1 // SPDX-License-Identifier: GPL-2.0
3 * Deadline Scheduling Class (SCHED_DEADLINE)
5 * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
7 * Tasks that periodically executes their instances for less than their
8 * runtime won't miss any of their deadlines.
9 * Tasks that are not periodic or sporadic or that tries to execute more
10 * than their reserved bandwidth will be slowed down (and may potentially
11 * miss some of their deadlines), and won't affect any other task.
13 * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
14 * Juri Lelli <juri.lelli@gmail.com>,
15 * Michael Trimarchi <michael@amarulasolutions.com>,
16 * Fabio Checconi <fchecconi@gmail.com>
21 struct dl_bandwidth def_dl_bandwidth;
23 static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
25 return container_of(dl_se, struct task_struct, dl);
28 static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
30 return container_of(dl_rq, struct rq, dl);
33 static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
35 struct task_struct *p = dl_task_of(dl_se);
36 struct rq *rq = task_rq(p);
41 static inline int on_dl_rq(struct sched_dl_entity *dl_se)
43 return !RB_EMPTY_NODE(&dl_se->rb_node);
47 static inline struct dl_bw *dl_bw_of(int i)
49 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
50 "sched RCU must be held");
51 return &cpu_rq(i)->rd->dl_bw;
54 static inline int dl_bw_cpus(int i)
56 struct root_domain *rd = cpu_rq(i)->rd;
59 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
60 "sched RCU must be held");
62 if (cpumask_subset(rd->span, cpu_active_mask))
63 return cpumask_weight(rd->span);
67 for_each_cpu_and(i, rd->span, cpu_active_mask)
73 static inline unsigned long __dl_bw_capacity(int i)
75 struct root_domain *rd = cpu_rq(i)->rd;
76 unsigned long cap = 0;
78 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
79 "sched RCU must be held");
81 for_each_cpu_and(i, rd->span, cpu_active_mask)
82 cap += capacity_orig_of(i);
88 * XXX Fix: If 'rq->rd == def_root_domain' perform AC against capacity
89 * of the CPU the task is running on rather rd's \Sum CPU capacity.
91 static inline unsigned long dl_bw_capacity(int i)
93 if (!static_branch_unlikely(&sched_asym_cpucapacity) &&
94 capacity_orig_of(i) == SCHED_CAPACITY_SCALE) {
95 return dl_bw_cpus(i) << SCHED_CAPACITY_SHIFT;
97 return __dl_bw_capacity(i);
101 static inline struct dl_bw *dl_bw_of(int i)
103 return &cpu_rq(i)->dl.dl_bw;
106 static inline int dl_bw_cpus(int i)
111 static inline unsigned long dl_bw_capacity(int i)
113 return SCHED_CAPACITY_SCALE;
118 void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
120 u64 old = dl_rq->running_bw;
122 lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);
123 dl_rq->running_bw += dl_bw;
124 SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
125 SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
126 /* kick cpufreq (see the comment in kernel/sched/sched.h). */
127 cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
131 void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
133 u64 old = dl_rq->running_bw;
135 lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);
136 dl_rq->running_bw -= dl_bw;
137 SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
138 if (dl_rq->running_bw > old)
139 dl_rq->running_bw = 0;
140 /* kick cpufreq (see the comment in kernel/sched/sched.h). */
141 cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
145 void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
147 u64 old = dl_rq->this_bw;
149 lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);
150 dl_rq->this_bw += dl_bw;
151 SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
155 void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
157 u64 old = dl_rq->this_bw;
159 lockdep_assert_held(&(rq_of_dl_rq(dl_rq))->lock);
160 dl_rq->this_bw -= dl_bw;
161 SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
162 if (dl_rq->this_bw > old)
164 SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
168 void add_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
170 if (!dl_entity_is_special(dl_se))
171 __add_rq_bw(dl_se->dl_bw, dl_rq);
175 void sub_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
177 if (!dl_entity_is_special(dl_se))
178 __sub_rq_bw(dl_se->dl_bw, dl_rq);
182 void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
184 if (!dl_entity_is_special(dl_se))
185 __add_running_bw(dl_se->dl_bw, dl_rq);
189 void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
191 if (!dl_entity_is_special(dl_se))
192 __sub_running_bw(dl_se->dl_bw, dl_rq);
195 static void dl_change_utilization(struct task_struct *p, u64 new_bw)
199 BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV);
201 if (task_on_rq_queued(p))
205 if (p->dl.dl_non_contending) {
206 sub_running_bw(&p->dl, &rq->dl);
207 p->dl.dl_non_contending = 0;
209 * If the timer handler is currently running and the
210 * timer cannot be cancelled, inactive_task_timer()
211 * will see that dl_not_contending is not set, and
212 * will not touch the rq's active utilization,
213 * so we are still safe.
215 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
218 __sub_rq_bw(p->dl.dl_bw, &rq->dl);
219 __add_rq_bw(new_bw, &rq->dl);
223 * The utilization of a task cannot be immediately removed from
224 * the rq active utilization (running_bw) when the task blocks.
225 * Instead, we have to wait for the so called "0-lag time".
227 * If a task blocks before the "0-lag time", a timer (the inactive
228 * timer) is armed, and running_bw is decreased when the timer
231 * If the task wakes up again before the inactive timer fires,
232 * the timer is cancelled, whereas if the task wakes up after the
233 * inactive timer fired (and running_bw has been decreased) the
234 * task's utilization has to be added to running_bw again.
235 * A flag in the deadline scheduling entity (dl_non_contending)
236 * is used to avoid race conditions between the inactive timer handler
239 * The following diagram shows how running_bw is updated. A task is
240 * "ACTIVE" when its utilization contributes to running_bw; an
241 * "ACTIVE contending" task is in the TASK_RUNNING state, while an
242 * "ACTIVE non contending" task is a blocked task for which the "0-lag time"
243 * has not passed yet. An "INACTIVE" task is a task for which the "0-lag"
244 * time already passed, which does not contribute to running_bw anymore.
245 * +------------------+
247 * +------------------>+ contending |
248 * | add_running_bw | |
249 * | +----+------+------+
252 * +--------+-------+ | |
253 * | | t >= 0-lag | | wakeup
254 * | INACTIVE |<---------------+ |
255 * | | sub_running_bw | |
256 * +--------+-------+ | |
261 * | +----+------+------+
262 * | sub_running_bw | ACTIVE |
263 * +-------------------+ |
264 * inactive timer | non contending |
265 * fired +------------------+
267 * The task_non_contending() function is invoked when a task
268 * blocks, and checks if the 0-lag time already passed or
269 * not (in the first case, it directly updates running_bw;
270 * in the second case, it arms the inactive timer).
272 * The task_contending() function is invoked when a task wakes
273 * up, and checks if the task is still in the "ACTIVE non contending"
274 * state or not (in the second case, it updates running_bw).
276 static void task_non_contending(struct task_struct *p)
278 struct sched_dl_entity *dl_se = &p->dl;
279 struct hrtimer *timer = &dl_se->inactive_timer;
280 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
281 struct rq *rq = rq_of_dl_rq(dl_rq);
285 * If this is a non-deadline task that has been boosted,
288 if (dl_se->dl_runtime == 0)
291 if (dl_entity_is_special(dl_se))
294 WARN_ON(dl_se->dl_non_contending);
296 zerolag_time = dl_se->deadline -
297 div64_long((dl_se->runtime * dl_se->dl_period),
301 * Using relative times instead of the absolute "0-lag time"
302 * allows to simplify the code
304 zerolag_time -= rq_clock(rq);
307 * If the "0-lag time" already passed, decrease the active
308 * utilization now, instead of starting a timer
310 if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
312 sub_running_bw(dl_se, dl_rq);
313 if (!dl_task(p) || p->state == TASK_DEAD) {
314 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
316 if (p->state == TASK_DEAD)
317 sub_rq_bw(&p->dl, &rq->dl);
318 raw_spin_lock(&dl_b->lock);
319 __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
320 __dl_clear_params(p);
321 raw_spin_unlock(&dl_b->lock);
327 dl_se->dl_non_contending = 1;
329 hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
332 static void task_contending(struct sched_dl_entity *dl_se, int flags)
334 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
337 * If this is a non-deadline task that has been boosted,
340 if (dl_se->dl_runtime == 0)
343 if (flags & ENQUEUE_MIGRATED)
344 add_rq_bw(dl_se, dl_rq);
346 if (dl_se->dl_non_contending) {
347 dl_se->dl_non_contending = 0;
349 * If the timer handler is currently running and the
350 * timer cannot be cancelled, inactive_task_timer()
351 * will see that dl_not_contending is not set, and
352 * will not touch the rq's active utilization,
353 * so we are still safe.
355 if (hrtimer_try_to_cancel(&dl_se->inactive_timer) == 1)
356 put_task_struct(dl_task_of(dl_se));
359 * Since "dl_non_contending" is not set, the
360 * task's utilization has already been removed from
361 * active utilization (either when the task blocked,
362 * when the "inactive timer" fired).
365 add_running_bw(dl_se, dl_rq);
369 static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
371 struct sched_dl_entity *dl_se = &p->dl;
373 return dl_rq->root.rb_leftmost == &dl_se->rb_node;
376 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
378 void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
380 raw_spin_lock_init(&dl_b->dl_runtime_lock);
381 dl_b->dl_period = period;
382 dl_b->dl_runtime = runtime;
385 void init_dl_bw(struct dl_bw *dl_b)
387 raw_spin_lock_init(&dl_b->lock);
388 raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
389 if (global_rt_runtime() == RUNTIME_INF)
392 dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
393 raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
397 void init_dl_rq(struct dl_rq *dl_rq)
399 dl_rq->root = RB_ROOT_CACHED;
402 /* zero means no -deadline tasks */
403 dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
405 dl_rq->dl_nr_migratory = 0;
406 dl_rq->overloaded = 0;
407 dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
409 init_dl_bw(&dl_rq->dl_bw);
412 dl_rq->running_bw = 0;
414 init_dl_rq_bw_ratio(dl_rq);
419 static inline int dl_overloaded(struct rq *rq)
421 return atomic_read(&rq->rd->dlo_count);
424 static inline void dl_set_overload(struct rq *rq)
429 cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
431 * Must be visible before the overload count is
432 * set (as in sched_rt.c).
434 * Matched by the barrier in pull_dl_task().
437 atomic_inc(&rq->rd->dlo_count);
440 static inline void dl_clear_overload(struct rq *rq)
445 atomic_dec(&rq->rd->dlo_count);
446 cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
449 static void update_dl_migration(struct dl_rq *dl_rq)
451 if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
452 if (!dl_rq->overloaded) {
453 dl_set_overload(rq_of_dl_rq(dl_rq));
454 dl_rq->overloaded = 1;
456 } else if (dl_rq->overloaded) {
457 dl_clear_overload(rq_of_dl_rq(dl_rq));
458 dl_rq->overloaded = 0;
462 static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
464 struct task_struct *p = dl_task_of(dl_se);
466 if (p->nr_cpus_allowed > 1)
467 dl_rq->dl_nr_migratory++;
469 update_dl_migration(dl_rq);
472 static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
474 struct task_struct *p = dl_task_of(dl_se);
476 if (p->nr_cpus_allowed > 1)
477 dl_rq->dl_nr_migratory--;
479 update_dl_migration(dl_rq);
483 * The list of pushable -deadline task is not a plist, like in
484 * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
486 static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
488 struct dl_rq *dl_rq = &rq->dl;
489 struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_root.rb_node;
490 struct rb_node *parent = NULL;
491 struct task_struct *entry;
492 bool leftmost = true;
494 BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
498 entry = rb_entry(parent, struct task_struct,
500 if (dl_entity_preempt(&p->dl, &entry->dl))
501 link = &parent->rb_left;
503 link = &parent->rb_right;
509 dl_rq->earliest_dl.next = p->dl.deadline;
511 rb_link_node(&p->pushable_dl_tasks, parent, link);
512 rb_insert_color_cached(&p->pushable_dl_tasks,
513 &dl_rq->pushable_dl_tasks_root, leftmost);
516 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
518 struct dl_rq *dl_rq = &rq->dl;
520 if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
523 if (dl_rq->pushable_dl_tasks_root.rb_leftmost == &p->pushable_dl_tasks) {
524 struct rb_node *next_node;
526 next_node = rb_next(&p->pushable_dl_tasks);
528 dl_rq->earliest_dl.next = rb_entry(next_node,
529 struct task_struct, pushable_dl_tasks)->dl.deadline;
533 rb_erase_cached(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
534 RB_CLEAR_NODE(&p->pushable_dl_tasks);
537 static inline int has_pushable_dl_tasks(struct rq *rq)
539 return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
542 static int push_dl_task(struct rq *rq);
544 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
546 return dl_task(prev);
549 static DEFINE_PER_CPU(struct callback_head, dl_push_head);
550 static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
552 static void push_dl_tasks(struct rq *);
553 static void pull_dl_task(struct rq *);
555 static inline void deadline_queue_push_tasks(struct rq *rq)
557 if (!has_pushable_dl_tasks(rq))
560 queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
563 static inline void deadline_queue_pull_task(struct rq *rq)
565 queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
568 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
570 static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
572 struct rq *later_rq = NULL;
575 later_rq = find_lock_later_rq(p, rq);
580 * If we cannot preempt any rq, fall back to pick any
583 cpu = cpumask_any_and(cpu_active_mask, p->cpus_ptr);
584 if (cpu >= nr_cpu_ids) {
586 * Failed to find any suitable CPU.
587 * The task will never come back!
589 BUG_ON(dl_bandwidth_enabled());
592 * If admission control is disabled we
593 * try a little harder to let the task
596 cpu = cpumask_any(cpu_active_mask);
598 later_rq = cpu_rq(cpu);
599 double_lock_balance(rq, later_rq);
602 if (p->dl.dl_non_contending || p->dl.dl_throttled) {
604 * Inactive timer is armed (or callback is running, but
605 * waiting for us to release rq locks). In any case, when it
606 * will fire (or continue), it will see running_bw of this
607 * task migrated to later_rq (and correctly handle it).
609 sub_running_bw(&p->dl, &rq->dl);
610 sub_rq_bw(&p->dl, &rq->dl);
612 add_rq_bw(&p->dl, &later_rq->dl);
613 add_running_bw(&p->dl, &later_rq->dl);
615 sub_rq_bw(&p->dl, &rq->dl);
616 add_rq_bw(&p->dl, &later_rq->dl);
620 * And we finally need to fixup root_domain(s) bandwidth accounting,
621 * since p is still hanging out in the old (now moved to default) root
624 dl_b = &rq->rd->dl_bw;
625 raw_spin_lock(&dl_b->lock);
626 __dl_sub(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
627 raw_spin_unlock(&dl_b->lock);
629 dl_b = &later_rq->rd->dl_bw;
630 raw_spin_lock(&dl_b->lock);
631 __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(later_rq->rd->span));
632 raw_spin_unlock(&dl_b->lock);
634 set_task_cpu(p, later_rq->cpu);
635 double_unlock_balance(later_rq, rq);
643 void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
648 void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
653 void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
658 void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
662 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
667 static inline void pull_dl_task(struct rq *rq)
671 static inline void deadline_queue_push_tasks(struct rq *rq)
675 static inline void deadline_queue_pull_task(struct rq *rq)
678 #endif /* CONFIG_SMP */
680 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
681 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
682 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, int flags);
685 * We are being explicitly informed that a new instance is starting,
686 * and this means that:
687 * - the absolute deadline of the entity has to be placed at
688 * current time + relative deadline;
689 * - the runtime of the entity has to be set to the maximum value.
691 * The capability of specifying such event is useful whenever a -deadline
692 * entity wants to (try to!) synchronize its behaviour with the scheduler's
693 * one, and to (try to!) reconcile itself with its own scheduling
696 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
698 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
699 struct rq *rq = rq_of_dl_rq(dl_rq);
701 WARN_ON(dl_se->dl_boosted);
702 WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
705 * We are racing with the deadline timer. So, do nothing because
706 * the deadline timer handler will take care of properly recharging
707 * the runtime and postponing the deadline
709 if (dl_se->dl_throttled)
713 * We use the regular wall clock time to set deadlines in the
714 * future; in fact, we must consider execution overheads (time
715 * spent on hardirq context, etc.).
717 dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
718 dl_se->runtime = dl_se->dl_runtime;
722 * Pure Earliest Deadline First (EDF) scheduling does not deal with the
723 * possibility of a entity lasting more than what it declared, and thus
724 * exhausting its runtime.
726 * Here we are interested in making runtime overrun possible, but we do
727 * not want a entity which is misbehaving to affect the scheduling of all
729 * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
730 * is used, in order to confine each entity within its own bandwidth.
732 * This function deals exactly with that, and ensures that when the runtime
733 * of a entity is replenished, its deadline is also postponed. That ensures
734 * the overrunning entity can't interfere with other entity in the system and
735 * can't make them miss their deadlines. Reasons why this kind of overruns
736 * could happen are, typically, a entity voluntarily trying to overcome its
737 * runtime, or it just underestimated it during sched_setattr().
739 static void replenish_dl_entity(struct sched_dl_entity *dl_se,
740 struct sched_dl_entity *pi_se)
742 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
743 struct rq *rq = rq_of_dl_rq(dl_rq);
745 BUG_ON(pi_se->dl_runtime <= 0);
748 * This could be the case for a !-dl task that is boosted.
749 * Just go with full inherited parameters.
751 if (dl_se->dl_deadline == 0) {
752 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
753 dl_se->runtime = pi_se->dl_runtime;
756 if (dl_se->dl_yielded && dl_se->runtime > 0)
760 * We keep moving the deadline away until we get some
761 * available runtime for the entity. This ensures correct
762 * handling of situations where the runtime overrun is
765 while (dl_se->runtime <= 0) {
766 dl_se->deadline += pi_se->dl_period;
767 dl_se->runtime += pi_se->dl_runtime;
771 * At this point, the deadline really should be "in
772 * the future" with respect to rq->clock. If it's
773 * not, we are, for some reason, lagging too much!
774 * Anyway, after having warn userspace abut that,
775 * we still try to keep the things running by
776 * resetting the deadline and the budget of the
779 if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
780 printk_deferred_once("sched: DL replenish lagged too much\n");
781 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
782 dl_se->runtime = pi_se->dl_runtime;
785 if (dl_se->dl_yielded)
786 dl_se->dl_yielded = 0;
787 if (dl_se->dl_throttled)
788 dl_se->dl_throttled = 0;
792 * Here we check if --at time t-- an entity (which is probably being
793 * [re]activated or, in general, enqueued) can use its remaining runtime
794 * and its current deadline _without_ exceeding the bandwidth it is
795 * assigned (function returns true if it can't). We are in fact applying
796 * one of the CBS rules: when a task wakes up, if the residual runtime
797 * over residual deadline fits within the allocated bandwidth, then we
798 * can keep the current (absolute) deadline and residual budget without
799 * disrupting the schedulability of the system. Otherwise, we should
800 * refill the runtime and set the deadline a period in the future,
801 * because keeping the current (absolute) deadline of the task would
802 * result in breaking guarantees promised to other tasks (refer to
803 * Documentation/scheduler/sched-deadline.rst for more information).
805 * This function returns true if:
807 * runtime / (deadline - t) > dl_runtime / dl_deadline ,
809 * IOW we can't recycle current parameters.
811 * Notice that the bandwidth check is done against the deadline. For
812 * task with deadline equal to period this is the same of using
813 * dl_period instead of dl_deadline in the equation above.
815 static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
816 struct sched_dl_entity *pi_se, u64 t)
821 * left and right are the two sides of the equation above,
822 * after a bit of shuffling to use multiplications instead
825 * Note that none of the time values involved in the two
826 * multiplications are absolute: dl_deadline and dl_runtime
827 * are the relative deadline and the maximum runtime of each
828 * instance, runtime is the runtime left for the last instance
829 * and (deadline - t), since t is rq->clock, is the time left
830 * to the (absolute) deadline. Even if overflowing the u64 type
831 * is very unlikely to occur in both cases, here we scale down
832 * as we want to avoid that risk at all. Scaling down by 10
833 * means that we reduce granularity to 1us. We are fine with it,
834 * since this is only a true/false check and, anyway, thinking
835 * of anything below microseconds resolution is actually fiction
836 * (but still we want to give the user that illusion >;).
838 left = (pi_se->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
839 right = ((dl_se->deadline - t) >> DL_SCALE) *
840 (pi_se->dl_runtime >> DL_SCALE);
842 return dl_time_before(right, left);
846 * Revised wakeup rule [1]: For self-suspending tasks, rather then
847 * re-initializing task's runtime and deadline, the revised wakeup
848 * rule adjusts the task's runtime to avoid the task to overrun its
851 * Reasoning: a task may overrun the density if:
852 * runtime / (deadline - t) > dl_runtime / dl_deadline
854 * Therefore, runtime can be adjusted to:
855 * runtime = (dl_runtime / dl_deadline) * (deadline - t)
857 * In such way that runtime will be equal to the maximum density
858 * the task can use without breaking any rule.
860 * [1] Luca Abeni, Giuseppe Lipari, and Juri Lelli. 2015. Constant
861 * bandwidth server revisited. SIGBED Rev. 11, 4 (January 2015), 19-24.
864 update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
866 u64 laxity = dl_se->deadline - rq_clock(rq);
869 * If the task has deadline < period, and the deadline is in the past,
870 * it should already be throttled before this check.
872 * See update_dl_entity() comments for further details.
874 WARN_ON(dl_time_before(dl_se->deadline, rq_clock(rq)));
876 dl_se->runtime = (dl_se->dl_density * laxity) >> BW_SHIFT;
880 * Regarding the deadline, a task with implicit deadline has a relative
881 * deadline == relative period. A task with constrained deadline has a
882 * relative deadline <= relative period.
884 * We support constrained deadline tasks. However, there are some restrictions
885 * applied only for tasks which do not have an implicit deadline. See
886 * update_dl_entity() to know more about such restrictions.
888 * The dl_is_implicit() returns true if the task has an implicit deadline.
890 static inline bool dl_is_implicit(struct sched_dl_entity *dl_se)
892 return dl_se->dl_deadline == dl_se->dl_period;
896 * When a deadline entity is placed in the runqueue, its runtime and deadline
897 * might need to be updated. This is done by a CBS wake up rule. There are two
898 * different rules: 1) the original CBS; and 2) the Revisited CBS.
900 * When the task is starting a new period, the Original CBS is used. In this
901 * case, the runtime is replenished and a new absolute deadline is set.
903 * When a task is queued before the begin of the next period, using the
904 * remaining runtime and deadline could make the entity to overflow, see
905 * dl_entity_overflow() to find more about runtime overflow. When such case
906 * is detected, the runtime and deadline need to be updated.
908 * If the task has an implicit deadline, i.e., deadline == period, the Original
909 * CBS is applied. the runtime is replenished and a new absolute deadline is
910 * set, as in the previous cases.
912 * However, the Original CBS does not work properly for tasks with
913 * deadline < period, which are said to have a constrained deadline. By
914 * applying the Original CBS, a constrained deadline task would be able to run
915 * runtime/deadline in a period. With deadline < period, the task would
916 * overrun the runtime/period allowed bandwidth, breaking the admission test.
918 * In order to prevent this misbehave, the Revisited CBS is used for
919 * constrained deadline tasks when a runtime overflow is detected. In the
920 * Revisited CBS, rather than replenishing & setting a new absolute deadline,
921 * the remaining runtime of the task is reduced to avoid runtime overflow.
922 * Please refer to the comments update_dl_revised_wakeup() function to find
923 * more about the Revised CBS rule.
925 static void update_dl_entity(struct sched_dl_entity *dl_se,
926 struct sched_dl_entity *pi_se)
928 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
929 struct rq *rq = rq_of_dl_rq(dl_rq);
931 if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
932 dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
934 if (unlikely(!dl_is_implicit(dl_se) &&
935 !dl_time_before(dl_se->deadline, rq_clock(rq)) &&
936 !dl_se->dl_boosted)){
937 update_dl_revised_wakeup(dl_se, rq);
941 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
942 dl_se->runtime = pi_se->dl_runtime;
946 static inline u64 dl_next_period(struct sched_dl_entity *dl_se)
948 return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period;
952 * If the entity depleted all its runtime, and if we want it to sleep
953 * while waiting for some new execution time to become available, we
954 * set the bandwidth replenishment timer to the replenishment instant
955 * and try to activate it.
957 * Notice that it is important for the caller to know if the timer
958 * actually started or not (i.e., the replenishment instant is in
959 * the future or in the past).
961 static int start_dl_timer(struct task_struct *p)
963 struct sched_dl_entity *dl_se = &p->dl;
964 struct hrtimer *timer = &dl_se->dl_timer;
965 struct rq *rq = task_rq(p);
969 lockdep_assert_held(&rq->lock);
972 * We want the timer to fire at the deadline, but considering
973 * that it is actually coming from rq->clock and not from
974 * hrtimer's time base reading.
976 act = ns_to_ktime(dl_next_period(dl_se));
977 now = hrtimer_cb_get_time(timer);
978 delta = ktime_to_ns(now) - rq_clock(rq);
979 act = ktime_add_ns(act, delta);
982 * If the expiry time already passed, e.g., because the value
983 * chosen as the deadline is too small, don't even try to
984 * start the timer in the past!
986 if (ktime_us_delta(act, now) < 0)
990 * !enqueued will guarantee another callback; even if one is already in
991 * progress. This ensures a balanced {get,put}_task_struct().
993 * The race against __run_timer() clearing the enqueued state is
994 * harmless because we're holding task_rq()->lock, therefore the timer
995 * expiring after we've done the check will wait on its task_rq_lock()
996 * and observe our state.
998 if (!hrtimer_is_queued(timer)) {
1000 hrtimer_start(timer, act, HRTIMER_MODE_ABS_HARD);
1007 * This is the bandwidth enforcement timer callback. If here, we know
1008 * a task is not on its dl_rq, since the fact that the timer was running
1009 * means the task is throttled and needs a runtime replenishment.
1011 * However, what we actually do depends on the fact the task is active,
1012 * (it is on its rq) or has been removed from there by a call to
1013 * dequeue_task_dl(). In the former case we must issue the runtime
1014 * replenishment and add the task back to the dl_rq; in the latter, we just
1015 * do nothing but clearing dl_throttled, so that runtime and deadline
1016 * updating (and the queueing back to dl_rq) will be done by the
1017 * next call to enqueue_task_dl().
1019 static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
1021 struct sched_dl_entity *dl_se = container_of(timer,
1022 struct sched_dl_entity,
1024 struct task_struct *p = dl_task_of(dl_se);
1028 rq = task_rq_lock(p, &rf);
1031 * The task might have changed its scheduling policy to something
1032 * different than SCHED_DEADLINE (through switched_from_dl()).
1038 * The task might have been boosted by someone else and might be in the
1039 * boosting/deboosting path, its not throttled.
1041 if (dl_se->dl_boosted)
1045 * Spurious timer due to start_dl_timer() race; or we already received
1046 * a replenishment from rt_mutex_setprio().
1048 if (!dl_se->dl_throttled)
1052 update_rq_clock(rq);
1055 * If the throttle happened during sched-out; like:
1062 * __dequeue_task_dl()
1065 * We can be both throttled and !queued. Replenish the counter
1066 * but do not enqueue -- wait for our wakeup to do that.
1068 if (!task_on_rq_queued(p)) {
1069 replenish_dl_entity(dl_se, dl_se);
1074 if (unlikely(!rq->online)) {
1076 * If the runqueue is no longer available, migrate the
1077 * task elsewhere. This necessarily changes rq.
1079 lockdep_unpin_lock(&rq->lock, rf.cookie);
1080 rq = dl_task_offline_migration(rq, p);
1081 rf.cookie = lockdep_pin_lock(&rq->lock);
1082 update_rq_clock(rq);
1085 * Now that the task has been migrated to the new RQ and we
1086 * have that locked, proceed as normal and enqueue the task
1092 enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
1093 if (dl_task(rq->curr))
1094 check_preempt_curr_dl(rq, p, 0);
1100 * Queueing this task back might have overloaded rq, check if we need
1101 * to kick someone away.
1103 if (has_pushable_dl_tasks(rq)) {
1105 * Nothing relies on rq->lock after this, so its safe to drop
1108 rq_unpin_lock(rq, &rf);
1110 rq_repin_lock(rq, &rf);
1115 task_rq_unlock(rq, p, &rf);
1118 * This can free the task_struct, including this hrtimer, do not touch
1119 * anything related to that after this.
1123 return HRTIMER_NORESTART;
1126 void init_dl_task_timer(struct sched_dl_entity *dl_se)
1128 struct hrtimer *timer = &dl_se->dl_timer;
1130 hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1131 timer->function = dl_task_timer;
1135 * During the activation, CBS checks if it can reuse the current task's
1136 * runtime and period. If the deadline of the task is in the past, CBS
1137 * cannot use the runtime, and so it replenishes the task. This rule
1138 * works fine for implicit deadline tasks (deadline == period), and the
1139 * CBS was designed for implicit deadline tasks. However, a task with
1140 * constrained deadline (deadline < period) might be awakened after the
1141 * deadline, but before the next period. In this case, replenishing the
1142 * task would allow it to run for runtime / deadline. As in this case
1143 * deadline < period, CBS enables a task to run for more than the
1144 * runtime / period. In a very loaded system, this can cause a domino
1145 * effect, making other tasks miss their deadlines.
1147 * To avoid this problem, in the activation of a constrained deadline
1148 * task after the deadline but before the next period, throttle the
1149 * task and set the replenishing timer to the begin of the next period,
1150 * unless it is boosted.
1152 static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
1154 struct task_struct *p = dl_task_of(dl_se);
1155 struct rq *rq = rq_of_dl_rq(dl_rq_of_se(dl_se));
1157 if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
1158 dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
1159 if (unlikely(dl_se->dl_boosted || !start_dl_timer(p)))
1161 dl_se->dl_throttled = 1;
1162 if (dl_se->runtime > 0)
1168 int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
1170 return (dl_se->runtime <= 0);
1173 extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
1176 * This function implements the GRUB accounting rule:
1177 * according to the GRUB reclaiming algorithm, the runtime is
1178 * not decreased as "dq = -dt", but as
1179 * "dq = -max{u / Umax, (1 - Uinact - Uextra)} dt",
1180 * where u is the utilization of the task, Umax is the maximum reclaimable
1181 * utilization, Uinact is the (per-runqueue) inactive utilization, computed
1182 * as the difference between the "total runqueue utilization" and the
1183 * runqueue active utilization, and Uextra is the (per runqueue) extra
1184 * reclaimable utilization.
1185 * Since rq->dl.running_bw and rq->dl.this_bw contain utilizations
1186 * multiplied by 2^BW_SHIFT, the result has to be shifted right by
1188 * Since rq->dl.bw_ratio contains 1 / Umax multipled by 2^RATIO_SHIFT,
1189 * dl_bw is multiped by rq->dl.bw_ratio and shifted right by RATIO_SHIFT.
1190 * Since delta is a 64 bit variable, to have an overflow its value
1191 * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
1192 * So, overflow is not an issue here.
1194 static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
1196 u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
1198 u64 u_act_min = (dl_se->dl_bw * rq->dl.bw_ratio) >> RATIO_SHIFT;
1201 * Instead of computing max{u * bw_ratio, (1 - u_inact - u_extra)},
1202 * we compare u_inact + rq->dl.extra_bw with
1203 * 1 - (u * rq->dl.bw_ratio >> RATIO_SHIFT), because
1204 * u_inact + rq->dl.extra_bw can be larger than
1205 * 1 * (so, 1 - u_inact - rq->dl.extra_bw would be negative
1206 * leading to wrong results)
1208 if (u_inact + rq->dl.extra_bw > BW_UNIT - u_act_min)
1211 u_act = BW_UNIT - u_inact - rq->dl.extra_bw;
1213 return (delta * u_act) >> BW_SHIFT;
1217 * Update the current task's runtime statistics (provided it is still
1218 * a -deadline task and has not been removed from the dl_rq).
1220 static void update_curr_dl(struct rq *rq)
1222 struct task_struct *curr = rq->curr;
1223 struct sched_dl_entity *dl_se = &curr->dl;
1224 u64 delta_exec, scaled_delta_exec;
1225 int cpu = cpu_of(rq);
1228 if (!dl_task(curr) || !on_dl_rq(dl_se))
1232 * Consumed budget is computed considering the time as
1233 * observed by schedulable tasks (excluding time spent
1234 * in hardirq context, etc.). Deadlines are instead
1235 * computed using hard walltime. This seems to be the more
1236 * natural solution, but the full ramifications of this
1237 * approach need further study.
1239 now = rq_clock_task(rq);
1240 delta_exec = now - curr->se.exec_start;
1241 if (unlikely((s64)delta_exec <= 0)) {
1242 if (unlikely(dl_se->dl_yielded))
1247 schedstat_set(curr->se.statistics.exec_max,
1248 max(curr->se.statistics.exec_max, delta_exec));
1250 curr->se.sum_exec_runtime += delta_exec;
1251 account_group_exec_runtime(curr, delta_exec);
1253 curr->se.exec_start = now;
1254 cgroup_account_cputime(curr, delta_exec);
1256 if (dl_entity_is_special(dl_se))
1260 * For tasks that participate in GRUB, we implement GRUB-PA: the
1261 * spare reclaimed bandwidth is used to clock down frequency.
1263 * For the others, we still need to scale reservation parameters
1264 * according to current frequency and CPU maximum capacity.
1266 if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
1267 scaled_delta_exec = grub_reclaim(delta_exec,
1271 unsigned long scale_freq = arch_scale_freq_capacity(cpu);
1272 unsigned long scale_cpu = arch_scale_cpu_capacity(cpu);
1274 scaled_delta_exec = cap_scale(delta_exec, scale_freq);
1275 scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
1278 dl_se->runtime -= scaled_delta_exec;
1281 if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
1282 dl_se->dl_throttled = 1;
1284 /* If requested, inform the user about runtime overruns. */
1285 if (dl_runtime_exceeded(dl_se) &&
1286 (dl_se->flags & SCHED_FLAG_DL_OVERRUN))
1287 dl_se->dl_overrun = 1;
1289 __dequeue_task_dl(rq, curr, 0);
1290 if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
1291 enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
1293 if (!is_leftmost(curr, &rq->dl))
1298 * Because -- for now -- we share the rt bandwidth, we need to
1299 * account our runtime there too, otherwise actual rt tasks
1300 * would be able to exceed the shared quota.
1302 * Account to the root rt group for now.
1304 * The solution we're working towards is having the RT groups scheduled
1305 * using deadline servers -- however there's a few nasties to figure
1306 * out before that can happen.
1308 if (rt_bandwidth_enabled()) {
1309 struct rt_rq *rt_rq = &rq->rt;
1311 raw_spin_lock(&rt_rq->rt_runtime_lock);
1313 * We'll let actual RT tasks worry about the overflow here, we
1314 * have our own CBS to keep us inline; only account when RT
1315 * bandwidth is relevant.
1317 if (sched_rt_bandwidth_account(rt_rq))
1318 rt_rq->rt_time += delta_exec;
1319 raw_spin_unlock(&rt_rq->rt_runtime_lock);
1323 static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
1325 struct sched_dl_entity *dl_se = container_of(timer,
1326 struct sched_dl_entity,
1328 struct task_struct *p = dl_task_of(dl_se);
1332 rq = task_rq_lock(p, &rf);
1335 update_rq_clock(rq);
1337 if (!dl_task(p) || p->state == TASK_DEAD) {
1338 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
1340 if (p->state == TASK_DEAD && dl_se->dl_non_contending) {
1341 sub_running_bw(&p->dl, dl_rq_of_se(&p->dl));
1342 sub_rq_bw(&p->dl, dl_rq_of_se(&p->dl));
1343 dl_se->dl_non_contending = 0;
1346 raw_spin_lock(&dl_b->lock);
1347 __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
1348 raw_spin_unlock(&dl_b->lock);
1349 __dl_clear_params(p);
1353 if (dl_se->dl_non_contending == 0)
1356 sub_running_bw(dl_se, &rq->dl);
1357 dl_se->dl_non_contending = 0;
1359 task_rq_unlock(rq, p, &rf);
1362 return HRTIMER_NORESTART;
1365 void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
1367 struct hrtimer *timer = &dl_se->inactive_timer;
1369 hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1370 timer->function = inactive_task_timer;
1375 static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1377 struct rq *rq = rq_of_dl_rq(dl_rq);
1379 if (dl_rq->earliest_dl.curr == 0 ||
1380 dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
1381 dl_rq->earliest_dl.curr = deadline;
1382 cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
1386 static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1388 struct rq *rq = rq_of_dl_rq(dl_rq);
1391 * Since we may have removed our earliest (and/or next earliest)
1392 * task we must recompute them.
1394 if (!dl_rq->dl_nr_running) {
1395 dl_rq->earliest_dl.curr = 0;
1396 dl_rq->earliest_dl.next = 0;
1397 cpudl_clear(&rq->rd->cpudl, rq->cpu);
1399 struct rb_node *leftmost = dl_rq->root.rb_leftmost;
1400 struct sched_dl_entity *entry;
1402 entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
1403 dl_rq->earliest_dl.curr = entry->deadline;
1404 cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
1410 static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
1411 static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
1413 #endif /* CONFIG_SMP */
1416 void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1418 int prio = dl_task_of(dl_se)->prio;
1419 u64 deadline = dl_se->deadline;
1421 WARN_ON(!dl_prio(prio));
1422 dl_rq->dl_nr_running++;
1423 add_nr_running(rq_of_dl_rq(dl_rq), 1);
1425 inc_dl_deadline(dl_rq, deadline);
1426 inc_dl_migration(dl_se, dl_rq);
1430 void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1432 int prio = dl_task_of(dl_se)->prio;
1434 WARN_ON(!dl_prio(prio));
1435 WARN_ON(!dl_rq->dl_nr_running);
1436 dl_rq->dl_nr_running--;
1437 sub_nr_running(rq_of_dl_rq(dl_rq), 1);
1439 dec_dl_deadline(dl_rq, dl_se->deadline);
1440 dec_dl_migration(dl_se, dl_rq);
1443 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
1445 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1446 struct rb_node **link = &dl_rq->root.rb_root.rb_node;
1447 struct rb_node *parent = NULL;
1448 struct sched_dl_entity *entry;
1451 BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
1455 entry = rb_entry(parent, struct sched_dl_entity, rb_node);
1456 if (dl_time_before(dl_se->deadline, entry->deadline))
1457 link = &parent->rb_left;
1459 link = &parent->rb_right;
1464 rb_link_node(&dl_se->rb_node, parent, link);
1465 rb_insert_color_cached(&dl_se->rb_node, &dl_rq->root, leftmost);
1467 inc_dl_tasks(dl_se, dl_rq);
1470 static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
1472 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1474 if (RB_EMPTY_NODE(&dl_se->rb_node))
1477 rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
1478 RB_CLEAR_NODE(&dl_se->rb_node);
1480 dec_dl_tasks(dl_se, dl_rq);
1484 enqueue_dl_entity(struct sched_dl_entity *dl_se,
1485 struct sched_dl_entity *pi_se, int flags)
1487 BUG_ON(on_dl_rq(dl_se));
1490 * If this is a wakeup or a new instance, the scheduling
1491 * parameters of the task might need updating. Otherwise,
1492 * we want a replenishment of its runtime.
1494 if (flags & ENQUEUE_WAKEUP) {
1495 task_contending(dl_se, flags);
1496 update_dl_entity(dl_se, pi_se);
1497 } else if (flags & ENQUEUE_REPLENISH) {
1498 replenish_dl_entity(dl_se, pi_se);
1499 } else if ((flags & ENQUEUE_RESTORE) &&
1500 dl_time_before(dl_se->deadline,
1501 rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
1502 setup_new_dl_entity(dl_se);
1505 __enqueue_dl_entity(dl_se);
1508 static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
1510 __dequeue_dl_entity(dl_se);
1513 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1515 struct task_struct *pi_task = rt_mutex_get_top_task(p);
1516 struct sched_dl_entity *pi_se = &p->dl;
1519 * Use the scheduling parameters of the top pi-waiter task if:
1520 * - we have a top pi-waiter which is a SCHED_DEADLINE task AND
1521 * - our dl_boosted is set (i.e. the pi-waiter's (absolute) deadline is
1522 * smaller than our deadline OR we are a !SCHED_DEADLINE task getting
1523 * boosted due to a SCHED_DEADLINE pi-waiter).
1524 * Otherwise we keep our runtime and deadline.
1526 if (pi_task && dl_prio(pi_task->normal_prio) && p->dl.dl_boosted) {
1527 pi_se = &pi_task->dl;
1529 * Because of delays in the detection of the overrun of a
1530 * thread's runtime, it might be the case that a thread
1531 * goes to sleep in a rt mutex with negative runtime. As
1532 * a consequence, the thread will be throttled.
1534 * While waiting for the mutex, this thread can also be
1535 * boosted via PI, resulting in a thread that is throttled
1536 * and boosted at the same time.
1538 * In this case, the boost overrides the throttle.
1540 if (p->dl.dl_throttled) {
1542 * The replenish timer needs to be canceled. No
1543 * problem if it fires concurrently: boosted threads
1544 * are ignored in dl_task_timer().
1546 hrtimer_try_to_cancel(&p->dl.dl_timer);
1547 p->dl.dl_throttled = 0;
1549 } else if (!dl_prio(p->normal_prio)) {
1551 * Special case in which we have a !SCHED_DEADLINE task that is going
1552 * to be deboosted, but exceeds its runtime while doing so. No point in
1553 * replenishing it, as it's going to return back to its original
1554 * scheduling class after this. If it has been throttled, we need to
1555 * clear the flag, otherwise the task may wake up as throttled after
1556 * being boosted again with no means to replenish the runtime and clear
1559 p->dl.dl_throttled = 0;
1560 BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
1565 * Check if a constrained deadline task was activated
1566 * after the deadline but before the next period.
1567 * If that is the case, the task will be throttled and
1568 * the replenishment timer will be set to the next period.
1570 if (!p->dl.dl_throttled && !dl_is_implicit(&p->dl))
1571 dl_check_constrained_dl(&p->dl);
1573 if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {
1574 add_rq_bw(&p->dl, &rq->dl);
1575 add_running_bw(&p->dl, &rq->dl);
1579 * If p is throttled, we do not enqueue it. In fact, if it exhausted
1580 * its budget it needs a replenishment and, since it now is on
1581 * its rq, the bandwidth timer callback (which clearly has not
1582 * run yet) will take care of this.
1583 * However, the active utilization does not depend on the fact
1584 * that the task is on the runqueue or not (but depends on the
1585 * task's state - in GRUB parlance, "inactive" vs "active contending").
1586 * In other words, even if a task is throttled its utilization must
1587 * be counted in the active utilization; hence, we need to call
1590 if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
1591 if (flags & ENQUEUE_WAKEUP)
1592 task_contending(&p->dl, flags);
1597 enqueue_dl_entity(&p->dl, pi_se, flags);
1599 if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1600 enqueue_pushable_dl_task(rq, p);
1603 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1605 dequeue_dl_entity(&p->dl);
1606 dequeue_pushable_dl_task(rq, p);
1609 static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1612 __dequeue_task_dl(rq, p, flags);
1614 if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
1615 sub_running_bw(&p->dl, &rq->dl);
1616 sub_rq_bw(&p->dl, &rq->dl);
1620 * This check allows to start the inactive timer (or to immediately
1621 * decrease the active utilization, if needed) in two cases:
1622 * when the task blocks and when it is terminating
1623 * (p->state == TASK_DEAD). We can handle the two cases in the same
1624 * way, because from GRUB's point of view the same thing is happening
1625 * (the task moves from "active contending" to "active non contending"
1628 if (flags & DEQUEUE_SLEEP)
1629 task_non_contending(p);
1633 * Yield task semantic for -deadline tasks is:
1635 * get off from the CPU until our next instance, with
1636 * a new runtime. This is of little use now, since we
1637 * don't have a bandwidth reclaiming mechanism. Anyway,
1638 * bandwidth reclaiming is planned for the future, and
1639 * yield_task_dl will indicate that some spare budget
1640 * is available for other task instances to use it.
1642 static void yield_task_dl(struct rq *rq)
1645 * We make the task go to sleep until its current deadline by
1646 * forcing its runtime to zero. This way, update_curr_dl() stops
1647 * it and the bandwidth timer will wake it up and will give it
1648 * new scheduling parameters (thanks to dl_yielded=1).
1650 rq->curr->dl.dl_yielded = 1;
1652 update_rq_clock(rq);
1655 * Tell update_rq_clock() that we've just updated,
1656 * so we don't do microscopic update in schedule()
1657 * and double the fastpath cost.
1659 rq_clock_skip_update(rq);
1664 static int find_later_rq(struct task_struct *task);
1667 select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
1669 struct task_struct *curr;
1673 if (sd_flag != SD_BALANCE_WAKE)
1679 curr = READ_ONCE(rq->curr); /* unlocked access */
1682 * If we are dealing with a -deadline task, we must
1683 * decide where to wake it up.
1684 * If it has a later deadline and the current task
1685 * on this rq can't move (provided the waking task
1686 * can!) we prefer to send it somewhere else. On the
1687 * other hand, if it has a shorter deadline, we
1688 * try to make it stay here, it might be important.
1690 select_rq = unlikely(dl_task(curr)) &&
1691 (curr->nr_cpus_allowed < 2 ||
1692 !dl_entity_preempt(&p->dl, &curr->dl)) &&
1693 p->nr_cpus_allowed > 1;
1696 * Take the capacity of the CPU into account to
1697 * ensure it fits the requirement of the task.
1699 if (static_branch_unlikely(&sched_asym_cpucapacity))
1700 select_rq |= !dl_task_fits_capacity(p, cpu);
1703 int target = find_later_rq(p);
1706 (dl_time_before(p->dl.deadline,
1707 cpu_rq(target)->dl.earliest_dl.curr) ||
1708 (cpu_rq(target)->dl.dl_nr_running == 0)))
1717 static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
1721 if (p->state != TASK_WAKING)
1726 * Since p->state == TASK_WAKING, set_task_cpu() has been called
1727 * from try_to_wake_up(). Hence, p->pi_lock is locked, but
1728 * rq->lock is not... So, lock it
1730 raw_spin_lock(&rq->lock);
1731 if (p->dl.dl_non_contending) {
1732 sub_running_bw(&p->dl, &rq->dl);
1733 p->dl.dl_non_contending = 0;
1735 * If the timer handler is currently running and the
1736 * timer cannot be cancelled, inactive_task_timer()
1737 * will see that dl_not_contending is not set, and
1738 * will not touch the rq's active utilization,
1739 * so we are still safe.
1741 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
1744 sub_rq_bw(&p->dl, &rq->dl);
1745 raw_spin_unlock(&rq->lock);
1748 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
1751 * Current can't be migrated, useless to reschedule,
1752 * let's hope p can move out.
1754 if (rq->curr->nr_cpus_allowed == 1 ||
1755 !cpudl_find(&rq->rd->cpudl, rq->curr, NULL))
1759 * p is migratable, so let's not schedule it and
1760 * see if it is pushed or pulled somewhere else.
1762 if (p->nr_cpus_allowed != 1 &&
1763 cpudl_find(&rq->rd->cpudl, p, NULL))
1769 static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
1771 if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
1773 * This is OK, because current is on_cpu, which avoids it being
1774 * picked for load-balance and preemption/IRQs are still
1775 * disabled avoiding further scheduler activity on it and we've
1776 * not yet started the picking loop.
1778 rq_unpin_lock(rq, rf);
1780 rq_repin_lock(rq, rf);
1783 return sched_stop_runnable(rq) || sched_dl_runnable(rq);
1785 #endif /* CONFIG_SMP */
1788 * Only called when both the current and waking task are -deadline
1791 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
1794 if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
1801 * In the unlikely case current and p have the same deadline
1802 * let us try to decide what's the best thing to do...
1804 if ((p->dl.deadline == rq->curr->dl.deadline) &&
1805 !test_tsk_need_resched(rq->curr))
1806 check_preempt_equal_dl(rq, p);
1807 #endif /* CONFIG_SMP */
1810 #ifdef CONFIG_SCHED_HRTICK
1811 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1813 hrtick_start(rq, p->dl.runtime);
1815 #else /* !CONFIG_SCHED_HRTICK */
1816 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1821 static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
1823 p->se.exec_start = rq_clock_task(rq);
1825 /* You can't push away the running task */
1826 dequeue_pushable_dl_task(rq, p);
1831 if (hrtick_enabled(rq))
1832 start_hrtick_dl(rq, p);
1834 if (rq->curr->sched_class != &dl_sched_class)
1835 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1837 deadline_queue_push_tasks(rq);
1840 static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
1841 struct dl_rq *dl_rq)
1843 struct rb_node *left = rb_first_cached(&dl_rq->root);
1848 return rb_entry(left, struct sched_dl_entity, rb_node);
1851 static struct task_struct *pick_next_task_dl(struct rq *rq)
1853 struct sched_dl_entity *dl_se;
1854 struct dl_rq *dl_rq = &rq->dl;
1855 struct task_struct *p;
1857 if (!sched_dl_runnable(rq))
1860 dl_se = pick_next_dl_entity(rq, dl_rq);
1862 p = dl_task_of(dl_se);
1863 set_next_task_dl(rq, p, true);
1867 static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
1871 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1872 if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
1873 enqueue_pushable_dl_task(rq, p);
1877 * scheduler tick hitting a task of our scheduling class.
1879 * NOTE: This function can be called remotely by the tick offload that
1880 * goes along full dynticks. Therefore no local assumption can be made
1881 * and everything must be accessed through the @rq and @curr passed in
1884 static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
1888 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1890 * Even when we have runtime, update_curr_dl() might have resulted in us
1891 * not being the leftmost task anymore. In that case NEED_RESCHED will
1892 * be set and schedule() will start a new hrtick for the next task.
1894 if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 &&
1895 is_leftmost(p, &rq->dl))
1896 start_hrtick_dl(rq, p);
1899 static void task_fork_dl(struct task_struct *p)
1902 * SCHED_DEADLINE tasks cannot fork and this is achieved through
1909 /* Only try algorithms three times */
1910 #define DL_MAX_TRIES 3
1912 static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
1914 if (!task_running(rq, p) &&
1915 cpumask_test_cpu(cpu, p->cpus_ptr))
1921 * Return the earliest pushable rq's task, which is suitable to be executed
1922 * on the CPU, NULL otherwise:
1924 static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
1926 struct rb_node *next_node = rq->dl.pushable_dl_tasks_root.rb_leftmost;
1927 struct task_struct *p = NULL;
1929 if (!has_pushable_dl_tasks(rq))
1934 p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
1936 if (pick_dl_task(rq, p, cpu))
1939 next_node = rb_next(next_node);
1946 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
1948 static int find_later_rq(struct task_struct *task)
1950 struct sched_domain *sd;
1951 struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
1952 int this_cpu = smp_processor_id();
1953 int cpu = task_cpu(task);
1955 /* Make sure the mask is initialized first */
1956 if (unlikely(!later_mask))
1959 if (task->nr_cpus_allowed == 1)
1963 * We have to consider system topology and task affinity
1964 * first, then we can look for a suitable CPU.
1966 if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
1970 * If we are here, some targets have been found, including
1971 * the most suitable which is, among the runqueues where the
1972 * current tasks have later deadlines than the task's one, the
1973 * rq with the latest possible one.
1975 * Now we check how well this matches with task's
1976 * affinity and system topology.
1978 * The last CPU where the task run is our first
1979 * guess, since it is most likely cache-hot there.
1981 if (cpumask_test_cpu(cpu, later_mask))
1984 * Check if this_cpu is to be skipped (i.e., it is
1985 * not in the mask) or not.
1987 if (!cpumask_test_cpu(this_cpu, later_mask))
1991 for_each_domain(cpu, sd) {
1992 if (sd->flags & SD_WAKE_AFFINE) {
1996 * If possible, preempting this_cpu is
1997 * cheaper than migrating.
1999 if (this_cpu != -1 &&
2000 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
2005 best_cpu = cpumask_first_and(later_mask,
2006 sched_domain_span(sd));
2008 * Last chance: if a CPU being in both later_mask
2009 * and current sd span is valid, that becomes our
2010 * choice. Of course, the latest possible CPU is
2011 * already under consideration through later_mask.
2013 if (best_cpu < nr_cpu_ids) {
2022 * At this point, all our guesses failed, we just return
2023 * 'something', and let the caller sort the things out.
2028 cpu = cpumask_any(later_mask);
2029 if (cpu < nr_cpu_ids)
2035 /* Locks the rq it finds */
2036 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
2038 struct rq *later_rq = NULL;
2042 for (tries = 0; tries < DL_MAX_TRIES; tries++) {
2043 cpu = find_later_rq(task);
2045 if ((cpu == -1) || (cpu == rq->cpu))
2048 later_rq = cpu_rq(cpu);
2050 if (later_rq->dl.dl_nr_running &&
2051 !dl_time_before(task->dl.deadline,
2052 later_rq->dl.earliest_dl.curr)) {
2054 * Target rq has tasks of equal or earlier deadline,
2055 * retrying does not release any lock and is unlikely
2056 * to yield a different result.
2062 /* Retry if something changed. */
2063 if (double_lock_balance(rq, later_rq)) {
2064 if (unlikely(task_rq(task) != rq ||
2065 !cpumask_test_cpu(later_rq->cpu, task->cpus_ptr) ||
2066 task_running(rq, task) ||
2068 !task_on_rq_queued(task))) {
2069 double_unlock_balance(rq, later_rq);
2076 * If the rq we found has no -deadline task, or
2077 * its earliest one has a later deadline than our
2078 * task, the rq is a good one.
2080 if (!later_rq->dl.dl_nr_running ||
2081 dl_time_before(task->dl.deadline,
2082 later_rq->dl.earliest_dl.curr))
2085 /* Otherwise we try again. */
2086 double_unlock_balance(rq, later_rq);
2093 static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
2095 struct task_struct *p;
2097 if (!has_pushable_dl_tasks(rq))
2100 p = rb_entry(rq->dl.pushable_dl_tasks_root.rb_leftmost,
2101 struct task_struct, pushable_dl_tasks);
2103 BUG_ON(rq->cpu != task_cpu(p));
2104 BUG_ON(task_current(rq, p));
2105 BUG_ON(p->nr_cpus_allowed <= 1);
2107 BUG_ON(!task_on_rq_queued(p));
2108 BUG_ON(!dl_task(p));
2114 * See if the non running -deadline tasks on this rq
2115 * can be sent to some other CPU where they can preempt
2116 * and start executing.
2118 static int push_dl_task(struct rq *rq)
2120 struct task_struct *next_task;
2121 struct rq *later_rq;
2124 if (!rq->dl.overloaded)
2127 next_task = pick_next_pushable_dl_task(rq);
2132 if (WARN_ON(next_task == rq->curr))
2136 * If next_task preempts rq->curr, and rq->curr
2137 * can move away, it makes sense to just reschedule
2138 * without going further in pushing next_task.
2140 if (dl_task(rq->curr) &&
2141 dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
2142 rq->curr->nr_cpus_allowed > 1) {
2147 /* We might release rq lock */
2148 get_task_struct(next_task);
2150 /* Will lock the rq it'll find */
2151 later_rq = find_lock_later_rq(next_task, rq);
2153 struct task_struct *task;
2156 * We must check all this again, since
2157 * find_lock_later_rq releases rq->lock and it is
2158 * then possible that next_task has migrated.
2160 task = pick_next_pushable_dl_task(rq);
2161 if (task == next_task) {
2163 * The task is still there. We don't try
2164 * again, some other CPU will pull it when ready.
2173 put_task_struct(next_task);
2178 deactivate_task(rq, next_task, 0);
2179 set_task_cpu(next_task, later_rq->cpu);
2182 * Update the later_rq clock here, because the clock is used
2183 * by the cpufreq_update_util() inside __add_running_bw().
2185 update_rq_clock(later_rq);
2186 activate_task(later_rq, next_task, ENQUEUE_NOCLOCK);
2189 resched_curr(later_rq);
2191 double_unlock_balance(rq, later_rq);
2194 put_task_struct(next_task);
2199 static void push_dl_tasks(struct rq *rq)
2201 /* push_dl_task() will return true if it moved a -deadline task */
2202 while (push_dl_task(rq))
2206 static void pull_dl_task(struct rq *this_rq)
2208 int this_cpu = this_rq->cpu, cpu;
2209 struct task_struct *p;
2210 bool resched = false;
2212 u64 dmin = LONG_MAX;
2214 if (likely(!dl_overloaded(this_rq)))
2218 * Match the barrier from dl_set_overloaded; this guarantees that if we
2219 * see overloaded we must also see the dlo_mask bit.
2223 for_each_cpu(cpu, this_rq->rd->dlo_mask) {
2224 if (this_cpu == cpu)
2227 src_rq = cpu_rq(cpu);
2230 * It looks racy, abd it is! However, as in sched_rt.c,
2231 * we are fine with this.
2233 if (this_rq->dl.dl_nr_running &&
2234 dl_time_before(this_rq->dl.earliest_dl.curr,
2235 src_rq->dl.earliest_dl.next))
2238 /* Might drop this_rq->lock */
2239 double_lock_balance(this_rq, src_rq);
2242 * If there are no more pullable tasks on the
2243 * rq, we're done with it.
2245 if (src_rq->dl.dl_nr_running <= 1)
2248 p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
2251 * We found a task to be pulled if:
2252 * - it preempts our current (if there's one),
2253 * - it will preempt the last one we pulled (if any).
2255 if (p && dl_time_before(p->dl.deadline, dmin) &&
2256 (!this_rq->dl.dl_nr_running ||
2257 dl_time_before(p->dl.deadline,
2258 this_rq->dl.earliest_dl.curr))) {
2259 WARN_ON(p == src_rq->curr);
2260 WARN_ON(!task_on_rq_queued(p));
2263 * Then we pull iff p has actually an earlier
2264 * deadline than the current task of its runqueue.
2266 if (dl_time_before(p->dl.deadline,
2267 src_rq->curr->dl.deadline))
2272 deactivate_task(src_rq, p, 0);
2273 set_task_cpu(p, this_cpu);
2274 activate_task(this_rq, p, 0);
2275 dmin = p->dl.deadline;
2277 /* Is there any other task even earlier? */
2280 double_unlock_balance(this_rq, src_rq);
2284 resched_curr(this_rq);
2288 * Since the task is not running and a reschedule is not going to happen
2289 * anytime soon on its runqueue, we try pushing it away now.
2291 static void task_woken_dl(struct rq *rq, struct task_struct *p)
2293 if (!task_running(rq, p) &&
2294 !test_tsk_need_resched(rq->curr) &&
2295 p->nr_cpus_allowed > 1 &&
2296 dl_task(rq->curr) &&
2297 (rq->curr->nr_cpus_allowed < 2 ||
2298 !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
2303 static void set_cpus_allowed_dl(struct task_struct *p,
2304 const struct cpumask *new_mask)
2306 struct root_domain *src_rd;
2309 BUG_ON(!dl_task(p));
2314 * Migrating a SCHED_DEADLINE task between exclusive
2315 * cpusets (different root_domains) entails a bandwidth
2316 * update. We already made space for us in the destination
2317 * domain (see cpuset_can_attach()).
2319 if (!cpumask_intersects(src_rd->span, new_mask)) {
2320 struct dl_bw *src_dl_b;
2322 src_dl_b = dl_bw_of(cpu_of(rq));
2324 * We now free resources of the root_domain we are migrating
2325 * off. In the worst case, sched_setattr() may temporary fail
2326 * until we complete the update.
2328 raw_spin_lock(&src_dl_b->lock);
2329 __dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
2330 raw_spin_unlock(&src_dl_b->lock);
2333 set_cpus_allowed_common(p, new_mask);
2336 /* Assumes rq->lock is held */
2337 static void rq_online_dl(struct rq *rq)
2339 if (rq->dl.overloaded)
2340 dl_set_overload(rq);
2342 cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
2343 if (rq->dl.dl_nr_running > 0)
2344 cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
2347 /* Assumes rq->lock is held */
2348 static void rq_offline_dl(struct rq *rq)
2350 if (rq->dl.overloaded)
2351 dl_clear_overload(rq);
2353 cpudl_clear(&rq->rd->cpudl, rq->cpu);
2354 cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
2357 void __init init_sched_dl_class(void)
2361 for_each_possible_cpu(i)
2362 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
2363 GFP_KERNEL, cpu_to_node(i));
2366 void dl_add_task_root_domain(struct task_struct *p)
2372 rq = task_rq_lock(p, &rf);
2376 dl_b = &rq->rd->dl_bw;
2377 raw_spin_lock(&dl_b->lock);
2379 __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
2381 raw_spin_unlock(&dl_b->lock);
2384 task_rq_unlock(rq, p, &rf);
2387 void dl_clear_root_domain(struct root_domain *rd)
2389 unsigned long flags;
2391 raw_spin_lock_irqsave(&rd->dl_bw.lock, flags);
2392 rd->dl_bw.total_bw = 0;
2393 raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags);
2396 #endif /* CONFIG_SMP */
2398 static void switched_from_dl(struct rq *rq, struct task_struct *p)
2401 * task_non_contending() can start the "inactive timer" (if the 0-lag
2402 * time is in the future). If the task switches back to dl before
2403 * the "inactive timer" fires, it can continue to consume its current
2404 * runtime using its current deadline. If it stays outside of
2405 * SCHED_DEADLINE until the 0-lag time passes, inactive_task_timer()
2406 * will reset the task parameters.
2408 if (task_on_rq_queued(p) && p->dl.dl_runtime)
2409 task_non_contending(p);
2411 if (!task_on_rq_queued(p)) {
2413 * Inactive timer is armed. However, p is leaving DEADLINE and
2414 * might migrate away from this rq while continuing to run on
2415 * some other class. We need to remove its contribution from
2416 * this rq running_bw now, or sub_rq_bw (below) will complain.
2418 if (p->dl.dl_non_contending)
2419 sub_running_bw(&p->dl, &rq->dl);
2420 sub_rq_bw(&p->dl, &rq->dl);
2424 * We cannot use inactive_task_timer() to invoke sub_running_bw()
2425 * at the 0-lag time, because the task could have been migrated
2426 * while SCHED_OTHER in the meanwhile.
2428 if (p->dl.dl_non_contending)
2429 p->dl.dl_non_contending = 0;
2432 * Since this might be the only -deadline task on the rq,
2433 * this is the right place to try to pull some other one
2434 * from an overloaded CPU, if any.
2436 if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
2439 deadline_queue_pull_task(rq);
2443 * When switching to -deadline, we may overload the rq, then
2444 * we try to push someone off, if possible.
2446 static void switched_to_dl(struct rq *rq, struct task_struct *p)
2448 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
2451 /* If p is not queued we will update its parameters at next wakeup. */
2452 if (!task_on_rq_queued(p)) {
2453 add_rq_bw(&p->dl, &rq->dl);
2458 if (rq->curr != p) {
2460 if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
2461 deadline_queue_push_tasks(rq);
2463 if (dl_task(rq->curr))
2464 check_preempt_curr_dl(rq, p, 0);
2471 * If the scheduling parameters of a -deadline task changed,
2472 * a push or pull operation might be needed.
2474 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
2477 if (task_on_rq_queued(p) || rq->curr == p) {
2480 * This might be too much, but unfortunately
2481 * we don't have the old deadline value, and
2482 * we can't argue if the task is increasing
2483 * or lowering its prio, so...
2485 if (!rq->dl.overloaded)
2486 deadline_queue_pull_task(rq);
2489 * If we now have a earlier deadline task than p,
2490 * then reschedule, provided p is still on this
2493 if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
2497 * Again, we don't know if p has a earlier
2498 * or later deadline, so let's blindly set a
2499 * (maybe not needed) rescheduling point.
2502 #endif /* CONFIG_SMP */
2506 const struct sched_class dl_sched_class
2507 __attribute__((section("__dl_sched_class"))) = {
2508 .enqueue_task = enqueue_task_dl,
2509 .dequeue_task = dequeue_task_dl,
2510 .yield_task = yield_task_dl,
2512 .check_preempt_curr = check_preempt_curr_dl,
2514 .pick_next_task = pick_next_task_dl,
2515 .put_prev_task = put_prev_task_dl,
2516 .set_next_task = set_next_task_dl,
2519 .balance = balance_dl,
2520 .select_task_rq = select_task_rq_dl,
2521 .migrate_task_rq = migrate_task_rq_dl,
2522 .set_cpus_allowed = set_cpus_allowed_dl,
2523 .rq_online = rq_online_dl,
2524 .rq_offline = rq_offline_dl,
2525 .task_woken = task_woken_dl,
2528 .task_tick = task_tick_dl,
2529 .task_fork = task_fork_dl,
2531 .prio_changed = prio_changed_dl,
2532 .switched_from = switched_from_dl,
2533 .switched_to = switched_to_dl,
2535 .update_curr = update_curr_dl,
2538 int sched_dl_global_validate(void)
2540 u64 runtime = global_rt_runtime();
2541 u64 period = global_rt_period();
2542 u64 new_bw = to_ratio(period, runtime);
2545 unsigned long flags;
2548 * Here we want to check the bandwidth not being set to some
2549 * value smaller than the currently allocated bandwidth in
2550 * any of the root_domains.
2552 * FIXME: Cycling on all the CPUs is overdoing, but simpler than
2553 * cycling on root_domains... Discussion on different/better
2554 * solutions is welcome!
2556 for_each_possible_cpu(cpu) {
2557 rcu_read_lock_sched();
2558 dl_b = dl_bw_of(cpu);
2560 raw_spin_lock_irqsave(&dl_b->lock, flags);
2561 if (new_bw < dl_b->total_bw)
2563 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2565 rcu_read_unlock_sched();
2574 static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
2576 if (global_rt_runtime() == RUNTIME_INF) {
2577 dl_rq->bw_ratio = 1 << RATIO_SHIFT;
2578 dl_rq->extra_bw = 1 << BW_SHIFT;
2580 dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
2581 global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
2582 dl_rq->extra_bw = to_ratio(global_rt_period(),
2583 global_rt_runtime());
2587 void sched_dl_do_global(void)
2592 unsigned long flags;
2594 def_dl_bandwidth.dl_period = global_rt_period();
2595 def_dl_bandwidth.dl_runtime = global_rt_runtime();
2597 if (global_rt_runtime() != RUNTIME_INF)
2598 new_bw = to_ratio(global_rt_period(), global_rt_runtime());
2601 * FIXME: As above...
2603 for_each_possible_cpu(cpu) {
2604 rcu_read_lock_sched();
2605 dl_b = dl_bw_of(cpu);
2607 raw_spin_lock_irqsave(&dl_b->lock, flags);
2609 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2611 rcu_read_unlock_sched();
2612 init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
2617 * We must be sure that accepting a new task (or allowing changing the
2618 * parameters of an existing one) is consistent with the bandwidth
2619 * constraints. If yes, this function also accordingly updates the currently
2620 * allocated bandwidth to reflect the new situation.
2622 * This function is called while holding p's rq->lock.
2624 int sched_dl_overflow(struct task_struct *p, int policy,
2625 const struct sched_attr *attr)
2627 u64 period = attr->sched_period ?: attr->sched_deadline;
2628 u64 runtime = attr->sched_runtime;
2629 u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2630 int cpus, err = -1, cpu = task_cpu(p);
2631 struct dl_bw *dl_b = dl_bw_of(cpu);
2634 if (attr->sched_flags & SCHED_FLAG_SUGOV)
2637 /* !deadline task may carry old deadline bandwidth */
2638 if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
2642 * Either if a task, enters, leave, or stays -deadline but changes
2643 * its parameters, we may need to update accordingly the total
2644 * allocated bandwidth of the container.
2646 raw_spin_lock(&dl_b->lock);
2647 cpus = dl_bw_cpus(cpu);
2648 cap = dl_bw_capacity(cpu);
2650 if (dl_policy(policy) && !task_has_dl_policy(p) &&
2651 !__dl_overflow(dl_b, cap, 0, new_bw)) {
2652 if (hrtimer_active(&p->dl.inactive_timer))
2653 __dl_sub(dl_b, p->dl.dl_bw, cpus);
2654 __dl_add(dl_b, new_bw, cpus);
2656 } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2657 !__dl_overflow(dl_b, cap, p->dl.dl_bw, new_bw)) {
2659 * XXX this is slightly incorrect: when the task
2660 * utilization decreases, we should delay the total
2661 * utilization change until the task's 0-lag point.
2662 * But this would require to set the task's "inactive
2663 * timer" when the task is not inactive.
2665 __dl_sub(dl_b, p->dl.dl_bw, cpus);
2666 __dl_add(dl_b, new_bw, cpus);
2667 dl_change_utilization(p, new_bw);
2669 } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2671 * Do not decrease the total deadline utilization here,
2672 * switched_from_dl() will take care to do it at the correct
2677 raw_spin_unlock(&dl_b->lock);
2683 * This function initializes the sched_dl_entity of a newly becoming
2684 * SCHED_DEADLINE task.
2686 * Only the static values are considered here, the actual runtime and the
2687 * absolute deadline will be properly calculated when the task is enqueued
2688 * for the first time with its new policy.
2690 void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
2692 struct sched_dl_entity *dl_se = &p->dl;
2694 dl_se->dl_runtime = attr->sched_runtime;
2695 dl_se->dl_deadline = attr->sched_deadline;
2696 dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
2697 dl_se->flags = attr->sched_flags;
2698 dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
2699 dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
2702 void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
2704 struct sched_dl_entity *dl_se = &p->dl;
2706 attr->sched_priority = p->rt_priority;
2707 attr->sched_runtime = dl_se->dl_runtime;
2708 attr->sched_deadline = dl_se->dl_deadline;
2709 attr->sched_period = dl_se->dl_period;
2710 attr->sched_flags = dl_se->flags;
2714 * Default limits for DL period; on the top end we guard against small util
2715 * tasks still getting rediculous long effective runtimes, on the bottom end we
2716 * guard against timer DoS.
2718 unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
2719 unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */
2722 * This function validates the new parameters of a -deadline task.
2723 * We ask for the deadline not being zero, and greater or equal
2724 * than the runtime, as well as the period of being zero or
2725 * greater than deadline. Furthermore, we have to be sure that
2726 * user parameters are above the internal resolution of 1us (we
2727 * check sched_runtime only since it is always the smaller one) and
2728 * below 2^63 ns (we have to check both sched_deadline and
2729 * sched_period, as the latter can be zero).
2731 bool __checkparam_dl(const struct sched_attr *attr)
2733 u64 period, max, min;
2735 /* special dl tasks don't actually use any parameter */
2736 if (attr->sched_flags & SCHED_FLAG_SUGOV)
2740 if (attr->sched_deadline == 0)
2744 * Since we truncate DL_SCALE bits, make sure we're at least
2747 if (attr->sched_runtime < (1ULL << DL_SCALE))
2751 * Since we use the MSB for wrap-around and sign issues, make
2752 * sure it's not set (mind that period can be equal to zero).
2754 if (attr->sched_deadline & (1ULL << 63) ||
2755 attr->sched_period & (1ULL << 63))
2758 period = attr->sched_period;
2760 period = attr->sched_deadline;
2762 /* runtime <= deadline <= period (if period != 0) */
2763 if (period < attr->sched_deadline ||
2764 attr->sched_deadline < attr->sched_runtime)
2767 max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
2768 min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
2770 if (period < min || period > max)
2777 * This function clears the sched_dl_entity static params.
2779 void __dl_clear_params(struct task_struct *p)
2781 struct sched_dl_entity *dl_se = &p->dl;
2783 dl_se->dl_runtime = 0;
2784 dl_se->dl_deadline = 0;
2785 dl_se->dl_period = 0;
2788 dl_se->dl_density = 0;
2790 dl_se->dl_boosted = 0;
2791 dl_se->dl_throttled = 0;
2792 dl_se->dl_yielded = 0;
2793 dl_se->dl_non_contending = 0;
2794 dl_se->dl_overrun = 0;
2797 bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
2799 struct sched_dl_entity *dl_se = &p->dl;
2801 if (dl_se->dl_runtime != attr->sched_runtime ||
2802 dl_se->dl_deadline != attr->sched_deadline ||
2803 dl_se->dl_period != attr->sched_period ||
2804 dl_se->flags != attr->sched_flags)
2811 int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed)
2813 unsigned long flags, cap;
2814 unsigned int dest_cpu;
2819 dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
2821 rcu_read_lock_sched();
2822 dl_b = dl_bw_of(dest_cpu);
2823 raw_spin_lock_irqsave(&dl_b->lock, flags);
2824 cap = dl_bw_capacity(dest_cpu);
2825 overflow = __dl_overflow(dl_b, cap, 0, p->dl.dl_bw);
2830 * We reserve space for this task in the destination
2831 * root_domain, as we can't fail after this point.
2832 * We will free resources in the source root_domain
2833 * later on (see set_cpus_allowed_dl()).
2835 int cpus = dl_bw_cpus(dest_cpu);
2837 __dl_add(dl_b, p->dl.dl_bw, cpus);
2840 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2841 rcu_read_unlock_sched();
2846 int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
2847 const struct cpumask *trial)
2849 int ret = 1, trial_cpus;
2850 struct dl_bw *cur_dl_b;
2851 unsigned long flags;
2853 rcu_read_lock_sched();
2854 cur_dl_b = dl_bw_of(cpumask_any(cur));
2855 trial_cpus = cpumask_weight(trial);
2857 raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
2858 if (cur_dl_b->bw != -1 &&
2859 cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
2861 raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
2862 rcu_read_unlock_sched();
2867 bool dl_cpu_busy(unsigned int cpu)
2869 unsigned long flags, cap;
2873 rcu_read_lock_sched();
2874 dl_b = dl_bw_of(cpu);
2875 raw_spin_lock_irqsave(&dl_b->lock, flags);
2876 cap = dl_bw_capacity(cpu);
2877 overflow = __dl_overflow(dl_b, cap, 0, 0);
2878 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2879 rcu_read_unlock_sched();
2885 #ifdef CONFIG_SCHED_DEBUG
2886 void print_dl_stats(struct seq_file *m, int cpu)
2888 print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
2890 #endif /* CONFIG_SCHED_DEBUG */