside stop_machine() and the rq is either stuck
5493 * in the stop_machine_cpu_stop() loop, or we're executing this code,
5494 * either way we should never end up calling schedule() until we're
5500 * put_prev_task() and pick_next_task() sched
5501 * class method both need to have an up-to-date
5502 * value of rq->clock[_task]
5504 update_rq_clock(rq
);
5508 * There's this thread running, bail when that's the only
5511 if (rq
->nr_running
== 1)
5515 * pick_next_task() assumes pinned rq->lock:
5517 next
= pick_next_task(rq
, &fake_task
, rf
);
5519 put_prev_task(rq
, next
);
5522 * Rules for changing task_struct::cpus_allowed are holding
5523 * both pi_lock and rq->lock, such that holding either
5524 * stabilizes the mask.
5526 * Drop rq->lock is not quite as disastrous as it usually is
5527 * because !cpu_active at this point, which means load-balance
5528 * will not interfere. Also, stop-machine.
5531 raw_spin_lock(&next
->pi_lock
);
5535 * Since we're inside stop-machine, _nothing_ should have
5536 * changed the task, WARN if weird stuff happened, because in
5537 * that case the above rq->lock drop is a fail too.
5539 if (WARN_ON(task_rq(next
) != rq
|| !task_on_rq_queued(next
))) {
5540 raw_spin_unlock(&next
->pi_lock
);
5544 /* Find suitable destination for @next, with force if needed. */
5545 dest_cpu
= select_fallback_rq(dead_rq
->cpu
, next
);
5546 rq
= __migrate_task(rq
, rf
, next
, dest_cpu
);
5547 if (rq
!= dead_rq
) {
5553 raw_spin_unlock(&next
->pi_lock
);
5558 #endif /* CONFIG_HOTPLUG_CPU */
5560 void set_rq_online(struct rq
*rq
)
5563 const struct sched_class
*class;
5565 cpumask_set_cpu(rq
->cpu
, rq
->rd
->online
);
5568 for_each_class(class) {
5569 if (class->rq_online
)
5570 class->rq_online(rq
);
5575 void set_rq_offline(struct rq
*rq
)
5578 const struct sched_class
*class;
5580 for_each_class(class) {
5581 if (class->rq_offline
)
5582 class->rq_offline(rq
);
5585 cpumask_clear_cpu(rq
->cpu
, rq
->rd
->online
);
5590 static void set_cpu_rq_start_time(unsigned int cpu
)
5592 struct rq
*rq
= cpu_rq(cpu
);
5594 rq
->age_stamp
= sched_clock_cpu(cpu
);
5598 * used to mark begin/end of suspend/resume:
5600 static int num_cpus_frozen
;
5603 * Update cpusets according to cpu_active mask. If cpusets are
5604 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
5605 * around partition_sched_domains().
5607 * If we come here as part of a suspend/resume, don't touch cpusets because we
5608 * want to restore it back to its original state upon resume anyway.
5610 static void cpuset_cpu_active(void)
5612 if (cpuhp_tasks_frozen
) {
5614 * num_cpus_frozen tracks how many CPUs are involved in suspend
5615 * resume sequence. As long as this is not the last online
5616 * operation in the resume sequence, just build a single sched
5617 * domain, ignoring cpusets.
5619 partition_sched_domains(1, NULL
, NULL
);
5620 if (--num_cpus_frozen
)
5623 * This is the last CPU online operation. So fall through and
5624 * restore the original sched domains by considering the
5625 * cpuset configurations.
5627 cpuset_force_rebuild();
5629 cpuset_update_active_cpus();
5632 static int cpuset_cpu_inactive(unsigned int cpu
)
5634 if (!cpuhp_tasks_frozen
) {
5635 if (dl_cpu_busy(cpu
))
5637 cpuset_update_active_cpus();
5640 partition_sched_domains(1, NULL
, NULL
);
5645 int sched_cpu_activate(unsigned int cpu
)
5647 struct rq
*rq
= cpu_rq(cpu
);
5650 set_cpu_active(cpu
, true);
5652 if (sched_smp_initialized
) {
5653 sched_domains_numa_masks_set(cpu
);
5654 cpuset_cpu_active();
5658 * Put the rq online, if not already. This happens:
5660 * 1) In the early boot process, because we build the real domains
5661 * after all CPUs have been brought up.
5663 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
5666 rq_lock_irqsave(rq
, &rf
);
5668 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
5671 rq_unlock_irqrestore(rq
, &rf
);
5673 update_max_interval();
5678 int sched_cpu_deactivate(unsigned int cpu
)
5682 set_cpu_active(cpu
, false);
5684 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
5685 * users of this state to go away such that all new such users will
5688 * Do sync before park smpboot threads to take care the rcu boost case.
5690 synchronize_rcu_mult(call_rcu
, call_rcu_sched
);
5692 if (!sched_smp_initialized
)
5695 ret
= cpuset_cpu_inactive(cpu
);
5697 set_cpu_active(cpu
, true);
5700 sched_domains_numa_masks_clear(cpu
);
5704 static void sched_rq_cpu_starting(unsigned int cpu
)
5706 struct rq
*rq
= cpu_rq(cpu
);
5708 rq
->calc_load_update
= calc_load_update
;
5709 update_max_interval();
5712 int sched_cpu_starting(unsigned int cpu
)
5714 set_cpu_rq_start_time(cpu
);
5715 sched_rq_cpu_starting(cpu
);
5719 #ifdef CONFIG_HOTPLUG_CPU
5720 int sched_cpu_dying(unsigned int cpu
)
5722 struct rq
*rq
= cpu_rq(cpu
);
5725 /* Handle pending wakeups and then migrate everything off */
5726 sched_ttwu_pending();
5728 rq_lock_irqsave(rq
, &rf
);
5730 BUG_ON(!cpumask_test_cpu(cpu
, rq
->rd
->span
));
5733 migrate_tasks(rq
, &rf
);
5734 BUG_ON(rq
->nr_running
!= 1);
5735 rq_unlock_irqrestore(rq
, &rf
);
5737 calc_load_migrate(rq
);
5738 update_max_interval();
5739 nohz_balance_exit_idle(cpu
);
5745 #ifdef CONFIG_SCHED_SMT
5746 DEFINE_STATIC_KEY_FALSE(sched_smt_present
);
5748 static void sched_init_smt(void)
5751 * We've enumerated all CPUs and will assume that if any CPU
5752 * has SMT siblings, CPU0 will too.
5754 if (cpumask_weight(cpu_smt_mask(0)) > 1)
5755 static_branch_enable(&sched_smt_present
);
5758 static inline void sched_init_smt(void) { }
5761 void __init
sched_init_smp(void)
5766 * There's no userspace yet to cause hotplug operations; hence all the
5767 * CPU masks are stable and all blatant races in the below code cannot
5770 mutex_lock(&sched_domains_mutex
);
5771 sched_init_domains(cpu_active_mask
);
5772 mutex_unlock(&sched_domains_mutex
);
5774 /* Move init over to a non-isolated CPU */
5775 if (set_cpus_allowed_ptr(current
, housekeeping_cpumask(HK_FLAG_DOMAIN
)) < 0)
5777 sched_init_granularity();
5779 init_sched_rt_class();
5780 init_sched_dl_class();
5784 sched_smp_initialized
= true;
5787 static int __init
migration_init(void)
5789 sched_rq_cpu_starting(smp_processor_id());
5792 early_initcall(migration_init
);
5795 void __init
sched_init_smp(void)
5797 sched_init_granularity();
5799 #endif /* CONFIG_SMP */
5801 int in_sched_functions(unsigned long addr
)
5803 return in_lock_functions(addr
) ||
5804 (addr
>= (unsigned long)__sched_text_start
5805 && addr
< (unsigned long)__sched_text_end
);
5808 #ifdef CONFIG_CGROUP_SCHED
5810 * Default task group.
5811 * Every task in system belongs to this group at bootup.
5813 struct task_group root_task_group
;
5814 LIST_HEAD(task_groups
);
5816 /* Cacheline aligned slab cache for task_group */
5817 static struct kmem_cache
*task_group_cache __read_mostly
;
5820 DECLARE_PER_CPU(cpumask_var_t
, load_balance_mask
);
5821 DECLARE_PER_CPU(cpumask_var_t
, select_idle_mask
);
5823 void __init
sched_init(void)
5826 unsigned long alloc_size
= 0, ptr
;
5831 #ifdef CONFIG_FAIR_GROUP_SCHED
5832 alloc_size
+= 2 * nr_cpu_ids
* sizeof(void **);
5834 #ifdef CONFIG_RT_GROUP_SCHED
5835 alloc_size
+= 2 * nr_cpu_ids
* sizeof(void **);
5838 ptr
= (unsigned long)kzalloc(alloc_size
, GFP_NOWAIT
);
5840 #ifdef CONFIG_FAIR_GROUP_SCHED
5841 root_task_group
.se
= (struct sched_entity
**)ptr
;
5842 ptr
+= nr_cpu_ids
* sizeof(void **);
5844 root_task_group
.cfs_rq
= (struct cfs_rq
**)ptr
;
5845 ptr
+= nr_cpu_ids
* sizeof(void **);
5847 #endif /* CONFIG_FAIR_GROUP_SCHED */
5848 #ifdef CONFIG_RT_GROUP_SCHED
5849 root_task_group
.rt_se
= (struct sched_rt_entity
**)ptr
;
5850 ptr
+= nr_cpu_ids
* sizeof(void **);
5852 root_task_group
.rt_rq
= (struct rt_rq
**)ptr
;
5853 ptr
+= nr_cpu_ids
* sizeof(void **);
5855 #endif /* CONFIG_RT_GROUP_SCHED */
5857 #ifdef CONFIG_CPUMASK_OFFSTACK
5858 for_each_possible_cpu(i
) {
5859 per_cpu(load_balance_mask
, i
) = (cpumask_var_t
)kzalloc_node(
5860 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
5861 per_cpu(select_idle_mask
, i
) = (cpumask_var_t
)kzalloc_node(
5862 cpumask_size(), GFP_KERNEL
, cpu_to_node(i
));
5864 #endif /* CONFIG_CPUMASK_OFFSTACK */
5866 init_rt_bandwidth(&def_rt_bandwidth
, global_rt_period(), global_rt_runtime());
5867 init_dl_bandwidth(&def_dl_bandwidth
, global_rt_period(), global_rt_runtime());
5870 init_defrootdomain();
5873 #ifdef CONFIG_RT_GROUP_SCHED
5874 init_rt_bandwidth(&root_task_group
.rt_bandwidth
,
5875 global_rt_period(), global_rt_runtime());
5876 #endif /* CONFIG_RT_GROUP_SCHED */
5878 #ifdef CONFIG_CGROUP_SCHED
5879 task_group_cache
= KMEM_CACHE(task_group
, 0);
5881 list_add(&root_task_group
.list
, &task_groups
);
5882 INIT_LIST_HEAD(&root_task_group
.children
);
5883 INIT_LIST_HEAD(&root_task_group
.siblings
);
5884 autogroup_init(&init_task
);
5885 #endif /* CONFIG_CGROUP_SCHED */
5887 for_each_possible_cpu(i
) {
5891 raw_spin_lock_init(&rq
->lock
);
5893 rq
->calc_load_active
= 0;
5894 rq
->calc_load_update
= jiffies
+ LOAD_FREQ
;
5895 init_cfs_rq(&rq
->cfs
);
5896 init_rt_rq(&rq
->rt
);
5897 init_dl_rq(&rq
->dl
);
5898 #ifdef CONFIG_FAIR_GROUP_SCHED
5899 root_task_group
.shares
= ROOT_TASK_GROUP_LOAD
;
5900 INIT_LIST_HEAD(&rq
->leaf_cfs_rq_list
);
5901 rq
->tmp_alone_branch
= &rq
->leaf_cfs_rq_list
;
5903 * How much CPU bandwidth does root_task_group get?
5905 * In case of task-groups formed thr' the cgroup filesystem, it
5906 * gets 100% of the CPU resources in the system. This overall
5907 * system CPU resource is divided among the tasks of
5908 * root_task_group and its child task-groups in a fair manner,
5909 * based on each entity's (task or task-group's) weight
5910 * (se->load.weight).
5912 * In other words, if root_task_group has 10 tasks of weight
5913 * 1024) and two child groups A0 and A1 (of weight 1024 each),
5914 * then A0's share of the CPU resource is:
5916 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
5918 * We achieve this by letting root_task_group's tasks sit
5919 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
5921 init_cfs_bandwidth(&root_task_group
.cfs_bandwidth
);
5922 init_tg_cfs_entry(&root_task_group
, &rq
->cfs
, NULL
, i
, NULL
);
5923 #endif /* CONFIG_FAIR_GROUP_SCHED */
5925 rq
->rt
.rt_runtime
= def_rt_bandwidth
.rt_runtime
;
5926 #ifdef CONFIG_RT_GROUP_SCHED
5927 init_tg_rt_entry(&root_task_group
, &rq
->rt
, NULL
, i
, NULL
);
5930 for (j
= 0; j
< CPU_LOAD_IDX_MAX
; j
++)
5931 rq
->cpu_load
[j
] = 0;
5936 rq
->cpu_capacity
= rq
->cpu_capacity_orig
= SCHED_CAPACITY_SCALE
;
5937 rq
->balance_callback
= NULL
;
5938 rq
->active_balance
= 0;
5939 rq
->next_balance
= jiffies
;
5944 rq
->avg_idle
= 2*sysctl_sched_migration_cost
;
5945 rq
->max_idle_balance_cost
= sysctl_sched_migration_cost
;
5947 INIT_LIST_HEAD(&rq
->cfs_tasks
);
5949 rq_attach_root(rq
, &def_root_domain
);
5950 #ifdef CONFIG_NO_HZ_COMMON
5951 rq
->last_load_update_tick
= jiffies
;
5954 #ifdef CONFIG_NO_HZ_FULL
5955 rq
->last_sched_tick
= 0;
5957 #endif /* CONFIG_SMP */
5959 atomic_set(&rq
->nr_iowait
, 0);
5962 set_load_weight(&init_task
, false);
5965 * The boot idle thread does lazy MMU switching as well:
5968 enter_lazy_tlb(&init_mm
, current
);
5971 * Make us the idle thread. Technically, schedule() should not be
5972 * called from this thread, however somewhere below it might be,
5973 * but because we are the idle thread, we just pick up running again
5974 * when this runqueue becomes "idle".
5976 init_idle(current
, smp_processor_id());
5978 calc_load_update
= jiffies
+ LOAD_FREQ
;
5981 idle_thread_set_boot_cpu();
5982 set_cpu_rq_start_time(smp_processor_id());
5984 init_sched_fair_class();
5988 scheduler_running
= 1;
5991 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5992 static inline int preempt_count_equals(int preempt_offset
)
5994 int nested
= preempt_count() + rcu_preempt_depth();
5996 return (nested
== preempt_offset
);
5999 void __might_sleep(const char *file
, int line
, int preempt_offset
)
6002 * Blocking primitives will set (and therefore destroy) current->state,
6003 * since we will exit with TASK_RUNNING make sure we enter with it,
6004 * otherwise we will destroy state.
6006 WARN_ONCE(current
->state
!= TASK_RUNNING
&& current
->task_state_change
,
6007 "do not call blocking ops when !TASK_RUNNING; "
6008 "state=%lx set at [<%p>] %pS\n",
6010 (void *)current
->task_state_change
,
6011 (void *)current
->task_state_change
);
6013 ___might_sleep(file
, line
, preempt_offset
);
6015 EXPORT_SYMBOL(__might_sleep
);
6017 void ___might_sleep(const char *file
, int line
, int preempt_offset
)
6019 /* Ratelimiting timestamp: */
6020 static unsigned long prev_jiffy
;
6022 unsigned long preempt_disable_ip
;
6024 /* WARN_ON_ONCE() by default, no rate limit required: */
6027 if ((preempt_count_equals(preempt_offset
) && !irqs_disabled() &&
6028 !is_idle_task(current
)) ||
6029 system_state
== SYSTEM_BOOTING
|| system_state
> SYSTEM_RUNNING
||
6033 if (time_before(jiffies
, prev_jiffy
+ HZ
) && prev_jiffy
)
6035 prev_jiffy
= jiffies
;
6037 /* Save this before calling printk(), since that will clobber it: */
6038 preempt_disable_ip
= get_preempt_disable_ip(current
);
6041 "BUG: sleeping function called from invalid context at %s:%d\n",
6044 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
6045 in_atomic(), irqs_disabled(),
6046 current
->pid
, current
->comm
);
6048 if (task_stack_end_corrupted(current
))
6049 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
6051 debug_show_held_locks(current
);
6052 if (irqs_disabled())
6053 print_irqtrace_events(current
);
6054 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT
)
6055 && !preempt_count_equals(preempt_offset
)) {
6056 pr_err("Preemption disabled at:");
6057 print_ip_sym(preempt_disable_ip
);
6061 add_taint(TAINT_WARN
, LOCKDEP_STILL_OK
);
6063 EXPORT_SYMBOL(___might_sleep
);
6066 #ifdef CONFIG_MAGIC_SYSRQ
6067 void normalize_rt_tasks(void)
6069 struct task_struct
*g
, *p
;
6070 struct sched_attr attr
= {
6071 .sched_policy
= SCHED_NORMAL
,
6074 read_lock(&tasklist_lock
);
6075 for_each_process_thread(g
, p
) {
6077 * Only normalize user tasks:
6079 if (p
->flags
& PF_KTHREAD
)
6082 p
->se
.exec_start
= 0;
6083 schedstat_set(p
->se
.statistics
.wait_start
, 0);
6084 schedstat_set(p
->se
.statistics
.sleep_start
, 0);
6085 schedstat_set(p
->se
.statistics
.block_start
, 0);
6087 if (!dl_task(p
) && !rt_task(p
)) {
6089 * Renice negative nice level userspace
6092 if (task_nice(p
) < 0)
6093 set_user_nice(p
, 0);
6097 __sched_setscheduler(p
, &attr
, false, false);
6099 read_unlock(&tasklist_lock
);
6102 #endif /* CONFIG_MAGIC_SYSRQ */
6104 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
6106 * These functions are only useful for the IA64 MCA handling, or kdb.
6108 * They can only be called when the whole system has been
6109 * stopped - every CPU needs to be quiescent, and no scheduling
6110 * activity can take place. Using them for anything else would
6111 * be a serious bug, and as a result, they aren't even visible
6112 * under any other configuration.
6116 * curr_task - return the current task for a given CPU.
6117 * @cpu: the processor in question.
6119 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6121 * Return: The current task for @cpu.
6123 struct task_struct
*curr_task(int cpu
)
6125 return cpu_curr(cpu
);
6128 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
6132 * set_curr_task - set the current task for a given CPU.
6133 * @cpu: the processor in question.
6134 * @p: the task pointer to set.
6136 * Description: This function must only be used when non-maskable interrupts
6137 * are serviced on a separate stack. It allows the architecture to switch the
6138 * notion of the current task on a CPU in a non-blocking manner. This function
6139 * must be called with all CPU's synchronized, and interrupts disabled, the
6140 * and caller must save the original value of the current task (see
6141 * curr_task() above) and restore that value before reenabling interrupts and
6142 * re-starting the system.
6144 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6146 void ia64_set_curr_task(int cpu
, struct task_struct
*p
)
6153 #ifdef CONFIG_CGROUP_SCHED
6154 /* task_group_lock serializes the addition/removal of task groups */
6155 static DEFINE_SPINLOCK(task_group_lock
);
6157 static void sched_free_group(struct task_group
*tg
)
6159 free_fair_sched_group(tg
);
6160 free_rt_sched_group(tg
);
6162 kmem_cache_free(task_group_cache
, tg
);
6165 /* allocate runqueue etc for a new task group */
6166 struct task_group
*sched_create_group(struct task_group
*parent
)
6168 struct task_group
*tg
;
6170 tg
= kmem_cache_alloc(task_group_cache
, GFP_KERNEL
| __GFP_ZERO
);
6172 return ERR_PTR(-ENOMEM
);
6174 if (!alloc_fair_sched_group(tg
, parent
))
6177 if (!alloc_rt_sched_group(tg
, parent
))
6183 sched_free_group(tg
);
6184 return ERR_PTR(-ENOMEM
);
6187 void sched_online_group(struct task_group
*tg
, struct task_group
*parent
)
6189 unsigned long flags
;
6191 spin_lock_irqsave(&task_group_lock
, flags
);
6192 list_add_rcu(&tg
->list
, &task_groups
);
6194 /* Root should already exist: */
6197 tg
->parent
= parent
;
6198 INIT_LIST_HEAD(&tg
->children
);
6199 list_add_rcu(&tg
->siblings
, &parent
->children
);
6200 spin_unlock_irqrestore(&task_group_lock
, flags
);
6202 online_fair_sched_group(tg
);
6205 /* rcu callback to free various structures associated with a task group */
6206 static void sched_free_group_rcu(struct rcu_head
*rhp
)
6208 /* Now it should be safe to free those cfs_rqs: */
6209 sched_free_group(container_of(rhp
, struct task_group
, rcu
));
6212 void sched_destroy_group(struct task_group
*tg
)
6214 /* Wait for possible concurrent references to cfs_rqs complete: */
6215 call_rcu(&tg
->rcu
, sched_free_group_rcu
);
6218 void sched_offline_group(struct task_group
*tg
)
6220 unsigned long flags
;
6222 /* End participation in shares distribution: */
6223 unregister_fair_sched_group(tg
);
6225 spin_lock_irqsave(&task_group_lock
, flags
);
6226 list_del_rcu(&tg
->list
);
6227 list_del_rcu(&tg
->siblings
);
6228 spin_unlock_irqrestore(&task_group_lock
, flags
);
6231 static void sched_change_group(struct task_struct
*tsk
, int type
)
6233 struct task_group
*tg
;
6236 * All callers are synchronized by task_rq_lock(); we do not use RCU
6237 * which is pointless here. Thus, we pass "true" to task_css_check()
6238 * to prevent lockdep warnings.
6240 tg
= container_of(task_css_check(tsk
, cpu_cgrp_id
, true),
6241 struct task_group
, css
);
6242 tg
= autogroup_task_group(tsk
, tg
);
6243 tsk
->sched_task_group
= tg
;
6245 #ifdef CONFIG_FAIR_GROUP_SCHED
6246 if (tsk
->sched_class
->task_change_group
)
6247 tsk
->sched_class
->task_change_group(tsk
, type
);
6250 set_task_rq(tsk
, task_cpu(tsk
));
6254 * Change task's runqueue when it moves between groups.
6256 * The caller of this function should have put the task in its new group by
6257 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
6260 void sched_move_task(struct task_struct
*tsk
)
6262 int queued
, running
, queue_flags
=
6263 DEQUEUE_SAVE
| DEQUEUE_MOVE
| DEQUEUE_NOCLOCK
;
6267 rq
= task_rq_lock(tsk
, &rf
);
6268 update_rq_clock(rq
);
6270 running
= task_current(rq
, tsk
);
6271 queued
= task_on_rq_queued(tsk
);
6274 dequeue_task(rq
, tsk
, queue_flags
);
6276 put_prev_task(rq
, tsk
);
6278 sched_change_group(tsk
, TASK_MOVE_GROUP
);
6281 enqueue_task(rq
, tsk
, queue_flags
);
6283 set_curr_task(rq
, tsk
);
6285 task_rq_unlock(rq
, tsk
, &rf
);
6288 static inline struct task_group
*css_tg(struct cgroup_subsys_state
*css
)
6290 return css
? container_of(css
, struct task_group
, css
) : NULL
;
6293 static struct cgroup_subsys_state
*
6294 cpu_cgroup_css_alloc(struct cgroup_subsys_state
*parent_css
)
6296 struct task_group
*parent
= css_tg(parent_css
);
6297 struct task_group
*tg
;
6300 /* This is early initialization for the top cgroup */
6301 return &root_task_group
.css
;
6304 tg
= sched_create_group(parent
);
6306 return ERR_PTR(-ENOMEM
);
6311 /* Expose task group only after completing cgroup initialization */
6312 static int cpu_cgroup_css_online(struct cgroup_subsys_state
*css
)
6314 struct task_group
*tg
= css_tg(css
);
6315 struct task_group
*parent
= css_tg(css
->parent
);
6318 sched_online_group(tg
, parent
);
6322 static void cpu_cgroup_css_released(struct cgroup_subsys_state
*css
)
6324 struct task_group
*tg
= css_tg(css
);
6326 sched_offline_group(tg
);
6329 static void cpu_cgroup_css_free(struct cgroup_subsys_state
*css
)
6331 struct task_group
*tg
= css_tg(css
);
6334 * Relies on the RCU grace period between css_released() and this.
6336 sched_free_group(tg
);
6340 * This is called before wake_up_new_task(), therefore we really only
6341 * have to set its group bits, all the other stuff does not apply.
6343 static void cpu_cgroup_fork(struct task_struct
*task
)
6348 rq
= task_rq_lock(task
, &rf
);
6350 update_rq_clock(rq
);
6351 sched_change_group(task
, TASK_SET_GROUP
);
6353 task_rq_unlock(rq
, task
, &rf
);
6356 static int cpu_cgroup_can_attach(struct cgroup_taskset
*tset
)
6358 struct task_struct
*task
;
6359 struct cgroup_subsys_state
*css
;
6362 cgroup_taskset_for_each(task
, css
, tset
) {
6363 #ifdef CONFIG_RT_GROUP_SCHED
6364 if (!sched_rt_can_attach(css_tg(css
), task
))
6367 /* We don't support RT-tasks being in separate groups */
6368 if (task
->sched_class
!= &fair_sched_class
)
6372 * Serialize against wake_up_new_task() such that if its
6373 * running, we're sure to observe its full state.
6375 raw_spin_lock_irq(&task
->pi_lock
);
6377 * Avoid calling sched_move_task() before wake_up_new_task()
6378 * has happened. This would lead to problems with PELT, due to
6379 * move wanting to detach+attach while we're not attached yet.
6381 if (task
->state
== TASK_NEW
)
6383 raw_spin_unlock_irq(&task
->pi_lock
);
6391 static void cpu_cgroup_attach(struct cgroup_taskset
*tset
)
6393 struct task_struct
*task
;
6394 struct cgroup_subsys_state
*css
;
6396 cgroup_taskset_for_each(task
, css
, tset
)
6397 sched_move_task(task
);
6400 #ifdef CONFIG_FAIR_GROUP_SCHED
6401 static int cpu_shares_write_u64(struct cgroup_subsys_state
*css
,
6402 struct cftype
*cftype
, u64 shareval
)
6404 return sched_group_set_shares(css_tg(css
), scale_load(shareval
));
6407 static u64
cpu_shares_read_u64(struct cgroup_subsys_state
*css
,
6410 struct task_group
*tg
= css_tg(css
);
6412 return (u64
) scale_load_down(tg
->shares
);
6415 #ifdef CONFIG_CFS_BANDWIDTH
6416 static DEFINE_MUTEX(cfs_constraints_mutex
);
6418 const u64 max_cfs_quota_period
= 1 * NSEC_PER_SEC
; /* 1s */
6419 const u64 min_cfs_quota_period
= 1 * NSEC_PER_MSEC
; /* 1ms */
6421 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 runtime
);
6423 static int tg_set_cfs_bandwidth(struct task_group
*tg
, u64 period
, u64 quota
)
6425 int i
, ret
= 0, runtime_enabled
, runtime_was_enabled
;
6426 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6428 if (tg
== &root_task_group
)
6432 * Ensure we have at some amount of bandwidth every period. This is
6433 * to prevent reaching a state of large arrears when throttled via
6434 * entity_tick() resulting in prolonged exit starvation.
6436 if (quota
< min_cfs_quota_period
|| period
< min_cfs_quota_period
)
6440 * Likewise, bound things on the otherside by preventing insane quota
6441 * periods. This also allows us to normalize in computing quota
6444 if (period
> max_cfs_quota_period
)
6448 * Prevent race between setting of cfs_rq->runtime_enabled and
6449 * unthrottle_offline_cfs_rqs().
6452 mutex_lock(&cfs_constraints_mutex
);
6453 ret
= __cfs_schedulable(tg
, period
, quota
);
6457 runtime_enabled
= quota
!= RUNTIME_INF
;
6458 runtime_was_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
6460 * If we need to toggle cfs_bandwidth_used, off->on must occur
6461 * before making related changes, and on->off must occur afterwards
6463 if (runtime_enabled
&& !runtime_was_enabled
)
6464 cfs_bandwidth_usage_inc();
6465 raw_spin_lock_irq(&cfs_b
->lock
);
6466 cfs_b
->period
= ns_to_ktime(period
);
6467 cfs_b
->quota
= quota
;
6469 __refill_cfs_bandwidth_runtime(cfs_b
);
6471 /* Restart the period timer (if active) to handle new period expiry: */
6472 if (runtime_enabled
)
6473 start_cfs_bandwidth(cfs_b
);
6475 raw_spin_unlock_irq(&cfs_b
->lock
);
6477 for_each_online_cpu(i
) {
6478 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[i
];
6479 struct rq
*rq
= cfs_rq
->rq
;
6482 rq_lock_irq(rq
, &rf
);
6483 cfs_rq
->runtime_enabled
= runtime_enabled
;
6484 cfs_rq
->runtime_remaining
= 0;
6486 if (cfs_rq
->throttled
)
6487 unthrottle_cfs_rq(cfs_rq
);
6488 rq_unlock_irq(rq
, &rf
);
6490 if (runtime_was_enabled
&& !runtime_enabled
)
6491 cfs_bandwidth_usage_dec();
6493 mutex_unlock(&cfs_constraints_mutex
);
6499 int tg_set_cfs_quota(struct task_group
*tg
, long cfs_quota_us
)
6503 period
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
6504 if (cfs_quota_us
< 0)
6505 quota
= RUNTIME_INF
;
6507 quota
= (u64
)cfs_quota_us
* NSEC_PER_USEC
;
6509 return tg_set_cfs_bandwidth(tg
, period
, quota
);
6512 long tg_get_cfs_quota(struct task_group
*tg
)
6516 if (tg
->cfs_bandwidth
.quota
== RUNTIME_INF
)
6519 quota_us
= tg
->cfs_bandwidth
.quota
;
6520 do_div(quota_us
, NSEC_PER_USEC
);
6525 int tg_set_cfs_period(struct task_group
*tg
, long cfs_period_us
)
6529 period
= (u64
)cfs_period_us
* NSEC_PER_USEC
;
6530 quota
= tg
->cfs_bandwidth
.quota
;
6532 return tg_set_cfs_bandwidth(tg
, period
, quota
);
6535 long tg_get_cfs_period(struct task_group
*tg
)
6539 cfs_period_us
= ktime_to_ns(tg
->cfs_bandwidth
.period
);
6540 do_div(cfs_period_us
, NSEC_PER_USEC
);
6542 return cfs_period_us
;
6545 static s64
cpu_cfs_quota_read_s64(struct cgroup_subsys_state
*css
,
6548 return tg_get_cfs_quota(css_tg(css
));
6551 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state
*css
,
6552 struct cftype
*cftype
, s64 cfs_quota_us
)
6554 return tg_set_cfs_quota(css_tg(css
), cfs_quota_us
);
6557 static u64
cpu_cfs_period_read_u64(struct cgroup_subsys_state
*css
,
6560 return tg_get_cfs_period(css_tg(css
));
6563 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state
*css
,
6564 struct cftype
*cftype
, u64 cfs_period_us
)
6566 return tg_set_cfs_period(css_tg(css
), cfs_period_us
);
6569 struct cfs_schedulable_data
{
6570 struct task_group
*tg
;
6575 * normalize group quota/period to be quota/max_period
6576 * note: units are usecs
6578 static u64
normalize_cfs_quota(struct task_group
*tg
,
6579 struct cfs_schedulable_data
*d
)
6587 period
= tg_get_cfs_period(tg
);
6588 quota
= tg_get_cfs_quota(tg
);
6591 /* note: these should typically be equivalent */
6592 if (quota
== RUNTIME_INF
|| quota
== -1)
6595 return to_ratio(period
, quota
);
6598 static int tg_cfs_schedulable_down(struct task_group
*tg
, void *data
)
6600 struct cfs_schedulable_data
*d
= data
;
6601 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6602 s64 quota
= 0, parent_quota
= -1;
6605 quota
= RUNTIME_INF
;
6607 struct cfs_bandwidth
*parent_b
= &tg
->parent
->cfs_bandwidth
;
6609 quota
= normalize_cfs_quota(tg
, d
);
6610 parent_quota
= parent_b
->hierarchical_quota
;
6613 * Ensure max(child_quota) <= parent_quota, inherit when no
6616 if (quota
== RUNTIME_INF
)
6617 quota
= parent_quota
;
6618 else if (parent_quota
!= RUNTIME_INF
&& quota
> parent_quota
)
6621 cfs_b
->hierarchical_quota
= quota
;
6626 static int __cfs_schedulable(struct task_group
*tg
, u64 period
, u64 quota
)
6629 struct cfs_schedulable_data data
= {
6635 if (quota
!= RUNTIME_INF
) {
6636 do_div(data
.period
, NSEC_PER_USEC
);
6637 do_div(data
.quota
, NSEC_PER_USEC
);
6641 ret
= walk_tg_tree(tg_cfs_schedulable_down
, tg_nop
, &data
);
6647 static int cpu_cfs_stat_show(struct seq_file
*sf
, void *v
)
6649 struct task_group
*tg
= css_tg(seq_css(sf
));
6650 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6652 seq_printf(sf
, "nr_periods %d\n", cfs_b
->nr_periods
);
6653 seq_printf(sf
, "nr_throttled %d\n", cfs_b
->nr_throttled
);
6654 seq_printf(sf
, "throttled_time %llu\n", cfs_b
->throttled_time
);
6658 #endif /* CONFIG_CFS_BANDWIDTH */
6659 #endif /* CONFIG_FAIR_GROUP_SCHED */
6661 #ifdef CONFIG_RT_GROUP_SCHED
6662 static int cpu_rt_runtime_write(struct cgroup_subsys_state
*css
,
6663 struct cftype
*cft
, s64 val
)
6665 return sched_group_set_rt_runtime(css_tg(css
), val
);
6668 static s64
cpu_rt_runtime_read(struct cgroup_subsys_state
*css
,
6671 return sched_group_rt_runtime(css_tg(css
));
6674 static int cpu_rt_period_write_uint(struct cgroup_subsys_state
*css
,
6675 struct cftype
*cftype
, u64 rt_period_us
)
6677 return sched_group_set_rt_period(css_tg(css
), rt_period_us
);
6680 static u64
cpu_rt_period_read_uint(struct cgroup_subsys_state
*css
,
6683 return sched_group_rt_period(css_tg(css
));
6685 #endif /* CONFIG_RT_GROUP_SCHED */
6687 static struct cftype cpu_legacy_files
[] = {
6688 #ifdef CONFIG_FAIR_GROUP_SCHED
6691 .read_u64
= cpu_shares_read_u64
,
6692 .write_u64
= cpu_shares_write_u64
,
6695 #ifdef CONFIG_CFS_BANDWIDTH
6697 .name
= "cfs_quota_us",
6698 .read_s64
= cpu_cfs_quota_read_s64
,
6699 .write_s64
= cpu_cfs_quota_write_s64
,
6702 .name
= "cfs_period_us",
6703 .read_u64
= cpu_cfs_period_read_u64
,
6704 .write_u64
= cpu_cfs_period_write_u64
,
6708 .seq_show
= cpu_cfs_stat_show
,
6711 #ifdef CONFIG_RT_GROUP_SCHED
6713 .name
= "rt_runtime_us",
6714 .read_s64
= cpu_rt_runtime_read
,
6715 .write_s64
= cpu_rt_runtime_write
,
6718 .name
= "rt_period_us",
6719 .read_u64
= cpu_rt_period_read_uint
,
6720 .write_u64
= cpu_rt_period_write_uint
,
6726 static int cpu_extra_stat_show(struct seq_file
*sf
,
6727 struct cgroup_subsys_state
*css
)
6729 #ifdef CONFIG_CFS_BANDWIDTH
6731 struct task_group
*tg
= css_tg(css
);
6732 struct cfs_bandwidth
*cfs_b
= &tg
->cfs_bandwidth
;
6735 throttled_usec
= cfs_b
->throttled_time
;
6736 do_div(throttled_usec
, NSEC_PER_USEC
);
6738 seq_printf(sf
, "nr_periods %d\n"
6740 "throttled_usec %llu\n",
6741 cfs_b
->nr_periods
, cfs_b
->nr_throttled
,
6748 #ifdef CONFIG_FAIR_GROUP_SCHED
6749 static u64
cpu_weight_read_u64(struct cgroup_subsys_state
*css
,
6752 struct task_group
*tg
= css_tg(css
);
6753 u64 weight
= scale_load_down(tg
->shares
);
6755 return DIV_ROUND_CLOSEST_ULL(weight
* CGROUP_WEIGHT_DFL
, 1024);
6758 static int cpu_weight_write_u64(struct cgroup_subsys_state
*css
,
6759 struct cftype
*cft
, u64 weight
)
6762 * cgroup weight knobs should use the common MIN, DFL and MAX
6763 * values which are 1, 100 and 10000 respectively. While it loses
6764 * a bit of range on both ends, it maps pretty well onto the shares
6765 * value used by scheduler and the round-trip conversions preserve
6766 * the original value over the entire range.
6768 if (weight
< CGROUP_WEIGHT_MIN
|| weight
> CGROUP_WEIGHT_MAX
)
6771 weight
= DIV_ROUND_CLOSEST_ULL(weight
* 1024, CGROUP_WEIGHT_DFL
);
6773 return sched_group_set_shares(css_tg(css
), scale_load(weight
));
6776 static s64
cpu_weight_nice_read_s64(struct cgroup_subsys_state
*css
,
6779 unsigned long weight
= scale_load_down(css_tg(css
)->shares
);
6780 int last_delta
= INT_MAX
;
6783 /* find the closest nice value to the current weight */
6784 for (prio
= 0; prio
< ARRAY_SIZE(sched_prio_to_weight
); prio
++) {
6785 delta
= abs(sched_prio_to_weight
[prio
] - weight
);
6786 if (delta
>= last_delta
)
6791 return PRIO_TO_NICE(prio
- 1 + MAX_RT_PRIO
);
6794 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state
*css
,
6795 struct cftype
*cft
, s64 nice
)
6797 unsigned long weight
;
6799 if (nice
< MIN_NICE
|| nice
> MAX_NICE
)
6802 weight
= sched_prio_to_weight
[NICE_TO_PRIO(nice
) - MAX_RT_PRIO
];
6803 return sched_group_set_shares(css_tg(css
), scale_load(weight
));
6807 static void __maybe_unused
cpu_period_quota_print(struct seq_file
*sf
,
6808 long period
, long quota
)
6811 seq_puts(sf
, "max");
6813 seq_printf(sf
, "%ld", quota
);
6815 seq_printf(sf
, " %ld\n", period
);
6818 /* caller should put the current value in *@periodp before calling */
6819 static int __maybe_unused
cpu_period_quota_parse(char *buf
,
6820 u64
*periodp
, u64
*quotap
)
6822 char tok
[21]; /* U64_MAX */
6824 if (!sscanf(buf
, "%s %llu", tok
, periodp
))
6827 *periodp
*= NSEC_PER_USEC
;
6829 if (sscanf(tok
, "%llu", quotap
))
6830 *quotap
*= NSEC_PER_USEC
;
6831 else if (!strcmp(tok
, "max"))
6832 *quotap
= RUNTIME_INF
;
6839 #ifdef CONFIG_CFS_BANDWIDTH
6840 static int cpu_max_show(struct seq_file
*sf
, void *v
)
6842 struct task_group
*tg
= css_tg(seq_css(sf
));
6844 cpu_period_quota_print(sf
, tg_get_cfs_period(tg
), tg_get_cfs_quota(tg
));
6848 static ssize_t
cpu_max_write(struct kernfs_open_file
*of
,
6849 char *buf
, size_t nbytes
, loff_t off
)
6851 struct task_group
*tg
= css_tg(of_css(of
));
6852 u64 period
= tg_get_cfs_period(tg
);
6856 ret
= cpu_period_quota_parse(buf
, &period
, "a
);
6858 ret
= tg_set_cfs_bandwidth(tg
, period
, quota
);
6859 return ret
?: nbytes
;
6863 static struct cftype cpu_files
[] = {
6864 #ifdef CONFIG_FAIR_GROUP_SCHED
6867 .flags
= CFTYPE_NOT_ON_ROOT
,
6868 .read_u64
= cpu_weight_read_u64
,
6869 .write_u64
= cpu_weight_write_u64
,
6872 .name
= "weight.nice",
6873 .flags
= CFTYPE_NOT_ON_ROOT
,
6874 .read_s64
= cpu_weight_nice_read_s64
,
6875 .write_s64
= cpu_weight_nice_write_s64
,
6878 #ifdef CONFIG_CFS_BANDWIDTH
6881 .flags
= CFTYPE_NOT_ON_ROOT
,
6882 .seq_show
= cpu_max_show
,
6883 .write
= cpu_max_write
,
6889 struct cgroup_subsys cpu_cgrp_subsys
= {
6890 .css_alloc
= cpu_cgroup_css_alloc
,
6891 .css_online
= cpu_cgroup_css_online
,
6892 .css_released
= cpu_cgroup_css_released
,
6893 .css_free
= cpu_cgroup_css_free
,
6894 .css_extra_stat_show
= cpu_extra_stat_show
,
6895 .fork
= cpu_cgroup_fork
,
6896 .can_attach
= cpu_cgroup_can_attach
,
6897 .attach
= cpu_cgroup_attach
,
6898 .legacy_cftypes
= cpu_legacy_files
,
6899 .dfl_cftypes
= cpu_files
,
6904 #endif /* CONFIG_CGROUP_SCHED */
6906 void dump_cpu_task(int cpu
)
6908 pr_info("Task dump for CPU %d:\n", cpu
);
6909 sched_show_task(cpu_curr(cpu
));
6913 * Nice levels are multiplicative, with a gentle 10% change for every
6914 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
6915 * nice 1, it will get ~10% less CPU time than another CPU-bound task
6916 * that remained on nice 0.
6918 * The "10% effect" is relative and cumulative: from _any_ nice level,
6919 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
6920 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
6921 * If a task goes up by ~10% and another task goes down by ~10% then
6922 * the relative distance between them is ~25%.)
6924 const int sched_prio_to_weight
[40] = {
6925 /* -20 */ 88761, 71755, 56483, 46273, 36291,
6926 /* -15 */ 29154, 23254, 18705, 14949, 11916,
6927 /* -10 */ 9548, 7620, 6100, 4904, 3906,
6928 /* -5 */ 3121, 2501, 1991, 1586, 1277,
6929 /* 0 */ 1024, 820, 655, 526, 423,
6930 /* 5 */ 335, 272, 215, 172, 137,
6931 /* 10 */ 110, 87, 70, 56, 45,
6932 /* 15 */ 36, 29, 23, 18, 15,
6936 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
6938 * In cases where the weight does not change often, we can use the
6939 * precalculated inverse to speed up arithmetics by turning divisions
6940 * into multiplications:
6942 const u32 sched_prio_to_wmult
[40] = {
6943 /* -20 */ 48388, 59856, 76040, 92818, 118348,
6944 /* -15 */ 147320, 184698, 229616, 287308, 360437,
6945 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
6946 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
6947 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
6948 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
6949 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
6950 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,