1 // SPDX-License-Identifier: GPL-2.0-only
5 * Core kernel scheduler code and related syscalls
7 * Copyright (C) 1991-2002 Linus Torvalds
9 #define CREATE_TRACE_POINTS
10 #include <trace/events/sched.h>
11 #undef CREATE_TRACE_POINTS
15 #include <linux/nospec.h>
17 #include <linux/kcov.h>
18 #include <linux/scs.h>
20 #include <asm/switch_to.h>
23 #include "../workqueue_internal.h"
24 #include "../../fs/io-wq.h"
25 #include "../smpboot.h"
31 * Export tracepoints that act as a bare tracehook (ie: have no trace event
32 * associated with them) to allow external modules to probe them.
34 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
35 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
36 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
37 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
38 EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
39 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
40 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
41 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
42 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
43 EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
45 DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
47 #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_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 measure -rt task CPU usage in us.
73 unsigned int sysctl_sched_rt_period = 1000000;
75 __read_mostly int scheduler_running;
78 * part of the period that we allow rt tasks to run in us.
81 int sysctl_sched_rt_runtime = 950000;
85 * Serialization rules:
91 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
94 * rq2->lock where: rq1 < rq2
98 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
99 * local CPU's rq->lock, it optionally removes the task from the runqueue and
100 * always looks at the local rq data structures to find the most elegible task
103 * Task enqueue is also under rq->lock, possibly taken from another CPU.
104 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
105 * the local CPU to avoid bouncing the runqueue state around [ see
106 * ttwu_queue_wakelist() ]
108 * Task wakeup, specifically wakeups that involve migration, are horribly
109 * complicated to avoid having to take two rq->locks.
113 * System-calls and anything external will use task_rq_lock() which acquires
114 * both p->pi_lock and rq->lock. As a consequence the state they change is
115 * stable while holding either lock:
117 * - sched_setaffinity()/
118 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
119 * - set_user_nice(): p->se.load, p->*prio
120 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
121 * p->se.load, p->rt_priority,
122 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
123 * - sched_setnuma(): p->numa_preferred_nid
124 * - sched_move_task()/
125 * cpu_cgroup_fork(): p->sched_task_group
126 * - uclamp_update_active() p->uclamp*
128 * p->state <- TASK_*:
130 * is changed locklessly using set_current_state(), __set_current_state() or
131 * set_special_state(), see their respective comments, or by
132 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
135 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
137 * is set by activate_task() and cleared by deactivate_task(), under
138 * rq->lock. Non-zero indicates the task is runnable, the special
139 * ON_RQ_MIGRATING state is used for migration without holding both
140 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
142 * p->on_cpu <- { 0, 1 }:
144 * is set by prepare_task() and cleared by finish_task() such that it will be
145 * set before p is scheduled-in and cleared after p is scheduled-out, both
146 * under rq->lock. Non-zero indicates the task is running on its CPU.
148 * [ The astute reader will observe that it is possible for two tasks on one
149 * CPU to have ->on_cpu = 1 at the same time. ]
151 * task_cpu(p): is changed by set_task_cpu(), the rules are:
153 * - Don't call set_task_cpu() on a blocked task:
155 * We don't care what CPU we're not running on, this simplifies hotplug,
156 * the CPU assignment of blocked tasks isn't required to be valid.
158 * - for try_to_wake_up(), called under p->pi_lock:
160 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
162 * - for migration called under rq->lock:
163 * [ see task_on_rq_migrating() in task_rq_lock() ]
165 * o move_queued_task()
168 * - for migration called under double_rq_lock():
170 * o __migrate_swap_task()
171 * o push_rt_task() / pull_rt_task()
172 * o push_dl_task() / pull_dl_task()
173 * o dl_task_offline_migration()
178 * __task_rq_lock - lock the rq @p resides on.
180 struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
185 lockdep_assert_held(&p->pi_lock);
189 raw_spin_lock(&rq->lock);
190 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
194 raw_spin_unlock(&rq->lock);
196 while (unlikely(task_on_rq_migrating(p)))
202 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
204 struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
205 __acquires(p->pi_lock)
211 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
213 raw_spin_lock(&rq->lock);
215 * move_queued_task() task_rq_lock()
218 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
219 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
220 * [S] ->cpu = new_cpu [L] task_rq()
224 * If we observe the old CPU in task_rq_lock(), the acquire of
225 * the old rq->lock will fully serialize against the stores.
227 * If we observe the new CPU in task_rq_lock(), the address
228 * dependency headed by '[L] rq = task_rq()' and the acquire
229 * will pair with the WMB to ensure we then also see migrating.
231 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
235 raw_spin_unlock(&rq->lock);
236 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
238 while (unlikely(task_on_rq_migrating(p)))
244 * RQ-clock updating methods:
247 static void update_rq_clock_task(struct rq *rq, s64 delta)
250 * In theory, the compile should just see 0 here, and optimize out the call
251 * to sched_rt_avg_update. But I don't trust it...
253 s64 __maybe_unused steal = 0, irq_delta = 0;
255 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
256 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
259 * Since irq_time is only updated on {soft,}irq_exit, we might run into
260 * this case when a previous update_rq_clock() happened inside a
263 * When this happens, we stop ->clock_task and only update the
264 * prev_irq_time stamp to account for the part that fit, so that a next
265 * update will consume the rest. This ensures ->clock_task is
268 * It does however cause some slight miss-attribution of {soft,}irq
269 * time, a more accurate solution would be to update the irq_time using
270 * the current rq->clock timestamp, except that would require using
273 if (irq_delta > delta)
276 rq->prev_irq_time += irq_delta;
279 #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
280 if (static_key_false((¶virt_steal_rq_enabled))) {
281 steal = paravirt_steal_clock(cpu_of(rq));
282 steal -= rq->prev_steal_time_rq;
284 if (unlikely(steal > delta))
287 rq->prev_steal_time_rq += steal;
292 rq->clock_task += delta;
294 #ifdef CONFIG_HAVE_SCHED_AVG_IRQ
295 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
296 update_irq_load_avg(rq, irq_delta + steal);
298 update_rq_clock_pelt(rq, delta);
301 void update_rq_clock(struct rq *rq)
305 lockdep_assert_held(&rq->lock);
307 if (rq->clock_update_flags & RQCF_ACT_SKIP)
310 #ifdef CONFIG_SCHED_DEBUG
311 if (sched_feat(WARN_DOUBLE_CLOCK))
312 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
313 rq->clock_update_flags |= RQCF_UPDATED;
316 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
320 update_rq_clock_task(rq, delta);
324 rq_csd_init(struct rq *rq, call_single_data_t *csd, smp_call_func_t func)
331 #ifdef CONFIG_SCHED_HRTICK
333 * Use HR-timers to deliver accurate preemption points.
336 static void hrtick_clear(struct rq *rq)
338 if (hrtimer_active(&rq->hrtick_timer))
339 hrtimer_cancel(&rq->hrtick_timer);
343 * High-resolution timer tick.
344 * Runs from hardirq context with interrupts disabled.
346 static enum hrtimer_restart hrtick(struct hrtimer *timer)
348 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
351 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
355 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
358 return HRTIMER_NORESTART;
363 static void __hrtick_restart(struct rq *rq)
365 struct hrtimer *timer = &rq->hrtick_timer;
367 hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED_HARD);
371 * called from hardirq (IPI) context
373 static void __hrtick_start(void *arg)
379 __hrtick_restart(rq);
384 * Called to set the hrtick timer state.
386 * called with rq->lock held and irqs disabled
388 void hrtick_start(struct rq *rq, u64 delay)
390 struct hrtimer *timer = &rq->hrtick_timer;
395 * Don't schedule slices shorter than 10000ns, that just
396 * doesn't make sense and can cause timer DoS.
398 delta = max_t(s64, delay, 10000LL);
399 time = ktime_add_ns(timer->base->get_time(), delta);
401 hrtimer_set_expires(timer, time);
404 __hrtick_restart(rq);
406 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
411 * Called to set the hrtick timer state.
413 * called with rq->lock held and irqs disabled
415 void hrtick_start(struct rq *rq, u64 delay)
418 * Don't schedule slices shorter than 10000ns, that just
419 * doesn't make sense. Rely on vruntime for fairness.
421 delay = max_t(u64, delay, 10000LL);
422 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
423 HRTIMER_MODE_REL_PINNED_HARD);
426 #endif /* CONFIG_SMP */
428 static void hrtick_rq_init(struct rq *rq)
431 rq_csd_init(rq, &rq->hrtick_csd, __hrtick_start);
433 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
434 rq->hrtick_timer.function = hrtick;
436 #else /* CONFIG_SCHED_HRTICK */
437 static inline void hrtick_clear(struct rq *rq)
441 static inline void hrtick_rq_init(struct rq *rq)
444 #endif /* CONFIG_SCHED_HRTICK */
447 * cmpxchg based fetch_or, macro so it works for different integer types
449 #define fetch_or(ptr, mask) \
451 typeof(ptr) _ptr = (ptr); \
452 typeof(mask) _mask = (mask); \
453 typeof(*_ptr) _old, _val = *_ptr; \
456 _old = cmpxchg(_ptr, _val, _val | _mask); \
464 #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
466 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
467 * this avoids any races wrt polling state changes and thereby avoids
470 static bool set_nr_and_not_polling(struct task_struct *p)
472 struct thread_info *ti = task_thread_info(p);
473 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
477 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
479 * If this returns true, then the idle task promises to call
480 * sched_ttwu_pending() and reschedule soon.
482 static bool set_nr_if_polling(struct task_struct *p)
484 struct thread_info *ti = task_thread_info(p);
485 typeof(ti->flags) old, val = READ_ONCE(ti->flags);
488 if (!(val & _TIF_POLLING_NRFLAG))
490 if (val & _TIF_NEED_RESCHED)
492 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
501 static bool set_nr_and_not_polling(struct task_struct *p)
503 set_tsk_need_resched(p);
508 static bool set_nr_if_polling(struct task_struct *p)
515 static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
517 struct wake_q_node *node = &task->wake_q;
520 * Atomically grab the task, if ->wake_q is !nil already it means
521 * its already queued (either by us or someone else) and will get the
522 * wakeup due to that.
524 * In order to ensure that a pending wakeup will observe our pending
525 * state, even in the failed case, an explicit smp_mb() must be used.
527 smp_mb__before_atomic();
528 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
532 * The head is context local, there can be no concurrency.
535 head->lastp = &node->next;
540 * wake_q_add() - queue a wakeup for 'later' waking.
541 * @head: the wake_q_head to add @task to
542 * @task: the task to queue for 'later' wakeup
544 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
545 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
548 * This function must be used as-if it were wake_up_process(); IOW the task
549 * must be ready to be woken at this location.
551 void wake_q_add(struct wake_q_head *head, struct task_struct *task)
553 if (__wake_q_add(head, task))
554 get_task_struct(task);
558 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
559 * @head: the wake_q_head to add @task to
560 * @task: the task to queue for 'later' wakeup
562 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
563 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
566 * This function must be used as-if it were wake_up_process(); IOW the task
567 * must be ready to be woken at this location.
569 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
570 * that already hold reference to @task can call the 'safe' version and trust
571 * wake_q to do the right thing depending whether or not the @task is already
574 void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
576 if (!__wake_q_add(head, task))
577 put_task_struct(task);
580 void wake_up_q(struct wake_q_head *head)
582 struct wake_q_node *node = head->first;
584 while (node != WAKE_Q_TAIL) {
585 struct task_struct *task;
587 task = container_of(node, struct task_struct, wake_q);
589 /* Task can safely be re-inserted now: */
591 task->wake_q.next = NULL;
594 * wake_up_process() executes a full barrier, which pairs with
595 * the queueing in wake_q_add() so as not to miss wakeups.
597 wake_up_process(task);
598 put_task_struct(task);
603 * resched_curr - mark rq's current task 'to be rescheduled now'.
605 * On UP this means the setting of the need_resched flag, on SMP it
606 * might also involve a cross-CPU call to trigger the scheduler on
609 void resched_curr(struct rq *rq)
611 struct task_struct *curr = rq->curr;
614 lockdep_assert_held(&rq->lock);
616 if (test_tsk_need_resched(curr))
621 if (cpu == smp_processor_id()) {
622 set_tsk_need_resched(curr);
623 set_preempt_need_resched();
627 if (set_nr_and_not_polling(curr))
628 smp_send_reschedule(cpu);
630 trace_sched_wake_idle_without_ipi(cpu);
633 void resched_cpu(int cpu)
635 struct rq *rq = cpu_rq(cpu);
638 raw_spin_lock_irqsave(&rq->lock, flags);
639 if (cpu_online(cpu) || cpu == smp_processor_id())
641 raw_spin_unlock_irqrestore(&rq->lock, flags);
645 #ifdef CONFIG_NO_HZ_COMMON
647 * In the semi idle case, use the nearest busy CPU for migrating timers
648 * from an idle CPU. This is good for power-savings.
650 * We don't do similar optimization for completely idle system, as
651 * selecting an idle CPU will add more delays to the timers than intended
652 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
654 int get_nohz_timer_target(void)
656 int i, cpu = smp_processor_id(), default_cpu = -1;
657 struct sched_domain *sd;
659 if (housekeeping_cpu(cpu, HK_FLAG_TIMER)) {
666 for_each_domain(cpu, sd) {
667 for_each_cpu_and(i, sched_domain_span(sd),
668 housekeeping_cpumask(HK_FLAG_TIMER)) {
679 if (default_cpu == -1)
680 default_cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
688 * When add_timer_on() enqueues a timer into the timer wheel of an
689 * idle CPU then this timer might expire before the next timer event
690 * which is scheduled to wake up that CPU. In case of a completely
691 * idle system the next event might even be infinite time into the
692 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
693 * leaves the inner idle loop so the newly added timer is taken into
694 * account when the CPU goes back to idle and evaluates the timer
695 * wheel for the next timer event.
697 static void wake_up_idle_cpu(int cpu)
699 struct rq *rq = cpu_rq(cpu);
701 if (cpu == smp_processor_id())
704 if (set_nr_and_not_polling(rq->idle))
705 smp_send_reschedule(cpu);
707 trace_sched_wake_idle_without_ipi(cpu);
710 static bool wake_up_full_nohz_cpu(int cpu)
713 * We just need the target to call irq_exit() and re-evaluate
714 * the next tick. The nohz full kick at least implies that.
715 * If needed we can still optimize that later with an
718 if (cpu_is_offline(cpu))
719 return true; /* Don't try to wake offline CPUs. */
720 if (tick_nohz_full_cpu(cpu)) {
721 if (cpu != smp_processor_id() ||
722 tick_nohz_tick_stopped())
723 tick_nohz_full_kick_cpu(cpu);
731 * Wake up the specified CPU. If the CPU is going offline, it is the
732 * caller's responsibility to deal with the lost wakeup, for example,
733 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
735 void wake_up_nohz_cpu(int cpu)
737 if (!wake_up_full_nohz_cpu(cpu))
738 wake_up_idle_cpu(cpu);
741 static void nohz_csd_func(void *info)
743 struct rq *rq = info;
744 int cpu = cpu_of(rq);
748 * Release the rq::nohz_csd.
750 flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
751 WARN_ON(!(flags & NOHZ_KICK_MASK));
753 rq->idle_balance = idle_cpu(cpu);
754 if (rq->idle_balance && !need_resched()) {
755 rq->nohz_idle_balance = flags;
756 raise_softirq_irqoff(SCHED_SOFTIRQ);
760 #endif /* CONFIG_NO_HZ_COMMON */
762 #ifdef CONFIG_NO_HZ_FULL
763 bool sched_can_stop_tick(struct rq *rq)
767 /* Deadline tasks, even if single, need the tick */
768 if (rq->dl.dl_nr_running)
772 * If there are more than one RR tasks, we need the tick to effect the
773 * actual RR behaviour.
775 if (rq->rt.rr_nr_running) {
776 if (rq->rt.rr_nr_running == 1)
783 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
784 * forced preemption between FIFO tasks.
786 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
791 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
792 * if there's more than one we need the tick for involuntary
795 if (rq->nr_running > 1)
800 #endif /* CONFIG_NO_HZ_FULL */
801 #endif /* CONFIG_SMP */
803 #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
804 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
806 * Iterate task_group tree rooted at *from, calling @down when first entering a
807 * node and @up when leaving it for the final time.
809 * Caller must hold rcu_lock or sufficient equivalent.
811 int walk_tg_tree_from(struct task_group *from,
812 tg_visitor down, tg_visitor up, void *data)
814 struct task_group *parent, *child;
820 ret = (*down)(parent, data);
823 list_for_each_entry_rcu(child, &parent->children, siblings) {
830 ret = (*up)(parent, data);
831 if (ret || parent == from)
835 parent = parent->parent;
842 int tg_nop(struct task_group *tg, void *data)
848 static void set_load_weight(struct task_struct *p, bool update_load)
850 int prio = p->static_prio - MAX_RT_PRIO;
851 struct load_weight *load = &p->se.load;
854 * SCHED_IDLE tasks get minimal weight:
856 if (task_has_idle_policy(p)) {
857 load->weight = scale_load(WEIGHT_IDLEPRIO);
858 load->inv_weight = WMULT_IDLEPRIO;
863 * SCHED_OTHER tasks have to update their load when changing their
866 if (update_load && p->sched_class == &fair_sched_class) {
867 reweight_task(p, prio);
869 load->weight = scale_load(sched_prio_to_weight[prio]);
870 load->inv_weight = sched_prio_to_wmult[prio];
874 #ifdef CONFIG_UCLAMP_TASK
876 * Serializes updates of utilization clamp values
878 * The (slow-path) user-space triggers utilization clamp value updates which
879 * can require updates on (fast-path) scheduler's data structures used to
880 * support enqueue/dequeue operations.
881 * While the per-CPU rq lock protects fast-path update operations, user-space
882 * requests are serialized using a mutex to reduce the risk of conflicting
883 * updates or API abuses.
885 static DEFINE_MUTEX(uclamp_mutex);
887 /* Max allowed minimum utilization */
888 unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
890 /* Max allowed maximum utilization */
891 unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
894 * By default RT tasks run at the maximum performance point/capacity of the
895 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
896 * SCHED_CAPACITY_SCALE.
898 * This knob allows admins to change the default behavior when uclamp is being
899 * used. In battery powered devices, particularly, running at the maximum
900 * capacity and frequency will increase energy consumption and shorten the
903 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
905 * This knob will not override the system default sched_util_clamp_min defined
908 unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
910 /* All clamps are required to be less or equal than these values */
911 static struct uclamp_se uclamp_default[UCLAMP_CNT];
914 * This static key is used to reduce the uclamp overhead in the fast path. It
915 * primarily disables the call to uclamp_rq_{inc, dec}() in
916 * enqueue/dequeue_task().
918 * This allows users to continue to enable uclamp in their kernel config with
919 * minimum uclamp overhead in the fast path.
921 * As soon as userspace modifies any of the uclamp knobs, the static key is
922 * enabled, since we have an actual users that make use of uclamp
925 * The knobs that would enable this static key are:
927 * * A task modifying its uclamp value with sched_setattr().
928 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
929 * * An admin modifying the cgroup cpu.uclamp.{min, max}
931 DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
933 /* Integer rounded range for each bucket */
934 #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
936 #define for_each_clamp_id(clamp_id) \
937 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
939 static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
941 return clamp_value / UCLAMP_BUCKET_DELTA;
944 static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
946 if (clamp_id == UCLAMP_MIN)
948 return SCHED_CAPACITY_SCALE;
951 static inline void uclamp_se_set(struct uclamp_se *uc_se,
952 unsigned int value, bool user_defined)
954 uc_se->value = value;
955 uc_se->bucket_id = uclamp_bucket_id(value);
956 uc_se->user_defined = user_defined;
959 static inline unsigned int
960 uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
961 unsigned int clamp_value)
964 * Avoid blocked utilization pushing up the frequency when we go
965 * idle (which drops the max-clamp) by retaining the last known
968 if (clamp_id == UCLAMP_MAX) {
969 rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
973 return uclamp_none(UCLAMP_MIN);
976 static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
977 unsigned int clamp_value)
979 /* Reset max-clamp retention only on idle exit */
980 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
983 WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
987 unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
988 unsigned int clamp_value)
990 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
991 int bucket_id = UCLAMP_BUCKETS - 1;
994 * Since both min and max clamps are max aggregated, find the
995 * top most bucket with tasks in.
997 for ( ; bucket_id >= 0; bucket_id--) {
998 if (!bucket[bucket_id].tasks)
1000 return bucket[bucket_id].value;
1003 /* No tasks -- default clamp values */
1004 return uclamp_idle_value(rq, clamp_id, clamp_value);
1007 static void __uclamp_update_util_min_rt_default(struct task_struct *p)
1009 unsigned int default_util_min;
1010 struct uclamp_se *uc_se;
1012 lockdep_assert_held(&p->pi_lock);
1014 uc_se = &p->uclamp_req[UCLAMP_MIN];
1016 /* Only sync if user didn't override the default */
1017 if (uc_se->user_defined)
1020 default_util_min = sysctl_sched_uclamp_util_min_rt_default;
1021 uclamp_se_set(uc_se, default_util_min, false);
1024 static void uclamp_update_util_min_rt_default(struct task_struct *p)
1032 /* Protect updates to p->uclamp_* */
1033 rq = task_rq_lock(p, &rf);
1034 __uclamp_update_util_min_rt_default(p);
1035 task_rq_unlock(rq, p, &rf);
1038 static void uclamp_sync_util_min_rt_default(void)
1040 struct task_struct *g, *p;
1043 * copy_process() sysctl_uclamp
1044 * uclamp_min_rt = X;
1045 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1046 * // link thread smp_mb__after_spinlock()
1047 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1048 * sched_post_fork() for_each_process_thread()
1049 * __uclamp_sync_rt() __uclamp_sync_rt()
1051 * Ensures that either sched_post_fork() will observe the new
1052 * uclamp_min_rt or for_each_process_thread() will observe the new
1055 read_lock(&tasklist_lock);
1056 smp_mb__after_spinlock();
1057 read_unlock(&tasklist_lock);
1060 for_each_process_thread(g, p)
1061 uclamp_update_util_min_rt_default(p);
1065 static inline struct uclamp_se
1066 uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
1068 struct uclamp_se uc_req = p->uclamp_req[clamp_id];
1069 #ifdef CONFIG_UCLAMP_TASK_GROUP
1070 struct uclamp_se uc_max;
1073 * Tasks in autogroups or root task group will be
1074 * restricted by system defaults.
1076 if (task_group_is_autogroup(task_group(p)))
1078 if (task_group(p) == &root_task_group)
1081 uc_max = task_group(p)->uclamp[clamp_id];
1082 if (uc_req.value > uc_max.value || !uc_req.user_defined)
1090 * The effective clamp bucket index of a task depends on, by increasing
1092 * - the task specific clamp value, when explicitly requested from userspace
1093 * - the task group effective clamp value, for tasks not either in the root
1094 * group or in an autogroup
1095 * - the system default clamp value, defined by the sysadmin
1097 static inline struct uclamp_se
1098 uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
1100 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
1101 struct uclamp_se uc_max = uclamp_default[clamp_id];
1103 /* System default restrictions always apply */
1104 if (unlikely(uc_req.value > uc_max.value))
1110 unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
1112 struct uclamp_se uc_eff;
1114 /* Task currently refcounted: use back-annotated (effective) value */
1115 if (p->uclamp[clamp_id].active)
1116 return (unsigned long)p->uclamp[clamp_id].value;
1118 uc_eff = uclamp_eff_get(p, clamp_id);
1120 return (unsigned long)uc_eff.value;
1124 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1125 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1126 * updates the rq's clamp value if required.
1128 * Tasks can have a task-specific value requested from user-space, track
1129 * within each bucket the maximum value for tasks refcounted in it.
1130 * This "local max aggregation" allows to track the exact "requested" value
1131 * for each bucket when all its RUNNABLE tasks require the same clamp.
1133 static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
1134 enum uclamp_id clamp_id)
1136 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1137 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1138 struct uclamp_bucket *bucket;
1140 lockdep_assert_held(&rq->lock);
1142 /* Update task effective clamp */
1143 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
1145 bucket = &uc_rq->bucket[uc_se->bucket_id];
1147 uc_se->active = true;
1149 uclamp_idle_reset(rq, clamp_id, uc_se->value);
1152 * Local max aggregation: rq buckets always track the max
1153 * "requested" clamp value of its RUNNABLE tasks.
1155 if (bucket->tasks == 1 || uc_se->value > bucket->value)
1156 bucket->value = uc_se->value;
1158 if (uc_se->value > READ_ONCE(uc_rq->value))
1159 WRITE_ONCE(uc_rq->value, uc_se->value);
1163 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1164 * is released. If this is the last task reference counting the rq's max
1165 * active clamp value, then the rq's clamp value is updated.
1167 * Both refcounted tasks and rq's cached clamp values are expected to be
1168 * always valid. If it's detected they are not, as defensive programming,
1169 * enforce the expected state and warn.
1171 static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
1172 enum uclamp_id clamp_id)
1174 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1175 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1176 struct uclamp_bucket *bucket;
1177 unsigned int bkt_clamp;
1178 unsigned int rq_clamp;
1180 lockdep_assert_held(&rq->lock);
1183 * If sched_uclamp_used was enabled after task @p was enqueued,
1184 * we could end up with unbalanced call to uclamp_rq_dec_id().
1186 * In this case the uc_se->active flag should be false since no uclamp
1187 * accounting was performed at enqueue time and we can just return
1190 * Need to be careful of the following enqeueue/dequeue ordering
1194 * // sched_uclamp_used gets enabled
1197 * // Must not decrement bukcet->tasks here
1200 * where we could end up with stale data in uc_se and
1201 * bucket[uc_se->bucket_id].
1203 * The following check here eliminates the possibility of such race.
1205 if (unlikely(!uc_se->active))
1208 bucket = &uc_rq->bucket[uc_se->bucket_id];
1210 SCHED_WARN_ON(!bucket->tasks);
1211 if (likely(bucket->tasks))
1214 uc_se->active = false;
1217 * Keep "local max aggregation" simple and accept to (possibly)
1218 * overboost some RUNNABLE tasks in the same bucket.
1219 * The rq clamp bucket value is reset to its base value whenever
1220 * there are no more RUNNABLE tasks refcounting it.
1222 if (likely(bucket->tasks))
1225 rq_clamp = READ_ONCE(uc_rq->value);
1227 * Defensive programming: this should never happen. If it happens,
1228 * e.g. due to future modification, warn and fixup the expected value.
1230 SCHED_WARN_ON(bucket->value > rq_clamp);
1231 if (bucket->value >= rq_clamp) {
1232 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
1233 WRITE_ONCE(uc_rq->value, bkt_clamp);
1237 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
1239 enum uclamp_id clamp_id;
1242 * Avoid any overhead until uclamp is actually used by the userspace.
1244 * The condition is constructed such that a NOP is generated when
1245 * sched_uclamp_used is disabled.
1247 if (!static_branch_unlikely(&sched_uclamp_used))
1250 if (unlikely(!p->sched_class->uclamp_enabled))
1253 for_each_clamp_id(clamp_id)
1254 uclamp_rq_inc_id(rq, p, clamp_id);
1256 /* Reset clamp idle holding when there is one RUNNABLE task */
1257 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
1258 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1261 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
1263 enum uclamp_id clamp_id;
1266 * Avoid any overhead until uclamp is actually used by the userspace.
1268 * The condition is constructed such that a NOP is generated when
1269 * sched_uclamp_used is disabled.
1271 if (!static_branch_unlikely(&sched_uclamp_used))
1274 if (unlikely(!p->sched_class->uclamp_enabled))
1277 for_each_clamp_id(clamp_id)
1278 uclamp_rq_dec_id(rq, p, clamp_id);
1282 uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
1288 * Lock the task and the rq where the task is (or was) queued.
1290 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1291 * price to pay to safely serialize util_{min,max} updates with
1292 * enqueues, dequeues and migration operations.
1293 * This is the same locking schema used by __set_cpus_allowed_ptr().
1295 rq = task_rq_lock(p, &rf);
1298 * Setting the clamp bucket is serialized by task_rq_lock().
1299 * If the task is not yet RUNNABLE and its task_struct is not
1300 * affecting a valid clamp bucket, the next time it's enqueued,
1301 * it will already see the updated clamp bucket value.
1303 if (p->uclamp[clamp_id].active) {
1304 uclamp_rq_dec_id(rq, p, clamp_id);
1305 uclamp_rq_inc_id(rq, p, clamp_id);
1308 task_rq_unlock(rq, p, &rf);
1311 #ifdef CONFIG_UCLAMP_TASK_GROUP
1313 uclamp_update_active_tasks(struct cgroup_subsys_state *css,
1314 unsigned int clamps)
1316 enum uclamp_id clamp_id;
1317 struct css_task_iter it;
1318 struct task_struct *p;
1320 css_task_iter_start(css, 0, &it);
1321 while ((p = css_task_iter_next(&it))) {
1322 for_each_clamp_id(clamp_id) {
1323 if ((0x1 << clamp_id) & clamps)
1324 uclamp_update_active(p, clamp_id);
1327 css_task_iter_end(&it);
1330 static void cpu_util_update_eff(struct cgroup_subsys_state *css);
1331 static void uclamp_update_root_tg(void)
1333 struct task_group *tg = &root_task_group;
1335 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
1336 sysctl_sched_uclamp_util_min, false);
1337 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
1338 sysctl_sched_uclamp_util_max, false);
1341 cpu_util_update_eff(&root_task_group.css);
1345 static void uclamp_update_root_tg(void) { }
1348 int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
1349 void *buffer, size_t *lenp, loff_t *ppos)
1351 bool update_root_tg = false;
1352 int old_min, old_max, old_min_rt;
1355 mutex_lock(&uclamp_mutex);
1356 old_min = sysctl_sched_uclamp_util_min;
1357 old_max = sysctl_sched_uclamp_util_max;
1358 old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
1360 result = proc_dointvec(table, write, buffer, lenp, ppos);
1366 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
1367 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
1368 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
1374 if (old_min != sysctl_sched_uclamp_util_min) {
1375 uclamp_se_set(&uclamp_default[UCLAMP_MIN],
1376 sysctl_sched_uclamp_util_min, false);
1377 update_root_tg = true;
1379 if (old_max != sysctl_sched_uclamp_util_max) {
1380 uclamp_se_set(&uclamp_default[UCLAMP_MAX],
1381 sysctl_sched_uclamp_util_max, false);
1382 update_root_tg = true;
1385 if (update_root_tg) {
1386 static_branch_enable(&sched_uclamp_used);
1387 uclamp_update_root_tg();
1390 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
1391 static_branch_enable(&sched_uclamp_used);
1392 uclamp_sync_util_min_rt_default();
1396 * We update all RUNNABLE tasks only when task groups are in use.
1397 * Otherwise, keep it simple and do just a lazy update at each next
1398 * task enqueue time.
1404 sysctl_sched_uclamp_util_min = old_min;
1405 sysctl_sched_uclamp_util_max = old_max;
1406 sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
1408 mutex_unlock(&uclamp_mutex);
1413 static int uclamp_validate(struct task_struct *p,
1414 const struct sched_attr *attr)
1416 unsigned int lower_bound = p->uclamp_req[UCLAMP_MIN].value;
1417 unsigned int upper_bound = p->uclamp_req[UCLAMP_MAX].value;
1419 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
1420 lower_bound = attr->sched_util_min;
1421 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX)
1422 upper_bound = attr->sched_util_max;
1424 if (lower_bound > upper_bound)
1426 if (upper_bound > SCHED_CAPACITY_SCALE)
1430 * We have valid uclamp attributes; make sure uclamp is enabled.
1432 * We need to do that here, because enabling static branches is a
1433 * blocking operation which obviously cannot be done while holding
1436 static_branch_enable(&sched_uclamp_used);
1441 static void __setscheduler_uclamp(struct task_struct *p,
1442 const struct sched_attr *attr)
1444 enum uclamp_id clamp_id;
1447 * On scheduling class change, reset to default clamps for tasks
1448 * without a task-specific value.
1450 for_each_clamp_id(clamp_id) {
1451 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
1453 /* Keep using defined clamps across class changes */
1454 if (uc_se->user_defined)
1458 * RT by default have a 100% boost value that could be modified
1461 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
1462 __uclamp_update_util_min_rt_default(p);
1464 uclamp_se_set(uc_se, uclamp_none(clamp_id), false);
1468 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
1471 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
1472 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
1473 attr->sched_util_min, true);
1476 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
1477 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
1478 attr->sched_util_max, true);
1482 static void uclamp_fork(struct task_struct *p)
1484 enum uclamp_id clamp_id;
1487 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
1488 * as the task is still at its early fork stages.
1490 for_each_clamp_id(clamp_id)
1491 p->uclamp[clamp_id].active = false;
1493 if (likely(!p->sched_reset_on_fork))
1496 for_each_clamp_id(clamp_id) {
1497 uclamp_se_set(&p->uclamp_req[clamp_id],
1498 uclamp_none(clamp_id), false);
1502 static void uclamp_post_fork(struct task_struct *p)
1504 uclamp_update_util_min_rt_default(p);
1507 static void __init init_uclamp_rq(struct rq *rq)
1509 enum uclamp_id clamp_id;
1510 struct uclamp_rq *uc_rq = rq->uclamp;
1512 for_each_clamp_id(clamp_id) {
1513 uc_rq[clamp_id] = (struct uclamp_rq) {
1514 .value = uclamp_none(clamp_id)
1518 rq->uclamp_flags = 0;
1521 static void __init init_uclamp(void)
1523 struct uclamp_se uc_max = {};
1524 enum uclamp_id clamp_id;
1527 for_each_possible_cpu(cpu)
1528 init_uclamp_rq(cpu_rq(cpu));
1530 for_each_clamp_id(clamp_id) {
1531 uclamp_se_set(&init_task.uclamp_req[clamp_id],
1532 uclamp_none(clamp_id), false);
1535 /* System defaults allow max clamp values for both indexes */
1536 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
1537 for_each_clamp_id(clamp_id) {
1538 uclamp_default[clamp_id] = uc_max;
1539 #ifdef CONFIG_UCLAMP_TASK_GROUP
1540 root_task_group.uclamp_req[clamp_id] = uc_max;
1541 root_task_group.uclamp[clamp_id] = uc_max;
1546 #else /* CONFIG_UCLAMP_TASK */
1547 static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
1548 static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
1549 static inline int uclamp_validate(struct task_struct *p,
1550 const struct sched_attr *attr)
1554 static void __setscheduler_uclamp(struct task_struct *p,
1555 const struct sched_attr *attr) { }
1556 static inline void uclamp_fork(struct task_struct *p) { }
1557 static inline void uclamp_post_fork(struct task_struct *p) { }
1558 static inline void init_uclamp(void) { }
1559 #endif /* CONFIG_UCLAMP_TASK */
1561 static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
1563 if (!(flags & ENQUEUE_NOCLOCK))
1564 update_rq_clock(rq);
1566 if (!(flags & ENQUEUE_RESTORE)) {
1567 sched_info_queued(rq, p);
1568 psi_enqueue(p, flags & ENQUEUE_WAKEUP);
1571 uclamp_rq_inc(rq, p);
1572 p->sched_class->enqueue_task(rq, p, flags);
1575 static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
1577 if (!(flags & DEQUEUE_NOCLOCK))
1578 update_rq_clock(rq);
1580 if (!(flags & DEQUEUE_SAVE)) {
1581 sched_info_dequeued(rq, p);
1582 psi_dequeue(p, flags & DEQUEUE_SLEEP);
1585 uclamp_rq_dec(rq, p);
1586 p->sched_class->dequeue_task(rq, p, flags);
1589 void activate_task(struct rq *rq, struct task_struct *p, int flags)
1591 enqueue_task(rq, p, flags);
1593 p->on_rq = TASK_ON_RQ_QUEUED;
1596 void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
1598 p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
1600 dequeue_task(rq, p, flags);
1604 * __normal_prio - return the priority that is based on the static prio
1606 static inline int __normal_prio(struct task_struct *p)
1608 return p->static_prio;
1612 * Calculate the expected normal priority: i.e. priority
1613 * without taking RT-inheritance into account. Might be
1614 * boosted by interactivity modifiers. Changes upon fork,
1615 * setprio syscalls, and whenever the interactivity
1616 * estimator recalculates.
1618 static inline int normal_prio(struct task_struct *p)
1622 if (task_has_dl_policy(p))
1623 prio = MAX_DL_PRIO-1;
1624 else if (task_has_rt_policy(p))
1625 prio = MAX_RT_PRIO-1 - p->rt_priority;
1627 prio = __normal_prio(p);
1632 * Calculate the current priority, i.e. the priority
1633 * taken into account by the scheduler. This value might
1634 * be boosted by RT tasks, or might be boosted by
1635 * interactivity modifiers. Will be RT if the task got
1636 * RT-boosted. If not then it returns p->normal_prio.
1638 static int effective_prio(struct task_struct *p)
1640 p->normal_prio = normal_prio(p);
1642 * If we are RT tasks or we were boosted to RT priority,
1643 * keep the priority unchanged. Otherwise, update priority
1644 * to the normal priority:
1646 if (!rt_prio(p->prio))
1647 return p->normal_prio;
1652 * task_curr - is this task currently executing on a CPU?
1653 * @p: the task in question.
1655 * Return: 1 if the task is currently executing. 0 otherwise.
1657 inline int task_curr(const struct task_struct *p)
1659 return cpu_curr(task_cpu(p)) == p;
1663 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
1664 * use the balance_callback list if you want balancing.
1666 * this means any call to check_class_changed() must be followed by a call to
1667 * balance_callback().
1669 static inline void check_class_changed(struct rq *rq, struct task_struct *p,
1670 const struct sched_class *prev_class,
1673 if (prev_class != p->sched_class) {
1674 if (prev_class->switched_from)
1675 prev_class->switched_from(rq, p);
1677 p->sched_class->switched_to(rq, p);
1678 } else if (oldprio != p->prio || dl_task(p))
1679 p->sched_class->prio_changed(rq, p, oldprio);
1682 void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
1684 if (p->sched_class == rq->curr->sched_class)
1685 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
1686 else if (p->sched_class > rq->curr->sched_class)
1690 * A queue event has occurred, and we're going to schedule. In
1691 * this case, we can save a useless back to back clock update.
1693 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
1694 rq_clock_skip_update(rq);
1700 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
1701 * __set_cpus_allowed_ptr() and select_fallback_rq().
1703 static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
1705 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
1708 if (is_per_cpu_kthread(p))
1709 return cpu_online(cpu);
1711 return cpu_active(cpu);
1715 * This is how migration works:
1717 * 1) we invoke migration_cpu_stop() on the target CPU using
1719 * 2) stopper starts to run (implicitly forcing the migrated thread
1721 * 3) it checks whether the migrated task is still in the wrong runqueue.
1722 * 4) if it's in the wrong runqueue then the migration thread removes
1723 * it and puts it into the right queue.
1724 * 5) stopper completes and stop_one_cpu() returns and the migration
1729 * move_queued_task - move a queued task to new rq.
1731 * Returns (locked) new rq. Old rq's lock is released.
1733 static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
1734 struct task_struct *p, int new_cpu)
1736 lockdep_assert_held(&rq->lock);
1738 deactivate_task(rq, p, DEQUEUE_NOCLOCK);
1739 set_task_cpu(p, new_cpu);
1742 rq = cpu_rq(new_cpu);
1745 BUG_ON(task_cpu(p) != new_cpu);
1746 activate_task(rq, p, 0);
1747 check_preempt_curr(rq, p, 0);
1752 struct migration_arg {
1753 struct task_struct *task;
1758 * Move (not current) task off this CPU, onto the destination CPU. We're doing
1759 * this because either it can't run here any more (set_cpus_allowed()
1760 * away from this CPU, or CPU going down), or because we're
1761 * attempting to rebalance this task on exec (sched_exec).
1763 * So we race with normal scheduler movements, but that's OK, as long
1764 * as the task is no longer on this CPU.
1766 static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
1767 struct task_struct *p, int dest_cpu)
1769 /* Affinity changed (again). */
1770 if (!is_cpu_allowed(p, dest_cpu))
1773 update_rq_clock(rq);
1774 rq = move_queued_task(rq, rf, p, dest_cpu);
1780 * migration_cpu_stop - this will be executed by a highprio stopper thread
1781 * and performs thread migration by bumping thread off CPU then
1782 * 'pushing' onto another runqueue.
1784 static int migration_cpu_stop(void *data)
1786 struct migration_arg *arg = data;
1787 struct task_struct *p = arg->task;
1788 struct rq *rq = this_rq();
1792 * The original target CPU might have gone down and we might
1793 * be on another CPU but it doesn't matter.
1795 local_irq_disable();
1797 * We need to explicitly wake pending tasks before running
1798 * __migrate_task() such that we will not miss enforcing cpus_ptr
1799 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
1801 flush_smp_call_function_from_idle();
1803 raw_spin_lock(&p->pi_lock);
1806 * If task_rq(p) != rq, it cannot be migrated here, because we're
1807 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1808 * we're holding p->pi_lock.
1810 if (task_rq(p) == rq) {
1811 if (task_on_rq_queued(p))
1812 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
1814 p->wake_cpu = arg->dest_cpu;
1817 raw_spin_unlock(&p->pi_lock);
1824 * sched_class::set_cpus_allowed must do the below, but is not required to
1825 * actually call this function.
1827 void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1829 cpumask_copy(&p->cpus_mask, new_mask);
1830 p->nr_cpus_allowed = cpumask_weight(new_mask);
1833 void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1835 struct rq *rq = task_rq(p);
1836 bool queued, running;
1838 lockdep_assert_held(&p->pi_lock);
1840 queued = task_on_rq_queued(p);
1841 running = task_current(rq, p);
1845 * Because __kthread_bind() calls this on blocked tasks without
1848 lockdep_assert_held(&rq->lock);
1849 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
1852 put_prev_task(rq, p);
1854 p->sched_class->set_cpus_allowed(p, new_mask);
1857 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
1859 set_next_task(rq, p);
1863 * Change a given task's CPU affinity. Migrate the thread to a
1864 * proper CPU and schedule it away if the CPU it's executing on
1865 * is removed from the allowed bitmask.
1867 * NOTE: the caller must have a valid reference to the task, the
1868 * task must not exit() & deallocate itself prematurely. The
1869 * call is not atomic; no spinlocks may be held.
1871 static int __set_cpus_allowed_ptr(struct task_struct *p,
1872 const struct cpumask *new_mask, bool check)
1874 const struct cpumask *cpu_valid_mask = cpu_active_mask;
1875 unsigned int dest_cpu;
1880 rq = task_rq_lock(p, &rf);
1881 update_rq_clock(rq);
1883 if (p->flags & PF_KTHREAD) {
1885 * Kernel threads are allowed on online && !active CPUs
1887 cpu_valid_mask = cpu_online_mask;
1891 * Must re-check here, to close a race against __kthread_bind(),
1892 * sched_setaffinity() is not guaranteed to observe the flag.
1894 if (check && (p->flags & PF_NO_SETAFFINITY)) {
1899 if (cpumask_equal(&p->cpus_mask, new_mask))
1903 * Picking a ~random cpu helps in cases where we are changing affinity
1904 * for groups of tasks (ie. cpuset), so that load balancing is not
1905 * immediately required to distribute the tasks within their new mask.
1907 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
1908 if (dest_cpu >= nr_cpu_ids) {
1913 do_set_cpus_allowed(p, new_mask);
1915 if (p->flags & PF_KTHREAD) {
1917 * For kernel threads that do indeed end up on online &&
1918 * !active we want to ensure they are strict per-CPU threads.
1920 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1921 !cpumask_intersects(new_mask, cpu_active_mask) &&
1922 p->nr_cpus_allowed != 1);
1925 /* Can the task run on the task's current CPU? If so, we're done */
1926 if (cpumask_test_cpu(task_cpu(p), new_mask))
1929 if (task_running(rq, p) || p->state == TASK_WAKING) {
1930 struct migration_arg arg = { p, dest_cpu };
1931 /* Need help from migration thread: drop lock and wait. */
1932 task_rq_unlock(rq, p, &rf);
1933 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1935 } else if (task_on_rq_queued(p)) {
1937 * OK, since we're going to drop the lock immediately
1938 * afterwards anyway.
1940 rq = move_queued_task(rq, &rf, p, dest_cpu);
1943 task_rq_unlock(rq, p, &rf);
1948 int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1950 return __set_cpus_allowed_ptr(p, new_mask, false);
1952 EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1954 void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1956 #ifdef CONFIG_SCHED_DEBUG
1958 * We should never call set_task_cpu() on a blocked task,
1959 * ttwu() will sort out the placement.
1961 WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1965 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1966 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1967 * time relying on p->on_rq.
1969 WARN_ON_ONCE(p->state == TASK_RUNNING &&
1970 p->sched_class == &fair_sched_class &&
1971 (p->on_rq && !task_on_rq_migrating(p)));
1973 #ifdef CONFIG_LOCKDEP
1975 * The caller should hold either p->pi_lock or rq->lock, when changing
1976 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1978 * sched_move_task() holds both and thus holding either pins the cgroup,
1981 * Furthermore, all task_rq users should acquire both locks, see
1984 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1985 lockdep_is_held(&task_rq(p)->lock)));
1988 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
1990 WARN_ON_ONCE(!cpu_online(new_cpu));
1993 trace_sched_migrate_task(p, new_cpu);
1995 if (task_cpu(p) != new_cpu) {
1996 if (p->sched_class->migrate_task_rq)
1997 p->sched_class->migrate_task_rq(p, new_cpu);
1998 p->se.nr_migrations++;
2000 perf_event_task_migrate(p);
2003 __set_task_cpu(p, new_cpu);
2006 #ifdef CONFIG_NUMA_BALANCING
2007 static void __migrate_swap_task(struct task_struct *p, int cpu)
2009 if (task_on_rq_queued(p)) {
2010 struct rq *src_rq, *dst_rq;
2011 struct rq_flags srf, drf;
2013 src_rq = task_rq(p);
2014 dst_rq = cpu_rq(cpu);
2016 rq_pin_lock(src_rq, &srf);
2017 rq_pin_lock(dst_rq, &drf);
2019 deactivate_task(src_rq, p, 0);
2020 set_task_cpu(p, cpu);
2021 activate_task(dst_rq, p, 0);
2022 check_preempt_curr(dst_rq, p, 0);
2024 rq_unpin_lock(dst_rq, &drf);
2025 rq_unpin_lock(src_rq, &srf);
2029 * Task isn't running anymore; make it appear like we migrated
2030 * it before it went to sleep. This means on wakeup we make the
2031 * previous CPU our target instead of where it really is.
2037 struct migration_swap_arg {
2038 struct task_struct *src_task, *dst_task;
2039 int src_cpu, dst_cpu;
2042 static int migrate_swap_stop(void *data)
2044 struct migration_swap_arg *arg = data;
2045 struct rq *src_rq, *dst_rq;
2048 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
2051 src_rq = cpu_rq(arg->src_cpu);
2052 dst_rq = cpu_rq(arg->dst_cpu);
2054 double_raw_lock(&arg->src_task->pi_lock,
2055 &arg->dst_task->pi_lock);
2056 double_rq_lock(src_rq, dst_rq);
2058 if (task_cpu(arg->dst_task) != arg->dst_cpu)
2061 if (task_cpu(arg->src_task) != arg->src_cpu)
2064 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
2067 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
2070 __migrate_swap_task(arg->src_task, arg->dst_cpu);
2071 __migrate_swap_task(arg->dst_task, arg->src_cpu);
2076 double_rq_unlock(src_rq, dst_rq);
2077 raw_spin_unlock(&arg->dst_task->pi_lock);
2078 raw_spin_unlock(&arg->src_task->pi_lock);
2084 * Cross migrate two tasks
2086 int migrate_swap(struct task_struct *cur, struct task_struct *p,
2087 int target_cpu, int curr_cpu)
2089 struct migration_swap_arg arg;
2092 arg = (struct migration_swap_arg){
2094 .src_cpu = curr_cpu,
2096 .dst_cpu = target_cpu,
2099 if (arg.src_cpu == arg.dst_cpu)
2103 * These three tests are all lockless; this is OK since all of them
2104 * will be re-checked with proper locks held further down the line.
2106 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
2109 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
2112 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
2115 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
2116 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
2121 #endif /* CONFIG_NUMA_BALANCING */
2124 * wait_task_inactive - wait for a thread to unschedule.
2126 * If @match_state is nonzero, it's the @p->state value just checked and
2127 * not expected to change. If it changes, i.e. @p might have woken up,
2128 * then return zero. When we succeed in waiting for @p to be off its CPU,
2129 * we return a positive number (its total switch count). If a second call
2130 * a short while later returns the same number, the caller can be sure that
2131 * @p has remained unscheduled the whole time.
2133 * The caller must ensure that the task *will* unschedule sometime soon,
2134 * else this function might spin for a *long* time. This function can't
2135 * be called with interrupts off, or it may introduce deadlock with
2136 * smp_call_function() if an IPI is sent by the same process we are
2137 * waiting to become inactive.
2139 unsigned long wait_task_inactive(struct task_struct *p, long match_state)
2141 int running, queued;
2148 * We do the initial early heuristics without holding
2149 * any task-queue locks at all. We'll only try to get
2150 * the runqueue lock when things look like they will
2156 * If the task is actively running on another CPU
2157 * still, just relax and busy-wait without holding
2160 * NOTE! Since we don't hold any locks, it's not
2161 * even sure that "rq" stays as the right runqueue!
2162 * But we don't care, since "task_running()" will
2163 * return false if the runqueue has changed and p
2164 * is actually now running somewhere else!
2166 while (task_running(rq, p)) {
2167 if (match_state && unlikely(p->state != match_state))
2173 * Ok, time to look more closely! We need the rq
2174 * lock now, to be *sure*. If we're wrong, we'll
2175 * just go back and repeat.
2177 rq = task_rq_lock(p, &rf);
2178 trace_sched_wait_task(p);
2179 running = task_running(rq, p);
2180 queued = task_on_rq_queued(p);
2182 if (!match_state || p->state == match_state)
2183 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
2184 task_rq_unlock(rq, p, &rf);
2187 * If it changed from the expected state, bail out now.
2189 if (unlikely(!ncsw))
2193 * Was it really running after all now that we
2194 * checked with the proper locks actually held?
2196 * Oops. Go back and try again..
2198 if (unlikely(running)) {
2204 * It's not enough that it's not actively running,
2205 * it must be off the runqueue _entirely_, and not
2208 * So if it was still runnable (but just not actively
2209 * running right now), it's preempted, and we should
2210 * yield - it could be a while.
2212 if (unlikely(queued)) {
2213 ktime_t to = NSEC_PER_SEC / HZ;
2215 set_current_state(TASK_UNINTERRUPTIBLE);
2216 schedule_hrtimeout(&to, HRTIMER_MODE_REL);
2221 * Ahh, all good. It wasn't running, and it wasn't
2222 * runnable, which means that it will never become
2223 * running in the future either. We're all done!
2232 * kick_process - kick a running thread to enter/exit the kernel
2233 * @p: the to-be-kicked thread
2235 * Cause a process which is running on another CPU to enter
2236 * kernel-mode, without any delay. (to get signals handled.)
2238 * NOTE: this function doesn't have to take the runqueue lock,
2239 * because all it wants to ensure is that the remote task enters
2240 * the kernel. If the IPI races and the task has been migrated
2241 * to another CPU then no harm is done and the purpose has been
2244 void kick_process(struct task_struct *p)
2250 if ((cpu != smp_processor_id()) && task_curr(p))
2251 smp_send_reschedule(cpu);
2254 EXPORT_SYMBOL_GPL(kick_process);
2257 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
2259 * A few notes on cpu_active vs cpu_online:
2261 * - cpu_active must be a subset of cpu_online
2263 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
2264 * see __set_cpus_allowed_ptr(). At this point the newly online
2265 * CPU isn't yet part of the sched domains, and balancing will not
2268 * - on CPU-down we clear cpu_active() to mask the sched domains and
2269 * avoid the load balancer to place new tasks on the to be removed
2270 * CPU. Existing tasks will remain running there and will be taken
2273 * This means that fallback selection must not select !active CPUs.
2274 * And can assume that any active CPU must be online. Conversely
2275 * select_task_rq() below may allow selection of !active CPUs in order
2276 * to satisfy the above rules.
2278 static int select_fallback_rq(int cpu, struct task_struct *p)
2280 int nid = cpu_to_node(cpu);
2281 const struct cpumask *nodemask = NULL;
2282 enum { cpuset, possible, fail } state = cpuset;
2286 * If the node that the CPU is on has been offlined, cpu_to_node()
2287 * will return -1. There is no CPU on the node, and we should
2288 * select the CPU on the other node.
2291 nodemask = cpumask_of_node(nid);
2293 /* Look for allowed, online CPU in same node. */
2294 for_each_cpu(dest_cpu, nodemask) {
2295 if (!cpu_active(dest_cpu))
2297 if (cpumask_test_cpu(dest_cpu, p->cpus_ptr))
2303 /* Any allowed, online CPU? */
2304 for_each_cpu(dest_cpu, p->cpus_ptr) {
2305 if (!is_cpu_allowed(p, dest_cpu))
2311 /* No more Mr. Nice Guy. */
2314 if (IS_ENABLED(CONFIG_CPUSETS)) {
2315 cpuset_cpus_allowed_fallback(p);
2321 do_set_cpus_allowed(p, cpu_possible_mask);
2332 if (state != cpuset) {
2334 * Don't tell them about moving exiting tasks or
2335 * kernel threads (both mm NULL), since they never
2338 if (p->mm && printk_ratelimit()) {
2339 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
2340 task_pid_nr(p), p->comm, cpu);
2348 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
2351 int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
2353 lockdep_assert_held(&p->pi_lock);
2355 if (p->nr_cpus_allowed > 1)
2356 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
2358 cpu = cpumask_any(p->cpus_ptr);
2361 * In order not to call set_task_cpu() on a blocking task we need
2362 * to rely on ttwu() to place the task on a valid ->cpus_ptr
2365 * Since this is common to all placement strategies, this lives here.
2367 * [ this allows ->select_task() to simply return task_cpu(p) and
2368 * not worry about this generic constraint ]
2370 if (unlikely(!is_cpu_allowed(p, cpu)))
2371 cpu = select_fallback_rq(task_cpu(p), p);
2376 void sched_set_stop_task(int cpu, struct task_struct *stop)
2378 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
2379 struct task_struct *old_stop = cpu_rq(cpu)->stop;
2383 * Make it appear like a SCHED_FIFO task, its something
2384 * userspace knows about and won't get confused about.
2386 * Also, it will make PI more or less work without too
2387 * much confusion -- but then, stop work should not
2388 * rely on PI working anyway.
2390 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
2392 stop->sched_class = &stop_sched_class;
2395 cpu_rq(cpu)->stop = stop;
2399 * Reset it back to a normal scheduling class so that
2400 * it can die in pieces.
2402 old_stop->sched_class = &rt_sched_class;
2408 static inline int __set_cpus_allowed_ptr(struct task_struct *p,
2409 const struct cpumask *new_mask, bool check)
2411 return set_cpus_allowed_ptr(p, new_mask);
2414 #endif /* CONFIG_SMP */
2417 ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
2421 if (!schedstat_enabled())
2427 if (cpu == rq->cpu) {
2428 __schedstat_inc(rq->ttwu_local);
2429 __schedstat_inc(p->se.statistics.nr_wakeups_local);
2431 struct sched_domain *sd;
2433 __schedstat_inc(p->se.statistics.nr_wakeups_remote);
2435 for_each_domain(rq->cpu, sd) {
2436 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
2437 __schedstat_inc(sd->ttwu_wake_remote);
2444 if (wake_flags & WF_MIGRATED)
2445 __schedstat_inc(p->se.statistics.nr_wakeups_migrate);
2446 #endif /* CONFIG_SMP */
2448 __schedstat_inc(rq->ttwu_count);
2449 __schedstat_inc(p->se.statistics.nr_wakeups);
2451 if (wake_flags & WF_SYNC)
2452 __schedstat_inc(p->se.statistics.nr_wakeups_sync);
2456 * Mark the task runnable and perform wakeup-preemption.
2458 static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
2459 struct rq_flags *rf)
2461 check_preempt_curr(rq, p, wake_flags);
2462 p->state = TASK_RUNNING;
2463 trace_sched_wakeup(p);
2466 if (p->sched_class->task_woken) {
2468 * Our task @p is fully woken up and running; so its safe to
2469 * drop the rq->lock, hereafter rq is only used for statistics.
2471 rq_unpin_lock(rq, rf);
2472 p->sched_class->task_woken(rq, p);
2473 rq_repin_lock(rq, rf);
2476 if (rq->idle_stamp) {
2477 u64 delta = rq_clock(rq) - rq->idle_stamp;
2478 u64 max = 2*rq->max_idle_balance_cost;
2480 update_avg(&rq->avg_idle, delta);
2482 if (rq->avg_idle > max)
2491 ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
2492 struct rq_flags *rf)
2494 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
2496 lockdep_assert_held(&rq->lock);
2498 if (p->sched_contributes_to_load)
2499 rq->nr_uninterruptible--;
2502 if (wake_flags & WF_MIGRATED)
2503 en_flags |= ENQUEUE_MIGRATED;
2506 activate_task(rq, p, en_flags);
2507 ttwu_do_wakeup(rq, p, wake_flags, rf);
2511 * Consider @p being inside a wait loop:
2514 * set_current_state(TASK_UNINTERRUPTIBLE);
2521 * __set_current_state(TASK_RUNNING);
2523 * between set_current_state() and schedule(). In this case @p is still
2524 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
2527 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
2528 * then schedule() must still happen and p->state can be changed to
2529 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
2530 * need to do a full wakeup with enqueue.
2532 * Returns: %true when the wakeup is done,
2535 static int ttwu_runnable(struct task_struct *p, int wake_flags)
2541 rq = __task_rq_lock(p, &rf);
2542 if (task_on_rq_queued(p)) {
2543 /* check_preempt_curr() may use rq clock */
2544 update_rq_clock(rq);
2545 ttwu_do_wakeup(rq, p, wake_flags, &rf);
2548 __task_rq_unlock(rq, &rf);
2554 void sched_ttwu_pending(void *arg)
2556 struct llist_node *llist = arg;
2557 struct rq *rq = this_rq();
2558 struct task_struct *p, *t;
2565 * rq::ttwu_pending racy indication of out-standing wakeups.
2566 * Races such that false-negatives are possible, since they
2567 * are shorter lived that false-positives would be.
2569 WRITE_ONCE(rq->ttwu_pending, 0);
2571 rq_lock_irqsave(rq, &rf);
2572 update_rq_clock(rq);
2574 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
2575 if (WARN_ON_ONCE(p->on_cpu))
2576 smp_cond_load_acquire(&p->on_cpu, !VAL);
2578 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
2579 set_task_cpu(p, cpu_of(rq));
2581 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
2584 rq_unlock_irqrestore(rq, &rf);
2587 void send_call_function_single_ipi(int cpu)
2589 struct rq *rq = cpu_rq(cpu);
2591 if (!set_nr_if_polling(rq->idle))
2592 arch_send_call_function_single_ipi(cpu);
2594 trace_sched_wake_idle_without_ipi(cpu);
2598 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
2599 * necessary. The wakee CPU on receipt of the IPI will queue the task
2600 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
2601 * of the wakeup instead of the waker.
2603 static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
2605 struct rq *rq = cpu_rq(cpu);
2607 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
2609 WRITE_ONCE(rq->ttwu_pending, 1);
2610 __smp_call_single_queue(cpu, &p->wake_entry.llist);
2613 void wake_up_if_idle(int cpu)
2615 struct rq *rq = cpu_rq(cpu);
2620 if (!is_idle_task(rcu_dereference(rq->curr)))
2623 if (set_nr_if_polling(rq->idle)) {
2624 trace_sched_wake_idle_without_ipi(cpu);
2626 rq_lock_irqsave(rq, &rf);
2627 if (is_idle_task(rq->curr))
2628 smp_send_reschedule(cpu);
2629 /* Else CPU is not idle, do nothing here: */
2630 rq_unlock_irqrestore(rq, &rf);
2637 bool cpus_share_cache(int this_cpu, int that_cpu)
2639 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
2642 static inline bool ttwu_queue_cond(int cpu, int wake_flags)
2645 * If the CPU does not share cache, then queue the task on the
2646 * remote rqs wakelist to avoid accessing remote data.
2648 if (!cpus_share_cache(smp_processor_id(), cpu))
2652 * If the task is descheduling and the only running task on the
2653 * CPU then use the wakelist to offload the task activation to
2654 * the soon-to-be-idle CPU as the current CPU is likely busy.
2655 * nr_running is checked to avoid unnecessary task stacking.
2657 if ((wake_flags & WF_ON_CPU) && cpu_rq(cpu)->nr_running <= 1)
2663 static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
2665 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(cpu, wake_flags)) {
2666 if (WARN_ON_ONCE(cpu == smp_processor_id()))
2669 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
2670 __ttwu_queue_wakelist(p, cpu, wake_flags);
2677 #else /* !CONFIG_SMP */
2679 static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
2684 #endif /* CONFIG_SMP */
2686 static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
2688 struct rq *rq = cpu_rq(cpu);
2691 if (ttwu_queue_wakelist(p, cpu, wake_flags))
2695 update_rq_clock(rq);
2696 ttwu_do_activate(rq, p, wake_flags, &rf);
2701 * Notes on Program-Order guarantees on SMP systems.
2705 * The basic program-order guarantee on SMP systems is that when a task [t]
2706 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
2707 * execution on its new CPU [c1].
2709 * For migration (of runnable tasks) this is provided by the following means:
2711 * A) UNLOCK of the rq(c0)->lock scheduling out task t
2712 * B) migration for t is required to synchronize *both* rq(c0)->lock and
2713 * rq(c1)->lock (if not at the same time, then in that order).
2714 * C) LOCK of the rq(c1)->lock scheduling in task
2716 * Release/acquire chaining guarantees that B happens after A and C after B.
2717 * Note: the CPU doing B need not be c0 or c1
2726 * UNLOCK rq(0)->lock
2728 * LOCK rq(0)->lock // orders against CPU0
2730 * UNLOCK rq(0)->lock
2734 * UNLOCK rq(1)->lock
2736 * LOCK rq(1)->lock // orders against CPU2
2739 * UNLOCK rq(1)->lock
2742 * BLOCKING -- aka. SLEEP + WAKEUP
2744 * For blocking we (obviously) need to provide the same guarantee as for
2745 * migration. However the means are completely different as there is no lock
2746 * chain to provide order. Instead we do:
2748 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
2749 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
2753 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
2755 * LOCK rq(0)->lock LOCK X->pi_lock
2758 * smp_store_release(X->on_cpu, 0);
2760 * smp_cond_load_acquire(&X->on_cpu, !VAL);
2766 * X->state = RUNNING
2767 * UNLOCK rq(2)->lock
2769 * LOCK rq(2)->lock // orders against CPU1
2772 * UNLOCK rq(2)->lock
2775 * UNLOCK rq(0)->lock
2778 * However, for wakeups there is a second guarantee we must provide, namely we
2779 * must ensure that CONDITION=1 done by the caller can not be reordered with
2780 * accesses to the task state; see try_to_wake_up() and set_current_state().
2784 * try_to_wake_up - wake up a thread
2785 * @p: the thread to be awakened
2786 * @state: the mask of task states that can be woken
2787 * @wake_flags: wake modifier flags (WF_*)
2789 * Conceptually does:
2791 * If (@state & @p->state) @p->state = TASK_RUNNING.
2793 * If the task was not queued/runnable, also place it back on a runqueue.
2795 * This function is atomic against schedule() which would dequeue the task.
2797 * It issues a full memory barrier before accessing @p->state, see the comment
2798 * with set_current_state().
2800 * Uses p->pi_lock to serialize against concurrent wake-ups.
2802 * Relies on p->pi_lock stabilizing:
2805 * - p->sched_task_group
2806 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
2808 * Tries really hard to only take one task_rq(p)->lock for performance.
2809 * Takes rq->lock in:
2810 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
2811 * - ttwu_queue() -- new rq, for enqueue of the task;
2812 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
2814 * As a consequence we race really badly with just about everything. See the
2815 * many memory barriers and their comments for details.
2817 * Return: %true if @p->state changes (an actual wakeup was done),
2821 try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
2823 unsigned long flags;
2824 int cpu, success = 0;
2829 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
2830 * == smp_processor_id()'. Together this means we can special
2831 * case the whole 'p->on_rq && ttwu_runnable()' case below
2832 * without taking any locks.
2835 * - we rely on Program-Order guarantees for all the ordering,
2836 * - we're serialized against set_special_state() by virtue of
2837 * it disabling IRQs (this allows not taking ->pi_lock).
2839 if (!(p->state & state))
2843 trace_sched_waking(p);
2844 p->state = TASK_RUNNING;
2845 trace_sched_wakeup(p);
2850 * If we are going to wake up a thread waiting for CONDITION we
2851 * need to ensure that CONDITION=1 done by the caller can not be
2852 * reordered with p->state check below. This pairs with smp_store_mb()
2853 * in set_current_state() that the waiting thread does.
2855 raw_spin_lock_irqsave(&p->pi_lock, flags);
2856 smp_mb__after_spinlock();
2857 if (!(p->state & state))
2860 trace_sched_waking(p);
2862 /* We're going to change ->state: */
2866 * Ensure we load p->on_rq _after_ p->state, otherwise it would
2867 * be possible to, falsely, observe p->on_rq == 0 and get stuck
2868 * in smp_cond_load_acquire() below.
2870 * sched_ttwu_pending() try_to_wake_up()
2871 * STORE p->on_rq = 1 LOAD p->state
2874 * __schedule() (switch to task 'p')
2875 * LOCK rq->lock smp_rmb();
2876 * smp_mb__after_spinlock();
2880 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
2882 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
2883 * __schedule(). See the comment for smp_mb__after_spinlock().
2885 * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
2888 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
2892 delayacct_blkio_end(p);
2893 atomic_dec(&task_rq(p)->nr_iowait);
2898 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2899 * possible to, falsely, observe p->on_cpu == 0.
2901 * One must be running (->on_cpu == 1) in order to remove oneself
2902 * from the runqueue.
2904 * __schedule() (switch to task 'p') try_to_wake_up()
2905 * STORE p->on_cpu = 1 LOAD p->on_rq
2908 * __schedule() (put 'p' to sleep)
2909 * LOCK rq->lock smp_rmb();
2910 * smp_mb__after_spinlock();
2911 * STORE p->on_rq = 0 LOAD p->on_cpu
2913 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
2914 * __schedule(). See the comment for smp_mb__after_spinlock().
2916 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
2917 * schedule()'s deactivate_task() has 'happened' and p will no longer
2918 * care about it's own p->state. See the comment in __schedule().
2920 smp_acquire__after_ctrl_dep();
2923 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
2924 * == 0), which means we need to do an enqueue, change p->state to
2925 * TASK_WAKING such that we can unlock p->pi_lock before doing the
2926 * enqueue, such as ttwu_queue_wakelist().
2928 p->state = TASK_WAKING;
2931 * If the owning (remote) CPU is still in the middle of schedule() with
2932 * this task as prev, considering queueing p on the remote CPUs wake_list
2933 * which potentially sends an IPI instead of spinning on p->on_cpu to
2934 * let the waker make forward progress. This is safe because IRQs are
2935 * disabled and the IPI will deliver after on_cpu is cleared.
2937 * Ensure we load task_cpu(p) after p->on_cpu:
2939 * set_task_cpu(p, cpu);
2940 * STORE p->cpu = @cpu
2941 * __schedule() (switch to task 'p')
2943 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
2944 * STORE p->on_cpu = 1 LOAD p->cpu
2946 * to ensure we observe the correct CPU on which the task is currently
2949 if (smp_load_acquire(&p->on_cpu) &&
2950 ttwu_queue_wakelist(p, task_cpu(p), wake_flags | WF_ON_CPU))
2954 * If the owning (remote) CPU is still in the middle of schedule() with
2955 * this task as prev, wait until its done referencing the task.
2957 * Pairs with the smp_store_release() in finish_task().
2959 * This ensures that tasks getting woken will be fully ordered against
2960 * their previous state and preserve Program Order.
2962 smp_cond_load_acquire(&p->on_cpu, !VAL);
2964 cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2965 if (task_cpu(p) != cpu) {
2966 wake_flags |= WF_MIGRATED;
2967 psi_ttwu_dequeue(p);
2968 set_task_cpu(p, cpu);
2972 #endif /* CONFIG_SMP */
2974 ttwu_queue(p, cpu, wake_flags);
2976 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2979 ttwu_stat(p, task_cpu(p), wake_flags);
2986 * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
2987 * @p: Process for which the function is to be invoked.
2988 * @func: Function to invoke.
2989 * @arg: Argument to function.
2991 * If the specified task can be quickly locked into a definite state
2992 * (either sleeping or on a given runqueue), arrange to keep it in that
2993 * state while invoking @func(@arg). This function can use ->on_rq and
2994 * task_curr() to work out what the state is, if required. Given that
2995 * @func can be invoked with a runqueue lock held, it had better be quite
2999 * @false if the task slipped out from under the locks.
3000 * @true if the task was locked onto a runqueue or is sleeping.
3001 * However, @func can override this by returning @false.
3003 bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
3009 lockdep_assert_irqs_enabled();
3010 raw_spin_lock_irq(&p->pi_lock);
3012 rq = __task_rq_lock(p, &rf);
3013 if (task_rq(p) == rq)
3022 smp_rmb(); // See smp_rmb() comment in try_to_wake_up().
3027 raw_spin_unlock_irq(&p->pi_lock);
3032 * wake_up_process - Wake up a specific process
3033 * @p: The process to be woken up.
3035 * Attempt to wake up the nominated process and move it to the set of runnable
3038 * Return: 1 if the process was woken up, 0 if it was already running.
3040 * This function executes a full memory barrier before accessing the task state.
3042 int wake_up_process(struct task_struct *p)
3044 return try_to_wake_up(p, TASK_NORMAL, 0);
3046 EXPORT_SYMBOL(wake_up_process);
3048 int wake_up_state(struct task_struct *p, unsigned int state)
3050 return try_to_wake_up(p, state, 0);
3054 * Perform scheduler related setup for a newly forked process p.
3055 * p is forked by current.
3057 * __sched_fork() is basic setup used by init_idle() too:
3059 static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
3064 p->se.exec_start = 0;
3065 p->se.sum_exec_runtime = 0;
3066 p->se.prev_sum_exec_runtime = 0;
3067 p->se.nr_migrations = 0;
3069 INIT_LIST_HEAD(&p->se.group_node);
3071 #ifdef CONFIG_FAIR_GROUP_SCHED
3072 p->se.cfs_rq = NULL;
3075 #ifdef CONFIG_SCHEDSTATS
3076 /* Even if schedstat is disabled, there should not be garbage */
3077 memset(&p->se.statistics, 0, sizeof(p->se.statistics));
3080 RB_CLEAR_NODE(&p->dl.rb_node);
3081 init_dl_task_timer(&p->dl);
3082 init_dl_inactive_task_timer(&p->dl);
3083 __dl_clear_params(p);
3085 INIT_LIST_HEAD(&p->rt.run_list);
3087 p->rt.time_slice = sched_rr_timeslice;
3091 #ifdef CONFIG_PREEMPT_NOTIFIERS
3092 INIT_HLIST_HEAD(&p->preempt_notifiers);
3095 #ifdef CONFIG_COMPACTION
3096 p->capture_control = NULL;
3098 init_numa_balancing(clone_flags, p);
3100 p->wake_entry.u_flags = CSD_TYPE_TTWU;
3104 DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
3106 #ifdef CONFIG_NUMA_BALANCING
3108 void set_numabalancing_state(bool enabled)
3111 static_branch_enable(&sched_numa_balancing);
3113 static_branch_disable(&sched_numa_balancing);
3116 #ifdef CONFIG_PROC_SYSCTL
3117 int sysctl_numa_balancing(struct ctl_table *table, int write,
3118 void *buffer, size_t *lenp, loff_t *ppos)
3122 int state = static_branch_likely(&sched_numa_balancing);
3124 if (write && !capable(CAP_SYS_ADMIN))
3129 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3133 set_numabalancing_state(state);
3139 #ifdef CONFIG_SCHEDSTATS
3141 DEFINE_STATIC_KEY_FALSE(sched_schedstats);
3142 static bool __initdata __sched_schedstats = false;
3144 static void set_schedstats(bool enabled)
3147 static_branch_enable(&sched_schedstats);
3149 static_branch_disable(&sched_schedstats);
3152 void force_schedstat_enabled(void)
3154 if (!schedstat_enabled()) {
3155 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
3156 static_branch_enable(&sched_schedstats);
3160 static int __init setup_schedstats(char *str)
3167 * This code is called before jump labels have been set up, so we can't
3168 * change the static branch directly just yet. Instead set a temporary
3169 * variable so init_schedstats() can do it later.
3171 if (!strcmp(str, "enable")) {
3172 __sched_schedstats = true;
3174 } else if (!strcmp(str, "disable")) {
3175 __sched_schedstats = false;
3180 pr_warn("Unable to parse schedstats=\n");
3184 __setup("schedstats=", setup_schedstats);
3186 static void __init init_schedstats(void)
3188 set_schedstats(__sched_schedstats);
3191 #ifdef CONFIG_PROC_SYSCTL
3192 int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
3193 size_t *lenp, loff_t *ppos)
3197 int state = static_branch_likely(&sched_schedstats);
3199 if (write && !capable(CAP_SYS_ADMIN))
3204 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
3208 set_schedstats(state);
3211 #endif /* CONFIG_PROC_SYSCTL */
3212 #else /* !CONFIG_SCHEDSTATS */
3213 static inline void init_schedstats(void) {}
3214 #endif /* CONFIG_SCHEDSTATS */
3217 * fork()/clone()-time setup:
3219 int sched_fork(unsigned long clone_flags, struct task_struct *p)
3221 unsigned long flags;
3223 __sched_fork(clone_flags, p);
3225 * We mark the process as NEW here. This guarantees that
3226 * nobody will actually run it, and a signal or other external
3227 * event cannot wake it up and insert it on the runqueue either.
3229 p->state = TASK_NEW;
3232 * Make sure we do not leak PI boosting priority to the child.
3234 p->prio = current->normal_prio;
3239 * Revert to default priority/policy on fork if requested.
3241 if (unlikely(p->sched_reset_on_fork)) {
3242 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3243 p->policy = SCHED_NORMAL;
3244 p->static_prio = NICE_TO_PRIO(0);
3246 } else if (PRIO_TO_NICE(p->static_prio) < 0)
3247 p->static_prio = NICE_TO_PRIO(0);
3249 p->prio = p->normal_prio = __normal_prio(p);
3250 set_load_weight(p, false);
3253 * We don't need the reset flag anymore after the fork. It has
3254 * fulfilled its duty:
3256 p->sched_reset_on_fork = 0;
3259 if (dl_prio(p->prio))
3261 else if (rt_prio(p->prio))
3262 p->sched_class = &rt_sched_class;
3264 p->sched_class = &fair_sched_class;
3266 init_entity_runnable_average(&p->se);
3269 * The child is not yet in the pid-hash so no cgroup attach races,
3270 * and the cgroup is pinned to this child due to cgroup_fork()
3271 * is ran before sched_fork().
3273 * Silence PROVE_RCU.
3275 raw_spin_lock_irqsave(&p->pi_lock, flags);
3278 * We're setting the CPU for the first time, we don't migrate,
3279 * so use __set_task_cpu().
3281 __set_task_cpu(p, smp_processor_id());
3282 if (p->sched_class->task_fork)
3283 p->sched_class->task_fork(p);
3284 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3286 #ifdef CONFIG_SCHED_INFO
3287 if (likely(sched_info_on()))
3288 memset(&p->sched_info, 0, sizeof(p->sched_info));
3290 #if defined(CONFIG_SMP)
3293 init_task_preempt_count(p);
3295 plist_node_init(&p->pushable_tasks, MAX_PRIO);
3296 RB_CLEAR_NODE(&p->pushable_dl_tasks);
3301 void sched_post_fork(struct task_struct *p)
3303 uclamp_post_fork(p);
3306 unsigned long to_ratio(u64 period, u64 runtime)
3308 if (runtime == RUNTIME_INF)
3312 * Doing this here saves a lot of checks in all
3313 * the calling paths, and returning zero seems
3314 * safe for them anyway.
3319 return div64_u64(runtime << BW_SHIFT, period);
3323 * wake_up_new_task - wake up a newly created task for the first time.
3325 * This function will do some initial scheduler statistics housekeeping
3326 * that must be done for every newly created context, then puts the task
3327 * on the runqueue and wakes it.
3329 void wake_up_new_task(struct task_struct *p)
3334 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
3335 p->state = TASK_RUNNING;
3338 * Fork balancing, do it here and not earlier because:
3339 * - cpus_ptr can change in the fork path
3340 * - any previously selected CPU might disappear through hotplug
3342 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
3343 * as we're not fully set-up yet.
3345 p->recent_used_cpu = task_cpu(p);
3347 __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
3349 rq = __task_rq_lock(p, &rf);
3350 update_rq_clock(rq);
3351 post_init_entity_util_avg(p);
3353 activate_task(rq, p, ENQUEUE_NOCLOCK);
3354 trace_sched_wakeup_new(p);
3355 check_preempt_curr(rq, p, WF_FORK);
3357 if (p->sched_class->task_woken) {
3359 * Nothing relies on rq->lock after this, so its fine to
3362 rq_unpin_lock(rq, &rf);
3363 p->sched_class->task_woken(rq, p);
3364 rq_repin_lock(rq, &rf);
3367 task_rq_unlock(rq, p, &rf);
3370 #ifdef CONFIG_PREEMPT_NOTIFIERS
3372 static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
3374 void preempt_notifier_inc(void)
3376 static_branch_inc(&preempt_notifier_key);
3378 EXPORT_SYMBOL_GPL(preempt_notifier_inc);
3380 void preempt_notifier_dec(void)
3382 static_branch_dec(&preempt_notifier_key);
3384 EXPORT_SYMBOL_GPL(preempt_notifier_dec);
3387 * preempt_notifier_register - tell me when current is being preempted & rescheduled
3388 * @notifier: notifier struct to register
3390 void preempt_notifier_register(struct preempt_notifier *notifier)
3392 if (!static_branch_unlikely(&preempt_notifier_key))
3393 WARN(1, "registering preempt_notifier while notifiers disabled\n");
3395 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
3397 EXPORT_SYMBOL_GPL(preempt_notifier_register);
3400 * preempt_notifier_unregister - no longer interested in preemption notifications
3401 * @notifier: notifier struct to unregister
3403 * This is *not* safe to call from within a preemption notifier.
3405 void preempt_notifier_unregister(struct preempt_notifier *notifier)
3407 hlist_del(¬ifier->link);
3409 EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
3411 static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
3413 struct preempt_notifier *notifier;
3415 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
3416 notifier->ops->sched_in(notifier, raw_smp_processor_id());
3419 static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
3421 if (static_branch_unlikely(&preempt_notifier_key))
3422 __fire_sched_in_preempt_notifiers(curr);
3426 __fire_sched_out_preempt_notifiers(struct task_struct *curr,
3427 struct task_struct *next)
3429 struct preempt_notifier *notifier;
3431 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
3432 notifier->ops->sched_out(notifier, next);
3435 static __always_inline void
3436 fire_sched_out_preempt_notifiers(struct task_struct *curr,
3437 struct task_struct *next)
3439 if (static_branch_unlikely(&preempt_notifier_key))
3440 __fire_sched_out_preempt_notifiers(curr, next);
3443 #else /* !CONFIG_PREEMPT_NOTIFIERS */
3445 static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
3450 fire_sched_out_preempt_notifiers(struct task_struct *curr,
3451 struct task_struct *next)
3455 #endif /* CONFIG_PREEMPT_NOTIFIERS */
3457 static inline void prepare_task(struct task_struct *next)
3461 * Claim the task as running, we do this before switching to it
3462 * such that any running task will have this set.
3464 * See the ttwu() WF_ON_CPU case and its ordering comment.
3466 WRITE_ONCE(next->on_cpu, 1);
3470 static inline void finish_task(struct task_struct *prev)
3474 * This must be the very last reference to @prev from this CPU. After
3475 * p->on_cpu is cleared, the task can be moved to a different CPU. We
3476 * must ensure this doesn't happen until the switch is completely
3479 * In particular, the load of prev->state in finish_task_switch() must
3480 * happen before this.
3482 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
3484 smp_store_release(&prev->on_cpu, 0);
3489 prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
3492 * Since the runqueue lock will be released by the next
3493 * task (which is an invalid locking op but in the case
3494 * of the scheduler it's an obvious special-case), so we
3495 * do an early lockdep release here:
3497 rq_unpin_lock(rq, rf);
3498 spin_release(&rq->lock.dep_map, _THIS_IP_);
3499 #ifdef CONFIG_DEBUG_SPINLOCK
3500 /* this is a valid case when another task releases the spinlock */
3501 rq->lock.owner = next;
3505 static inline void finish_lock_switch(struct rq *rq)
3508 * If we are tracking spinlock dependencies then we have to
3509 * fix up the runqueue lock - which gets 'carried over' from
3510 * prev into current:
3512 spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
3513 raw_spin_unlock_irq(&rq->lock);
3517 * NOP if the arch has not defined these:
3520 #ifndef prepare_arch_switch
3521 # define prepare_arch_switch(next) do { } while (0)
3524 #ifndef finish_arch_post_lock_switch
3525 # define finish_arch_post_lock_switch() do { } while (0)
3529 * prepare_task_switch - prepare to switch tasks
3530 * @rq: the runqueue preparing to switch
3531 * @prev: the current task that is being switched out
3532 * @next: the task we are going to switch to.
3534 * This is called with the rq lock held and interrupts off. It must
3535 * be paired with a subsequent finish_task_switch after the context
3538 * prepare_task_switch sets up locking and calls architecture specific
3542 prepare_task_switch(struct rq *rq, struct task_struct *prev,
3543 struct task_struct *next)
3545 kcov_prepare_switch(prev);
3546 sched_info_switch(rq, prev, next);
3547 perf_event_task_sched_out(prev, next);
3549 fire_sched_out_preempt_notifiers(prev, next);
3551 prepare_arch_switch(next);
3555 * finish_task_switch - clean up after a task-switch
3556 * @prev: the thread we just switched away from.
3558 * finish_task_switch must be called after the context switch, paired
3559 * with a prepare_task_switch call before the context switch.
3560 * finish_task_switch will reconcile locking set up by prepare_task_switch,
3561 * and do any other architecture-specific cleanup actions.
3563 * Note that we may have delayed dropping an mm in context_switch(). If
3564 * so, we finish that here outside of the runqueue lock. (Doing it
3565 * with the lock held can cause deadlocks; see schedule() for
3568 * The context switch have flipped the stack from under us and restored the
3569 * local variables which were saved when this task called schedule() in the
3570 * past. prev == current is still correct but we need to recalculate this_rq
3571 * because prev may have moved to another CPU.
3573 static struct rq *finish_task_switch(struct task_struct *prev)
3574 __releases(rq->lock)
3576 struct rq *rq = this_rq();
3577 struct mm_struct *mm = rq->prev_mm;
3581 * The previous task will have left us with a preempt_count of 2
3582 * because it left us after:
3585 * preempt_disable(); // 1
3587 * raw_spin_lock_irq(&rq->lock) // 2
3589 * Also, see FORK_PREEMPT_COUNT.
3591 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
3592 "corrupted preempt_count: %s/%d/0x%x\n",
3593 current->comm, current->pid, preempt_count()))
3594 preempt_count_set(FORK_PREEMPT_COUNT);
3599 * A task struct has one reference for the use as "current".
3600 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
3601 * schedule one last time. The schedule call will never return, and
3602 * the scheduled task must drop that reference.
3604 * We must observe prev->state before clearing prev->on_cpu (in
3605 * finish_task), otherwise a concurrent wakeup can get prev
3606 * running on another CPU and we could rave with its RUNNING -> DEAD
3607 * transition, resulting in a double drop.
3609 prev_state = prev->state;
3610 vtime_task_switch(prev);
3611 perf_event_task_sched_in(prev, current);
3613 finish_lock_switch(rq);
3614 finish_arch_post_lock_switch();
3615 kcov_finish_switch(current);
3617 fire_sched_in_preempt_notifiers(current);
3619 * When switching through a kernel thread, the loop in
3620 * membarrier_{private,global}_expedited() may have observed that
3621 * kernel thread and not issued an IPI. It is therefore possible to
3622 * schedule between user->kernel->user threads without passing though
3623 * switch_mm(). Membarrier requires a barrier after storing to
3624 * rq->curr, before returning to userspace, so provide them here:
3626 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
3627 * provided by mmdrop(),
3628 * - a sync_core for SYNC_CORE.
3631 membarrier_mm_sync_core_before_usermode(mm);
3634 if (unlikely(prev_state == TASK_DEAD)) {
3635 if (prev->sched_class->task_dead)
3636 prev->sched_class->task_dead(prev);
3639 * Remove function-return probe instances associated with this
3640 * task and put them back on the free list.
3642 kprobe_flush_task(prev);
3644 /* Task is done with its stack. */
3645 put_task_stack(prev);
3647 put_task_struct_rcu_user(prev);
3650 tick_nohz_task_switch();
3656 /* rq->lock is NOT held, but preemption is disabled */
3657 static void __balance_callback(struct rq *rq)
3659 struct callback_head *head, *next;
3660 void (*func)(struct rq *rq);
3661 unsigned long flags;
3663 raw_spin_lock_irqsave(&rq->lock, flags);
3664 head = rq->balance_callback;
3665 rq->balance_callback = NULL;
3667 func = (void (*)(struct rq *))head->func;
3674 raw_spin_unlock_irqrestore(&rq->lock, flags);
3677 static inline void balance_callback(struct rq *rq)
3679 if (unlikely(rq->balance_callback))
3680 __balance_callback(rq);
3685 static inline void balance_callback(struct rq *rq)
3692 * schedule_tail - first thing a freshly forked thread must call.
3693 * @prev: the thread we just switched away from.
3695 asmlinkage __visible void schedule_tail(struct task_struct *prev)
3696 __releases(rq->lock)
3701 * New tasks start with FORK_PREEMPT_COUNT, see there and
3702 * finish_task_switch() for details.
3704 * finish_task_switch() will drop rq->lock() and lower preempt_count
3705 * and the preempt_enable() will end up enabling preemption (on
3706 * PREEMPT_COUNT kernels).
3709 rq = finish_task_switch(prev);
3710 balance_callback(rq);
3713 if (current->set_child_tid)
3714 put_user(task_pid_vnr(current), current->set_child_tid);
3716 calculate_sigpending();
3720 * context_switch - switch to the new MM and the new thread's register state.
3722 static __always_inline struct rq *
3723 context_switch(struct rq *rq, struct task_struct *prev,
3724 struct task_struct *next, struct rq_flags *rf)
3726 prepare_task_switch(rq, prev, next);
3729 * For paravirt, this is coupled with an exit in switch_to to
3730 * combine the page table reload and the switch backend into
3733 arch_start_context_switch(prev);
3736 * kernel -> kernel lazy + transfer active
3737 * user -> kernel lazy + mmgrab() active
3739 * kernel -> user switch + mmdrop() active
3740 * user -> user switch
3742 if (!next->mm) { // to kernel
3743 enter_lazy_tlb(prev->active_mm, next);
3745 next->active_mm = prev->active_mm;
3746 if (prev->mm) // from user
3747 mmgrab(prev->active_mm);
3749 prev->active_mm = NULL;
3751 membarrier_switch_mm(rq, prev->active_mm, next->mm);
3753 * sys_membarrier() requires an smp_mb() between setting
3754 * rq->curr / membarrier_switch_mm() and returning to userspace.
3756 * The below provides this either through switch_mm(), or in
3757 * case 'prev->active_mm == next->mm' through
3758 * finish_task_switch()'s mmdrop().
3760 switch_mm_irqs_off(prev->active_mm, next->mm, next);
3762 if (!prev->mm) { // from kernel
3763 /* will mmdrop() in finish_task_switch(). */
3764 rq->prev_mm = prev->active_mm;
3765 prev->active_mm = NULL;
3769 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
3771 prepare_lock_switch(rq, next, rf);
3773 /* Here we just switch the register state and the stack. */
3774 switch_to(prev, next, prev);
3777 return finish_task_switch(prev);
3781 * nr_running and nr_context_switches:
3783 * externally visible scheduler statistics: current number of runnable
3784 * threads, total number of context switches performed since bootup.
3786 unsigned long nr_running(void)
3788 unsigned long i, sum = 0;
3790 for_each_online_cpu(i)
3791 sum += cpu_rq(i)->nr_running;
3797 * Check if only the current task is running on the CPU.
3799 * Caution: this function does not check that the caller has disabled
3800 * preemption, thus the result might have a time-of-check-to-time-of-use
3801 * race. The caller is responsible to use it correctly, for example:
3803 * - from a non-preemptible section (of course)
3805 * - from a thread that is bound to a single CPU
3807 * - in a loop with very short iterations (e.g. a polling loop)
3809 bool single_task_running(void)
3811 return raw_rq()->nr_running == 1;
3813 EXPORT_SYMBOL(single_task_running);
3815 unsigned long long nr_context_switches(void)
3818 unsigned long long sum = 0;
3820 for_each_possible_cpu(i)
3821 sum += cpu_rq(i)->nr_switches;
3827 * Consumers of these two interfaces, like for example the cpuidle menu
3828 * governor, are using nonsensical data. Preferring shallow idle state selection
3829 * for a CPU that has IO-wait which might not even end up running the task when
3830 * it does become runnable.
3833 unsigned long nr_iowait_cpu(int cpu)
3835 return atomic_read(&cpu_rq(cpu)->nr_iowait);
3839 * IO-wait accounting, and how its mostly bollocks (on SMP).
3841 * The idea behind IO-wait account is to account the idle time that we could
3842 * have spend running if it were not for IO. That is, if we were to improve the
3843 * storage performance, we'd have a proportional reduction in IO-wait time.
3845 * This all works nicely on UP, where, when a task blocks on IO, we account
3846 * idle time as IO-wait, because if the storage were faster, it could've been
3847 * running and we'd not be idle.
3849 * This has been extended to SMP, by doing the same for each CPU. This however
3852 * Imagine for instance the case where two tasks block on one CPU, only the one
3853 * CPU will have IO-wait accounted, while the other has regular idle. Even
3854 * though, if the storage were faster, both could've ran at the same time,
3855 * utilising both CPUs.
3857 * This means, that when looking globally, the current IO-wait accounting on
3858 * SMP is a lower bound, by reason of under accounting.
3860 * Worse, since the numbers are provided per CPU, they are sometimes
3861 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
3862 * associated with any one particular CPU, it can wake to another CPU than it
3863 * blocked on. This means the per CPU IO-wait number is meaningless.
3865 * Task CPU affinities can make all that even more 'interesting'.
3868 unsigned long nr_iowait(void)
3870 unsigned long i, sum = 0;
3872 for_each_possible_cpu(i)
3873 sum += nr_iowait_cpu(i);
3881 * sched_exec - execve() is a valuable balancing opportunity, because at
3882 * this point the task has the smallest effective memory and cache footprint.
3884 void sched_exec(void)
3886 struct task_struct *p = current;
3887 unsigned long flags;
3890 raw_spin_lock_irqsave(&p->pi_lock, flags);
3891 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
3892 if (dest_cpu == smp_processor_id())
3895 if (likely(cpu_active(dest_cpu))) {
3896 struct migration_arg arg = { p, dest_cpu };
3898 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3899 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
3903 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3908 DEFINE_PER_CPU(struct kernel_stat, kstat);
3909 DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
3911 EXPORT_PER_CPU_SYMBOL(kstat);
3912 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
3915 * The function fair_sched_class.update_curr accesses the struct curr
3916 * and its field curr->exec_start; when called from task_sched_runtime(),
3917 * we observe a high rate of cache misses in practice.
3918 * Prefetching this data results in improved performance.
3920 static inline void prefetch_curr_exec_start(struct task_struct *p)
3922 #ifdef CONFIG_FAIR_GROUP_SCHED
3923 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
3925 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
3928 prefetch(&curr->exec_start);
3932 * Return accounted runtime for the task.
3933 * In case the task is currently running, return the runtime plus current's
3934 * pending runtime that have not been accounted yet.
3936 unsigned long long task_sched_runtime(struct task_struct *p)
3942 #if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3944 * 64-bit doesn't need locks to atomically read a 64-bit value.
3945 * So we have a optimization chance when the task's delta_exec is 0.
3946 * Reading ->on_cpu is racy, but this is ok.
3948 * If we race with it leaving CPU, we'll take a lock. So we're correct.
3949 * If we race with it entering CPU, unaccounted time is 0. This is
3950 * indistinguishable from the read occurring a few cycles earlier.
3951 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3952 * been accounted, so we're correct here as well.
3954 if (!p->on_cpu || !task_on_rq_queued(p))
3955 return p->se.sum_exec_runtime;
3958 rq = task_rq_lock(p, &rf);
3960 * Must be ->curr _and_ ->on_rq. If dequeued, we would
3961 * project cycles that may never be accounted to this
3962 * thread, breaking clock_gettime().
3964 if (task_current(rq, p) && task_on_rq_queued(p)) {
3965 prefetch_curr_exec_start(p);
3966 update_rq_clock(rq);
3967 p->sched_class->update_curr(rq);
3969 ns = p->se.sum_exec_runtime;
3970 task_rq_unlock(rq, p, &rf);
3976 * This function gets called by the timer code, with HZ frequency.
3977 * We call it with interrupts disabled.
3979 void scheduler_tick(void)
3981 int cpu = smp_processor_id();
3982 struct rq *rq = cpu_rq(cpu);
3983 struct task_struct *curr = rq->curr;
3985 unsigned long thermal_pressure;
3987 arch_scale_freq_tick();
3992 update_rq_clock(rq);
3993 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
3994 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
3995 curr->sched_class->task_tick(rq, curr, 0);
3996 calc_global_load_tick(rq);
4001 perf_event_task_tick();
4004 rq->idle_balance = idle_cpu(cpu);
4005 trigger_load_balance(rq);
4009 #ifdef CONFIG_NO_HZ_FULL
4014 struct delayed_work work;
4016 /* Values for ->state, see diagram below. */
4017 #define TICK_SCHED_REMOTE_OFFLINE 0
4018 #define TICK_SCHED_REMOTE_OFFLINING 1
4019 #define TICK_SCHED_REMOTE_RUNNING 2
4022 * State diagram for ->state:
4025 * TICK_SCHED_REMOTE_OFFLINE
4028 * | | sched_tick_remote()
4031 * +--TICK_SCHED_REMOTE_OFFLINING
4034 * sched_tick_start() | | sched_tick_stop()
4037 * TICK_SCHED_REMOTE_RUNNING
4040 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
4041 * and sched_tick_start() are happy to leave the state in RUNNING.
4044 static struct tick_work __percpu *tick_work_cpu;
4046 static void sched_tick_remote(struct work_struct *work)
4048 struct delayed_work *dwork = to_delayed_work(work);
4049 struct tick_work *twork = container_of(dwork, struct tick_work, work);
4050 int cpu = twork->cpu;
4051 struct rq *rq = cpu_rq(cpu);
4052 struct task_struct *curr;
4058 * Handle the tick only if it appears the remote CPU is running in full
4059 * dynticks mode. The check is racy by nature, but missing a tick or
4060 * having one too much is no big deal because the scheduler tick updates
4061 * statistics and checks timeslices in a time-independent way, regardless
4062 * of when exactly it is running.
4064 if (!tick_nohz_tick_stopped_cpu(cpu))
4067 rq_lock_irq(rq, &rf);
4069 if (cpu_is_offline(cpu))
4072 update_rq_clock(rq);
4074 if (!is_idle_task(curr)) {
4076 * Make sure the next tick runs within a reasonable
4079 delta = rq_clock_task(rq) - curr->se.exec_start;
4080 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
4082 curr->sched_class->task_tick(rq, curr, 0);
4084 calc_load_nohz_remote(rq);
4086 rq_unlock_irq(rq, &rf);
4090 * Run the remote tick once per second (1Hz). This arbitrary
4091 * frequency is large enough to avoid overload but short enough
4092 * to keep scheduler internal stats reasonably up to date. But
4093 * first update state to reflect hotplug activity if required.
4095 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
4096 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
4097 if (os == TICK_SCHED_REMOTE_RUNNING)
4098 queue_delayed_work(system_unbound_wq, dwork, HZ);
4101 static void sched_tick_start(int cpu)
4104 struct tick_work *twork;
4106 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
4109 WARN_ON_ONCE(!tick_work_cpu);
4111 twork = per_cpu_ptr(tick_work_cpu, cpu);
4112 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
4113 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
4114 if (os == TICK_SCHED_REMOTE_OFFLINE) {
4116 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
4117 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
4121 #ifdef CONFIG_HOTPLUG_CPU
4122 static void sched_tick_stop(int cpu)
4124 struct tick_work *twork;
4127 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
4130 WARN_ON_ONCE(!tick_work_cpu);
4132 twork = per_cpu_ptr(tick_work_cpu, cpu);
4133 /* There cannot be competing actions, but don't rely on stop-machine. */
4134 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
4135 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
4136 /* Don't cancel, as this would mess up the state machine. */
4138 #endif /* CONFIG_HOTPLUG_CPU */
4140 int __init sched_tick_offload_init(void)
4142 tick_work_cpu = alloc_percpu(struct tick_work);
4143 BUG_ON(!tick_work_cpu);
4147 #else /* !CONFIG_NO_HZ_FULL */
4148 static inline void sched_tick_start(int cpu) { }
4149 static inline void sched_tick_stop(int cpu) { }
4152 #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
4153 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
4155 * If the value passed in is equal to the current preempt count
4156 * then we just disabled preemption. Start timing the latency.
4158 static inline void preempt_latency_start(int val)
4160 if (preempt_count() == val) {
4161 unsigned long ip = get_lock_parent_ip();
4162 #ifdef CONFIG_DEBUG_PREEMPT
4163 current->preempt_disable_ip = ip;
4165 trace_preempt_off(CALLER_ADDR0, ip);
4169 void preempt_count_add(int val)
4171 #ifdef CONFIG_DEBUG_PREEMPT
4175 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
4178 __preempt_count_add(val);
4179 #ifdef CONFIG_DEBUG_PREEMPT
4181 * Spinlock count overflowing soon?
4183 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
4186 preempt_latency_start(val);
4188 EXPORT_SYMBOL(preempt_count_add);
4189 NOKPROBE_SYMBOL(preempt_count_add);
4192 * If the value passed in equals to the current preempt count
4193 * then we just enabled preemption. Stop timing the latency.
4195 static inline void preempt_latency_stop(int val)
4197 if (preempt_count() == val)
4198 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
4201 void preempt_count_sub(int val)
4203 #ifdef CONFIG_DEBUG_PREEMPT
4207 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
4210 * Is the spinlock portion underflowing?
4212 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
4213 !(preempt_count() & PREEMPT_MASK)))
4217 preempt_latency_stop(val);
4218 __preempt_count_sub(val);
4220 EXPORT_SYMBOL(preempt_count_sub);
4221 NOKPROBE_SYMBOL(preempt_count_sub);
4224 static inline void preempt_latency_start(int val) { }
4225 static inline void preempt_latency_stop(int val) { }
4228 static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
4230 #ifdef CONFIG_DEBUG_PREEMPT
4231 return p->preempt_disable_ip;
4238 * Print scheduling while atomic bug:
4240 static noinline void __schedule_bug(struct task_struct *prev)
4242 /* Save this before calling printk(), since that will clobber it */
4243 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
4245 if (oops_in_progress)
4248 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
4249 prev->comm, prev->pid, preempt_count());
4251 debug_show_held_locks(prev);
4253 if (irqs_disabled())
4254 print_irqtrace_events(prev);
4255 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
4256 && in_atomic_preempt_off()) {
4257 pr_err("Preemption disabled at:");
4258 print_ip_sym(KERN_ERR, preempt_disable_ip);
4261 panic("scheduling while atomic\n");
4264 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
4268 * Various schedule()-time debugging checks and statistics:
4270 static inline void schedule_debug(struct task_struct *prev, bool preempt)
4272 #ifdef CONFIG_SCHED_STACK_END_CHECK
4273 if (task_stack_end_corrupted(prev))
4274 panic("corrupted stack end detected inside scheduler\n");
4276 if (task_scs_end_corrupted(prev))
4277 panic("corrupted shadow stack detected inside scheduler\n");
4280 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
4281 if (!preempt && prev->state && prev->non_block_count) {
4282 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
4283 prev->comm, prev->pid, prev->non_block_count);
4285 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
4289 if (unlikely(in_atomic_preempt_off())) {
4290 __schedule_bug(prev);
4291 preempt_count_set(PREEMPT_DISABLED);
4295 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
4297 schedstat_inc(this_rq()->sched_count);
4300 static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
4301 struct rq_flags *rf)
4304 const struct sched_class *class;
4306 * We must do the balancing pass before put_prev_task(), such
4307 * that when we release the rq->lock the task is in the same
4308 * state as before we took rq->lock.
4310 * We can terminate the balance pass as soon as we know there is
4311 * a runnable task of @class priority or higher.
4313 for_class_range(class, prev->sched_class, &idle_sched_class) {
4314 if (class->balance(rq, prev, rf))
4319 put_prev_task(rq, prev);
4323 * Pick up the highest-prio task:
4325 static inline struct task_struct *
4326 pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
4328 const struct sched_class *class;
4329 struct task_struct *p;
4332 * Optimization: we know that if all tasks are in the fair class we can
4333 * call that function directly, but only if the @prev task wasn't of a
4334 * higher scheduling class, because otherwise those loose the
4335 * opportunity to pull in more work from other CPUs.
4337 if (likely(prev->sched_class <= &fair_sched_class &&
4338 rq->nr_running == rq->cfs.h_nr_running)) {
4340 p = pick_next_task_fair(rq, prev, rf);
4341 if (unlikely(p == RETRY_TASK))
4344 /* Assumes fair_sched_class->next == idle_sched_class */
4346 put_prev_task(rq, prev);
4347 p = pick_next_task_idle(rq);
4354 put_prev_task_balance(rq, prev, rf);
4356 for_each_class(class) {
4357 p = class->pick_next_task(rq);
4362 /* The idle class should always have a runnable task: */
4367 * __schedule() is the main scheduler function.
4369 * The main means of driving the scheduler and thus entering this function are:
4371 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
4373 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
4374 * paths. For example, see arch/x86/entry_64.S.
4376 * To drive preemption between tasks, the scheduler sets the flag in timer
4377 * interrupt handler scheduler_tick().
4379 * 3. Wakeups don't really cause entry into schedule(). They add a
4380 * task to the run-queue and that's it.
4382 * Now, if the new task added to the run-queue preempts the current
4383 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
4384 * called on the nearest possible occasion:
4386 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
4388 * - in syscall or exception context, at the next outmost
4389 * preempt_enable(). (this might be as soon as the wake_up()'s
4392 * - in IRQ context, return from interrupt-handler to
4393 * preemptible context
4395 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
4398 * - cond_resched() call
4399 * - explicit schedule() call
4400 * - return from syscall or exception to user-space
4401 * - return from interrupt-handler to user-space
4403 * WARNING: must be called with preemption disabled!
4405 static void __sched notrace __schedule(bool preempt)
4407 struct task_struct *prev, *next;
4408 unsigned long *switch_count;
4409 unsigned long prev_state;
4414 cpu = smp_processor_id();
4418 schedule_debug(prev, preempt);
4420 if (sched_feat(HRTICK))
4423 local_irq_disable();
4424 rcu_note_context_switch(preempt);
4427 * Make sure that signal_pending_state()->signal_pending() below
4428 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
4429 * done by the caller to avoid the race with signal_wake_up():
4431 * __set_current_state(@state) signal_wake_up()
4432 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
4433 * wake_up_state(p, state)
4434 * LOCK rq->lock LOCK p->pi_state
4435 * smp_mb__after_spinlock() smp_mb__after_spinlock()
4436 * if (signal_pending_state()) if (p->state & @state)
4438 * Also, the membarrier system call requires a full memory barrier
4439 * after coming from user-space, before storing to rq->curr.
4442 smp_mb__after_spinlock();
4444 /* Promote REQ to ACT */
4445 rq->clock_update_flags <<= 1;
4446 update_rq_clock(rq);
4448 switch_count = &prev->nivcsw;
4451 * We must load prev->state once (task_struct::state is volatile), such
4454 * - we form a control dependency vs deactivate_task() below.
4455 * - ptrace_{,un}freeze_traced() can change ->state underneath us.
4457 prev_state = prev->state;
4458 if (!preempt && prev_state) {
4459 if (signal_pending_state(prev_state, prev)) {
4460 prev->state = TASK_RUNNING;
4462 prev->sched_contributes_to_load =
4463 (prev_state & TASK_UNINTERRUPTIBLE) &&
4464 !(prev_state & TASK_NOLOAD) &&
4465 !(prev->flags & PF_FROZEN);
4467 if (prev->sched_contributes_to_load)
4468 rq->nr_uninterruptible++;
4471 * __schedule() ttwu()
4472 * prev_state = prev->state; if (p->on_rq && ...)
4473 * if (prev_state) goto out;
4474 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
4475 * p->state = TASK_WAKING
4477 * Where __schedule() and ttwu() have matching control dependencies.
4479 * After this, schedule() must not care about p->state any more.
4481 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
4483 if (prev->in_iowait) {
4484 atomic_inc(&rq->nr_iowait);
4485 delayacct_blkio_start();
4488 switch_count = &prev->nvcsw;
4491 next = pick_next_task(rq, prev, &rf);
4492 clear_tsk_need_resched(prev);
4493 clear_preempt_need_resched();
4495 if (likely(prev != next)) {
4498 * RCU users of rcu_dereference(rq->curr) may not see
4499 * changes to task_struct made by pick_next_task().
4501 RCU_INIT_POINTER(rq->curr, next);
4503 * The membarrier system call requires each architecture
4504 * to have a full memory barrier after updating
4505 * rq->curr, before returning to user-space.
4507 * Here are the schemes providing that barrier on the
4508 * various architectures:
4509 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
4510 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
4511 * - finish_lock_switch() for weakly-ordered
4512 * architectures where spin_unlock is a full barrier,
4513 * - switch_to() for arm64 (weakly-ordered, spin_unlock
4514 * is a RELEASE barrier),
4518 psi_sched_switch(prev, next, !task_on_rq_queued(prev));
4520 trace_sched_switch(preempt, prev, next);
4522 /* Also unlocks the rq: */
4523 rq = context_switch(rq, prev, next, &rf);
4525 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
4526 rq_unlock_irq(rq, &rf);
4529 balance_callback(rq);
4532 void __noreturn do_task_dead(void)
4534 /* Causes final put_task_struct in finish_task_switch(): */
4535 set_special_state(TASK_DEAD);
4537 /* Tell freezer to ignore us: */
4538 current->flags |= PF_NOFREEZE;
4543 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
4548 static inline void sched_submit_work(struct task_struct *tsk)
4550 unsigned int task_flags;
4555 task_flags = tsk->flags;
4557 * If a worker went to sleep, notify and ask workqueue whether
4558 * it wants to wake up a task to maintain concurrency.
4559 * As this function is called inside the schedule() context,
4560 * we disable preemption to avoid it calling schedule() again
4561 * in the possible wakeup of a kworker and because wq_worker_sleeping()
4564 if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
4566 if (task_flags & PF_WQ_WORKER)
4567 wq_worker_sleeping(tsk);
4569 io_wq_worker_sleeping(tsk);
4570 preempt_enable_no_resched();
4573 if (tsk_is_pi_blocked(tsk))
4577 * If we are going to sleep and we have plugged IO queued,
4578 * make sure to submit it to avoid deadlocks.
4580 if (blk_needs_flush_plug(tsk))
4581 blk_schedule_flush_plug(tsk);
4584 static void sched_update_worker(struct task_struct *tsk)
4586 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
4587 if (tsk->flags & PF_WQ_WORKER)
4588 wq_worker_running(tsk);
4590 io_wq_worker_running(tsk);
4594 asmlinkage __visible void __sched schedule(void)
4596 struct task_struct *tsk = current;
4598 sched_submit_work(tsk);
4602 sched_preempt_enable_no_resched();
4603 } while (need_resched());
4604 sched_update_worker(tsk);
4606 EXPORT_SYMBOL(schedule);
4609 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
4610 * state (have scheduled out non-voluntarily) by making sure that all
4611 * tasks have either left the run queue or have gone into user space.
4612 * As idle tasks do not do either, they must not ever be preempted
4613 * (schedule out non-voluntarily).
4615 * schedule_idle() is similar to schedule_preempt_disable() except that it
4616 * never enables preemption because it does not call sched_submit_work().
4618 void __sched schedule_idle(void)
4621 * As this skips calling sched_submit_work(), which the idle task does
4622 * regardless because that function is a nop when the task is in a
4623 * TASK_RUNNING state, make sure this isn't used someplace that the
4624 * current task can be in any other state. Note, idle is always in the
4625 * TASK_RUNNING state.
4627 WARN_ON_ONCE(current->state);
4630 } while (need_resched());
4633 #ifdef CONFIG_CONTEXT_TRACKING
4634 asmlinkage __visible void __sched schedule_user(void)
4637 * If we come here after a random call to set_need_resched(),
4638 * or we have been woken up remotely but the IPI has not yet arrived,
4639 * we haven't yet exited the RCU idle mode. Do it here manually until
4640 * we find a better solution.
4642 * NB: There are buggy callers of this function. Ideally we
4643 * should warn if prev_state != CONTEXT_USER, but that will trigger
4644 * too frequently to make sense yet.
4646 enum ctx_state prev_state = exception_enter();
4648 exception_exit(prev_state);
4653 * schedule_preempt_disabled - called with preemption disabled
4655 * Returns with preemption disabled. Note: preempt_count must be 1
4657 void __sched schedule_preempt_disabled(void)
4659 sched_preempt_enable_no_resched();
4664 static void __sched notrace preempt_schedule_common(void)
4668 * Because the function tracer can trace preempt_count_sub()
4669 * and it also uses preempt_enable/disable_notrace(), if
4670 * NEED_RESCHED is set, the preempt_enable_notrace() called
4671 * by the function tracer will call this function again and
4672 * cause infinite recursion.
4674 * Preemption must be disabled here before the function
4675 * tracer can trace. Break up preempt_disable() into two
4676 * calls. One to disable preemption without fear of being
4677 * traced. The other to still record the preemption latency,
4678 * which can also be traced by the function tracer.
4680 preempt_disable_notrace();
4681 preempt_latency_start(1);
4683 preempt_latency_stop(1);
4684 preempt_enable_no_resched_notrace();
4687 * Check again in case we missed a preemption opportunity
4688 * between schedule and now.
4690 } while (need_resched());
4693 #ifdef CONFIG_PREEMPTION
4695 * This is the entry point to schedule() from in-kernel preemption
4696 * off of preempt_enable.
4698 asmlinkage __visible void __sched notrace preempt_schedule(void)
4701 * If there is a non-zero preempt_count or interrupts are disabled,
4702 * we do not want to preempt the current task. Just return..
4704 if (likely(!preemptible()))
4707 preempt_schedule_common();
4709 NOKPROBE_SYMBOL(preempt_schedule);
4710 EXPORT_SYMBOL(preempt_schedule);
4713 * preempt_schedule_notrace - preempt_schedule called by tracing
4715 * The tracing infrastructure uses preempt_enable_notrace to prevent
4716 * recursion and tracing preempt enabling caused by the tracing
4717 * infrastructure itself. But as tracing can happen in areas coming
4718 * from userspace or just about to enter userspace, a preempt enable
4719 * can occur before user_exit() is called. This will cause the scheduler
4720 * to be called when the system is still in usermode.
4722 * To prevent this, the preempt_enable_notrace will use this function
4723 * instead of preempt_schedule() to exit user context if needed before
4724 * calling the scheduler.
4726 asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
4728 enum ctx_state prev_ctx;
4730 if (likely(!preemptible()))
4735 * Because the function tracer can trace preempt_count_sub()
4736 * and it also uses preempt_enable/disable_notrace(), if
4737 * NEED_RESCHED is set, the preempt_enable_notrace() called
4738 * by the function tracer will call this function again and
4739 * cause infinite recursion.
4741 * Preemption must be disabled here before the function
4742 * tracer can trace. Break up preempt_disable() into two
4743 * calls. One to disable preemption without fear of being
4744 * traced. The other to still record the preemption latency,
4745 * which can also be traced by the function tracer.
4747 preempt_disable_notrace();
4748 preempt_latency_start(1);
4750 * Needs preempt disabled in case user_exit() is traced
4751 * and the tracer calls preempt_enable_notrace() causing
4752 * an infinite recursion.
4754 prev_ctx = exception_enter();
4756 exception_exit(prev_ctx);
4758 preempt_latency_stop(1);
4759 preempt_enable_no_resched_notrace();
4760 } while (need_resched());
4762 EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
4764 #endif /* CONFIG_PREEMPTION */
4767 * This is the entry point to schedule() from kernel preemption
4768 * off of irq context.
4769 * Note, that this is called and return with irqs disabled. This will
4770 * protect us against recursive calling from irq.
4772 asmlinkage __visible void __sched preempt_schedule_irq(void)
4774 enum ctx_state prev_state;
4776 /* Catch callers which need to be fixed */
4777 BUG_ON(preempt_count() || !irqs_disabled());
4779 prev_state = exception_enter();
4785 local_irq_disable();
4786 sched_preempt_enable_no_resched();
4787 } while (need_resched());
4789 exception_exit(prev_state);
4792 int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
4795 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
4796 return try_to_wake_up(curr->private, mode, wake_flags);
4798 EXPORT_SYMBOL(default_wake_function);
4800 #ifdef CONFIG_RT_MUTEXES
4802 static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
4805 prio = min(prio, pi_task->prio);
4810 static inline int rt_effective_prio(struct task_struct *p, int prio)
4812 struct task_struct *pi_task = rt_mutex_get_top_task(p);
4814 return __rt_effective_prio(pi_task, prio);
4818 * rt_mutex_setprio - set the current priority of a task
4820 * @pi_task: donor task
4822 * This function changes the 'effective' priority of a task. It does
4823 * not touch ->normal_prio like __setscheduler().
4825 * Used by the rt_mutex code to implement priority inheritance
4826 * logic. Call site only calls if the priority of the task changed.
4828 void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
4830 int prio, oldprio, queued, running, queue_flag =
4831 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
4832 const struct sched_class *prev_class;
4836 /* XXX used to be waiter->prio, not waiter->task->prio */
4837 prio = __rt_effective_prio(pi_task, p->normal_prio);
4840 * If nothing changed; bail early.
4842 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
4845 rq = __task_rq_lock(p, &rf);
4846 update_rq_clock(rq);
4848 * Set under pi_lock && rq->lock, such that the value can be used under
4851 * Note that there is loads of tricky to make this pointer cache work
4852 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
4853 * ensure a task is de-boosted (pi_task is set to NULL) before the
4854 * task is allowed to run again (and can exit). This ensures the pointer
4855 * points to a blocked task -- which guaratees the task is present.
4857 p->pi_top_task = pi_task;
4860 * For FIFO/RR we only need to set prio, if that matches we're done.
4862 if (prio == p->prio && !dl_prio(prio))
4866 * Idle task boosting is a nono in general. There is one
4867 * exception, when PREEMPT_RT and NOHZ is active:
4869 * The idle task calls get_next_timer_interrupt() and holds
4870 * the timer wheel base->lock on the CPU and another CPU wants
4871 * to access the timer (probably to cancel it). We can safely
4872 * ignore the boosting request, as the idle CPU runs this code
4873 * with interrupts disabled and will complete the lock
4874 * protected section without being interrupted. So there is no
4875 * real need to boost.
4877 if (unlikely(p == rq->idle)) {
4878 WARN_ON(p != rq->curr);
4879 WARN_ON(p->pi_blocked_on);
4883 trace_sched_pi_setprio(p, pi_task);
4886 if (oldprio == prio)
4887 queue_flag &= ~DEQUEUE_MOVE;
4889 prev_class = p->sched_class;
4890 queued = task_on_rq_queued(p);
4891 running = task_current(rq, p);
4893 dequeue_task(rq, p, queue_flag);
4895 put_prev_task(rq, p);
4898 * Boosting condition are:
4899 * 1. -rt task is running and holds mutex A
4900 * --> -dl task blocks on mutex A
4902 * 2. -dl task is running and holds mutex A
4903 * --> -dl task blocks on mutex A and could preempt the
4906 if (dl_prio(prio)) {
4907 if (!dl_prio(p->normal_prio) ||
4908 (pi_task && dl_prio(pi_task->prio) &&
4909 dl_entity_preempt(&pi_task->dl, &p->dl))) {
4910 p->dl.dl_boosted = 1;
4911 queue_flag |= ENQUEUE_REPLENISH;
4913 p->dl.dl_boosted = 0;
4914 p->sched_class = &dl_sched_class;
4915 } else if (rt_prio(prio)) {
4916 if (dl_prio(oldprio))
4917 p->dl.dl_boosted = 0;
4919 queue_flag |= ENQUEUE_HEAD;
4920 p->sched_class = &rt_sched_class;
4922 if (dl_prio(oldprio))
4923 p->dl.dl_boosted = 0;
4924 if (rt_prio(oldprio))
4926 p->sched_class = &fair_sched_class;
4932 enqueue_task(rq, p, queue_flag);
4934 set_next_task(rq, p);
4936 check_class_changed(rq, p, prev_class, oldprio);
4938 /* Avoid rq from going away on us: */
4940 __task_rq_unlock(rq, &rf);
4942 balance_callback(rq);
4946 static inline int rt_effective_prio(struct task_struct *p, int prio)
4952 void set_user_nice(struct task_struct *p, long nice)
4954 bool queued, running;
4959 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
4962 * We have to be careful, if called from sys_setpriority(),
4963 * the task might be in the middle of scheduling on another CPU.
4965 rq = task_rq_lock(p, &rf);
4966 update_rq_clock(rq);
4969 * The RT priorities are set via sched_setscheduler(), but we still
4970 * allow the 'normal' nice value to be set - but as expected
4971 * it wont have any effect on scheduling until the task is
4972 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
4974 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
4975 p->static_prio = NICE_TO_PRIO(nice);
4978 queued = task_on_rq_queued(p);
4979 running = task_current(rq, p);
4981 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
4983 put_prev_task(rq, p);
4985 p->static_prio = NICE_TO_PRIO(nice);
4986 set_load_weight(p, true);
4988 p->prio = effective_prio(p);
4991 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
4993 set_next_task(rq, p);
4996 * If the task increased its priority or is running and
4997 * lowered its priority, then reschedule its CPU:
4999 p->sched_class->prio_changed(rq, p, old_prio);
5002 task_rq_unlock(rq, p, &rf);
5004 EXPORT_SYMBOL(set_user_nice);
5007 * can_nice - check if a task can reduce its nice value
5011 int can_nice(const struct task_struct *p, const int nice)
5013 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
5014 int nice_rlim = nice_to_rlimit(nice);
5016 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
5017 capable(CAP_SYS_NICE));
5020 #ifdef __ARCH_WANT_SYS_NICE
5023 * sys_nice - change the priority of the current process.
5024 * @increment: priority increment
5026 * sys_setpriority is a more generic, but much slower function that
5027 * does similar things.
5029 SYSCALL_DEFINE1(nice, int, increment)
5034 * Setpriority might change our priority at the same moment.
5035 * We don't have to worry. Conceptually one call occurs first
5036 * and we have a single winner.
5038 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
5039 nice = task_nice(current) + increment;
5041 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
5042 if (increment < 0 && !can_nice(current, nice))
5045 retval = security_task_setnice(current, nice);
5049 set_user_nice(current, nice);
5056 * task_prio - return the priority value of a given task.
5057 * @p: the task in question.
5059 * Return: The priority value as seen by users in /proc.
5060 * RT tasks are offset by -200. Normal tasks are centered
5061 * around 0, value goes from -16 to +15.
5063 int task_prio(const struct task_struct *p)
5065 return p->prio - MAX_RT_PRIO;
5069 * idle_cpu - is a given CPU idle currently?
5070 * @cpu: the processor in question.
5072 * Return: 1 if the CPU is currently idle. 0 otherwise.
5074 int idle_cpu(int cpu)
5076 struct rq *rq = cpu_rq(cpu);
5078 if (rq->curr != rq->idle)
5085 if (rq->ttwu_pending)
5093 * available_idle_cpu - is a given CPU idle for enqueuing work.
5094 * @cpu: the CPU in question.
5096 * Return: 1 if the CPU is currently idle. 0 otherwise.
5098 int available_idle_cpu(int cpu)
5103 if (vcpu_is_preempted(cpu))
5110 * idle_task - return the idle task for a given CPU.
5111 * @cpu: the processor in question.
5113 * Return: The idle task for the CPU @cpu.
5115 struct task_struct *idle_task(int cpu)
5117 return cpu_rq(cpu)->idle;
5121 * find_process_by_pid - find a process with a matching PID value.
5122 * @pid: the pid in question.
5124 * The task of @pid, if found. %NULL otherwise.
5126 static struct task_struct *find_process_by_pid(pid_t pid)
5128 return pid ? find_task_by_vpid(pid) : current;
5132 * sched_setparam() passes in -1 for its policy, to let the functions
5133 * it calls know not to change it.
5135 #define SETPARAM_POLICY -1
5137 static void __setscheduler_params(struct task_struct *p,
5138 const struct sched_attr *attr)
5140 int policy = attr->sched_policy;
5142 if (policy == SETPARAM_POLICY)
5147 if (dl_policy(policy))
5148 __setparam_dl(p, attr);
5149 else if (fair_policy(policy))
5150 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
5153 * __sched_setscheduler() ensures attr->sched_priority == 0 when
5154 * !rt_policy. Always setting this ensures that things like
5155 * getparam()/getattr() don't report silly values for !rt tasks.
5157 p->rt_priority = attr->sched_priority;
5158 p->normal_prio = normal_prio(p);
5159 set_load_weight(p, true);
5162 /* Actually do priority change: must hold pi & rq lock. */
5163 static void __setscheduler(struct rq *rq, struct task_struct *p,
5164 const struct sched_attr *attr, bool keep_boost)
5167 * If params can't change scheduling class changes aren't allowed
5170 if (attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)
5173 __setscheduler_params(p, attr);
5176 * Keep a potential priority boosting if called from
5177 * sched_setscheduler().
5179 p->prio = normal_prio(p);
5181 p->prio = rt_effective_prio(p, p->prio);
5183 if (dl_prio(p->prio))
5184 p->sched_class = &dl_sched_class;
5185 else if (rt_prio(p->prio))
5186 p->sched_class = &rt_sched_class;
5188 p->sched_class = &fair_sched_class;
5192 * Check the target process has a UID that matches the current process's:
5194 static bool check_same_owner(struct task_struct *p)
5196 const struct cred *cred = current_cred(), *pcred;
5200 pcred = __task_cred(p);
5201 match = (uid_eq(cred->euid, pcred->euid) ||
5202 uid_eq(cred->euid, pcred->uid));
5207 static int __sched_setscheduler(struct task_struct *p,
5208 const struct sched_attr *attr,
5211 int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
5212 MAX_RT_PRIO - 1 - attr->sched_priority;
5213 int retval, oldprio, oldpolicy = -1, queued, running;
5214 int new_effective_prio, policy = attr->sched_policy;
5215 const struct sched_class *prev_class;
5218 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
5221 /* The pi code expects interrupts enabled */
5222 BUG_ON(pi && in_interrupt());
5224 /* Double check policy once rq lock held: */
5226 reset_on_fork = p->sched_reset_on_fork;
5227 policy = oldpolicy = p->policy;
5229 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
5231 if (!valid_policy(policy))
5235 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
5239 * Valid priorities for SCHED_FIFO and SCHED_RR are
5240 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
5241 * SCHED_BATCH and SCHED_IDLE is 0.
5243 if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
5244 (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
5246 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
5247 (rt_policy(policy) != (attr->sched_priority != 0)))
5251 * Allow unprivileged RT tasks to decrease priority:
5253 if (user && !capable(CAP_SYS_NICE)) {
5254 if (fair_policy(policy)) {
5255 if (attr->sched_nice < task_nice(p) &&
5256 !can_nice(p, attr->sched_nice))
5260 if (rt_policy(policy)) {
5261 unsigned long rlim_rtprio =
5262 task_rlimit(p, RLIMIT_RTPRIO);
5264 /* Can't set/change the rt policy: */
5265 if (policy != p->policy && !rlim_rtprio)
5268 /* Can't increase priority: */
5269 if (attr->sched_priority > p->rt_priority &&
5270 attr->sched_priority > rlim_rtprio)
5275 * Can't set/change SCHED_DEADLINE policy at all for now
5276 * (safest behavior); in the future we would like to allow
5277 * unprivileged DL tasks to increase their relative deadline
5278 * or reduce their runtime (both ways reducing utilization)
5280 if (dl_policy(policy))
5284 * Treat SCHED_IDLE as nice 20. Only allow a switch to
5285 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
5287 if (task_has_idle_policy(p) && !idle_policy(policy)) {
5288 if (!can_nice(p, task_nice(p)))
5292 /* Can't change other user's priorities: */
5293 if (!check_same_owner(p))
5296 /* Normal users shall not reset the sched_reset_on_fork flag: */
5297 if (p->sched_reset_on_fork && !reset_on_fork)
5302 if (attr->sched_flags & SCHED_FLAG_SUGOV)
5305 retval = security_task_setscheduler(p);
5310 /* Update task specific "requested" clamps */
5311 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
5312 retval = uclamp_validate(p, attr);
5321 * Make sure no PI-waiters arrive (or leave) while we are
5322 * changing the priority of the task:
5324 * To be able to change p->policy safely, the appropriate
5325 * runqueue lock must be held.
5327 rq = task_rq_lock(p, &rf);
5328 update_rq_clock(rq);
5331 * Changing the policy of the stop threads its a very bad idea:
5333 if (p == rq->stop) {
5339 * If not changing anything there's no need to proceed further,
5340 * but store a possible modification of reset_on_fork.
5342 if (unlikely(policy == p->policy)) {
5343 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
5345 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
5347 if (dl_policy(policy) && dl_param_changed(p, attr))
5349 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
5352 p->sched_reset_on_fork = reset_on_fork;
5359 #ifdef CONFIG_RT_GROUP_SCHED
5361 * Do not allow realtime tasks into groups that have no runtime
5364 if (rt_bandwidth_enabled() && rt_policy(policy) &&
5365 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
5366 !task_group_is_autogroup(task_group(p))) {
5372 if (dl_bandwidth_enabled() && dl_policy(policy) &&
5373 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
5374 cpumask_t *span = rq->rd->span;
5377 * Don't allow tasks with an affinity mask smaller than
5378 * the entire root_domain to become SCHED_DEADLINE. We
5379 * will also fail if there's no bandwidth available.
5381 if (!cpumask_subset(span, p->cpus_ptr) ||
5382 rq->rd->dl_bw.bw == 0) {
5390 /* Re-check policy now with rq lock held: */
5391 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
5392 policy = oldpolicy = -1;
5393 task_rq_unlock(rq, p, &rf);
5395 cpuset_read_unlock();
5400 * If setscheduling to SCHED_DEADLINE (or changing the parameters
5401 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
5404 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
5409 p->sched_reset_on_fork = reset_on_fork;
5414 * Take priority boosted tasks into account. If the new
5415 * effective priority is unchanged, we just store the new
5416 * normal parameters and do not touch the scheduler class and
5417 * the runqueue. This will be done when the task deboost
5420 new_effective_prio = rt_effective_prio(p, newprio);
5421 if (new_effective_prio == oldprio)
5422 queue_flags &= ~DEQUEUE_MOVE;
5425 queued = task_on_rq_queued(p);
5426 running = task_current(rq, p);
5428 dequeue_task(rq, p, queue_flags);
5430 put_prev_task(rq, p);
5432 prev_class = p->sched_class;
5434 __setscheduler(rq, p, attr, pi);
5435 __setscheduler_uclamp(p, attr);
5439 * We enqueue to tail when the priority of a task is
5440 * increased (user space view).
5442 if (oldprio < p->prio)
5443 queue_flags |= ENQUEUE_HEAD;
5445 enqueue_task(rq, p, queue_flags);
5448 set_next_task(rq, p);
5450 check_class_changed(rq, p, prev_class, oldprio);
5452 /* Avoid rq from going away on us: */
5454 task_rq_unlock(rq, p, &rf);
5457 cpuset_read_unlock();
5458 rt_mutex_adjust_pi(p);
5461 /* Run balance callbacks after we've adjusted the PI chain: */
5462 balance_callback(rq);
5468 task_rq_unlock(rq, p, &rf);
5470 cpuset_read_unlock();
5474 static int _sched_setscheduler(struct task_struct *p, int policy,
5475 const struct sched_param *param, bool check)
5477 struct sched_attr attr = {
5478 .sched_policy = policy,
5479 .sched_priority = param->sched_priority,
5480 .sched_nice = PRIO_TO_NICE(p->static_prio),
5483 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
5484 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
5485 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
5486 policy &= ~SCHED_RESET_ON_FORK;
5487 attr.sched_policy = policy;
5490 return __sched_setscheduler(p, &attr, check, true);
5493 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
5494 * @p: the task in question.
5495 * @policy: new policy.
5496 * @param: structure containing the new RT priority.
5498 * Use sched_set_fifo(), read its comment.
5500 * Return: 0 on success. An error code otherwise.
5502 * NOTE that the task may be already dead.
5504 int sched_setscheduler(struct task_struct *p, int policy,
5505 const struct sched_param *param)
5507 return _sched_setscheduler(p, policy, param, true);
5510 int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
5512 return __sched_setscheduler(p, attr, true, true);
5515 int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
5517 return __sched_setscheduler(p, attr, false, true);
5521 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
5522 * @p: the task in question.
5523 * @policy: new policy.
5524 * @param: structure containing the new RT priority.
5526 * Just like sched_setscheduler, only don't bother checking if the
5527 * current context has permission. For example, this is needed in
5528 * stop_machine(): we create temporary high priority worker threads,
5529 * but our caller might not have that capability.
5531 * Return: 0 on success. An error code otherwise.
5533 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
5534 const struct sched_param *param)
5536 return _sched_setscheduler(p, policy, param, false);
5540 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
5541 * incapable of resource management, which is the one thing an OS really should
5544 * This is of course the reason it is limited to privileged users only.
5546 * Worse still; it is fundamentally impossible to compose static priority
5547 * workloads. You cannot take two correctly working static prio workloads
5548 * and smash them together and still expect them to work.
5550 * For this reason 'all' FIFO tasks the kernel creates are basically at:
5554 * The administrator _MUST_ configure the system, the kernel simply doesn't
5555 * know enough information to make a sensible choice.
5557 void sched_set_fifo(struct task_struct *p)
5559 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
5560 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
5562 EXPORT_SYMBOL_GPL(sched_set_fifo);
5565 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
5567 void sched_set_fifo_low(struct task_struct *p)
5569 struct sched_param sp = { .sched_priority = 1 };
5570 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
5572 EXPORT_SYMBOL_GPL(sched_set_fifo_low);
5574 void sched_set_normal(struct task_struct *p, int nice)
5576 struct sched_attr attr = {
5577 .sched_policy = SCHED_NORMAL,
5580 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
5582 EXPORT_SYMBOL_GPL(sched_set_normal);
5585 do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
5587 struct sched_param lparam;
5588 struct task_struct *p;
5591 if (!param || pid < 0)
5593 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
5598 p = find_process_by_pid(pid);
5604 retval = sched_setscheduler(p, policy, &lparam);
5612 * Mimics kernel/events/core.c perf_copy_attr().
5614 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
5619 /* Zero the full structure, so that a short copy will be nice: */
5620 memset(attr, 0, sizeof(*attr));
5622 ret = get_user(size, &uattr->size);
5626 /* ABI compatibility quirk: */
5628 size = SCHED_ATTR_SIZE_VER0;
5629 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
5632 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
5639 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
5640 size < SCHED_ATTR_SIZE_VER1)
5644 * XXX: Do we want to be lenient like existing syscalls; or do we want
5645 * to be strict and return an error on out-of-bounds values?
5647 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
5652 put_user(sizeof(*attr), &uattr->size);
5657 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
5658 * @pid: the pid in question.
5659 * @policy: new policy.
5660 * @param: structure containing the new RT priority.
5662 * Return: 0 on success. An error code otherwise.
5664 SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
5669 return do_sched_setscheduler(pid, policy, param);
5673 * sys_sched_setparam - set/change the RT priority of a thread
5674 * @pid: the pid in question.
5675 * @param: structure containing the new RT priority.
5677 * Return: 0 on success. An error code otherwise.
5679 SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
5681 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
5685 * sys_sched_setattr - same as above, but with extended sched_attr
5686 * @pid: the pid in question.
5687 * @uattr: structure containing the extended parameters.
5688 * @flags: for future extension.
5690 SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
5691 unsigned int, flags)
5693 struct sched_attr attr;
5694 struct task_struct *p;
5697 if (!uattr || pid < 0 || flags)
5700 retval = sched_copy_attr(uattr, &attr);
5704 if ((int)attr.sched_policy < 0)
5706 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
5707 attr.sched_policy = SETPARAM_POLICY;
5711 p = find_process_by_pid(pid);
5717 retval = sched_setattr(p, &attr);
5725 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
5726 * @pid: the pid in question.
5728 * Return: On success, the policy of the thread. Otherwise, a negative error
5731 SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
5733 struct task_struct *p;
5741 p = find_process_by_pid(pid);
5743 retval = security_task_getscheduler(p);
5746 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
5753 * sys_sched_getparam - get the RT priority of a thread
5754 * @pid: the pid in question.
5755 * @param: structure containing the RT priority.
5757 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
5760 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
5762 struct sched_param lp = { .sched_priority = 0 };
5763 struct task_struct *p;
5766 if (!param || pid < 0)
5770 p = find_process_by_pid(pid);
5775 retval = security_task_getscheduler(p);
5779 if (task_has_rt_policy(p))
5780 lp.sched_priority = p->rt_priority;
5784 * This one might sleep, we cannot do it with a spinlock held ...
5786 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
5796 * Copy the kernel size attribute structure (which might be larger
5797 * than what user-space knows about) to user-space.
5799 * Note that all cases are valid: user-space buffer can be larger or
5800 * smaller than the kernel-space buffer. The usual case is that both
5801 * have the same size.
5804 sched_attr_copy_to_user(struct sched_attr __user *uattr,
5805 struct sched_attr *kattr,
5808 unsigned int ksize = sizeof(*kattr);
5810 if (!access_ok(uattr, usize))
5814 * sched_getattr() ABI forwards and backwards compatibility:
5816 * If usize == ksize then we just copy everything to user-space and all is good.
5818 * If usize < ksize then we only copy as much as user-space has space for,
5819 * this keeps ABI compatibility as well. We skip the rest.
5821 * If usize > ksize then user-space is using a newer version of the ABI,
5822 * which part the kernel doesn't know about. Just ignore it - tooling can
5823 * detect the kernel's knowledge of attributes from the attr->size value
5824 * which is set to ksize in this case.
5826 kattr->size = min(usize, ksize);
5828 if (copy_to_user(uattr, kattr, kattr->size))
5835 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
5836 * @pid: the pid in question.
5837 * @uattr: structure containing the extended parameters.
5838 * @usize: sizeof(attr) for fwd/bwd comp.
5839 * @flags: for future extension.
5841 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
5842 unsigned int, usize, unsigned int, flags)
5844 struct sched_attr kattr = { };
5845 struct task_struct *p;
5848 if (!uattr || pid < 0 || usize > PAGE_SIZE ||
5849 usize < SCHED_ATTR_SIZE_VER0 || flags)
5853 p = find_process_by_pid(pid);
5858 retval = security_task_getscheduler(p);
5862 kattr.sched_policy = p->policy;
5863 if (p->sched_reset_on_fork)
5864 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
5865 if (task_has_dl_policy(p))
5866 __getparam_dl(p, &kattr);
5867 else if (task_has_rt_policy(p))
5868 kattr.sched_priority = p->rt_priority;
5870 kattr.sched_nice = task_nice(p);
5872 #ifdef CONFIG_UCLAMP_TASK
5874 * This could race with another potential updater, but this is fine
5875 * because it'll correctly read the old or the new value. We don't need
5876 * to guarantee who wins the race as long as it doesn't return garbage.
5878 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
5879 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
5884 return sched_attr_copy_to_user(uattr, &kattr, usize);
5891 long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
5893 cpumask_var_t cpus_allowed, new_mask;
5894 struct task_struct *p;
5899 p = find_process_by_pid(pid);
5905 /* Prevent p going away */
5909 if (p->flags & PF_NO_SETAFFINITY) {
5913 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
5917 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
5919 goto out_free_cpus_allowed;
5922 if (!check_same_owner(p)) {
5924 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
5926 goto out_free_new_mask;
5931 retval = security_task_setscheduler(p);
5933 goto out_free_new_mask;
5936 cpuset_cpus_allowed(p, cpus_allowed);
5937 cpumask_and(new_mask, in_mask, cpus_allowed);
5940 * Since bandwidth control happens on root_domain basis,
5941 * if admission test is enabled, we only admit -deadline
5942 * tasks allowed to run on all the CPUs in the task's
5946 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
5948 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
5951 goto out_free_new_mask;
5957 retval = __set_cpus_allowed_ptr(p, new_mask, true);
5960 cpuset_cpus_allowed(p, cpus_allowed);
5961 if (!cpumask_subset(new_mask, cpus_allowed)) {
5963 * We must have raced with a concurrent cpuset
5964 * update. Just reset the cpus_allowed to the
5965 * cpuset's cpus_allowed
5967 cpumask_copy(new_mask, cpus_allowed);
5972 free_cpumask_var(new_mask);
5973 out_free_cpus_allowed:
5974 free_cpumask_var(cpus_allowed);
5980 static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
5981 struct cpumask *new_mask)
5983 if (len < cpumask_size())
5984 cpumask_clear(new_mask);
5985 else if (len > cpumask_size())
5986 len = cpumask_size();
5988 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
5992 * sys_sched_setaffinity - set the CPU affinity of a process
5993 * @pid: pid of the process
5994 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
5995 * @user_mask_ptr: user-space pointer to the new CPU mask
5997 * Return: 0 on success. An error code otherwise.
5999 SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
6000 unsigned long __user *, user_mask_ptr)
6002 cpumask_var_t new_mask;
6005 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
6008 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
6010 retval = sched_setaffinity(pid, new_mask);
6011 free_cpumask_var(new_mask);
6015 long sched_getaffinity(pid_t pid, struct cpumask *mask)
6017 struct task_struct *p;
6018 unsigned long flags;
6024 p = find_process_by_pid(pid);
6028 retval = security_task_getscheduler(p);
6032 raw_spin_lock_irqsave(&p->pi_lock, flags);
6033 cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
6034 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
6043 * sys_sched_getaffinity - get the CPU affinity of a process
6044 * @pid: pid of the process
6045 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
6046 * @user_mask_ptr: user-space pointer to hold the current CPU mask
6048 * Return: size of CPU mask copied to user_mask_ptr on success. An
6049 * error code otherwise.
6051 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
6052 unsigned long __user *, user_mask_ptr)
6057 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
6059 if (len & (sizeof(unsigned long)-1))
6062 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
6065 ret = sched_getaffinity(pid, mask);
6067 unsigned int retlen = min(len, cpumask_size());
6069 if (copy_to_user(user_mask_ptr, mask, retlen))
6074 free_cpumask_var(mask);
6080 * sys_sched_yield - yield the current processor to other threads.
6082 * This function yields the current CPU to other tasks. If there are no
6083 * other threads running on this CPU then this function will return.
6087 static void do_sched_yield(void)
6092 rq = this_rq_lock_irq(&rf);
6094 schedstat_inc(rq->yld_count);
6095 current->sched_class->yield_task(rq);
6098 * Since we are going to call schedule() anyway, there's
6099 * no need to preempt or enable interrupts:
6103 sched_preempt_enable_no_resched();
6108 SYSCALL_DEFINE0(sched_yield)
6114 #ifndef CONFIG_PREEMPTION
6115 int __sched _cond_resched(void)
6117 if (should_resched(0)) {
6118 preempt_schedule_common();
6124 EXPORT_SYMBOL(_cond_resched);
6128 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
6129 * call schedule, and on return reacquire the lock.
6131 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
6132 * operations here to prevent schedule() from being called twice (once via
6133 * spin_unlock(), once by hand).
6135 int __cond_resched_lock(spinlock_t *lock)
6137 int resched = should_resched(PREEMPT_LOCK_OFFSET);
6140 lockdep_assert_held(lock);
6142 if (spin_needbreak(lock) || resched) {
6145 preempt_schedule_common();
6153 EXPORT_SYMBOL(__cond_resched_lock);
6156 * yield - yield the current processor to other threads.
6158 * Do not ever use this function, there's a 99% chance you're doing it wrong.
6160 * The scheduler is at all times free to pick the calling task as the most
6161 * eligible task to run, if removing the yield() call from your code breaks
6162 * it, its already broken.
6164 * Typical broken usage is:
6169 * where one assumes that yield() will let 'the other' process run that will
6170 * make event true. If the current task is a SCHED_FIFO task that will never
6171 * happen. Never use yield() as a progress guarantee!!
6173 * If you want to use yield() to wait for something, use wait_event().
6174 * If you want to use yield() to be 'nice' for others, use cond_resched().
6175 * If you still want to use yield(), do not!
6177 void __sched yield(void)
6179 set_current_state(TASK_RUNNING);
6182 EXPORT_SYMBOL(yield);
6185 * yield_to - yield the current processor to another thread in
6186 * your thread group, or accelerate that thread toward the
6187 * processor it's on.
6189 * @preempt: whether task preemption is allowed or not
6191 * It's the caller's job to ensure that the target task struct
6192 * can't go away on us before we can do any checks.
6195 * true (>0) if we indeed boosted the target task.
6196 * false (0) if we failed to boost the target.
6197 * -ESRCH if there's no task to yield to.
6199 int __sched yield_to(struct task_struct *p, bool preempt)
6201 struct task_struct *curr = current;
6202 struct rq *rq, *p_rq;
6203 unsigned long flags;
6206 local_irq_save(flags);
6212 * If we're the only runnable task on the rq and target rq also
6213 * has only one task, there's absolutely no point in yielding.
6215 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
6220 double_rq_lock(rq, p_rq);
6221 if (task_rq(p) != p_rq) {
6222 double_rq_unlock(rq, p_rq);
6226 if (!curr->sched_class->yield_to_task)
6229 if (curr->sched_class != p->sched_class)
6232 if (task_running(p_rq, p) || p->state)
6235 yielded = curr->sched_class->yield_to_task(rq, p);
6237 schedstat_inc(rq->yld_count);
6239 * Make p's CPU reschedule; pick_next_entity takes care of
6242 if (preempt && rq != p_rq)
6247 double_rq_unlock(rq, p_rq);
6249 local_irq_restore(flags);
6256 EXPORT_SYMBOL_GPL(yield_to);
6258 int io_schedule_prepare(void)
6260 int old_iowait = current->in_iowait;
6262 current->in_iowait = 1;
6263 blk_schedule_flush_plug(current);
6268 void io_schedule_finish(int token)
6270 current->in_iowait = token;
6274 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
6275 * that process accounting knows that this is a task in IO wait state.
6277 long __sched io_schedule_timeout(long timeout)
6282 token = io_schedule_prepare();
6283 ret = schedule_timeout(timeout);
6284 io_schedule_finish(token);
6288 EXPORT_SYMBOL(io_schedule_timeout);
6290 void __sched io_schedule(void)
6294 token = io_schedule_prepare();
6296 io_schedule_finish(token);
6298 EXPORT_SYMBOL(io_schedule);
6301 * sys_sched_get_priority_max - return maximum RT priority.
6302 * @policy: scheduling class.
6304 * Return: On success, this syscall returns the maximum
6305 * rt_priority that can be used by a given scheduling class.
6306 * On failure, a negative error code is returned.
6308 SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
6315 ret = MAX_USER_RT_PRIO-1;
6317 case SCHED_DEADLINE:
6328 * sys_sched_get_priority_min - return minimum RT priority.
6329 * @policy: scheduling class.
6331 * Return: On success, this syscall returns the minimum
6332 * rt_priority that can be used by a given scheduling class.
6333 * On failure, a negative error code is returned.
6335 SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
6344 case SCHED_DEADLINE:
6353 static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
6355 struct task_struct *p;
6356 unsigned int time_slice;
6366 p = find_process_by_pid(pid);
6370 retval = security_task_getscheduler(p);
6374 rq = task_rq_lock(p, &rf);
6376 if (p->sched_class->get_rr_interval)
6377 time_slice = p->sched_class->get_rr_interval(rq, p);
6378 task_rq_unlock(rq, p, &rf);
6381 jiffies_to_timespec64(time_slice, t);
6390 * sys_sched_rr_get_interval - return the default timeslice of a process.
6391 * @pid: pid of the process.
6392 * @interval: userspace pointer to the timeslice value.
6394 * this syscall writes the default timeslice value of a given process
6395 * into the user-space timespec buffer. A value of '0' means infinity.
6397 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
6400 SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
6401 struct __kernel_timespec __user *, interval)
6403 struct timespec64 t;
6404 int retval = sched_rr_get_interval(pid, &t);
6407 retval = put_timespec64(&t, interval);
6412 #ifdef CONFIG_COMPAT_32BIT_TIME
6413 SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
6414 struct old_timespec32 __user *, interval)
6416 struct timespec64 t;
6417 int retval = sched_rr_get_interval(pid, &t);
6420 retval = put_old_timespec32(&t, interval);
6425 void sched_show_task(struct task_struct *p)
6427 unsigned long free = 0;
6430 if (!try_get_task_stack(p))
6433 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
6435 if (p->state == TASK_RUNNING)
6436 pr_cont(" running task ");
6437 #ifdef CONFIG_DEBUG_STACK_USAGE
6438 free = stack_not_used(p);
6443 ppid = task_pid_nr(rcu_dereference(p->real_parent));
6445 pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n",
6446 free, task_pid_nr(p), ppid,
6447 (unsigned long)task_thread_info(p)->flags);
6449 print_worker_info(KERN_INFO, p);
6450 show_stack(p, NULL, KERN_INFO);
6453 EXPORT_SYMBOL_GPL(sched_show_task);
6456 state_filter_match(unsigned long state_filter, struct task_struct *p)
6458 /* no filter, everything matches */
6462 /* filter, but doesn't match */
6463 if (!(p->state & state_filter))
6467 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
6470 if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE)
6477 void show_state_filter(unsigned long state_filter)
6479 struct task_struct *g, *p;
6482 for_each_process_thread(g, p) {
6484 * reset the NMI-timeout, listing all files on a slow
6485 * console might take a lot of time:
6486 * Also, reset softlockup watchdogs on all CPUs, because
6487 * another CPU might be blocked waiting for us to process
6490 touch_nmi_watchdog();
6491 touch_all_softlockup_watchdogs();
6492 if (state_filter_match(state_filter, p))
6496 #ifdef CONFIG_SCHED_DEBUG
6498 sysrq_sched_debug_show();
6502 * Only show locks if all tasks are dumped:
6505 debug_show_all_locks();
6509 * init_idle - set up an idle thread for a given CPU
6510 * @idle: task in question
6511 * @cpu: CPU the idle task belongs to
6513 * NOTE: this function does not set the idle thread's NEED_RESCHED
6514 * flag, to make booting more robust.
6516 void init_idle(struct task_struct *idle, int cpu)
6518 struct rq *rq = cpu_rq(cpu);
6519 unsigned long flags;
6521 __sched_fork(0, idle);
6523 raw_spin_lock_irqsave(&idle->pi_lock, flags);
6524 raw_spin_lock(&rq->lock);
6526 idle->state = TASK_RUNNING;
6527 idle->se.exec_start = sched_clock();
6528 idle->flags |= PF_IDLE;
6530 scs_task_reset(idle);
6531 kasan_unpoison_task_stack(idle);
6535 * Its possible that init_idle() gets called multiple times on a task,
6536 * in that case do_set_cpus_allowed() will not do the right thing.
6538 * And since this is boot we can forgo the serialization.
6540 set_cpus_allowed_common(idle, cpumask_of(cpu));
6543 * We're having a chicken and egg problem, even though we are
6544 * holding rq->lock, the CPU isn't yet set to this CPU so the
6545 * lockdep check in task_group() will fail.
6547 * Similar case to sched_fork(). / Alternatively we could
6548 * use task_rq_lock() here and obtain the other rq->lock.
6553 __set_task_cpu(idle, cpu);
6557 rcu_assign_pointer(rq->curr, idle);
6558 idle->on_rq = TASK_ON_RQ_QUEUED;
6562 raw_spin_unlock(&rq->lock);
6563 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
6565 /* Set the preempt count _outside_ the spinlocks! */
6566 init_idle_preempt_count(idle, cpu);
6569 * The idle tasks have their own, simple scheduling class:
6571 idle->sched_class = &idle_sched_class;
6572 ftrace_graph_init_idle_task(idle, cpu);
6573 vtime_init_idle(idle, cpu);
6575 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
6581 int cpuset_cpumask_can_shrink(const struct cpumask *cur,
6582 const struct cpumask *trial)
6586 if (!cpumask_weight(cur))
6589 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
6594 int task_can_attach(struct task_struct *p,
6595 const struct cpumask *cs_cpus_allowed)
6600 * Kthreads which disallow setaffinity shouldn't be moved
6601 * to a new cpuset; we don't want to change their CPU
6602 * affinity and isolating such threads by their set of
6603 * allowed nodes is unnecessary. Thus, cpusets are not
6604 * applicable for such threads. This prevents checking for
6605 * success of set_cpus_allowed_ptr() on all attached tasks
6606 * before cpus_mask may be changed.
6608 if (p->flags & PF_NO_SETAFFINITY) {
6613 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
6615 ret = dl_task_can_attach(p, cs_cpus_allowed);
6621 bool sched_smp_initialized __read_mostly;
6623 #ifdef CONFIG_NUMA_BALANCING
6624 /* Migrate current task p to target_cpu */
6625 int migrate_task_to(struct task_struct *p, int target_cpu)
6627 struct migration_arg arg = { p, target_cpu };
6628 int curr_cpu = task_cpu(p);
6630 if (curr_cpu == target_cpu)
6633 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
6636 /* TODO: This is not properly updating schedstats */
6638 trace_sched_move_numa(p, curr_cpu, target_cpu);
6639 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
6643 * Requeue a task on a given node and accurately track the number of NUMA
6644 * tasks on the runqueues
6646 void sched_setnuma(struct task_struct *p, int nid)
6648 bool queued, running;
6652 rq = task_rq_lock(p, &rf);
6653 queued = task_on_rq_queued(p);
6654 running = task_current(rq, p);
6657 dequeue_task(rq, p, DEQUEUE_SAVE);
6659 put_prev_task(rq, p);
6661 p->numa_preferred_nid = nid;
6664 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
6666 set_next_task(rq, p);
6667 task_rq_unlock(rq, p, &rf);
6669 #endif /* CONFIG_NUMA_BALANCING */
6671 #ifdef CONFIG_HOTPLUG_CPU
6673 * Ensure that the idle task is using init_mm right before its CPU goes
6676 void idle_task_exit(void)
6678 struct mm_struct *mm = current->active_mm;
6680 BUG_ON(cpu_online(smp_processor_id()));
6681 BUG_ON(current != this_rq()->idle);
6683 if (mm != &init_mm) {
6684 switch_mm(mm, &init_mm, current);
6685 finish_arch_post_lock_switch();
6688 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
6692 * Since this CPU is going 'away' for a while, fold any nr_active delta
6693 * we might have. Assumes we're called after migrate_tasks() so that the
6694 * nr_active count is stable. We need to take the teardown thread which
6695 * is calling this into account, so we hand in adjust = 1 to the load
6698 * Also see the comment "Global load-average calculations".
6700 static void calc_load_migrate(struct rq *rq)
6702 long delta = calc_load_fold_active(rq, 1);
6704 atomic_long_add(delta, &calc_load_tasks);
6707 static struct task_struct *__pick_migrate_task(struct rq *rq)
6709 const struct sched_class *class;
6710 struct task_struct *next;
6712 for_each_class(class) {
6713 next = class->pick_next_task(rq);
6715 next->sched_class->put_prev_task(rq, next);
6720 /* The idle class should always have a runnable task */
6725 * Migrate all tasks from the rq, sleeping tasks will be migrated by
6726 * try_to_wake_up()->select_task_rq().
6728 * Called with rq->lock held even though we'er in stop_machine() and
6729 * there's no concurrency possible, we hold the required locks anyway
6730 * because of lock validation efforts.
6732 static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
6734 struct rq *rq = dead_rq;
6735 struct task_struct *next, *stop = rq->stop;
6736 struct rq_flags orf = *rf;
6740 * Fudge the rq selection such that the below task selection loop
6741 * doesn't get stuck on the currently eligible stop task.
6743 * We're currently inside stop_machine() and the rq is either stuck
6744 * in the stop_machine_cpu_stop() loop, or we're executing this code,
6745 * either way we should never end up calling schedule() until we're
6751 * put_prev_task() and pick_next_task() sched
6752 * class method both need to have an up-to-date
6753 * value of rq->clock[_task]
6755 update_rq_clock(rq);
6759 * There's this thread running, bail when that's the only
6762 if (rq->nr_running == 1)
6765 next = __pick_migrate_task(rq);
6768 * Rules for changing task_struct::cpus_mask are holding
6769 * both pi_lock and rq->lock, such that holding either
6770 * stabilizes the mask.
6772 * Drop rq->lock is not quite as disastrous as it usually is
6773 * because !cpu_active at this point, which means load-balance
6774 * will not interfere. Also, stop-machine.
6777 raw_spin_lock(&next->pi_lock);
6781 * Since we're inside stop-machine, _nothing_ should have
6782 * changed the task, WARN if weird stuff happened, because in
6783 * that case the above rq->lock drop is a fail too.
6785 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
6786 raw_spin_unlock(&next->pi_lock);
6790 /* Find suitable destination for @next, with force if needed. */
6791 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
6792 rq = __migrate_task(rq, rf, next, dest_cpu);
6793 if (rq != dead_rq) {
6799 raw_spin_unlock(&next->pi_lock);
6804 #endif /* CONFIG_HOTPLUG_CPU */
6806 void set_rq_online(struct rq *rq)
6809 const struct sched_class *class;
6811 cpumask_set_cpu(rq->cpu, rq->rd->online);
6814 for_each_class(class) {
6815 if (class->rq_online)
6816 class->rq_online(rq);
6821 void set_rq_offline(struct rq *rq)
6824 const struct sched_class *class;
6826 for_each_class(class) {
6827 if (class->rq_offline)
6828 class->rq_offline(rq);
6831 cpumask_clear_cpu(rq->cpu, rq->rd->online);
6837 * used to mark begin/end of suspend/resume:
6839 static int num_cpus_frozen;
6842 * Update cpusets according to cpu_active mask. If cpusets are
6843 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
6844 * around partition_sched_domains().
6846 * If we come here as part of a suspend/resume, don't touch cpusets because we
6847 * want to restore it back to its original state upon resume anyway.
6849 static void cpuset_cpu_active(void)
6851 if (cpuhp_tasks_frozen) {
6853 * num_cpus_frozen tracks how many CPUs are involved in suspend
6854 * resume sequence. As long as this is not the last online
6855 * operation in the resume sequence, just build a single sched
6856 * domain, ignoring cpusets.
6858 partition_sched_domains(1, NULL, NULL);
6859 if (--num_cpus_frozen)
6862 * This is the last CPU online operation. So fall through and
6863 * restore the original sched domains by considering the
6864 * cpuset configurations.
6866 cpuset_force_rebuild();
6868 cpuset_update_active_cpus();
6871 static int cpuset_cpu_inactive(unsigned int cpu)
6873 if (!cpuhp_tasks_frozen) {
6874 if (dl_cpu_busy(cpu))
6876 cpuset_update_active_cpus();
6879 partition_sched_domains(1, NULL, NULL);
6884 int sched_cpu_activate(unsigned int cpu)
6886 struct rq *rq = cpu_rq(cpu);
6889 #ifdef CONFIG_SCHED_SMT
6891 * When going up, increment the number of cores with SMT present.
6893 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
6894 static_branch_inc_cpuslocked(&sched_smt_present);
6896 set_cpu_active(cpu, true);
6898 if (sched_smp_initialized) {
6899 sched_domains_numa_masks_set(cpu);
6900 cpuset_cpu_active();
6904 * Put the rq online, if not already. This happens:
6906 * 1) In the early boot process, because we build the real domains
6907 * after all CPUs have been brought up.
6909 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
6912 rq_lock_irqsave(rq, &rf);
6914 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
6917 rq_unlock_irqrestore(rq, &rf);
6922 int sched_cpu_deactivate(unsigned int cpu)
6926 set_cpu_active(cpu, false);
6928 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
6929 * users of this state to go away such that all new such users will
6932 * Do sync before park smpboot threads to take care the rcu boost case.
6936 #ifdef CONFIG_SCHED_SMT
6938 * When going down, decrement the number of cores with SMT present.
6940 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
6941 static_branch_dec_cpuslocked(&sched_smt_present);
6944 if (!sched_smp_initialized)
6947 ret = cpuset_cpu_inactive(cpu);
6949 set_cpu_active(cpu, true);
6952 sched_domains_numa_masks_clear(cpu);
6956 static void sched_rq_cpu_starting(unsigned int cpu)
6958 struct rq *rq = cpu_rq(cpu);
6960 rq->calc_load_update = calc_load_update;
6961 update_max_interval();
6964 int sched_cpu_starting(unsigned int cpu)
6966 sched_rq_cpu_starting(cpu);
6967 sched_tick_start(cpu);
6971 #ifdef CONFIG_HOTPLUG_CPU
6972 int sched_cpu_dying(unsigned int cpu)
6974 struct rq *rq = cpu_rq(cpu);
6977 /* Handle pending wakeups and then migrate everything off */
6978 sched_tick_stop(cpu);
6980 rq_lock_irqsave(rq, &rf);
6982 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
6985 migrate_tasks(rq, &rf);
6986 BUG_ON(rq->nr_running != 1);
6987 rq_unlock_irqrestore(rq, &rf);
6989 calc_load_migrate(rq);
6990 update_max_interval();
6991 nohz_balance_exit_idle(rq);
6997 void __init sched_init_smp(void)
7002 * There's no userspace yet to cause hotplug operations; hence all the
7003 * CPU masks are stable and all blatant races in the below code cannot
7006 mutex_lock(&sched_domains_mutex);
7007 sched_init_domains(cpu_active_mask);
7008 mutex_unlock(&sched_domains_mutex);
7010 /* Move init over to a non-isolated CPU */
7011 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
7013 sched_init_granularity();
7015 init_sched_rt_class();
7016 init_sched_dl_class();
7018 sched_smp_initialized = true;
7021 static int __init migration_init(void)
7023 sched_cpu_starting(smp_processor_id());
7026 early_initcall(migration_init);
7029 void __init sched_init_smp(void)
7031 sched_init_granularity();
7033 #endif /* CONFIG_SMP */
7035 int in_sched_functions(unsigned long addr)
7037 return in_lock_functions(addr) ||
7038 (addr >= (unsigned long)__sched_text_start
7039 && addr < (unsigned long)__sched_text_end);
7042 #ifdef CONFIG_CGROUP_SCHED
7044 * Default task group.
7045 * Every task in system belongs to this group at bootup.
7047 struct task_group root_task_group;
7048 LIST_HEAD(task_groups);
7050 /* Cacheline aligned slab cache for task_group */
7051 static struct kmem_cache *task_group_cache __read_mostly;
7054 DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
7055 DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
7057 void __init sched_init(void)
7059 unsigned long ptr = 0;
7062 /* Make sure the linker didn't screw up */
7063 BUG_ON(&idle_sched_class + 1 != &fair_sched_class ||
7064 &fair_sched_class + 1 != &rt_sched_class ||
7065 &rt_sched_class + 1 != &dl_sched_class);
7067 BUG_ON(&dl_sched_class + 1 != &stop_sched_class);
7072 #ifdef CONFIG_FAIR_GROUP_SCHED
7073 ptr += 2 * nr_cpu_ids * sizeof(void **);
7075 #ifdef CONFIG_RT_GROUP_SCHED
7076 ptr += 2 * nr_cpu_ids * sizeof(void **);
7079 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
7081 #ifdef CONFIG_FAIR_GROUP_SCHED
7082 root_task_group.se = (struct sched_entity **)ptr;
7083 ptr += nr_cpu_ids * sizeof(void **);
7085 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
7086 ptr += nr_cpu_ids * sizeof(void **);
7088 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
7089 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
7090 #endif /* CONFIG_FAIR_GROUP_SCHED */
7091 #ifdef CONFIG_RT_GROUP_SCHED
7092 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
7093 ptr += nr_cpu_ids * sizeof(void **);
7095 root_task_group.rt_rq = (struct rt_rq **)ptr;
7096 ptr += nr_cpu_ids * sizeof(void **);
7098 #endif /* CONFIG_RT_GROUP_SCHED */
7100 #ifdef CONFIG_CPUMASK_OFFSTACK
7101 for_each_possible_cpu(i) {
7102 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
7103 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
7104 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
7105 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
7107 #endif /* CONFIG_CPUMASK_OFFSTACK */
7109 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
7110 init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
7113 init_defrootdomain();
7116 #ifdef CONFIG_RT_GROUP_SCHED
7117 init_rt_bandwidth(&root_task_group.rt_bandwidth,
7118 global_rt_period(), global_rt_runtime());
7119 #endif /* CONFIG_RT_GROUP_SCHED */
7121 #ifdef CONFIG_CGROUP_SCHED
7122 task_group_cache = KMEM_CACHE(task_group, 0);
7124 list_add(&root_task_group.list, &task_groups);
7125 INIT_LIST_HEAD(&root_task_group.children);
7126 INIT_LIST_HEAD(&root_task_group.siblings);
7127 autogroup_init(&init_task);
7128 #endif /* CONFIG_CGROUP_SCHED */
7130 for_each_possible_cpu(i) {
7134 raw_spin_lock_init(&rq->lock);
7136 rq->calc_load_active = 0;
7137 rq->calc_load_update = jiffies + LOAD_FREQ;
7138 init_cfs_rq(&rq->cfs);
7139 init_rt_rq(&rq->rt);
7140 init_dl_rq(&rq->dl);
7141 #ifdef CONFIG_FAIR_GROUP_SCHED
7142 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
7143 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
7145 * How much CPU bandwidth does root_task_group get?
7147 * In case of task-groups formed thr' the cgroup filesystem, it
7148 * gets 100% of the CPU resources in the system. This overall
7149 * system CPU resource is divided among the tasks of
7150 * root_task_group and its child task-groups in a fair manner,
7151 * based on each entity's (task or task-group's) weight
7152 * (se->load.weight).
7154 * In other words, if root_task_group has 10 tasks of weight
7155 * 1024) and two child groups A0 and A1 (of weight 1024 each),
7156 * then A0's share of the CPU resource is:
7158 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
7160 * We achieve this by letting root_task_group's tasks sit
7161 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
7163 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
7164 #endif /* CONFIG_FAIR_GROUP_SCHED */
7166 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
7167 #ifdef CONFIG_RT_GROUP_SCHED
7168 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
7173 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
7174 rq->balance_callback = NULL;
7175 rq->active_balance = 0;
7176 rq->next_balance = jiffies;
7181 rq->avg_idle = 2*sysctl_sched_migration_cost;
7182 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
7184 INIT_LIST_HEAD(&rq->cfs_tasks);
7186 rq_attach_root(rq, &def_root_domain);
7187 #ifdef CONFIG_NO_HZ_COMMON
7188 rq->last_blocked_load_update_tick = jiffies;
7189 atomic_set(&rq->nohz_flags, 0);
7191 rq_csd_init(rq, &rq->nohz_csd, nohz_csd_func);
7193 #endif /* CONFIG_SMP */
7195 atomic_set(&rq->nr_iowait, 0);
7198 set_load_weight(&init_task, false);
7201 * The boot idle thread does lazy MMU switching as well:
7204 enter_lazy_tlb(&init_mm, current);
7207 * Make us the idle thread. Technically, schedule() should not be
7208 * called from this thread, however somewhere below it might be,
7209 * but because we are the idle thread, we just pick up running again
7210 * when this runqueue becomes "idle".
7212 init_idle(current, smp_processor_id());
7214 calc_load_update = jiffies + LOAD_FREQ;
7217 idle_thread_set_boot_cpu();
7219 init_sched_fair_class();
7227 scheduler_running = 1;
7230 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
7231 static inline int preempt_count_equals(int preempt_offset)
7233 int nested = preempt_count() + rcu_preempt_depth();
7235 return (nested == preempt_offset);
7238 void __might_sleep(const char *file, int line, int preempt_offset)
7241 * Blocking primitives will set (and therefore destroy) current->state,
7242 * since we will exit with TASK_RUNNING make sure we enter with it,
7243 * otherwise we will destroy state.
7245 WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
7246 "do not call blocking ops when !TASK_RUNNING; "
7247 "state=%lx set at [<%p>] %pS\n",
7249 (void *)current->task_state_change,
7250 (void *)current->task_state_change);
7252 ___might_sleep(file, line, preempt_offset);
7254 EXPORT_SYMBOL(__might_sleep);
7256 void ___might_sleep(const char *file, int line, int preempt_offset)
7258 /* Ratelimiting timestamp: */
7259 static unsigned long prev_jiffy;
7261 unsigned long preempt_disable_ip;
7263 /* WARN_ON_ONCE() by default, no rate limit required: */
7266 if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
7267 !is_idle_task(current) && !current->non_block_count) ||
7268 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
7272 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
7274 prev_jiffy = jiffies;
7276 /* Save this before calling printk(), since that will clobber it: */
7277 preempt_disable_ip = get_preempt_disable_ip(current);
7280 "BUG: sleeping function called from invalid context at %s:%d\n",
7283 "in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
7284 in_atomic(), irqs_disabled(), current->non_block_count,
7285 current->pid, current->comm);
7287 if (task_stack_end_corrupted(current))
7288 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
7290 debug_show_held_locks(current);
7291 if (irqs_disabled())
7292 print_irqtrace_events(current);
7293 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
7294 && !preempt_count_equals(preempt_offset)) {
7295 pr_err("Preemption disabled at:");
7296 print_ip_sym(KERN_ERR, preempt_disable_ip);
7299 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
7301 EXPORT_SYMBOL(___might_sleep);
7303 void __cant_sleep(const char *file, int line, int preempt_offset)
7305 static unsigned long prev_jiffy;
7307 if (irqs_disabled())
7310 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
7313 if (preempt_count() > preempt_offset)
7316 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
7318 prev_jiffy = jiffies;
7320 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
7321 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
7322 in_atomic(), irqs_disabled(),
7323 current->pid, current->comm);
7325 debug_show_held_locks(current);
7327 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
7329 EXPORT_SYMBOL_GPL(__cant_sleep);
7332 #ifdef CONFIG_MAGIC_SYSRQ
7333 void normalize_rt_tasks(void)
7335 struct task_struct *g, *p;
7336 struct sched_attr attr = {
7337 .sched_policy = SCHED_NORMAL,
7340 read_lock(&tasklist_lock);
7341 for_each_process_thread(g, p) {
7343 * Only normalize user tasks:
7345 if (p->flags & PF_KTHREAD)
7348 p->se.exec_start = 0;
7349 schedstat_set(p->se.statistics.wait_start, 0);
7350 schedstat_set(p->se.statistics.sleep_start, 0);
7351 schedstat_set(p->se.statistics.block_start, 0);
7353 if (!dl_task(p) && !rt_task(p)) {
7355 * Renice negative nice level userspace
7358 if (task_nice(p) < 0)
7359 set_user_nice(p, 0);
7363 __sched_setscheduler(p, &attr, false, false);
7365 read_unlock(&tasklist_lock);
7368 #endif /* CONFIG_MAGIC_SYSRQ */
7370 #if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
7372 * These functions are only useful for the IA64 MCA handling, or kdb.
7374 * They can only be called when the whole system has been
7375 * stopped - every CPU needs to be quiescent, and no scheduling
7376 * activity can take place. Using them for anything else would
7377 * be a serious bug, and as a result, they aren't even visible
7378 * under any other configuration.
7382 * curr_task - return the current task for a given CPU.
7383 * @cpu: the processor in question.
7385 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7387 * Return: The current task for @cpu.
7389 struct task_struct *curr_task(int cpu)
7391 return cpu_curr(cpu);
7394 #endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
7398 * ia64_set_curr_task - set the current task for a given CPU.
7399 * @cpu: the processor in question.
7400 * @p: the task pointer to set.
7402 * Description: This function must only be used when non-maskable interrupts
7403 * are serviced on a separate stack. It allows the architecture to switch the
7404 * notion of the current task on a CPU in a non-blocking manner. This function
7405 * must be called with all CPU's synchronized, and interrupts disabled, the
7406 * and caller must save the original value of the current task (see
7407 * curr_task() above) and restore that value before reenabling interrupts and
7408 * re-starting the system.
7410 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
7412 void ia64_set_curr_task(int cpu, struct task_struct *p)
7419 #ifdef CONFIG_CGROUP_SCHED
7420 /* task_group_lock serializes the addition/removal of task groups */
7421 static DEFINE_SPINLOCK(task_group_lock);
7423 static inline void alloc_uclamp_sched_group(struct task_group *tg,
7424 struct task_group *parent)
7426 #ifdef CONFIG_UCLAMP_TASK_GROUP
7427 enum uclamp_id clamp_id;
7429 for_each_clamp_id(clamp_id) {
7430 uclamp_se_set(&tg->uclamp_req[clamp_id],
7431 uclamp_none(clamp_id), false);
7432 tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
7437 static void sched_free_group(struct task_group *tg)
7439 free_fair_sched_group(tg);
7440 free_rt_sched_group(tg);
7442 kmem_cache_free(task_group_cache, tg);
7445 /* allocate runqueue etc for a new task group */
7446 struct task_group *sched_create_group(struct task_group *parent)
7448 struct task_group *tg;
7450 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
7452 return ERR_PTR(-ENOMEM);
7454 if (!alloc_fair_sched_group(tg, parent))
7457 if (!alloc_rt_sched_group(tg, parent))
7460 alloc_uclamp_sched_group(tg, parent);
7465 sched_free_group(tg);
7466 return ERR_PTR(-ENOMEM);
7469 void sched_online_group(struct task_group *tg, struct task_group *parent)
7471 unsigned long flags;
7473 spin_lock_irqsave(&task_group_lock, flags);
7474 list_add_rcu(&tg->list, &task_groups);
7476 /* Root should already exist: */
7479 tg->parent = parent;
7480 INIT_LIST_HEAD(&tg->children);
7481 list_add_rcu(&tg->siblings, &parent->children);
7482 spin_unlock_irqrestore(&task_group_lock, flags);
7484 online_fair_sched_group(tg);
7487 /* rcu callback to free various structures associated with a task group */
7488 static void sched_free_group_rcu(struct rcu_head *rhp)
7490 /* Now it should be safe to free those cfs_rqs: */
7491 sched_free_group(container_of(rhp, struct task_group, rcu));
7494 void sched_destroy_group(struct task_group *tg)
7496 /* Wait for possible concurrent references to cfs_rqs complete: */
7497 call_rcu(&tg->rcu, sched_free_group_rcu);
7500 void sched_offline_group(struct task_group *tg)
7502 unsigned long flags;
7504 /* End participation in shares distribution: */
7505 unregister_fair_sched_group(tg);
7507 spin_lock_irqsave(&task_group_lock, flags);
7508 list_del_rcu(&tg->list);
7509 list_del_rcu(&tg->siblings);
7510 spin_unlock_irqrestore(&task_group_lock, flags);
7513 static void sched_change_group(struct task_struct *tsk, int type)
7515 struct task_group *tg;
7518 * All callers are synchronized by task_rq_lock(); we do not use RCU
7519 * which is pointless here. Thus, we pass "true" to task_css_check()
7520 * to prevent lockdep warnings.
7522 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
7523 struct task_group, css);
7524 tg = autogroup_task_group(tsk, tg);
7525 tsk->sched_task_group = tg;
7527 #ifdef CONFIG_FAIR_GROUP_SCHED
7528 if (tsk->sched_class->task_change_group)
7529 tsk->sched_class->task_change_group(tsk, type);
7532 set_task_rq(tsk, task_cpu(tsk));
7536 * Change task's runqueue when it moves between groups.
7538 * The caller of this function should have put the task in its new group by
7539 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
7542 void sched_move_task(struct task_struct *tsk)
7544 int queued, running, queue_flags =
7545 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7549 rq = task_rq_lock(tsk, &rf);
7550 update_rq_clock(rq);
7552 running = task_current(rq, tsk);
7553 queued = task_on_rq_queued(tsk);
7556 dequeue_task(rq, tsk, queue_flags);
7558 put_prev_task(rq, tsk);
7560 sched_change_group(tsk, TASK_MOVE_GROUP);
7563 enqueue_task(rq, tsk, queue_flags);
7565 set_next_task(rq, tsk);
7567 * After changing group, the running task may have joined a
7568 * throttled one but it's still the running task. Trigger a
7569 * resched to make sure that task can still run.
7574 task_rq_unlock(rq, tsk, &rf);
7577 static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
7579 return css ? container_of(css, struct task_group, css) : NULL;
7582 static struct cgroup_subsys_state *
7583 cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
7585 struct task_group *parent = css_tg(parent_css);
7586 struct task_group *tg;
7589 /* This is early initialization for the top cgroup */
7590 return &root_task_group.css;
7593 tg = sched_create_group(parent);
7595 return ERR_PTR(-ENOMEM);
7600 /* Expose task group only after completing cgroup initialization */
7601 static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
7603 struct task_group *tg = css_tg(css);
7604 struct task_group *parent = css_tg(css->parent);
7607 sched_online_group(tg, parent);
7609 #ifdef CONFIG_UCLAMP_TASK_GROUP
7610 /* Propagate the effective uclamp value for the new group */
7611 cpu_util_update_eff(css);
7617 static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
7619 struct task_group *tg = css_tg(css);
7621 sched_offline_group(tg);
7624 static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
7626 struct task_group *tg = css_tg(css);
7629 * Relies on the RCU grace period between css_released() and this.
7631 sched_free_group(tg);
7635 * This is called before wake_up_new_task(), therefore we really only
7636 * have to set its group bits, all the other stuff does not apply.
7638 static void cpu_cgroup_fork(struct task_struct *task)
7643 rq = task_rq_lock(task, &rf);
7645 update_rq_clock(rq);
7646 sched_change_group(task, TASK_SET_GROUP);
7648 task_rq_unlock(rq, task, &rf);
7651 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
7653 struct task_struct *task;
7654 struct cgroup_subsys_state *css;
7657 cgroup_taskset_for_each(task, css, tset) {
7658 #ifdef CONFIG_RT_GROUP_SCHED
7659 if (!sched_rt_can_attach(css_tg(css), task))
7663 * Serialize against wake_up_new_task() such that if its
7664 * running, we're sure to observe its full state.
7666 raw_spin_lock_irq(&task->pi_lock);
7668 * Avoid calling sched_move_task() before wake_up_new_task()
7669 * has happened. This would lead to problems with PELT, due to
7670 * move wanting to detach+attach while we're not attached yet.
7672 if (task->state == TASK_NEW)
7674 raw_spin_unlock_irq(&task->pi_lock);
7682 static void cpu_cgroup_attach(struct cgroup_taskset *tset)
7684 struct task_struct *task;
7685 struct cgroup_subsys_state *css;
7687 cgroup_taskset_for_each(task, css, tset)
7688 sched_move_task(task);
7691 #ifdef CONFIG_UCLAMP_TASK_GROUP
7692 static void cpu_util_update_eff(struct cgroup_subsys_state *css)
7694 struct cgroup_subsys_state *top_css = css;
7695 struct uclamp_se *uc_parent = NULL;
7696 struct uclamp_se *uc_se = NULL;
7697 unsigned int eff[UCLAMP_CNT];
7698 enum uclamp_id clamp_id;
7699 unsigned int clamps;
7701 css_for_each_descendant_pre(css, top_css) {
7702 uc_parent = css_tg(css)->parent
7703 ? css_tg(css)->parent->uclamp : NULL;
7705 for_each_clamp_id(clamp_id) {
7706 /* Assume effective clamps matches requested clamps */
7707 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
7708 /* Cap effective clamps with parent's effective clamps */
7710 eff[clamp_id] > uc_parent[clamp_id].value) {
7711 eff[clamp_id] = uc_parent[clamp_id].value;
7714 /* Ensure protection is always capped by limit */
7715 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
7717 /* Propagate most restrictive effective clamps */
7719 uc_se = css_tg(css)->uclamp;
7720 for_each_clamp_id(clamp_id) {
7721 if (eff[clamp_id] == uc_se[clamp_id].value)
7723 uc_se[clamp_id].value = eff[clamp_id];
7724 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
7725 clamps |= (0x1 << clamp_id);
7728 css = css_rightmost_descendant(css);
7732 /* Immediately update descendants RUNNABLE tasks */
7733 uclamp_update_active_tasks(css, clamps);
7738 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
7739 * C expression. Since there is no way to convert a macro argument (N) into a
7740 * character constant, use two levels of macros.
7742 #define _POW10(exp) ((unsigned int)1e##exp)
7743 #define POW10(exp) _POW10(exp)
7745 struct uclamp_request {
7746 #define UCLAMP_PERCENT_SHIFT 2
7747 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
7753 static inline struct uclamp_request
7754 capacity_from_percent(char *buf)
7756 struct uclamp_request req = {
7757 .percent = UCLAMP_PERCENT_SCALE,
7758 .util = SCHED_CAPACITY_SCALE,
7763 if (strcmp(buf, "max")) {
7764 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
7768 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
7773 req.util = req.percent << SCHED_CAPACITY_SHIFT;
7774 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
7780 static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
7781 size_t nbytes, loff_t off,
7782 enum uclamp_id clamp_id)
7784 struct uclamp_request req;
7785 struct task_group *tg;
7787 req = capacity_from_percent(buf);
7791 static_branch_enable(&sched_uclamp_used);
7793 mutex_lock(&uclamp_mutex);
7796 tg = css_tg(of_css(of));
7797 if (tg->uclamp_req[clamp_id].value != req.util)
7798 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
7801 * Because of not recoverable conversion rounding we keep track of the
7802 * exact requested value
7804 tg->uclamp_pct[clamp_id] = req.percent;
7806 /* Update effective clamps to track the most restrictive value */
7807 cpu_util_update_eff(of_css(of));
7810 mutex_unlock(&uclamp_mutex);
7815 static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
7816 char *buf, size_t nbytes,
7819 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
7822 static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
7823 char *buf, size_t nbytes,
7826 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
7829 static inline void cpu_uclamp_print(struct seq_file *sf,
7830 enum uclamp_id clamp_id)
7832 struct task_group *tg;
7838 tg = css_tg(seq_css(sf));
7839 util_clamp = tg->uclamp_req[clamp_id].value;
7842 if (util_clamp == SCHED_CAPACITY_SCALE) {
7843 seq_puts(sf, "max\n");
7847 percent = tg->uclamp_pct[clamp_id];
7848 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
7849 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
7852 static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
7854 cpu_uclamp_print(sf, UCLAMP_MIN);
7858 static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
7860 cpu_uclamp_print(sf, UCLAMP_MAX);
7863 #endif /* CONFIG_UCLAMP_TASK_GROUP */
7865 #ifdef CONFIG_FAIR_GROUP_SCHED
7866 static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
7867 struct cftype *cftype, u64 shareval)
7869 if (shareval > scale_load_down(ULONG_MAX))
7870 shareval = MAX_SHARES;
7871 return sched_group_set_shares(css_tg(css), scale_load(shareval));
7874 static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
7877 struct task_group *tg = css_tg(css);
7879 return (u64) scale_load_down(tg->shares);
7882 #ifdef CONFIG_CFS_BANDWIDTH
7883 static DEFINE_MUTEX(cfs_constraints_mutex);
7885 const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
7886 static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
7887 /* More than 203 days if BW_SHIFT equals 20. */
7888 static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
7890 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
7892 static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
7894 int i, ret = 0, runtime_enabled, runtime_was_enabled;
7895 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
7897 if (tg == &root_task_group)
7901 * Ensure we have at some amount of bandwidth every period. This is
7902 * to prevent reaching a state of large arrears when throttled via
7903 * entity_tick() resulting in prolonged exit starvation.
7905 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
7909 * Likewise, bound things on the otherside by preventing insane quota
7910 * periods. This also allows us to normalize in computing quota
7913 if (period > max_cfs_quota_period)
7917 * Bound quota to defend quota against overflow during bandwidth shift.
7919 if (quota != RUNTIME_INF && quota > max_cfs_runtime)
7923 * Prevent race between setting of cfs_rq->runtime_enabled and
7924 * unthrottle_offline_cfs_rqs().
7927 mutex_lock(&cfs_constraints_mutex);
7928 ret = __cfs_schedulable(tg, period, quota);
7932 runtime_enabled = quota != RUNTIME_INF;
7933 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
7935 * If we need to toggle cfs_bandwidth_used, off->on must occur
7936 * before making related changes, and on->off must occur afterwards
7938 if (runtime_enabled && !runtime_was_enabled)
7939 cfs_bandwidth_usage_inc();
7940 raw_spin_lock_irq(&cfs_b->lock);
7941 cfs_b->period = ns_to_ktime(period);
7942 cfs_b->quota = quota;
7944 __refill_cfs_bandwidth_runtime(cfs_b);
7946 /* Restart the period timer (if active) to handle new period expiry: */
7947 if (runtime_enabled)
7948 start_cfs_bandwidth(cfs_b);
7950 raw_spin_unlock_irq(&cfs_b->lock);
7952 for_each_online_cpu(i) {
7953 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
7954 struct rq *rq = cfs_rq->rq;
7957 rq_lock_irq(rq, &rf);
7958 cfs_rq->runtime_enabled = runtime_enabled;
7959 cfs_rq->runtime_remaining = 0;
7961 if (cfs_rq->throttled)
7962 unthrottle_cfs_rq(cfs_rq);
7963 rq_unlock_irq(rq, &rf);
7965 if (runtime_was_enabled && !runtime_enabled)
7966 cfs_bandwidth_usage_dec();
7968 mutex_unlock(&cfs_constraints_mutex);
7974 static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
7978 period = ktime_to_ns(tg->cfs_bandwidth.period);
7979 if (cfs_quota_us < 0)
7980 quota = RUNTIME_INF;
7981 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
7982 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
7986 return tg_set_cfs_bandwidth(tg, period, quota);
7989 static long tg_get_cfs_quota(struct task_group *tg)
7993 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
7996 quota_us = tg->cfs_bandwidth.quota;
7997 do_div(quota_us, NSEC_PER_USEC);
8002 static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
8006 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
8009 period = (u64)cfs_period_us * NSEC_PER_USEC;
8010 quota = tg->cfs_bandwidth.quota;
8012 return tg_set_cfs_bandwidth(tg, period, quota);
8015 static long tg_get_cfs_period(struct task_group *tg)
8019 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
8020 do_div(cfs_period_us, NSEC_PER_USEC);
8022 return cfs_period_us;
8025 static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
8028 return tg_get_cfs_quota(css_tg(css));
8031 static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
8032 struct cftype *cftype, s64 cfs_quota_us)
8034 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
8037 static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
8040 return tg_get_cfs_period(css_tg(css));
8043 static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
8044 struct cftype *cftype, u64 cfs_period_us)
8046 return tg_set_cfs_period(css_tg(css), cfs_period_us);
8049 struct cfs_schedulable_data {
8050 struct task_group *tg;
8055 * normalize group quota/period to be quota/max_period
8056 * note: units are usecs
8058 static u64 normalize_cfs_quota(struct task_group *tg,
8059 struct cfs_schedulable_data *d)
8067 period = tg_get_cfs_period(tg);
8068 quota = tg_get_cfs_quota(tg);
8071 /* note: these should typically be equivalent */
8072 if (quota == RUNTIME_INF || quota == -1)
8075 return to_ratio(period, quota);
8078 static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
8080 struct cfs_schedulable_data *d = data;
8081 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8082 s64 quota = 0, parent_quota = -1;
8085 quota = RUNTIME_INF;
8087 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
8089 quota = normalize_cfs_quota(tg, d);
8090 parent_quota = parent_b->hierarchical_quota;
8093 * Ensure max(child_quota) <= parent_quota. On cgroup2,
8094 * always take the min. On cgroup1, only inherit when no
8097 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
8098 quota = min(quota, parent_quota);
8100 if (quota == RUNTIME_INF)
8101 quota = parent_quota;
8102 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
8106 cfs_b->hierarchical_quota = quota;
8111 static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
8114 struct cfs_schedulable_data data = {
8120 if (quota != RUNTIME_INF) {
8121 do_div(data.period, NSEC_PER_USEC);
8122 do_div(data.quota, NSEC_PER_USEC);
8126 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
8132 static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
8134 struct task_group *tg = css_tg(seq_css(sf));
8135 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8137 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
8138 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
8139 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
8141 if (schedstat_enabled() && tg != &root_task_group) {
8145 for_each_possible_cpu(i)
8146 ws += schedstat_val(tg->se[i]->statistics.wait_sum);
8148 seq_printf(sf, "wait_sum %llu\n", ws);
8153 #endif /* CONFIG_CFS_BANDWIDTH */
8154 #endif /* CONFIG_FAIR_GROUP_SCHED */
8156 #ifdef CONFIG_RT_GROUP_SCHED
8157 static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
8158 struct cftype *cft, s64 val)
8160 return sched_group_set_rt_runtime(css_tg(css), val);
8163 static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
8166 return sched_group_rt_runtime(css_tg(css));
8169 static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
8170 struct cftype *cftype, u64 rt_period_us)
8172 return sched_group_set_rt_period(css_tg(css), rt_period_us);
8175 static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
8178 return sched_group_rt_period(css_tg(css));
8180 #endif /* CONFIG_RT_GROUP_SCHED */
8182 static struct cftype cpu_legacy_files[] = {
8183 #ifdef CONFIG_FAIR_GROUP_SCHED
8186 .read_u64 = cpu_shares_read_u64,
8187 .write_u64 = cpu_shares_write_u64,
8190 #ifdef CONFIG_CFS_BANDWIDTH
8192 .name = "cfs_quota_us",
8193 .read_s64 = cpu_cfs_quota_read_s64,
8194 .write_s64 = cpu_cfs_quota_write_s64,
8197 .name = "cfs_period_us",
8198 .read_u64 = cpu_cfs_period_read_u64,
8199 .write_u64 = cpu_cfs_period_write_u64,
8203 .seq_show = cpu_cfs_stat_show,
8206 #ifdef CONFIG_RT_GROUP_SCHED
8208 .name = "rt_runtime_us",
8209 .read_s64 = cpu_rt_runtime_read,
8210 .write_s64 = cpu_rt_runtime_write,
8213 .name = "rt_period_us",
8214 .read_u64 = cpu_rt_period_read_uint,
8215 .write_u64 = cpu_rt_period_write_uint,
8218 #ifdef CONFIG_UCLAMP_TASK_GROUP
8220 .name = "uclamp.min",
8221 .flags = CFTYPE_NOT_ON_ROOT,
8222 .seq_show = cpu_uclamp_min_show,
8223 .write = cpu_uclamp_min_write,
8226 .name = "uclamp.max",
8227 .flags = CFTYPE_NOT_ON_ROOT,
8228 .seq_show = cpu_uclamp_max_show,
8229 .write = cpu_uclamp_max_write,
8235 static int cpu_extra_stat_show(struct seq_file *sf,
8236 struct cgroup_subsys_state *css)
8238 #ifdef CONFIG_CFS_BANDWIDTH
8240 struct task_group *tg = css_tg(css);
8241 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
8244 throttled_usec = cfs_b->throttled_time;
8245 do_div(throttled_usec, NSEC_PER_USEC);
8247 seq_printf(sf, "nr_periods %d\n"
8249 "throttled_usec %llu\n",
8250 cfs_b->nr_periods, cfs_b->nr_throttled,
8257 #ifdef CONFIG_FAIR_GROUP_SCHED
8258 static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
8261 struct task_group *tg = css_tg(css);
8262 u64 weight = scale_load_down(tg->shares);
8264 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
8267 static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
8268 struct cftype *cft, u64 weight)
8271 * cgroup weight knobs should use the common MIN, DFL and MAX
8272 * values which are 1, 100 and 10000 respectively. While it loses
8273 * a bit of range on both ends, it maps pretty well onto the shares
8274 * value used by scheduler and the round-trip conversions preserve
8275 * the original value over the entire range.
8277 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
8280 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
8282 return sched_group_set_shares(css_tg(css), scale_load(weight));
8285 static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
8288 unsigned long weight = scale_load_down(css_tg(css)->shares);
8289 int last_delta = INT_MAX;
8292 /* find the closest nice value to the current weight */
8293 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
8294 delta = abs(sched_prio_to_weight[prio] - weight);
8295 if (delta >= last_delta)
8300 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
8303 static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
8304 struct cftype *cft, s64 nice)
8306 unsigned long weight;
8309 if (nice < MIN_NICE || nice > MAX_NICE)
8312 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
8313 idx = array_index_nospec(idx, 40);
8314 weight = sched_prio_to_weight[idx];
8316 return sched_group_set_shares(css_tg(css), scale_load(weight));
8320 static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
8321 long period, long quota)
8324 seq_puts(sf, "max");
8326 seq_printf(sf, "%ld", quota);
8328 seq_printf(sf, " %ld\n", period);
8331 /* caller should put the current value in *@periodp before calling */
8332 static int __maybe_unused cpu_period_quota_parse(char *buf,
8333 u64 *periodp, u64 *quotap)
8335 char tok[21]; /* U64_MAX */
8337 if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
8340 *periodp *= NSEC_PER_USEC;
8342 if (sscanf(tok, "%llu", quotap))
8343 *quotap *= NSEC_PER_USEC;
8344 else if (!strcmp(tok, "max"))
8345 *quotap = RUNTIME_INF;
8352 #ifdef CONFIG_CFS_BANDWIDTH
8353 static int cpu_max_show(struct seq_file *sf, void *v)
8355 struct task_group *tg = css_tg(seq_css(sf));
8357 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
8361 static ssize_t cpu_max_write(struct kernfs_open_file *of,
8362 char *buf, size_t nbytes, loff_t off)
8364 struct task_group *tg = css_tg(of_css(of));
8365 u64 period = tg_get_cfs_period(tg);
8369 ret = cpu_period_quota_parse(buf, &period, "a);
8371 ret = tg_set_cfs_bandwidth(tg, period, quota);
8372 return ret ?: nbytes;
8376 static struct cftype cpu_files[] = {
8377 #ifdef CONFIG_FAIR_GROUP_SCHED
8380 .flags = CFTYPE_NOT_ON_ROOT,
8381 .read_u64 = cpu_weight_read_u64,
8382 .write_u64 = cpu_weight_write_u64,
8385 .name = "weight.nice",
8386 .flags = CFTYPE_NOT_ON_ROOT,
8387 .read_s64 = cpu_weight_nice_read_s64,
8388 .write_s64 = cpu_weight_nice_write_s64,
8391 #ifdef CONFIG_CFS_BANDWIDTH
8394 .flags = CFTYPE_NOT_ON_ROOT,
8395 .seq_show = cpu_max_show,
8396 .write = cpu_max_write,
8399 #ifdef CONFIG_UCLAMP_TASK_GROUP
8401 .name = "uclamp.min",
8402 .flags = CFTYPE_NOT_ON_ROOT,
8403 .seq_show = cpu_uclamp_min_show,
8404 .write = cpu_uclamp_min_write,
8407 .name = "uclamp.max",
8408 .flags = CFTYPE_NOT_ON_ROOT,
8409 .seq_show = cpu_uclamp_max_show,
8410 .write = cpu_uclamp_max_write,
8416 struct cgroup_subsys cpu_cgrp_subsys = {
8417 .css_alloc = cpu_cgroup_css_alloc,
8418 .css_online = cpu_cgroup_css_online,
8419 .css_released = cpu_cgroup_css_released,
8420 .css_free = cpu_cgroup_css_free,
8421 .css_extra_stat_show = cpu_extra_stat_show,
8422 .fork = cpu_cgroup_fork,
8423 .can_attach = cpu_cgroup_can_attach,
8424 .attach = cpu_cgroup_attach,
8425 .legacy_cftypes = cpu_legacy_files,
8426 .dfl_cftypes = cpu_files,
8431 #endif /* CONFIG_CGROUP_SCHED */
8433 void dump_cpu_task(int cpu)
8435 pr_info("Task dump for CPU %d:\n", cpu);
8436 sched_show_task(cpu_curr(cpu));
8440 * Nice levels are multiplicative, with a gentle 10% change for every
8441 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
8442 * nice 1, it will get ~10% less CPU time than another CPU-bound task
8443 * that remained on nice 0.
8445 * The "10% effect" is relative and cumulative: from _any_ nice level,
8446 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
8447 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
8448 * If a task goes up by ~10% and another task goes down by ~10% then
8449 * the relative distance between them is ~25%.)
8451 const int sched_prio_to_weight[40] = {
8452 /* -20 */ 88761, 71755, 56483, 46273, 36291,
8453 /* -15 */ 29154, 23254, 18705, 14949, 11916,
8454 /* -10 */ 9548, 7620, 6100, 4904, 3906,
8455 /* -5 */ 3121, 2501, 1991, 1586, 1277,
8456 /* 0 */ 1024, 820, 655, 526, 423,
8457 /* 5 */ 335, 272, 215, 172, 137,
8458 /* 10 */ 110, 87, 70, 56, 45,
8459 /* 15 */ 36, 29, 23, 18, 15,
8463 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
8465 * In cases where the weight does not change often, we can use the
8466 * precalculated inverse to speed up arithmetics by turning divisions
8467 * into multiplications:
8469 const u32 sched_prio_to_wmult[40] = {
8470 /* -20 */ 48388, 59856, 76040, 92818, 118348,
8471 /* -15 */ 147320, 184698, 229616, 287308, 360437,
8472 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
8473 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
8474 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
8475 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
8476 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
8477 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
8480 void call_trace_sched_update_nr_running(struct rq *rq, int count)
8482 trace_sched_update_nr_running_tp(rq, count);