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1/*
2 * Deadline Scheduling Class (SCHED_DEADLINE)
3 *
4 * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
5 *
6 * Tasks that periodically executes their instances for less than their
7 * runtime won't miss any of their deadlines.
8 * Tasks that are not periodic or sporadic or that tries to execute more
9 * than their reserved bandwidth will be slowed down (and may potentially
10 * miss some of their deadlines), and won't affect any other task.
11 *
12 * Copyright (C) 2012 Dario Faggioli <raistlin@linux.it>,
13 * Juri Lelli <juri.lelli@gmail.com>,
14 * Michael Trimarchi <michael@amarulasolutions.com>,
15 * Fabio Checconi <fchecconi@gmail.com>
16 */
17#include "sched.h"
18
19#include <linux/slab.h>
20
21struct dl_bandwidth def_dl_bandwidth;
22
23static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
24{
25 return container_of(dl_se, struct task_struct, dl);
26}
27
28static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
29{
30 return container_of(dl_rq, struct rq, dl);
31}
32
33static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
34{
35 struct task_struct *p = dl_task_of(dl_se);
36 struct rq *rq = task_rq(p);
37
38 return &rq->dl;
39}
40
41static inline int on_dl_rq(struct sched_dl_entity *dl_se)
42{
43 return !RB_EMPTY_NODE(&dl_se->rb_node);
44}
45
46static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
47{
48 struct sched_dl_entity *dl_se = &p->dl;
49
50 return dl_rq->rb_leftmost == &dl_se->rb_node;
51}
52
53void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
54{
55 raw_spin_lock_init(&dl_b->dl_runtime_lock);
56 dl_b->dl_period = period;
57 dl_b->dl_runtime = runtime;
58}
59
60void init_dl_bw(struct dl_bw *dl_b)
61{
62 raw_spin_lock_init(&dl_b->lock);
63 raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
64 if (global_rt_runtime() == RUNTIME_INF)
65 dl_b->bw = -1;
66 else
67 dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
68 raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
69 dl_b->total_bw = 0;
70}
71
72void init_dl_rq(struct dl_rq *dl_rq)
73{
74 dl_rq->rb_root = RB_ROOT;
75
76#ifdef CONFIG_SMP
77 /* zero means no -deadline tasks */
78 dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
79
80 dl_rq->dl_nr_migratory = 0;
81 dl_rq->overloaded = 0;
82 dl_rq->pushable_dl_tasks_root = RB_ROOT;
83#else
84 init_dl_bw(&dl_rq->dl_bw);
85#endif
86}
87
88#ifdef CONFIG_SMP
89
90static inline int dl_overloaded(struct rq *rq)
91{
92 return atomic_read(&rq->rd->dlo_count);
93}
94
95static inline void dl_set_overload(struct rq *rq)
96{
97 if (!rq->online)
98 return;
99
100 cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
101 /*
102 * Must be visible before the overload count is
103 * set (as in sched_rt.c).
104 *
105 * Matched by the barrier in pull_dl_task().
106 */
107 smp_wmb();
108 atomic_inc(&rq->rd->dlo_count);
109}
110
111static inline void dl_clear_overload(struct rq *rq)
112{
113 if (!rq->online)
114 return;
115
116 atomic_dec(&rq->rd->dlo_count);
117 cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
118}
119
120static void update_dl_migration(struct dl_rq *dl_rq)
121{
122 if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
123 if (!dl_rq->overloaded) {
124 dl_set_overload(rq_of_dl_rq(dl_rq));
125 dl_rq->overloaded = 1;
126 }
127 } else if (dl_rq->overloaded) {
128 dl_clear_overload(rq_of_dl_rq(dl_rq));
129 dl_rq->overloaded = 0;
130 }
131}
132
133static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
134{
135 struct task_struct *p = dl_task_of(dl_se);
136
137 if (tsk_nr_cpus_allowed(p) > 1)
138 dl_rq->dl_nr_migratory++;
139
140 update_dl_migration(dl_rq);
141}
142
143static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
144{
145 struct task_struct *p = dl_task_of(dl_se);
146
147 if (tsk_nr_cpus_allowed(p) > 1)
148 dl_rq->dl_nr_migratory--;
149
150 update_dl_migration(dl_rq);
151}
152
153/*
154 * The list of pushable -deadline task is not a plist, like in
155 * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
156 */
157static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
158{
159 struct dl_rq *dl_rq = &rq->dl;
160 struct rb_node **link = &dl_rq->pushable_dl_tasks_root.rb_node;
161 struct rb_node *parent = NULL;
162 struct task_struct *entry;
163 int leftmost = 1;
164
165 BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
166
167 while (*link) {
168 parent = *link;
169 entry = rb_entry(parent, struct task_struct,
170 pushable_dl_tasks);
171 if (dl_entity_preempt(&p->dl, &entry->dl))
172 link = &parent->rb_left;
173 else {
174 link = &parent->rb_right;
175 leftmost = 0;
176 }
177 }
178
179 if (leftmost) {
180 dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
181 dl_rq->earliest_dl.next = p->dl.deadline;
182 }
183
184 rb_link_node(&p->pushable_dl_tasks, parent, link);
185 rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
186}
187
188static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
189{
190 struct dl_rq *dl_rq = &rq->dl;
191
192 if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
193 return;
194
195 if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
196 struct rb_node *next_node;
197
198 next_node = rb_next(&p->pushable_dl_tasks);
199 dl_rq->pushable_dl_tasks_leftmost = next_node;
200 if (next_node) {
201 dl_rq->earliest_dl.next = rb_entry(next_node,
202 struct task_struct, pushable_dl_tasks)->dl.deadline;
203 }
204 }
205
206 rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
207 RB_CLEAR_NODE(&p->pushable_dl_tasks);
208}
209
210static inline int has_pushable_dl_tasks(struct rq *rq)
211{
212 return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
213}
214
215static int push_dl_task(struct rq *rq);
216
217static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
218{
219 return dl_task(prev);
220}
221
222static DEFINE_PER_CPU(struct callback_head, dl_push_head);
223static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
224
225static void push_dl_tasks(struct rq *);
226static void pull_dl_task(struct rq *);
227
228static inline void queue_push_tasks(struct rq *rq)
229{
230 if (!has_pushable_dl_tasks(rq))
231 return;
232
233 queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
234}
235
236static inline void queue_pull_task(struct rq *rq)
237{
238 queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
239}
240
241static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
242
243static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
244{
245 struct rq *later_rq = NULL;
246
247 later_rq = find_lock_later_rq(p, rq);
248 if (!later_rq) {
249 int cpu;
250
251 /*
252 * If we cannot preempt any rq, fall back to pick any
253 * online cpu.
254 */
255 cpu = cpumask_any_and(cpu_active_mask, tsk_cpus_allowed(p));
256 if (cpu >= nr_cpu_ids) {
257 /*
258 * Fail to find any suitable cpu.
259 * The task will never come back!
260 */
261 BUG_ON(dl_bandwidth_enabled());
262
263 /*
264 * If admission control is disabled we
265 * try a little harder to let the task
266 * run.
267 */
268 cpu = cpumask_any(cpu_active_mask);
269 }
270 later_rq = cpu_rq(cpu);
271 double_lock_balance(rq, later_rq);
272 }
273
274 set_task_cpu(p, later_rq->cpu);
275 double_unlock_balance(later_rq, rq);
276
277 return later_rq;
278}
279
280#else
281
282static inline
283void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
284{
285}
286
287static inline
288void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
289{
290}
291
292static inline
293void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
294{
295}
296
297static inline
298void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
299{
300}
301
302static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
303{
304 return false;
305}
306
307static inline void pull_dl_task(struct rq *rq)
308{
309}
310
311static inline void queue_push_tasks(struct rq *rq)
312{
313}
314
315static inline void queue_pull_task(struct rq *rq)
316{
317}
318#endif /* CONFIG_SMP */
319
320static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
321static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
322static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
323 int flags);
324
325/*
326 * We are being explicitly informed that a new instance is starting,
327 * and this means that:
328 * - the absolute deadline of the entity has to be placed at
329 * current time + relative deadline;
330 * - the runtime of the entity has to be set to the maximum value.
331 *
332 * The capability of specifying such event is useful whenever a -deadline
333 * entity wants to (try to!) synchronize its behaviour with the scheduler's
334 * one, and to (try to!) reconcile itself with its own scheduling
335 * parameters.
336 */
337static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
338{
339 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
340 struct rq *rq = rq_of_dl_rq(dl_rq);
341
342 WARN_ON(dl_se->dl_boosted);
343 WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
344
345 /*
346 * We are racing with the deadline timer. So, do nothing because
347 * the deadline timer handler will take care of properly recharging
348 * the runtime and postponing the deadline
349 */
350 if (dl_se->dl_throttled)
351 return;
352
353 /*
354 * We use the regular wall clock time to set deadlines in the
355 * future; in fact, we must consider execution overheads (time
356 * spent on hardirq context, etc.).
357 */
358 dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
359 dl_se->runtime = dl_se->dl_runtime;
360}
361
362/*
363 * Pure Earliest Deadline First (EDF) scheduling does not deal with the
364 * possibility of a entity lasting more than what it declared, and thus
365 * exhausting its runtime.
366 *
367 * Here we are interested in making runtime overrun possible, but we do
368 * not want a entity which is misbehaving to affect the scheduling of all
369 * other entities.
370 * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
371 * is used, in order to confine each entity within its own bandwidth.
372 *
373 * This function deals exactly with that, and ensures that when the runtime
374 * of a entity is replenished, its deadline is also postponed. That ensures
375 * the overrunning entity can't interfere with other entity in the system and
376 * can't make them miss their deadlines. Reasons why this kind of overruns
377 * could happen are, typically, a entity voluntarily trying to overcome its
378 * runtime, or it just underestimated it during sched_setattr().
379 */
380static void replenish_dl_entity(struct sched_dl_entity *dl_se,
381 struct sched_dl_entity *pi_se)
382{
383 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
384 struct rq *rq = rq_of_dl_rq(dl_rq);
385
386 BUG_ON(pi_se->dl_runtime <= 0);
387
388 /*
389 * This could be the case for a !-dl task that is boosted.
390 * Just go with full inherited parameters.
391 */
392 if (dl_se->dl_deadline == 0) {
393 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
394 dl_se->runtime = pi_se->dl_runtime;
395 }
396
397 if (dl_se->dl_yielded && dl_se->runtime > 0)
398 dl_se->runtime = 0;
399
400 /*
401 * We keep moving the deadline away until we get some
402 * available runtime for the entity. This ensures correct
403 * handling of situations where the runtime overrun is
404 * arbitrary large.
405 */
406 while (dl_se->runtime <= 0) {
407 dl_se->deadline += pi_se->dl_period;
408 dl_se->runtime += pi_se->dl_runtime;
409 }
410
411 /*
412 * At this point, the deadline really should be "in
413 * the future" with respect to rq->clock. If it's
414 * not, we are, for some reason, lagging too much!
415 * Anyway, after having warn userspace abut that,
416 * we still try to keep the things running by
417 * resetting the deadline and the budget of the
418 * entity.
419 */
420 if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
421 printk_deferred_once("sched: DL replenish lagged too much\n");
422 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
423 dl_se->runtime = pi_se->dl_runtime;
424 }
425
426 if (dl_se->dl_yielded)
427 dl_se->dl_yielded = 0;
428 if (dl_se->dl_throttled)
429 dl_se->dl_throttled = 0;
430}
431
432/*
433 * Here we check if --at time t-- an entity (which is probably being
434 * [re]activated or, in general, enqueued) can use its remaining runtime
435 * and its current deadline _without_ exceeding the bandwidth it is
436 * assigned (function returns true if it can't). We are in fact applying
437 * one of the CBS rules: when a task wakes up, if the residual runtime
438 * over residual deadline fits within the allocated bandwidth, then we
439 * can keep the current (absolute) deadline and residual budget without
440 * disrupting the schedulability of the system. Otherwise, we should
441 * refill the runtime and set the deadline a period in the future,
442 * because keeping the current (absolute) deadline of the task would
443 * result in breaking guarantees promised to other tasks (refer to
444 * Documentation/scheduler/sched-deadline.txt for more informations).
445 *
446 * This function returns true if:
447 *
448 * runtime / (deadline - t) > dl_runtime / dl_period ,
449 *
450 * IOW we can't recycle current parameters.
451 *
452 * Notice that the bandwidth check is done against the period. For
453 * task with deadline equal to period this is the same of using
454 * dl_deadline instead of dl_period in the equation above.
455 */
456static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
457 struct sched_dl_entity *pi_se, u64 t)
458{
459 u64 left, right;
460
461 /*
462 * left and right are the two sides of the equation above,
463 * after a bit of shuffling to use multiplications instead
464 * of divisions.
465 *
466 * Note that none of the time values involved in the two
467 * multiplications are absolute: dl_deadline and dl_runtime
468 * are the relative deadline and the maximum runtime of each
469 * instance, runtime is the runtime left for the last instance
470 * and (deadline - t), since t is rq->clock, is the time left
471 * to the (absolute) deadline. Even if overflowing the u64 type
472 * is very unlikely to occur in both cases, here we scale down
473 * as we want to avoid that risk at all. Scaling down by 10
474 * means that we reduce granularity to 1us. We are fine with it,
475 * since this is only a true/false check and, anyway, thinking
476 * of anything below microseconds resolution is actually fiction
477 * (but still we want to give the user that illusion >;).
478 */
479 left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
480 right = ((dl_se->deadline - t) >> DL_SCALE) *
481 (pi_se->dl_runtime >> DL_SCALE);
482
483 return dl_time_before(right, left);
484}
485
486/*
487 * When a -deadline entity is queued back on the runqueue, its runtime and
488 * deadline might need updating.
489 *
490 * The policy here is that we update the deadline of the entity only if:
491 * - the current deadline is in the past,
492 * - using the remaining runtime with the current deadline would make
493 * the entity exceed its bandwidth.
494 */
495static void update_dl_entity(struct sched_dl_entity *dl_se,
496 struct sched_dl_entity *pi_se)
497{
498 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
499 struct rq *rq = rq_of_dl_rq(dl_rq);
500
501 if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
502 dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
503 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
504 dl_se->runtime = pi_se->dl_runtime;
505 }
506}
507
508/*
509 * If the entity depleted all its runtime, and if we want it to sleep
510 * while waiting for some new execution time to become available, we
511 * set the bandwidth enforcement timer to the replenishment instant
512 * and try to activate it.
513 *
514 * Notice that it is important for the caller to know if the timer
515 * actually started or not (i.e., the replenishment instant is in
516 * the future or in the past).
517 */
518static int start_dl_timer(struct task_struct *p)
519{
520 struct sched_dl_entity *dl_se = &p->dl;
521 struct hrtimer *timer = &dl_se->dl_timer;
522 struct rq *rq = task_rq(p);
523 ktime_t now, act;
524 s64 delta;
525
526 lockdep_assert_held(&rq->lock);
527
528 /*
529 * We want the timer to fire at the deadline, but considering
530 * that it is actually coming from rq->clock and not from
531 * hrtimer's time base reading.
532 */
533 act = ns_to_ktime(dl_se->deadline);
534 now = hrtimer_cb_get_time(timer);
535 delta = ktime_to_ns(now) - rq_clock(rq);
536 act = ktime_add_ns(act, delta);
537
538 /*
539 * If the expiry time already passed, e.g., because the value
540 * chosen as the deadline is too small, don't even try to
541 * start the timer in the past!
542 */
543 if (ktime_us_delta(act, now) < 0)
544 return 0;
545
546 /*
547 * !enqueued will guarantee another callback; even if one is already in
548 * progress. This ensures a balanced {get,put}_task_struct().
549 *
550 * The race against __run_timer() clearing the enqueued state is
551 * harmless because we're holding task_rq()->lock, therefore the timer
552 * expiring after we've done the check will wait on its task_rq_lock()
553 * and observe our state.
554 */
555 if (!hrtimer_is_queued(timer)) {
556 get_task_struct(p);
557 hrtimer_start(timer, act, HRTIMER_MODE_ABS);
558 }
559
560 return 1;
561}
562
563/*
564 * This is the bandwidth enforcement timer callback. If here, we know
565 * a task is not on its dl_rq, since the fact that the timer was running
566 * means the task is throttled and needs a runtime replenishment.
567 *
568 * However, what we actually do depends on the fact the task is active,
569 * (it is on its rq) or has been removed from there by a call to
570 * dequeue_task_dl(). In the former case we must issue the runtime
571 * replenishment and add the task back to the dl_rq; in the latter, we just
572 * do nothing but clearing dl_throttled, so that runtime and deadline
573 * updating (and the queueing back to dl_rq) will be done by the
574 * next call to enqueue_task_dl().
575 */
576static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
577{
578 struct sched_dl_entity *dl_se = container_of(timer,
579 struct sched_dl_entity,
580 dl_timer);
581 struct task_struct *p = dl_task_of(dl_se);
582 struct rq_flags rf;
583 struct rq *rq;
584
585 rq = task_rq_lock(p, &rf);
586
587 /*
588 * The task might have changed its scheduling policy to something
589 * different than SCHED_DEADLINE (through switched_from_dl()).
590 */
591 if (!dl_task(p)) {
592 __dl_clear_params(p);
593 goto unlock;
594 }
595
596 /*
597 * The task might have been boosted by someone else and might be in the
598 * boosting/deboosting path, its not throttled.
599 */
600 if (dl_se->dl_boosted)
601 goto unlock;
602
603 /*
604 * Spurious timer due to start_dl_timer() race; or we already received
605 * a replenishment from rt_mutex_setprio().
606 */
607 if (!dl_se->dl_throttled)
608 goto unlock;
609
610 sched_clock_tick();
611 update_rq_clock(rq);
612
613 /*
614 * If the throttle happened during sched-out; like:
615 *
616 * schedule()
617 * deactivate_task()
618 * dequeue_task_dl()
619 * update_curr_dl()
620 * start_dl_timer()
621 * __dequeue_task_dl()
622 * prev->on_rq = 0;
623 *
624 * We can be both throttled and !queued. Replenish the counter
625 * but do not enqueue -- wait for our wakeup to do that.
626 */
627 if (!task_on_rq_queued(p)) {
628 replenish_dl_entity(dl_se, dl_se);
629 goto unlock;
630 }
631
632#ifdef CONFIG_SMP
633 if (unlikely(!rq->online)) {
634 /*
635 * If the runqueue is no longer available, migrate the
636 * task elsewhere. This necessarily changes rq.
637 */
638 lockdep_unpin_lock(&rq->lock, rf.cookie);
639 rq = dl_task_offline_migration(rq, p);
640 rf.cookie = lockdep_pin_lock(&rq->lock);
641
642 /*
643 * Now that the task has been migrated to the new RQ and we
644 * have that locked, proceed as normal and enqueue the task
645 * there.
646 */
647 }
648#endif
649
650 enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
651 if (dl_task(rq->curr))
652 check_preempt_curr_dl(rq, p, 0);
653 else
654 resched_curr(rq);
655
656#ifdef CONFIG_SMP
657 /*
658 * Queueing this task back might have overloaded rq, check if we need
659 * to kick someone away.
660 */
661 if (has_pushable_dl_tasks(rq)) {
662 /*
663 * Nothing relies on rq->lock after this, so its safe to drop
664 * rq->lock.
665 */
666 lockdep_unpin_lock(&rq->lock, rf.cookie);
667 push_dl_task(rq);
668 lockdep_repin_lock(&rq->lock, rf.cookie);
669 }
670#endif
671
672unlock:
673 task_rq_unlock(rq, p, &rf);
674
675 /*
676 * This can free the task_struct, including this hrtimer, do not touch
677 * anything related to that after this.
678 */
679 put_task_struct(p);
680
681 return HRTIMER_NORESTART;
682}
683
684void init_dl_task_timer(struct sched_dl_entity *dl_se)
685{
686 struct hrtimer *timer = &dl_se->dl_timer;
687
688 hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
689 timer->function = dl_task_timer;
690}
691
692static
693int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
694{
695 return (dl_se->runtime <= 0);
696}
697
698extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
699
700/*
701 * Update the current task's runtime statistics (provided it is still
702 * a -deadline task and has not been removed from the dl_rq).
703 */
704static void update_curr_dl(struct rq *rq)
705{
706 struct task_struct *curr = rq->curr;
707 struct sched_dl_entity *dl_se = &curr->dl;
708 u64 delta_exec;
709
710 if (!dl_task(curr) || !on_dl_rq(dl_se))
711 return;
712
713 /*
714 * Consumed budget is computed considering the time as
715 * observed by schedulable tasks (excluding time spent
716 * in hardirq context, etc.). Deadlines are instead
717 * computed using hard walltime. This seems to be the more
718 * natural solution, but the full ramifications of this
719 * approach need further study.
720 */
721 delta_exec = rq_clock_task(rq) - curr->se.exec_start;
722 if (unlikely((s64)delta_exec <= 0)) {
723 if (unlikely(dl_se->dl_yielded))
724 goto throttle;
725 return;
726 }
727
728 /* kick cpufreq (see the comment in kernel/sched/sched.h). */
729 cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_DL);
730
731 schedstat_set(curr->se.statistics.exec_max,
732 max(curr->se.statistics.exec_max, delta_exec));
733
734 curr->se.sum_exec_runtime += delta_exec;
735 account_group_exec_runtime(curr, delta_exec);
736
737 curr->se.exec_start = rq_clock_task(rq);
738 cpuacct_charge(curr, delta_exec);
739
740 sched_rt_avg_update(rq, delta_exec);
741
742 dl_se->runtime -= delta_exec;
743
744throttle:
745 if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
746 dl_se->dl_throttled = 1;
747 __dequeue_task_dl(rq, curr, 0);
748 if (unlikely(dl_se->dl_boosted || !start_dl_timer(curr)))
749 enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
750
751 if (!is_leftmost(curr, &rq->dl))
752 resched_curr(rq);
753 }
754
755 /*
756 * Because -- for now -- we share the rt bandwidth, we need to
757 * account our runtime there too, otherwise actual rt tasks
758 * would be able to exceed the shared quota.
759 *
760 * Account to the root rt group for now.
761 *
762 * The solution we're working towards is having the RT groups scheduled
763 * using deadline servers -- however there's a few nasties to figure
764 * out before that can happen.
765 */
766 if (rt_bandwidth_enabled()) {
767 struct rt_rq *rt_rq = &rq->rt;
768
769 raw_spin_lock(&rt_rq->rt_runtime_lock);
770 /*
771 * We'll let actual RT tasks worry about the overflow here, we
772 * have our own CBS to keep us inline; only account when RT
773 * bandwidth is relevant.
774 */
775 if (sched_rt_bandwidth_account(rt_rq))
776 rt_rq->rt_time += delta_exec;
777 raw_spin_unlock(&rt_rq->rt_runtime_lock);
778 }
779}
780
781#ifdef CONFIG_SMP
782
783static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
784{
785 struct rq *rq = rq_of_dl_rq(dl_rq);
786
787 if (dl_rq->earliest_dl.curr == 0 ||
788 dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
789 dl_rq->earliest_dl.curr = deadline;
790 cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
791 }
792}
793
794static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
795{
796 struct rq *rq = rq_of_dl_rq(dl_rq);
797
798 /*
799 * Since we may have removed our earliest (and/or next earliest)
800 * task we must recompute them.
801 */
802 if (!dl_rq->dl_nr_running) {
803 dl_rq->earliest_dl.curr = 0;
804 dl_rq->earliest_dl.next = 0;
805 cpudl_clear(&rq->rd->cpudl, rq->cpu);
806 } else {
807 struct rb_node *leftmost = dl_rq->rb_leftmost;
808 struct sched_dl_entity *entry;
809
810 entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
811 dl_rq->earliest_dl.curr = entry->deadline;
812 cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
813 }
814}
815
816#else
817
818static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
819static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
820
821#endif /* CONFIG_SMP */
822
823static inline
824void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
825{
826 int prio = dl_task_of(dl_se)->prio;
827 u64 deadline = dl_se->deadline;
828
829 WARN_ON(!dl_prio(prio));
830 dl_rq->dl_nr_running++;
831 add_nr_running(rq_of_dl_rq(dl_rq), 1);
832
833 inc_dl_deadline(dl_rq, deadline);
834 inc_dl_migration(dl_se, dl_rq);
835}
836
837static inline
838void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
839{
840 int prio = dl_task_of(dl_se)->prio;
841
842 WARN_ON(!dl_prio(prio));
843 WARN_ON(!dl_rq->dl_nr_running);
844 dl_rq->dl_nr_running--;
845 sub_nr_running(rq_of_dl_rq(dl_rq), 1);
846
847 dec_dl_deadline(dl_rq, dl_se->deadline);
848 dec_dl_migration(dl_se, dl_rq);
849}
850
851static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
852{
853 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
854 struct rb_node **link = &dl_rq->rb_root.rb_node;
855 struct rb_node *parent = NULL;
856 struct sched_dl_entity *entry;
857 int leftmost = 1;
858
859 BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
860
861 while (*link) {
862 parent = *link;
863 entry = rb_entry(parent, struct sched_dl_entity, rb_node);
864 if (dl_time_before(dl_se->deadline, entry->deadline))
865 link = &parent->rb_left;
866 else {
867 link = &parent->rb_right;
868 leftmost = 0;
869 }
870 }
871
872 if (leftmost)
873 dl_rq->rb_leftmost = &dl_se->rb_node;
874
875 rb_link_node(&dl_se->rb_node, parent, link);
876 rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
877
878 inc_dl_tasks(dl_se, dl_rq);
879}
880
881static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
882{
883 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
884
885 if (RB_EMPTY_NODE(&dl_se->rb_node))
886 return;
887
888 if (dl_rq->rb_leftmost == &dl_se->rb_node) {
889 struct rb_node *next_node;
890
891 next_node = rb_next(&dl_se->rb_node);
892 dl_rq->rb_leftmost = next_node;
893 }
894
895 rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
896 RB_CLEAR_NODE(&dl_se->rb_node);
897
898 dec_dl_tasks(dl_se, dl_rq);
899}
900
901static void
902enqueue_dl_entity(struct sched_dl_entity *dl_se,
903 struct sched_dl_entity *pi_se, int flags)
904{
905 BUG_ON(on_dl_rq(dl_se));
906
907 /*
908 * If this is a wakeup or a new instance, the scheduling
909 * parameters of the task might need updating. Otherwise,
910 * we want a replenishment of its runtime.
911 */
912 if (flags & ENQUEUE_WAKEUP)
913 update_dl_entity(dl_se, pi_se);
914 else if (flags & ENQUEUE_REPLENISH)
915 replenish_dl_entity(dl_se, pi_se);
916
917 __enqueue_dl_entity(dl_se);
918}
919
920static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
921{
922 __dequeue_dl_entity(dl_se);
923}
924
925static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
926{
927 struct task_struct *pi_task = rt_mutex_get_top_task(p);
928 struct sched_dl_entity *pi_se = &p->dl;
929
930 /*
931 * Use the scheduling parameters of the top pi-waiter
932 * task if we have one and its (absolute) deadline is
933 * smaller than our one... OTW we keep our runtime and
934 * deadline.
935 */
936 if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio)) {
937 pi_se = &pi_task->dl;
938 } else if (!dl_prio(p->normal_prio)) {
939 /*
940 * Special case in which we have a !SCHED_DEADLINE task
941 * that is going to be deboosted, but exceedes its
942 * runtime while doing so. No point in replenishing
943 * it, as it's going to return back to its original
944 * scheduling class after this.
945 */
946 BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
947 return;
948 }
949
950 /*
951 * If p is throttled, we do nothing. In fact, if it exhausted
952 * its budget it needs a replenishment and, since it now is on
953 * its rq, the bandwidth timer callback (which clearly has not
954 * run yet) will take care of this.
955 */
956 if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))
957 return;
958
959 enqueue_dl_entity(&p->dl, pi_se, flags);
960
961 if (!task_current(rq, p) && tsk_nr_cpus_allowed(p) > 1)
962 enqueue_pushable_dl_task(rq, p);
963}
964
965static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
966{
967 dequeue_dl_entity(&p->dl);
968 dequeue_pushable_dl_task(rq, p);
969}
970
971static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
972{
973 update_curr_dl(rq);
974 __dequeue_task_dl(rq, p, flags);
975}
976
977/*
978 * Yield task semantic for -deadline tasks is:
979 *
980 * get off from the CPU until our next instance, with
981 * a new runtime. This is of little use now, since we
982 * don't have a bandwidth reclaiming mechanism. Anyway,
983 * bandwidth reclaiming is planned for the future, and
984 * yield_task_dl will indicate that some spare budget
985 * is available for other task instances to use it.
986 */
987static void yield_task_dl(struct rq *rq)
988{
989 /*
990 * We make the task go to sleep until its current deadline by
991 * forcing its runtime to zero. This way, update_curr_dl() stops
992 * it and the bandwidth timer will wake it up and will give it
993 * new scheduling parameters (thanks to dl_yielded=1).
994 */
995 rq->curr->dl.dl_yielded = 1;
996
997 update_rq_clock(rq);
998 update_curr_dl(rq);
999 /*
1000 * Tell update_rq_clock() that we've just updated,
1001 * so we don't do microscopic update in schedule()
1002 * and double the fastpath cost.
1003 */
1004 rq_clock_skip_update(rq, true);
1005}
1006
1007#ifdef CONFIG_SMP
1008
1009static int find_later_rq(struct task_struct *task);
1010
1011static int
1012select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
1013{
1014 struct task_struct *curr;
1015 struct rq *rq;
1016
1017 if (sd_flag != SD_BALANCE_WAKE)
1018 goto out;
1019
1020 rq = cpu_rq(cpu);
1021
1022 rcu_read_lock();
1023 curr = READ_ONCE(rq->curr); /* unlocked access */
1024
1025 /*
1026 * If we are dealing with a -deadline task, we must
1027 * decide where to wake it up.
1028 * If it has a later deadline and the current task
1029 * on this rq can't move (provided the waking task
1030 * can!) we prefer to send it somewhere else. On the
1031 * other hand, if it has a shorter deadline, we
1032 * try to make it stay here, it might be important.
1033 */
1034 if (unlikely(dl_task(curr)) &&
1035 (tsk_nr_cpus_allowed(curr) < 2 ||
1036 !dl_entity_preempt(&p->dl, &curr->dl)) &&
1037 (tsk_nr_cpus_allowed(p) > 1)) {
1038 int target = find_later_rq(p);
1039
1040 if (target != -1 &&
1041 (dl_time_before(p->dl.deadline,
1042 cpu_rq(target)->dl.earliest_dl.curr) ||
1043 (cpu_rq(target)->dl.dl_nr_running == 0)))
1044 cpu = target;
1045 }
1046 rcu_read_unlock();
1047
1048out:
1049 return cpu;
1050}
1051
1052static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
1053{
1054 /*
1055 * Current can't be migrated, useless to reschedule,
1056 * let's hope p can move out.
1057 */
1058 if (tsk_nr_cpus_allowed(rq->curr) == 1 ||
1059 cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
1060 return;
1061
1062 /*
1063 * p is migratable, so let's not schedule it and
1064 * see if it is pushed or pulled somewhere else.
1065 */
1066 if (tsk_nr_cpus_allowed(p) != 1 &&
1067 cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
1068 return;
1069
1070 resched_curr(rq);
1071}
1072
1073#endif /* CONFIG_SMP */
1074
1075/*
1076 * Only called when both the current and waking task are -deadline
1077 * tasks.
1078 */
1079static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
1080 int flags)
1081{
1082 if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
1083 resched_curr(rq);
1084 return;
1085 }
1086
1087#ifdef CONFIG_SMP
1088 /*
1089 * In the unlikely case current and p have the same deadline
1090 * let us try to decide what's the best thing to do...
1091 */
1092 if ((p->dl.deadline == rq->curr->dl.deadline) &&
1093 !test_tsk_need_resched(rq->curr))
1094 check_preempt_equal_dl(rq, p);
1095#endif /* CONFIG_SMP */
1096}
1097
1098#ifdef CONFIG_SCHED_HRTICK
1099static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1100{
1101 hrtick_start(rq, p->dl.runtime);
1102}
1103#else /* !CONFIG_SCHED_HRTICK */
1104static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1105{
1106}
1107#endif
1108
1109static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
1110 struct dl_rq *dl_rq)
1111{
1112 struct rb_node *left = dl_rq->rb_leftmost;
1113
1114 if (!left)
1115 return NULL;
1116
1117 return rb_entry(left, struct sched_dl_entity, rb_node);
1118}
1119
1120struct task_struct *
1121pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
1122{
1123 struct sched_dl_entity *dl_se;
1124 struct task_struct *p;
1125 struct dl_rq *dl_rq;
1126
1127 dl_rq = &rq->dl;
1128
1129 if (need_pull_dl_task(rq, prev)) {
1130 /*
1131 * This is OK, because current is on_cpu, which avoids it being
1132 * picked for load-balance and preemption/IRQs are still
1133 * disabled avoiding further scheduler activity on it and we're
1134 * being very careful to re-start the picking loop.
1135 */
1136 lockdep_unpin_lock(&rq->lock, cookie);
1137 pull_dl_task(rq);
1138 lockdep_repin_lock(&rq->lock, cookie);
1139 /*
1140 * pull_dl_task() can drop (and re-acquire) rq->lock; this
1141 * means a stop task can slip in, in which case we need to
1142 * re-start task selection.
1143 */
1144 if (rq->stop && task_on_rq_queued(rq->stop))
1145 return RETRY_TASK;
1146 }
1147
1148 /*
1149 * When prev is DL, we may throttle it in put_prev_task().
1150 * So, we update time before we check for dl_nr_running.
1151 */
1152 if (prev->sched_class == &dl_sched_class)
1153 update_curr_dl(rq);
1154
1155 if (unlikely(!dl_rq->dl_nr_running))
1156 return NULL;
1157
1158 put_prev_task(rq, prev);
1159
1160 dl_se = pick_next_dl_entity(rq, dl_rq);
1161 BUG_ON(!dl_se);
1162
1163 p = dl_task_of(dl_se);
1164 p->se.exec_start = rq_clock_task(rq);
1165
1166 /* Running task will never be pushed. */
1167 dequeue_pushable_dl_task(rq, p);
1168
1169 if (hrtick_enabled(rq))
1170 start_hrtick_dl(rq, p);
1171
1172 queue_push_tasks(rq);
1173
1174 return p;
1175}
1176
1177static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
1178{
1179 update_curr_dl(rq);
1180
1181 if (on_dl_rq(&p->dl) && tsk_nr_cpus_allowed(p) > 1)
1182 enqueue_pushable_dl_task(rq, p);
1183}
1184
1185static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
1186{
1187 update_curr_dl(rq);
1188
1189 /*
1190 * Even when we have runtime, update_curr_dl() might have resulted in us
1191 * not being the leftmost task anymore. In that case NEED_RESCHED will
1192 * be set and schedule() will start a new hrtick for the next task.
1193 */
1194 if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 &&
1195 is_leftmost(p, &rq->dl))
1196 start_hrtick_dl(rq, p);
1197}
1198
1199static void task_fork_dl(struct task_struct *p)
1200{
1201 /*
1202 * SCHED_DEADLINE tasks cannot fork and this is achieved through
1203 * sched_fork()
1204 */
1205}
1206
1207static void task_dead_dl(struct task_struct *p)
1208{
1209 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
1210
1211 /*
1212 * Since we are TASK_DEAD we won't slip out of the domain!
1213 */
1214 raw_spin_lock_irq(&dl_b->lock);
1215 /* XXX we should retain the bw until 0-lag */
1216 dl_b->total_bw -= p->dl.dl_bw;
1217 raw_spin_unlock_irq(&dl_b->lock);
1218}
1219
1220static void set_curr_task_dl(struct rq *rq)
1221{
1222 struct task_struct *p = rq->curr;
1223
1224 p->se.exec_start = rq_clock_task(rq);
1225
1226 /* You can't push away the running task */
1227 dequeue_pushable_dl_task(rq, p);
1228}
1229
1230#ifdef CONFIG_SMP
1231
1232/* Only try algorithms three times */
1233#define DL_MAX_TRIES 3
1234
1235static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
1236{
1237 if (!task_running(rq, p) &&
1238 cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
1239 return 1;
1240 return 0;
1241}
1242
1243/*
1244 * Return the earliest pushable rq's task, which is suitable to be executed
1245 * on the CPU, NULL otherwise:
1246 */
1247static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
1248{
1249 struct rb_node *next_node = rq->dl.pushable_dl_tasks_leftmost;
1250 struct task_struct *p = NULL;
1251
1252 if (!has_pushable_dl_tasks(rq))
1253 return NULL;
1254
1255next_node:
1256 if (next_node) {
1257 p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
1258
1259 if (pick_dl_task(rq, p, cpu))
1260 return p;
1261
1262 next_node = rb_next(next_node);
1263 goto next_node;
1264 }
1265
1266 return NULL;
1267}
1268
1269static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
1270
1271static int find_later_rq(struct task_struct *task)
1272{
1273 struct sched_domain *sd;
1274 struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
1275 int this_cpu = smp_processor_id();
1276 int best_cpu, cpu = task_cpu(task);
1277
1278 /* Make sure the mask is initialized first */
1279 if (unlikely(!later_mask))
1280 return -1;
1281
1282 if (tsk_nr_cpus_allowed(task) == 1)
1283 return -1;
1284
1285 /*
1286 * We have to consider system topology and task affinity
1287 * first, then we can look for a suitable cpu.
1288 */
1289 best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
1290 task, later_mask);
1291 if (best_cpu == -1)
1292 return -1;
1293
1294 /*
1295 * If we are here, some target has been found,
1296 * the most suitable of which is cached in best_cpu.
1297 * This is, among the runqueues where the current tasks
1298 * have later deadlines than the task's one, the rq
1299 * with the latest possible one.
1300 *
1301 * Now we check how well this matches with task's
1302 * affinity and system topology.
1303 *
1304 * The last cpu where the task run is our first
1305 * guess, since it is most likely cache-hot there.
1306 */
1307 if (cpumask_test_cpu(cpu, later_mask))
1308 return cpu;
1309 /*
1310 * Check if this_cpu is to be skipped (i.e., it is
1311 * not in the mask) or not.
1312 */
1313 if (!cpumask_test_cpu(this_cpu, later_mask))
1314 this_cpu = -1;
1315
1316 rcu_read_lock();
1317 for_each_domain(cpu, sd) {
1318 if (sd->flags & SD_WAKE_AFFINE) {
1319
1320 /*
1321 * If possible, preempting this_cpu is
1322 * cheaper than migrating.
1323 */
1324 if (this_cpu != -1 &&
1325 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1326 rcu_read_unlock();
1327 return this_cpu;
1328 }
1329
1330 /*
1331 * Last chance: if best_cpu is valid and is
1332 * in the mask, that becomes our choice.
1333 */
1334 if (best_cpu < nr_cpu_ids &&
1335 cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
1336 rcu_read_unlock();
1337 return best_cpu;
1338 }
1339 }
1340 }
1341 rcu_read_unlock();
1342
1343 /*
1344 * At this point, all our guesses failed, we just return
1345 * 'something', and let the caller sort the things out.
1346 */
1347 if (this_cpu != -1)
1348 return this_cpu;
1349
1350 cpu = cpumask_any(later_mask);
1351 if (cpu < nr_cpu_ids)
1352 return cpu;
1353
1354 return -1;
1355}
1356
1357/* Locks the rq it finds */
1358static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
1359{
1360 struct rq *later_rq = NULL;
1361 int tries;
1362 int cpu;
1363
1364 for (tries = 0; tries < DL_MAX_TRIES; tries++) {
1365 cpu = find_later_rq(task);
1366
1367 if ((cpu == -1) || (cpu == rq->cpu))
1368 break;
1369
1370 later_rq = cpu_rq(cpu);
1371
1372 if (later_rq->dl.dl_nr_running &&
1373 !dl_time_before(task->dl.deadline,
1374 later_rq->dl.earliest_dl.curr)) {
1375 /*
1376 * Target rq has tasks of equal or earlier deadline,
1377 * retrying does not release any lock and is unlikely
1378 * to yield a different result.
1379 */
1380 later_rq = NULL;
1381 break;
1382 }
1383
1384 /* Retry if something changed. */
1385 if (double_lock_balance(rq, later_rq)) {
1386 if (unlikely(task_rq(task) != rq ||
1387 !cpumask_test_cpu(later_rq->cpu,
1388 tsk_cpus_allowed(task)) ||
1389 task_running(rq, task) ||
1390 !dl_task(task) ||
1391 !task_on_rq_queued(task))) {
1392 double_unlock_balance(rq, later_rq);
1393 later_rq = NULL;
1394 break;
1395 }
1396 }
1397
1398 /*
1399 * If the rq we found has no -deadline task, or
1400 * its earliest one has a later deadline than our
1401 * task, the rq is a good one.
1402 */
1403 if (!later_rq->dl.dl_nr_running ||
1404 dl_time_before(task->dl.deadline,
1405 later_rq->dl.earliest_dl.curr))
1406 break;
1407
1408 /* Otherwise we try again. */
1409 double_unlock_balance(rq, later_rq);
1410 later_rq = NULL;
1411 }
1412
1413 return later_rq;
1414}
1415
1416static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
1417{
1418 struct task_struct *p;
1419
1420 if (!has_pushable_dl_tasks(rq))
1421 return NULL;
1422
1423 p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
1424 struct task_struct, pushable_dl_tasks);
1425
1426 BUG_ON(rq->cpu != task_cpu(p));
1427 BUG_ON(task_current(rq, p));
1428 BUG_ON(tsk_nr_cpus_allowed(p) <= 1);
1429
1430 BUG_ON(!task_on_rq_queued(p));
1431 BUG_ON(!dl_task(p));
1432
1433 return p;
1434}
1435
1436/*
1437 * See if the non running -deadline tasks on this rq
1438 * can be sent to some other CPU where they can preempt
1439 * and start executing.
1440 */
1441static int push_dl_task(struct rq *rq)
1442{
1443 struct task_struct *next_task;
1444 struct rq *later_rq;
1445 int ret = 0;
1446
1447 if (!rq->dl.overloaded)
1448 return 0;
1449
1450 next_task = pick_next_pushable_dl_task(rq);
1451 if (!next_task)
1452 return 0;
1453
1454retry:
1455 if (unlikely(next_task == rq->curr)) {
1456 WARN_ON(1);
1457 return 0;
1458 }
1459
1460 /*
1461 * If next_task preempts rq->curr, and rq->curr
1462 * can move away, it makes sense to just reschedule
1463 * without going further in pushing next_task.
1464 */
1465 if (dl_task(rq->curr) &&
1466 dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
1467 tsk_nr_cpus_allowed(rq->curr) > 1) {
1468 resched_curr(rq);
1469 return 0;
1470 }
1471
1472 /* We might release rq lock */
1473 get_task_struct(next_task);
1474
1475 /* Will lock the rq it'll find */
1476 later_rq = find_lock_later_rq(next_task, rq);
1477 if (!later_rq) {
1478 struct task_struct *task;
1479
1480 /*
1481 * We must check all this again, since
1482 * find_lock_later_rq releases rq->lock and it is
1483 * then possible that next_task has migrated.
1484 */
1485 task = pick_next_pushable_dl_task(rq);
1486 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1487 /*
1488 * The task is still there. We don't try
1489 * again, some other cpu will pull it when ready.
1490 */
1491 goto out;
1492 }
1493
1494 if (!task)
1495 /* No more tasks */
1496 goto out;
1497
1498 put_task_struct(next_task);
1499 next_task = task;
1500 goto retry;
1501 }
1502
1503 deactivate_task(rq, next_task, 0);
1504 set_task_cpu(next_task, later_rq->cpu);
1505 activate_task(later_rq, next_task, 0);
1506 ret = 1;
1507
1508 resched_curr(later_rq);
1509
1510 double_unlock_balance(rq, later_rq);
1511
1512out:
1513 put_task_struct(next_task);
1514
1515 return ret;
1516}
1517
1518static void push_dl_tasks(struct rq *rq)
1519{
1520 /* push_dl_task() will return true if it moved a -deadline task */
1521 while (push_dl_task(rq))
1522 ;
1523}
1524
1525static void pull_dl_task(struct rq *this_rq)
1526{
1527 int this_cpu = this_rq->cpu, cpu;
1528 struct task_struct *p;
1529 bool resched = false;
1530 struct rq *src_rq;
1531 u64 dmin = LONG_MAX;
1532
1533 if (likely(!dl_overloaded(this_rq)))
1534 return;
1535
1536 /*
1537 * Match the barrier from dl_set_overloaded; this guarantees that if we
1538 * see overloaded we must also see the dlo_mask bit.
1539 */
1540 smp_rmb();
1541
1542 for_each_cpu(cpu, this_rq->rd->dlo_mask) {
1543 if (this_cpu == cpu)
1544 continue;
1545
1546 src_rq = cpu_rq(cpu);
1547
1548 /*
1549 * It looks racy, abd it is! However, as in sched_rt.c,
1550 * we are fine with this.
1551 */
1552 if (this_rq->dl.dl_nr_running &&
1553 dl_time_before(this_rq->dl.earliest_dl.curr,
1554 src_rq->dl.earliest_dl.next))
1555 continue;
1556
1557 /* Might drop this_rq->lock */
1558 double_lock_balance(this_rq, src_rq);
1559
1560 /*
1561 * If there are no more pullable tasks on the
1562 * rq, we're done with it.
1563 */
1564 if (src_rq->dl.dl_nr_running <= 1)
1565 goto skip;
1566
1567 p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
1568
1569 /*
1570 * We found a task to be pulled if:
1571 * - it preempts our current (if there's one),
1572 * - it will preempt the last one we pulled (if any).
1573 */
1574 if (p && dl_time_before(p->dl.deadline, dmin) &&
1575 (!this_rq->dl.dl_nr_running ||
1576 dl_time_before(p->dl.deadline,
1577 this_rq->dl.earliest_dl.curr))) {
1578 WARN_ON(p == src_rq->curr);
1579 WARN_ON(!task_on_rq_queued(p));
1580
1581 /*
1582 * Then we pull iff p has actually an earlier
1583 * deadline than the current task of its runqueue.
1584 */
1585 if (dl_time_before(p->dl.deadline,
1586 src_rq->curr->dl.deadline))
1587 goto skip;
1588
1589 resched = true;
1590
1591 deactivate_task(src_rq, p, 0);
1592 set_task_cpu(p, this_cpu);
1593 activate_task(this_rq, p, 0);
1594 dmin = p->dl.deadline;
1595
1596 /* Is there any other task even earlier? */
1597 }
1598skip:
1599 double_unlock_balance(this_rq, src_rq);
1600 }
1601
1602 if (resched)
1603 resched_curr(this_rq);
1604}
1605
1606/*
1607 * Since the task is not running and a reschedule is not going to happen
1608 * anytime soon on its runqueue, we try pushing it away now.
1609 */
1610static void task_woken_dl(struct rq *rq, struct task_struct *p)
1611{
1612 if (!task_running(rq, p) &&
1613 !test_tsk_need_resched(rq->curr) &&
1614 tsk_nr_cpus_allowed(p) > 1 &&
1615 dl_task(rq->curr) &&
1616 (tsk_nr_cpus_allowed(rq->curr) < 2 ||
1617 !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
1618 push_dl_tasks(rq);
1619 }
1620}
1621
1622static void set_cpus_allowed_dl(struct task_struct *p,
1623 const struct cpumask *new_mask)
1624{
1625 struct root_domain *src_rd;
1626 struct rq *rq;
1627
1628 BUG_ON(!dl_task(p));
1629
1630 rq = task_rq(p);
1631 src_rd = rq->rd;
1632 /*
1633 * Migrating a SCHED_DEADLINE task between exclusive
1634 * cpusets (different root_domains) entails a bandwidth
1635 * update. We already made space for us in the destination
1636 * domain (see cpuset_can_attach()).
1637 */
1638 if (!cpumask_intersects(src_rd->span, new_mask)) {
1639 struct dl_bw *src_dl_b;
1640
1641 src_dl_b = dl_bw_of(cpu_of(rq));
1642 /*
1643 * We now free resources of the root_domain we are migrating
1644 * off. In the worst case, sched_setattr() may temporary fail
1645 * until we complete the update.
1646 */
1647 raw_spin_lock(&src_dl_b->lock);
1648 __dl_clear(src_dl_b, p->dl.dl_bw);
1649 raw_spin_unlock(&src_dl_b->lock);
1650 }
1651
1652 set_cpus_allowed_common(p, new_mask);
1653}
1654
1655/* Assumes rq->lock is held */
1656static void rq_online_dl(struct rq *rq)
1657{
1658 if (rq->dl.overloaded)
1659 dl_set_overload(rq);
1660
1661 cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
1662 if (rq->dl.dl_nr_running > 0)
1663 cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
1664}
1665
1666/* Assumes rq->lock is held */
1667static void rq_offline_dl(struct rq *rq)
1668{
1669 if (rq->dl.overloaded)
1670 dl_clear_overload(rq);
1671
1672 cpudl_clear(&rq->rd->cpudl, rq->cpu);
1673 cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
1674}
1675
1676void __init init_sched_dl_class(void)
1677{
1678 unsigned int i;
1679
1680 for_each_possible_cpu(i)
1681 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
1682 GFP_KERNEL, cpu_to_node(i));
1683}
1684
1685#endif /* CONFIG_SMP */
1686
1687static void switched_from_dl(struct rq *rq, struct task_struct *p)
1688{
1689 /*
1690 * Start the deadline timer; if we switch back to dl before this we'll
1691 * continue consuming our current CBS slice. If we stay outside of
1692 * SCHED_DEADLINE until the deadline passes, the timer will reset the
1693 * task.
1694 */
1695 if (!start_dl_timer(p))
1696 __dl_clear_params(p);
1697
1698 /*
1699 * Since this might be the only -deadline task on the rq,
1700 * this is the right place to try to pull some other one
1701 * from an overloaded cpu, if any.
1702 */
1703 if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
1704 return;
1705
1706 queue_pull_task(rq);
1707}
1708
1709/*
1710 * When switching to -deadline, we may overload the rq, then
1711 * we try to push someone off, if possible.
1712 */
1713static void switched_to_dl(struct rq *rq, struct task_struct *p)
1714{
1715
1716 /* If p is not queued we will update its parameters at next wakeup. */
1717 if (!task_on_rq_queued(p))
1718 return;
1719
1720 /*
1721 * If p is boosted we already updated its params in
1722 * rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
1723 * p's deadline being now already after rq_clock(rq).
1724 */
1725 if (dl_time_before(p->dl.deadline, rq_clock(rq)))
1726 setup_new_dl_entity(&p->dl);
1727
1728 if (rq->curr != p) {
1729#ifdef CONFIG_SMP
1730 if (tsk_nr_cpus_allowed(p) > 1 && rq->dl.overloaded)
1731 queue_push_tasks(rq);
1732#endif
1733 if (dl_task(rq->curr))
1734 check_preempt_curr_dl(rq, p, 0);
1735 else
1736 resched_curr(rq);
1737 }
1738}
1739
1740/*
1741 * If the scheduling parameters of a -deadline task changed,
1742 * a push or pull operation might be needed.
1743 */
1744static void prio_changed_dl(struct rq *rq, struct task_struct *p,
1745 int oldprio)
1746{
1747 if (task_on_rq_queued(p) || rq->curr == p) {
1748#ifdef CONFIG_SMP
1749 /*
1750 * This might be too much, but unfortunately
1751 * we don't have the old deadline value, and
1752 * we can't argue if the task is increasing
1753 * or lowering its prio, so...
1754 */
1755 if (!rq->dl.overloaded)
1756 queue_pull_task(rq);
1757
1758 /*
1759 * If we now have a earlier deadline task than p,
1760 * then reschedule, provided p is still on this
1761 * runqueue.
1762 */
1763 if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
1764 resched_curr(rq);
1765#else
1766 /*
1767 * Again, we don't know if p has a earlier
1768 * or later deadline, so let's blindly set a
1769 * (maybe not needed) rescheduling point.
1770 */
1771 resched_curr(rq);
1772#endif /* CONFIG_SMP */
1773 }
1774}
1775
1776const struct sched_class dl_sched_class = {
1777 .next = &rt_sched_class,
1778 .enqueue_task = enqueue_task_dl,
1779 .dequeue_task = dequeue_task_dl,
1780 .yield_task = yield_task_dl,
1781
1782 .check_preempt_curr = check_preempt_curr_dl,
1783
1784 .pick_next_task = pick_next_task_dl,
1785 .put_prev_task = put_prev_task_dl,
1786
1787#ifdef CONFIG_SMP
1788 .select_task_rq = select_task_rq_dl,
1789 .set_cpus_allowed = set_cpus_allowed_dl,
1790 .rq_online = rq_online_dl,
1791 .rq_offline = rq_offline_dl,
1792 .task_woken = task_woken_dl,
1793#endif
1794
1795 .set_curr_task = set_curr_task_dl,
1796 .task_tick = task_tick_dl,
1797 .task_fork = task_fork_dl,
1798 .task_dead = task_dead_dl,
1799
1800 .prio_changed = prio_changed_dl,
1801 .switched_from = switched_from_dl,
1802 .switched_to = switched_to_dl,
1803
1804 .update_curr = update_curr_dl,
1805};
1806
1807#ifdef CONFIG_SCHED_DEBUG
1808extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
1809
1810void print_dl_stats(struct seq_file *m, int cpu)
1811{
1812 print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
1813}
1814#endif /* CONFIG_SCHED_DEBUG */
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Deadline Scheduling Class (SCHED_DEADLINE)
4 *
5 * Earliest Deadline First (EDF) + Constant Bandwidth Server (CBS).
6 *
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.
12 *
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>
17 */
18#include "sched.h"
19#include "pelt.h"
20
21struct dl_bandwidth def_dl_bandwidth;
22
23static inline struct task_struct *dl_task_of(struct sched_dl_entity *dl_se)
24{
25 return container_of(dl_se, struct task_struct, dl);
26}
27
28static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
29{
30 return container_of(dl_rq, struct rq, dl);
31}
32
33static inline struct dl_rq *dl_rq_of_se(struct sched_dl_entity *dl_se)
34{
35 struct task_struct *p = dl_task_of(dl_se);
36 struct rq *rq = task_rq(p);
37
38 return &rq->dl;
39}
40
41static inline int on_dl_rq(struct sched_dl_entity *dl_se)
42{
43 return !RB_EMPTY_NODE(&dl_se->rb_node);
44}
45
46#ifdef CONFIG_RT_MUTEXES
47static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
48{
49 return dl_se->pi_se;
50}
51
52static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
53{
54 return pi_of(dl_se) != dl_se;
55}
56#else
57static inline struct sched_dl_entity *pi_of(struct sched_dl_entity *dl_se)
58{
59 return dl_se;
60}
61
62static inline bool is_dl_boosted(struct sched_dl_entity *dl_se)
63{
64 return false;
65}
66#endif
67
68#ifdef CONFIG_SMP
69static inline struct dl_bw *dl_bw_of(int i)
70{
71 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
72 "sched RCU must be held");
73 return &cpu_rq(i)->rd->dl_bw;
74}
75
76static inline int dl_bw_cpus(int i)
77{
78 struct root_domain *rd = cpu_rq(i)->rd;
79 int cpus;
80
81 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
82 "sched RCU must be held");
83
84 if (cpumask_subset(rd->span, cpu_active_mask))
85 return cpumask_weight(rd->span);
86
87 cpus = 0;
88
89 for_each_cpu_and(i, rd->span, cpu_active_mask)
90 cpus++;
91
92 return cpus;
93}
94
95static inline unsigned long __dl_bw_capacity(int i)
96{
97 struct root_domain *rd = cpu_rq(i)->rd;
98 unsigned long cap = 0;
99
100 RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
101 "sched RCU must be held");
102
103 for_each_cpu_and(i, rd->span, cpu_active_mask)
104 cap += capacity_orig_of(i);
105
106 return cap;
107}
108
109/*
110 * XXX Fix: If 'rq->rd == def_root_domain' perform AC against capacity
111 * of the CPU the task is running on rather rd's \Sum CPU capacity.
112 */
113static inline unsigned long dl_bw_capacity(int i)
114{
115 if (!static_branch_unlikely(&sched_asym_cpucapacity) &&
116 capacity_orig_of(i) == SCHED_CAPACITY_SCALE) {
117 return dl_bw_cpus(i) << SCHED_CAPACITY_SHIFT;
118 } else {
119 return __dl_bw_capacity(i);
120 }
121}
122
123static inline bool dl_bw_visited(int cpu, u64 gen)
124{
125 struct root_domain *rd = cpu_rq(cpu)->rd;
126
127 if (rd->visit_gen == gen)
128 return true;
129
130 rd->visit_gen = gen;
131 return false;
132}
133#else
134static inline struct dl_bw *dl_bw_of(int i)
135{
136 return &cpu_rq(i)->dl.dl_bw;
137}
138
139static inline int dl_bw_cpus(int i)
140{
141 return 1;
142}
143
144static inline unsigned long dl_bw_capacity(int i)
145{
146 return SCHED_CAPACITY_SCALE;
147}
148
149static inline bool dl_bw_visited(int cpu, u64 gen)
150{
151 return false;
152}
153#endif
154
155static inline
156void __add_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
157{
158 u64 old = dl_rq->running_bw;
159
160 lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
161 dl_rq->running_bw += dl_bw;
162 SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */
163 SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
164 /* kick cpufreq (see the comment in kernel/sched/sched.h). */
165 cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
166}
167
168static inline
169void __sub_running_bw(u64 dl_bw, struct dl_rq *dl_rq)
170{
171 u64 old = dl_rq->running_bw;
172
173 lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
174 dl_rq->running_bw -= dl_bw;
175 SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */
176 if (dl_rq->running_bw > old)
177 dl_rq->running_bw = 0;
178 /* kick cpufreq (see the comment in kernel/sched/sched.h). */
179 cpufreq_update_util(rq_of_dl_rq(dl_rq), 0);
180}
181
182static inline
183void __add_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
184{
185 u64 old = dl_rq->this_bw;
186
187 lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
188 dl_rq->this_bw += dl_bw;
189 SCHED_WARN_ON(dl_rq->this_bw < old); /* overflow */
190}
191
192static inline
193void __sub_rq_bw(u64 dl_bw, struct dl_rq *dl_rq)
194{
195 u64 old = dl_rq->this_bw;
196
197 lockdep_assert_rq_held(rq_of_dl_rq(dl_rq));
198 dl_rq->this_bw -= dl_bw;
199 SCHED_WARN_ON(dl_rq->this_bw > old); /* underflow */
200 if (dl_rq->this_bw > old)
201 dl_rq->this_bw = 0;
202 SCHED_WARN_ON(dl_rq->running_bw > dl_rq->this_bw);
203}
204
205static inline
206void add_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
207{
208 if (!dl_entity_is_special(dl_se))
209 __add_rq_bw(dl_se->dl_bw, dl_rq);
210}
211
212static inline
213void sub_rq_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
214{
215 if (!dl_entity_is_special(dl_se))
216 __sub_rq_bw(dl_se->dl_bw, dl_rq);
217}
218
219static inline
220void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
221{
222 if (!dl_entity_is_special(dl_se))
223 __add_running_bw(dl_se->dl_bw, dl_rq);
224}
225
226static inline
227void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
228{
229 if (!dl_entity_is_special(dl_se))
230 __sub_running_bw(dl_se->dl_bw, dl_rq);
231}
232
233static void dl_change_utilization(struct task_struct *p, u64 new_bw)
234{
235 struct rq *rq;
236
237 BUG_ON(p->dl.flags & SCHED_FLAG_SUGOV);
238
239 if (task_on_rq_queued(p))
240 return;
241
242 rq = task_rq(p);
243 if (p->dl.dl_non_contending) {
244 sub_running_bw(&p->dl, &rq->dl);
245 p->dl.dl_non_contending = 0;
246 /*
247 * If the timer handler is currently running and the
248 * timer cannot be canceled, inactive_task_timer()
249 * will see that dl_not_contending is not set, and
250 * will not touch the rq's active utilization,
251 * so we are still safe.
252 */
253 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
254 put_task_struct(p);
255 }
256 __sub_rq_bw(p->dl.dl_bw, &rq->dl);
257 __add_rq_bw(new_bw, &rq->dl);
258}
259
260/*
261 * The utilization of a task cannot be immediately removed from
262 * the rq active utilization (running_bw) when the task blocks.
263 * Instead, we have to wait for the so called "0-lag time".
264 *
265 * If a task blocks before the "0-lag time", a timer (the inactive
266 * timer) is armed, and running_bw is decreased when the timer
267 * fires.
268 *
269 * If the task wakes up again before the inactive timer fires,
270 * the timer is canceled, whereas if the task wakes up after the
271 * inactive timer fired (and running_bw has been decreased) the
272 * task's utilization has to be added to running_bw again.
273 * A flag in the deadline scheduling entity (dl_non_contending)
274 * is used to avoid race conditions between the inactive timer handler
275 * and task wakeups.
276 *
277 * The following diagram shows how running_bw is updated. A task is
278 * "ACTIVE" when its utilization contributes to running_bw; an
279 * "ACTIVE contending" task is in the TASK_RUNNING state, while an
280 * "ACTIVE non contending" task is a blocked task for which the "0-lag time"
281 * has not passed yet. An "INACTIVE" task is a task for which the "0-lag"
282 * time already passed, which does not contribute to running_bw anymore.
283 * +------------------+
284 * wakeup | ACTIVE |
285 * +------------------>+ contending |
286 * | add_running_bw | |
287 * | +----+------+------+
288 * | | ^
289 * | dequeue | |
290 * +--------+-------+ | |
291 * | | t >= 0-lag | | wakeup
292 * | INACTIVE |<---------------+ |
293 * | | sub_running_bw | |
294 * +--------+-------+ | |
295 * ^ | |
296 * | t < 0-lag | |
297 * | | |
298 * | V |
299 * | +----+------+------+
300 * | sub_running_bw | ACTIVE |
301 * +-------------------+ |
302 * inactive timer | non contending |
303 * fired +------------------+
304 *
305 * The task_non_contending() function is invoked when a task
306 * blocks, and checks if the 0-lag time already passed or
307 * not (in the first case, it directly updates running_bw;
308 * in the second case, it arms the inactive timer).
309 *
310 * The task_contending() function is invoked when a task wakes
311 * up, and checks if the task is still in the "ACTIVE non contending"
312 * state or not (in the second case, it updates running_bw).
313 */
314static void task_non_contending(struct task_struct *p)
315{
316 struct sched_dl_entity *dl_se = &p->dl;
317 struct hrtimer *timer = &dl_se->inactive_timer;
318 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
319 struct rq *rq = rq_of_dl_rq(dl_rq);
320 s64 zerolag_time;
321
322 /*
323 * If this is a non-deadline task that has been boosted,
324 * do nothing
325 */
326 if (dl_se->dl_runtime == 0)
327 return;
328
329 if (dl_entity_is_special(dl_se))
330 return;
331
332 WARN_ON(dl_se->dl_non_contending);
333
334 zerolag_time = dl_se->deadline -
335 div64_long((dl_se->runtime * dl_se->dl_period),
336 dl_se->dl_runtime);
337
338 /*
339 * Using relative times instead of the absolute "0-lag time"
340 * allows to simplify the code
341 */
342 zerolag_time -= rq_clock(rq);
343
344 /*
345 * If the "0-lag time" already passed, decrease the active
346 * utilization now, instead of starting a timer
347 */
348 if ((zerolag_time < 0) || hrtimer_active(&dl_se->inactive_timer)) {
349 if (dl_task(p))
350 sub_running_bw(dl_se, dl_rq);
351 if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
352 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
353
354 if (READ_ONCE(p->__state) == TASK_DEAD)
355 sub_rq_bw(&p->dl, &rq->dl);
356 raw_spin_lock(&dl_b->lock);
357 __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
358 __dl_clear_params(p);
359 raw_spin_unlock(&dl_b->lock);
360 }
361
362 return;
363 }
364
365 dl_se->dl_non_contending = 1;
366 get_task_struct(p);
367 hrtimer_start(timer, ns_to_ktime(zerolag_time), HRTIMER_MODE_REL_HARD);
368}
369
370static void task_contending(struct sched_dl_entity *dl_se, int flags)
371{
372 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
373
374 /*
375 * If this is a non-deadline task that has been boosted,
376 * do nothing
377 */
378 if (dl_se->dl_runtime == 0)
379 return;
380
381 if (flags & ENQUEUE_MIGRATED)
382 add_rq_bw(dl_se, dl_rq);
383
384 if (dl_se->dl_non_contending) {
385 dl_se->dl_non_contending = 0;
386 /*
387 * If the timer handler is currently running and the
388 * timer cannot be canceled, inactive_task_timer()
389 * will see that dl_not_contending is not set, and
390 * will not touch the rq's active utilization,
391 * so we are still safe.
392 */
393 if (hrtimer_try_to_cancel(&dl_se->inactive_timer) == 1)
394 put_task_struct(dl_task_of(dl_se));
395 } else {
396 /*
397 * Since "dl_non_contending" is not set, the
398 * task's utilization has already been removed from
399 * active utilization (either when the task blocked,
400 * when the "inactive timer" fired).
401 * So, add it back.
402 */
403 add_running_bw(dl_se, dl_rq);
404 }
405}
406
407static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
408{
409 struct sched_dl_entity *dl_se = &p->dl;
410
411 return dl_rq->root.rb_leftmost == &dl_se->rb_node;
412}
413
414static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq);
415
416void init_dl_bandwidth(struct dl_bandwidth *dl_b, u64 period, u64 runtime)
417{
418 raw_spin_lock_init(&dl_b->dl_runtime_lock);
419 dl_b->dl_period = period;
420 dl_b->dl_runtime = runtime;
421}
422
423void init_dl_bw(struct dl_bw *dl_b)
424{
425 raw_spin_lock_init(&dl_b->lock);
426 raw_spin_lock(&def_dl_bandwidth.dl_runtime_lock);
427 if (global_rt_runtime() == RUNTIME_INF)
428 dl_b->bw = -1;
429 else
430 dl_b->bw = to_ratio(global_rt_period(), global_rt_runtime());
431 raw_spin_unlock(&def_dl_bandwidth.dl_runtime_lock);
432 dl_b->total_bw = 0;
433}
434
435void init_dl_rq(struct dl_rq *dl_rq)
436{
437 dl_rq->root = RB_ROOT_CACHED;
438
439#ifdef CONFIG_SMP
440 /* zero means no -deadline tasks */
441 dl_rq->earliest_dl.curr = dl_rq->earliest_dl.next = 0;
442
443 dl_rq->dl_nr_migratory = 0;
444 dl_rq->overloaded = 0;
445 dl_rq->pushable_dl_tasks_root = RB_ROOT_CACHED;
446#else
447 init_dl_bw(&dl_rq->dl_bw);
448#endif
449
450 dl_rq->running_bw = 0;
451 dl_rq->this_bw = 0;
452 init_dl_rq_bw_ratio(dl_rq);
453}
454
455#ifdef CONFIG_SMP
456
457static inline int dl_overloaded(struct rq *rq)
458{
459 return atomic_read(&rq->rd->dlo_count);
460}
461
462static inline void dl_set_overload(struct rq *rq)
463{
464 if (!rq->online)
465 return;
466
467 cpumask_set_cpu(rq->cpu, rq->rd->dlo_mask);
468 /*
469 * Must be visible before the overload count is
470 * set (as in sched_rt.c).
471 *
472 * Matched by the barrier in pull_dl_task().
473 */
474 smp_wmb();
475 atomic_inc(&rq->rd->dlo_count);
476}
477
478static inline void dl_clear_overload(struct rq *rq)
479{
480 if (!rq->online)
481 return;
482
483 atomic_dec(&rq->rd->dlo_count);
484 cpumask_clear_cpu(rq->cpu, rq->rd->dlo_mask);
485}
486
487static void update_dl_migration(struct dl_rq *dl_rq)
488{
489 if (dl_rq->dl_nr_migratory && dl_rq->dl_nr_running > 1) {
490 if (!dl_rq->overloaded) {
491 dl_set_overload(rq_of_dl_rq(dl_rq));
492 dl_rq->overloaded = 1;
493 }
494 } else if (dl_rq->overloaded) {
495 dl_clear_overload(rq_of_dl_rq(dl_rq));
496 dl_rq->overloaded = 0;
497 }
498}
499
500static void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
501{
502 struct task_struct *p = dl_task_of(dl_se);
503
504 if (p->nr_cpus_allowed > 1)
505 dl_rq->dl_nr_migratory++;
506
507 update_dl_migration(dl_rq);
508}
509
510static void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
511{
512 struct task_struct *p = dl_task_of(dl_se);
513
514 if (p->nr_cpus_allowed > 1)
515 dl_rq->dl_nr_migratory--;
516
517 update_dl_migration(dl_rq);
518}
519
520#define __node_2_pdl(node) \
521 rb_entry((node), struct task_struct, pushable_dl_tasks)
522
523static inline bool __pushable_less(struct rb_node *a, const struct rb_node *b)
524{
525 return dl_entity_preempt(&__node_2_pdl(a)->dl, &__node_2_pdl(b)->dl);
526}
527
528/*
529 * The list of pushable -deadline task is not a plist, like in
530 * sched_rt.c, it is an rb-tree with tasks ordered by deadline.
531 */
532static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
533{
534 struct rb_node *leftmost;
535
536 BUG_ON(!RB_EMPTY_NODE(&p->pushable_dl_tasks));
537
538 leftmost = rb_add_cached(&p->pushable_dl_tasks,
539 &rq->dl.pushable_dl_tasks_root,
540 __pushable_less);
541 if (leftmost)
542 rq->dl.earliest_dl.next = p->dl.deadline;
543}
544
545static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
546{
547 struct dl_rq *dl_rq = &rq->dl;
548 struct rb_root_cached *root = &dl_rq->pushable_dl_tasks_root;
549 struct rb_node *leftmost;
550
551 if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
552 return;
553
554 leftmost = rb_erase_cached(&p->pushable_dl_tasks, root);
555 if (leftmost)
556 dl_rq->earliest_dl.next = __node_2_pdl(leftmost)->dl.deadline;
557
558 RB_CLEAR_NODE(&p->pushable_dl_tasks);
559}
560
561static inline int has_pushable_dl_tasks(struct rq *rq)
562{
563 return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root.rb_root);
564}
565
566static int push_dl_task(struct rq *rq);
567
568static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
569{
570 return rq->online && dl_task(prev);
571}
572
573static DEFINE_PER_CPU(struct callback_head, dl_push_head);
574static DEFINE_PER_CPU(struct callback_head, dl_pull_head);
575
576static void push_dl_tasks(struct rq *);
577static void pull_dl_task(struct rq *);
578
579static inline void deadline_queue_push_tasks(struct rq *rq)
580{
581 if (!has_pushable_dl_tasks(rq))
582 return;
583
584 queue_balance_callback(rq, &per_cpu(dl_push_head, rq->cpu), push_dl_tasks);
585}
586
587static inline void deadline_queue_pull_task(struct rq *rq)
588{
589 queue_balance_callback(rq, &per_cpu(dl_pull_head, rq->cpu), pull_dl_task);
590}
591
592static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
593
594static struct rq *dl_task_offline_migration(struct rq *rq, struct task_struct *p)
595{
596 struct rq *later_rq = NULL;
597 struct dl_bw *dl_b;
598
599 later_rq = find_lock_later_rq(p, rq);
600 if (!later_rq) {
601 int cpu;
602
603 /*
604 * If we cannot preempt any rq, fall back to pick any
605 * online CPU:
606 */
607 cpu = cpumask_any_and(cpu_active_mask, p->cpus_ptr);
608 if (cpu >= nr_cpu_ids) {
609 /*
610 * Failed to find any suitable CPU.
611 * The task will never come back!
612 */
613 BUG_ON(dl_bandwidth_enabled());
614
615 /*
616 * If admission control is disabled we
617 * try a little harder to let the task
618 * run.
619 */
620 cpu = cpumask_any(cpu_active_mask);
621 }
622 later_rq = cpu_rq(cpu);
623 double_lock_balance(rq, later_rq);
624 }
625
626 if (p->dl.dl_non_contending || p->dl.dl_throttled) {
627 /*
628 * Inactive timer is armed (or callback is running, but
629 * waiting for us to release rq locks). In any case, when it
630 * will fire (or continue), it will see running_bw of this
631 * task migrated to later_rq (and correctly handle it).
632 */
633 sub_running_bw(&p->dl, &rq->dl);
634 sub_rq_bw(&p->dl, &rq->dl);
635
636 add_rq_bw(&p->dl, &later_rq->dl);
637 add_running_bw(&p->dl, &later_rq->dl);
638 } else {
639 sub_rq_bw(&p->dl, &rq->dl);
640 add_rq_bw(&p->dl, &later_rq->dl);
641 }
642
643 /*
644 * And we finally need to fixup root_domain(s) bandwidth accounting,
645 * since p is still hanging out in the old (now moved to default) root
646 * domain.
647 */
648 dl_b = &rq->rd->dl_bw;
649 raw_spin_lock(&dl_b->lock);
650 __dl_sub(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
651 raw_spin_unlock(&dl_b->lock);
652
653 dl_b = &later_rq->rd->dl_bw;
654 raw_spin_lock(&dl_b->lock);
655 __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(later_rq->rd->span));
656 raw_spin_unlock(&dl_b->lock);
657
658 set_task_cpu(p, later_rq->cpu);
659 double_unlock_balance(later_rq, rq);
660
661 return later_rq;
662}
663
664#else
665
666static inline
667void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
668{
669}
670
671static inline
672void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
673{
674}
675
676static inline
677void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
678{
679}
680
681static inline
682void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
683{
684}
685
686static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
687{
688 return false;
689}
690
691static inline void pull_dl_task(struct rq *rq)
692{
693}
694
695static inline void deadline_queue_push_tasks(struct rq *rq)
696{
697}
698
699static inline void deadline_queue_pull_task(struct rq *rq)
700{
701}
702#endif /* CONFIG_SMP */
703
704static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
705static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
706static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p, int flags);
707
708/*
709 * We are being explicitly informed that a new instance is starting,
710 * and this means that:
711 * - the absolute deadline of the entity has to be placed at
712 * current time + relative deadline;
713 * - the runtime of the entity has to be set to the maximum value.
714 *
715 * The capability of specifying such event is useful whenever a -deadline
716 * entity wants to (try to!) synchronize its behaviour with the scheduler's
717 * one, and to (try to!) reconcile itself with its own scheduling
718 * parameters.
719 */
720static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
721{
722 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
723 struct rq *rq = rq_of_dl_rq(dl_rq);
724
725 WARN_ON(is_dl_boosted(dl_se));
726 WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
727
728 /*
729 * We are racing with the deadline timer. So, do nothing because
730 * the deadline timer handler will take care of properly recharging
731 * the runtime and postponing the deadline
732 */
733 if (dl_se->dl_throttled)
734 return;
735
736 /*
737 * We use the regular wall clock time to set deadlines in the
738 * future; in fact, we must consider execution overheads (time
739 * spent on hardirq context, etc.).
740 */
741 dl_se->deadline = rq_clock(rq) + dl_se->dl_deadline;
742 dl_se->runtime = dl_se->dl_runtime;
743}
744
745/*
746 * Pure Earliest Deadline First (EDF) scheduling does not deal with the
747 * possibility of a entity lasting more than what it declared, and thus
748 * exhausting its runtime.
749 *
750 * Here we are interested in making runtime overrun possible, but we do
751 * not want a entity which is misbehaving to affect the scheduling of all
752 * other entities.
753 * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
754 * is used, in order to confine each entity within its own bandwidth.
755 *
756 * This function deals exactly with that, and ensures that when the runtime
757 * of a entity is replenished, its deadline is also postponed. That ensures
758 * the overrunning entity can't interfere with other entity in the system and
759 * can't make them miss their deadlines. Reasons why this kind of overruns
760 * could happen are, typically, a entity voluntarily trying to overcome its
761 * runtime, or it just underestimated it during sched_setattr().
762 */
763static void replenish_dl_entity(struct sched_dl_entity *dl_se)
764{
765 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
766 struct rq *rq = rq_of_dl_rq(dl_rq);
767
768 BUG_ON(pi_of(dl_se)->dl_runtime <= 0);
769
770 /*
771 * This could be the case for a !-dl task that is boosted.
772 * Just go with full inherited parameters.
773 */
774 if (dl_se->dl_deadline == 0) {
775 dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
776 dl_se->runtime = pi_of(dl_se)->dl_runtime;
777 }
778
779 if (dl_se->dl_yielded && dl_se->runtime > 0)
780 dl_se->runtime = 0;
781
782 /*
783 * We keep moving the deadline away until we get some
784 * available runtime for the entity. This ensures correct
785 * handling of situations where the runtime overrun is
786 * arbitrary large.
787 */
788 while (dl_se->runtime <= 0) {
789 dl_se->deadline += pi_of(dl_se)->dl_period;
790 dl_se->runtime += pi_of(dl_se)->dl_runtime;
791 }
792
793 /*
794 * At this point, the deadline really should be "in
795 * the future" with respect to rq->clock. If it's
796 * not, we are, for some reason, lagging too much!
797 * Anyway, after having warn userspace abut that,
798 * we still try to keep the things running by
799 * resetting the deadline and the budget of the
800 * entity.
801 */
802 if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
803 printk_deferred_once("sched: DL replenish lagged too much\n");
804 dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
805 dl_se->runtime = pi_of(dl_se)->dl_runtime;
806 }
807
808 if (dl_se->dl_yielded)
809 dl_se->dl_yielded = 0;
810 if (dl_se->dl_throttled)
811 dl_se->dl_throttled = 0;
812}
813
814/*
815 * Here we check if --at time t-- an entity (which is probably being
816 * [re]activated or, in general, enqueued) can use its remaining runtime
817 * and its current deadline _without_ exceeding the bandwidth it is
818 * assigned (function returns true if it can't). We are in fact applying
819 * one of the CBS rules: when a task wakes up, if the residual runtime
820 * over residual deadline fits within the allocated bandwidth, then we
821 * can keep the current (absolute) deadline and residual budget without
822 * disrupting the schedulability of the system. Otherwise, we should
823 * refill the runtime and set the deadline a period in the future,
824 * because keeping the current (absolute) deadline of the task would
825 * result in breaking guarantees promised to other tasks (refer to
826 * Documentation/scheduler/sched-deadline.rst for more information).
827 *
828 * This function returns true if:
829 *
830 * runtime / (deadline - t) > dl_runtime / dl_deadline ,
831 *
832 * IOW we can't recycle current parameters.
833 *
834 * Notice that the bandwidth check is done against the deadline. For
835 * task with deadline equal to period this is the same of using
836 * dl_period instead of dl_deadline in the equation above.
837 */
838static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
839{
840 u64 left, right;
841
842 /*
843 * left and right are the two sides of the equation above,
844 * after a bit of shuffling to use multiplications instead
845 * of divisions.
846 *
847 * Note that none of the time values involved in the two
848 * multiplications are absolute: dl_deadline and dl_runtime
849 * are the relative deadline and the maximum runtime of each
850 * instance, runtime is the runtime left for the last instance
851 * and (deadline - t), since t is rq->clock, is the time left
852 * to the (absolute) deadline. Even if overflowing the u64 type
853 * is very unlikely to occur in both cases, here we scale down
854 * as we want to avoid that risk at all. Scaling down by 10
855 * means that we reduce granularity to 1us. We are fine with it,
856 * since this is only a true/false check and, anyway, thinking
857 * of anything below microseconds resolution is actually fiction
858 * (but still we want to give the user that illusion >;).
859 */
860 left = (pi_of(dl_se)->dl_deadline >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
861 right = ((dl_se->deadline - t) >> DL_SCALE) *
862 (pi_of(dl_se)->dl_runtime >> DL_SCALE);
863
864 return dl_time_before(right, left);
865}
866
867/*
868 * Revised wakeup rule [1]: For self-suspending tasks, rather then
869 * re-initializing task's runtime and deadline, the revised wakeup
870 * rule adjusts the task's runtime to avoid the task to overrun its
871 * density.
872 *
873 * Reasoning: a task may overrun the density if:
874 * runtime / (deadline - t) > dl_runtime / dl_deadline
875 *
876 * Therefore, runtime can be adjusted to:
877 * runtime = (dl_runtime / dl_deadline) * (deadline - t)
878 *
879 * In such way that runtime will be equal to the maximum density
880 * the task can use without breaking any rule.
881 *
882 * [1] Luca Abeni, Giuseppe Lipari, and Juri Lelli. 2015. Constant
883 * bandwidth server revisited. SIGBED Rev. 11, 4 (January 2015), 19-24.
884 */
885static void
886update_dl_revised_wakeup(struct sched_dl_entity *dl_se, struct rq *rq)
887{
888 u64 laxity = dl_se->deadline - rq_clock(rq);
889
890 /*
891 * If the task has deadline < period, and the deadline is in the past,
892 * it should already be throttled before this check.
893 *
894 * See update_dl_entity() comments for further details.
895 */
896 WARN_ON(dl_time_before(dl_se->deadline, rq_clock(rq)));
897
898 dl_se->runtime = (dl_se->dl_density * laxity) >> BW_SHIFT;
899}
900
901/*
902 * Regarding the deadline, a task with implicit deadline has a relative
903 * deadline == relative period. A task with constrained deadline has a
904 * relative deadline <= relative period.
905 *
906 * We support constrained deadline tasks. However, there are some restrictions
907 * applied only for tasks which do not have an implicit deadline. See
908 * update_dl_entity() to know more about such restrictions.
909 *
910 * The dl_is_implicit() returns true if the task has an implicit deadline.
911 */
912static inline bool dl_is_implicit(struct sched_dl_entity *dl_se)
913{
914 return dl_se->dl_deadline == dl_se->dl_period;
915}
916
917/*
918 * When a deadline entity is placed in the runqueue, its runtime and deadline
919 * might need to be updated. This is done by a CBS wake up rule. There are two
920 * different rules: 1) the original CBS; and 2) the Revisited CBS.
921 *
922 * When the task is starting a new period, the Original CBS is used. In this
923 * case, the runtime is replenished and a new absolute deadline is set.
924 *
925 * When a task is queued before the begin of the next period, using the
926 * remaining runtime and deadline could make the entity to overflow, see
927 * dl_entity_overflow() to find more about runtime overflow. When such case
928 * is detected, the runtime and deadline need to be updated.
929 *
930 * If the task has an implicit deadline, i.e., deadline == period, the Original
931 * CBS is applied. the runtime is replenished and a new absolute deadline is
932 * set, as in the previous cases.
933 *
934 * However, the Original CBS does not work properly for tasks with
935 * deadline < period, which are said to have a constrained deadline. By
936 * applying the Original CBS, a constrained deadline task would be able to run
937 * runtime/deadline in a period. With deadline < period, the task would
938 * overrun the runtime/period allowed bandwidth, breaking the admission test.
939 *
940 * In order to prevent this misbehave, the Revisited CBS is used for
941 * constrained deadline tasks when a runtime overflow is detected. In the
942 * Revisited CBS, rather than replenishing & setting a new absolute deadline,
943 * the remaining runtime of the task is reduced to avoid runtime overflow.
944 * Please refer to the comments update_dl_revised_wakeup() function to find
945 * more about the Revised CBS rule.
946 */
947static void update_dl_entity(struct sched_dl_entity *dl_se)
948{
949 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
950 struct rq *rq = rq_of_dl_rq(dl_rq);
951
952 if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
953 dl_entity_overflow(dl_se, rq_clock(rq))) {
954
955 if (unlikely(!dl_is_implicit(dl_se) &&
956 !dl_time_before(dl_se->deadline, rq_clock(rq)) &&
957 !is_dl_boosted(dl_se))) {
958 update_dl_revised_wakeup(dl_se, rq);
959 return;
960 }
961
962 dl_se->deadline = rq_clock(rq) + pi_of(dl_se)->dl_deadline;
963 dl_se->runtime = pi_of(dl_se)->dl_runtime;
964 }
965}
966
967static inline u64 dl_next_period(struct sched_dl_entity *dl_se)
968{
969 return dl_se->deadline - dl_se->dl_deadline + dl_se->dl_period;
970}
971
972/*
973 * If the entity depleted all its runtime, and if we want it to sleep
974 * while waiting for some new execution time to become available, we
975 * set the bandwidth replenishment timer to the replenishment instant
976 * and try to activate it.
977 *
978 * Notice that it is important for the caller to know if the timer
979 * actually started or not (i.e., the replenishment instant is in
980 * the future or in the past).
981 */
982static int start_dl_timer(struct task_struct *p)
983{
984 struct sched_dl_entity *dl_se = &p->dl;
985 struct hrtimer *timer = &dl_se->dl_timer;
986 struct rq *rq = task_rq(p);
987 ktime_t now, act;
988 s64 delta;
989
990 lockdep_assert_rq_held(rq);
991
992 /*
993 * We want the timer to fire at the deadline, but considering
994 * that it is actually coming from rq->clock and not from
995 * hrtimer's time base reading.
996 */
997 act = ns_to_ktime(dl_next_period(dl_se));
998 now = hrtimer_cb_get_time(timer);
999 delta = ktime_to_ns(now) - rq_clock(rq);
1000 act = ktime_add_ns(act, delta);
1001
1002 /*
1003 * If the expiry time already passed, e.g., because the value
1004 * chosen as the deadline is too small, don't even try to
1005 * start the timer in the past!
1006 */
1007 if (ktime_us_delta(act, now) < 0)
1008 return 0;
1009
1010 /*
1011 * !enqueued will guarantee another callback; even if one is already in
1012 * progress. This ensures a balanced {get,put}_task_struct().
1013 *
1014 * The race against __run_timer() clearing the enqueued state is
1015 * harmless because we're holding task_rq()->lock, therefore the timer
1016 * expiring after we've done the check will wait on its task_rq_lock()
1017 * and observe our state.
1018 */
1019 if (!hrtimer_is_queued(timer)) {
1020 get_task_struct(p);
1021 hrtimer_start(timer, act, HRTIMER_MODE_ABS_HARD);
1022 }
1023
1024 return 1;
1025}
1026
1027/*
1028 * This is the bandwidth enforcement timer callback. If here, we know
1029 * a task is not on its dl_rq, since the fact that the timer was running
1030 * means the task is throttled and needs a runtime replenishment.
1031 *
1032 * However, what we actually do depends on the fact the task is active,
1033 * (it is on its rq) or has been removed from there by a call to
1034 * dequeue_task_dl(). In the former case we must issue the runtime
1035 * replenishment and add the task back to the dl_rq; in the latter, we just
1036 * do nothing but clearing dl_throttled, so that runtime and deadline
1037 * updating (and the queueing back to dl_rq) will be done by the
1038 * next call to enqueue_task_dl().
1039 */
1040static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
1041{
1042 struct sched_dl_entity *dl_se = container_of(timer,
1043 struct sched_dl_entity,
1044 dl_timer);
1045 struct task_struct *p = dl_task_of(dl_se);
1046 struct rq_flags rf;
1047 struct rq *rq;
1048
1049 rq = task_rq_lock(p, &rf);
1050
1051 /*
1052 * The task might have changed its scheduling policy to something
1053 * different than SCHED_DEADLINE (through switched_from_dl()).
1054 */
1055 if (!dl_task(p))
1056 goto unlock;
1057
1058 /*
1059 * The task might have been boosted by someone else and might be in the
1060 * boosting/deboosting path, its not throttled.
1061 */
1062 if (is_dl_boosted(dl_se))
1063 goto unlock;
1064
1065 /*
1066 * Spurious timer due to start_dl_timer() race; or we already received
1067 * a replenishment from rt_mutex_setprio().
1068 */
1069 if (!dl_se->dl_throttled)
1070 goto unlock;
1071
1072 sched_clock_tick();
1073 update_rq_clock(rq);
1074
1075 /*
1076 * If the throttle happened during sched-out; like:
1077 *
1078 * schedule()
1079 * deactivate_task()
1080 * dequeue_task_dl()
1081 * update_curr_dl()
1082 * start_dl_timer()
1083 * __dequeue_task_dl()
1084 * prev->on_rq = 0;
1085 *
1086 * We can be both throttled and !queued. Replenish the counter
1087 * but do not enqueue -- wait for our wakeup to do that.
1088 */
1089 if (!task_on_rq_queued(p)) {
1090 replenish_dl_entity(dl_se);
1091 goto unlock;
1092 }
1093
1094#ifdef CONFIG_SMP
1095 if (unlikely(!rq->online)) {
1096 /*
1097 * If the runqueue is no longer available, migrate the
1098 * task elsewhere. This necessarily changes rq.
1099 */
1100 lockdep_unpin_lock(__rq_lockp(rq), rf.cookie);
1101 rq = dl_task_offline_migration(rq, p);
1102 rf.cookie = lockdep_pin_lock(__rq_lockp(rq));
1103 update_rq_clock(rq);
1104
1105 /*
1106 * Now that the task has been migrated to the new RQ and we
1107 * have that locked, proceed as normal and enqueue the task
1108 * there.
1109 */
1110 }
1111#endif
1112
1113 enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
1114 if (dl_task(rq->curr))
1115 check_preempt_curr_dl(rq, p, 0);
1116 else
1117 resched_curr(rq);
1118
1119#ifdef CONFIG_SMP
1120 /*
1121 * Queueing this task back might have overloaded rq, check if we need
1122 * to kick someone away.
1123 */
1124 if (has_pushable_dl_tasks(rq)) {
1125 /*
1126 * Nothing relies on rq->lock after this, so its safe to drop
1127 * rq->lock.
1128 */
1129 rq_unpin_lock(rq, &rf);
1130 push_dl_task(rq);
1131 rq_repin_lock(rq, &rf);
1132 }
1133#endif
1134
1135unlock:
1136 task_rq_unlock(rq, p, &rf);
1137
1138 /*
1139 * This can free the task_struct, including this hrtimer, do not touch
1140 * anything related to that after this.
1141 */
1142 put_task_struct(p);
1143
1144 return HRTIMER_NORESTART;
1145}
1146
1147void init_dl_task_timer(struct sched_dl_entity *dl_se)
1148{
1149 struct hrtimer *timer = &dl_se->dl_timer;
1150
1151 hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1152 timer->function = dl_task_timer;
1153}
1154
1155/*
1156 * During the activation, CBS checks if it can reuse the current task's
1157 * runtime and period. If the deadline of the task is in the past, CBS
1158 * cannot use the runtime, and so it replenishes the task. This rule
1159 * works fine for implicit deadline tasks (deadline == period), and the
1160 * CBS was designed for implicit deadline tasks. However, a task with
1161 * constrained deadline (deadline < period) might be awakened after the
1162 * deadline, but before the next period. In this case, replenishing the
1163 * task would allow it to run for runtime / deadline. As in this case
1164 * deadline < period, CBS enables a task to run for more than the
1165 * runtime / period. In a very loaded system, this can cause a domino
1166 * effect, making other tasks miss their deadlines.
1167 *
1168 * To avoid this problem, in the activation of a constrained deadline
1169 * task after the deadline but before the next period, throttle the
1170 * task and set the replenishing timer to the begin of the next period,
1171 * unless it is boosted.
1172 */
1173static inline void dl_check_constrained_dl(struct sched_dl_entity *dl_se)
1174{
1175 struct task_struct *p = dl_task_of(dl_se);
1176 struct rq *rq = rq_of_dl_rq(dl_rq_of_se(dl_se));
1177
1178 if (dl_time_before(dl_se->deadline, rq_clock(rq)) &&
1179 dl_time_before(rq_clock(rq), dl_next_period(dl_se))) {
1180 if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(p)))
1181 return;
1182 dl_se->dl_throttled = 1;
1183 if (dl_se->runtime > 0)
1184 dl_se->runtime = 0;
1185 }
1186}
1187
1188static
1189int dl_runtime_exceeded(struct sched_dl_entity *dl_se)
1190{
1191 return (dl_se->runtime <= 0);
1192}
1193
1194extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
1195
1196/*
1197 * This function implements the GRUB accounting rule:
1198 * according to the GRUB reclaiming algorithm, the runtime is
1199 * not decreased as "dq = -dt", but as
1200 * "dq = -max{u / Umax, (1 - Uinact - Uextra)} dt",
1201 * where u is the utilization of the task, Umax is the maximum reclaimable
1202 * utilization, Uinact is the (per-runqueue) inactive utilization, computed
1203 * as the difference between the "total runqueue utilization" and the
1204 * runqueue active utilization, and Uextra is the (per runqueue) extra
1205 * reclaimable utilization.
1206 * Since rq->dl.running_bw and rq->dl.this_bw contain utilizations
1207 * multiplied by 2^BW_SHIFT, the result has to be shifted right by
1208 * BW_SHIFT.
1209 * Since rq->dl.bw_ratio contains 1 / Umax multiplied by 2^RATIO_SHIFT,
1210 * dl_bw is multiped by rq->dl.bw_ratio and shifted right by RATIO_SHIFT.
1211 * Since delta is a 64 bit variable, to have an overflow its value
1212 * should be larger than 2^(64 - 20 - 8), which is more than 64 seconds.
1213 * So, overflow is not an issue here.
1214 */
1215static u64 grub_reclaim(u64 delta, struct rq *rq, struct sched_dl_entity *dl_se)
1216{
1217 u64 u_inact = rq->dl.this_bw - rq->dl.running_bw; /* Utot - Uact */
1218 u64 u_act;
1219 u64 u_act_min = (dl_se->dl_bw * rq->dl.bw_ratio) >> RATIO_SHIFT;
1220
1221 /*
1222 * Instead of computing max{u * bw_ratio, (1 - u_inact - u_extra)},
1223 * we compare u_inact + rq->dl.extra_bw with
1224 * 1 - (u * rq->dl.bw_ratio >> RATIO_SHIFT), because
1225 * u_inact + rq->dl.extra_bw can be larger than
1226 * 1 * (so, 1 - u_inact - rq->dl.extra_bw would be negative
1227 * leading to wrong results)
1228 */
1229 if (u_inact + rq->dl.extra_bw > BW_UNIT - u_act_min)
1230 u_act = u_act_min;
1231 else
1232 u_act = BW_UNIT - u_inact - rq->dl.extra_bw;
1233
1234 return (delta * u_act) >> BW_SHIFT;
1235}
1236
1237/*
1238 * Update the current task's runtime statistics (provided it is still
1239 * a -deadline task and has not been removed from the dl_rq).
1240 */
1241static void update_curr_dl(struct rq *rq)
1242{
1243 struct task_struct *curr = rq->curr;
1244 struct sched_dl_entity *dl_se = &curr->dl;
1245 u64 delta_exec, scaled_delta_exec;
1246 int cpu = cpu_of(rq);
1247 u64 now;
1248
1249 if (!dl_task(curr) || !on_dl_rq(dl_se))
1250 return;
1251
1252 /*
1253 * Consumed budget is computed considering the time as
1254 * observed by schedulable tasks (excluding time spent
1255 * in hardirq context, etc.). Deadlines are instead
1256 * computed using hard walltime. This seems to be the more
1257 * natural solution, but the full ramifications of this
1258 * approach need further study.
1259 */
1260 now = rq_clock_task(rq);
1261 delta_exec = now - curr->se.exec_start;
1262 if (unlikely((s64)delta_exec <= 0)) {
1263 if (unlikely(dl_se->dl_yielded))
1264 goto throttle;
1265 return;
1266 }
1267
1268 schedstat_set(curr->se.statistics.exec_max,
1269 max(curr->se.statistics.exec_max, delta_exec));
1270
1271 curr->se.sum_exec_runtime += delta_exec;
1272 account_group_exec_runtime(curr, delta_exec);
1273
1274 curr->se.exec_start = now;
1275 cgroup_account_cputime(curr, delta_exec);
1276
1277 if (dl_entity_is_special(dl_se))
1278 return;
1279
1280 /*
1281 * For tasks that participate in GRUB, we implement GRUB-PA: the
1282 * spare reclaimed bandwidth is used to clock down frequency.
1283 *
1284 * For the others, we still need to scale reservation parameters
1285 * according to current frequency and CPU maximum capacity.
1286 */
1287 if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {
1288 scaled_delta_exec = grub_reclaim(delta_exec,
1289 rq,
1290 &curr->dl);
1291 } else {
1292 unsigned long scale_freq = arch_scale_freq_capacity(cpu);
1293 unsigned long scale_cpu = arch_scale_cpu_capacity(cpu);
1294
1295 scaled_delta_exec = cap_scale(delta_exec, scale_freq);
1296 scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);
1297 }
1298
1299 dl_se->runtime -= scaled_delta_exec;
1300
1301throttle:
1302 if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {
1303 dl_se->dl_throttled = 1;
1304
1305 /* If requested, inform the user about runtime overruns. */
1306 if (dl_runtime_exceeded(dl_se) &&
1307 (dl_se->flags & SCHED_FLAG_DL_OVERRUN))
1308 dl_se->dl_overrun = 1;
1309
1310 __dequeue_task_dl(rq, curr, 0);
1311 if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(curr)))
1312 enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
1313
1314 if (!is_leftmost(curr, &rq->dl))
1315 resched_curr(rq);
1316 }
1317
1318 /*
1319 * Because -- for now -- we share the rt bandwidth, we need to
1320 * account our runtime there too, otherwise actual rt tasks
1321 * would be able to exceed the shared quota.
1322 *
1323 * Account to the root rt group for now.
1324 *
1325 * The solution we're working towards is having the RT groups scheduled
1326 * using deadline servers -- however there's a few nasties to figure
1327 * out before that can happen.
1328 */
1329 if (rt_bandwidth_enabled()) {
1330 struct rt_rq *rt_rq = &rq->rt;
1331
1332 raw_spin_lock(&rt_rq->rt_runtime_lock);
1333 /*
1334 * We'll let actual RT tasks worry about the overflow here, we
1335 * have our own CBS to keep us inline; only account when RT
1336 * bandwidth is relevant.
1337 */
1338 if (sched_rt_bandwidth_account(rt_rq))
1339 rt_rq->rt_time += delta_exec;
1340 raw_spin_unlock(&rt_rq->rt_runtime_lock);
1341 }
1342}
1343
1344static enum hrtimer_restart inactive_task_timer(struct hrtimer *timer)
1345{
1346 struct sched_dl_entity *dl_se = container_of(timer,
1347 struct sched_dl_entity,
1348 inactive_timer);
1349 struct task_struct *p = dl_task_of(dl_se);
1350 struct rq_flags rf;
1351 struct rq *rq;
1352
1353 rq = task_rq_lock(p, &rf);
1354
1355 sched_clock_tick();
1356 update_rq_clock(rq);
1357
1358 if (!dl_task(p) || READ_ONCE(p->__state) == TASK_DEAD) {
1359 struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
1360
1361 if (READ_ONCE(p->__state) == TASK_DEAD && dl_se->dl_non_contending) {
1362 sub_running_bw(&p->dl, dl_rq_of_se(&p->dl));
1363 sub_rq_bw(&p->dl, dl_rq_of_se(&p->dl));
1364 dl_se->dl_non_contending = 0;
1365 }
1366
1367 raw_spin_lock(&dl_b->lock);
1368 __dl_sub(dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
1369 raw_spin_unlock(&dl_b->lock);
1370 __dl_clear_params(p);
1371
1372 goto unlock;
1373 }
1374 if (dl_se->dl_non_contending == 0)
1375 goto unlock;
1376
1377 sub_running_bw(dl_se, &rq->dl);
1378 dl_se->dl_non_contending = 0;
1379unlock:
1380 task_rq_unlock(rq, p, &rf);
1381 put_task_struct(p);
1382
1383 return HRTIMER_NORESTART;
1384}
1385
1386void init_dl_inactive_task_timer(struct sched_dl_entity *dl_se)
1387{
1388 struct hrtimer *timer = &dl_se->inactive_timer;
1389
1390 hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
1391 timer->function = inactive_task_timer;
1392}
1393
1394#ifdef CONFIG_SMP
1395
1396static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1397{
1398 struct rq *rq = rq_of_dl_rq(dl_rq);
1399
1400 if (dl_rq->earliest_dl.curr == 0 ||
1401 dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
1402 if (dl_rq->earliest_dl.curr == 0)
1403 cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
1404 dl_rq->earliest_dl.curr = deadline;
1405 cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
1406 }
1407}
1408
1409static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
1410{
1411 struct rq *rq = rq_of_dl_rq(dl_rq);
1412
1413 /*
1414 * Since we may have removed our earliest (and/or next earliest)
1415 * task we must recompute them.
1416 */
1417 if (!dl_rq->dl_nr_running) {
1418 dl_rq->earliest_dl.curr = 0;
1419 dl_rq->earliest_dl.next = 0;
1420 cpudl_clear(&rq->rd->cpudl, rq->cpu);
1421 cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1422 } else {
1423 struct rb_node *leftmost = dl_rq->root.rb_leftmost;
1424 struct sched_dl_entity *entry;
1425
1426 entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
1427 dl_rq->earliest_dl.curr = entry->deadline;
1428 cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline);
1429 }
1430}
1431
1432#else
1433
1434static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
1435static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
1436
1437#endif /* CONFIG_SMP */
1438
1439static inline
1440void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1441{
1442 int prio = dl_task_of(dl_se)->prio;
1443 u64 deadline = dl_se->deadline;
1444
1445 WARN_ON(!dl_prio(prio));
1446 dl_rq->dl_nr_running++;
1447 add_nr_running(rq_of_dl_rq(dl_rq), 1);
1448
1449 inc_dl_deadline(dl_rq, deadline);
1450 inc_dl_migration(dl_se, dl_rq);
1451}
1452
1453static inline
1454void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
1455{
1456 int prio = dl_task_of(dl_se)->prio;
1457
1458 WARN_ON(!dl_prio(prio));
1459 WARN_ON(!dl_rq->dl_nr_running);
1460 dl_rq->dl_nr_running--;
1461 sub_nr_running(rq_of_dl_rq(dl_rq), 1);
1462
1463 dec_dl_deadline(dl_rq, dl_se->deadline);
1464 dec_dl_migration(dl_se, dl_rq);
1465}
1466
1467#define __node_2_dle(node) \
1468 rb_entry((node), struct sched_dl_entity, rb_node)
1469
1470static inline bool __dl_less(struct rb_node *a, const struct rb_node *b)
1471{
1472 return dl_time_before(__node_2_dle(a)->deadline, __node_2_dle(b)->deadline);
1473}
1474
1475static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
1476{
1477 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1478
1479 BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
1480
1481 rb_add_cached(&dl_se->rb_node, &dl_rq->root, __dl_less);
1482
1483 inc_dl_tasks(dl_se, dl_rq);
1484}
1485
1486static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
1487{
1488 struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
1489
1490 if (RB_EMPTY_NODE(&dl_se->rb_node))
1491 return;
1492
1493 rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
1494
1495 RB_CLEAR_NODE(&dl_se->rb_node);
1496
1497 dec_dl_tasks(dl_se, dl_rq);
1498}
1499
1500static void
1501enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
1502{
1503 BUG_ON(on_dl_rq(dl_se));
1504
1505 /*
1506 * If this is a wakeup or a new instance, the scheduling
1507 * parameters of the task might need updating. Otherwise,
1508 * we want a replenishment of its runtime.
1509 */
1510 if (flags & ENQUEUE_WAKEUP) {
1511 task_contending(dl_se, flags);
1512 update_dl_entity(dl_se);
1513 } else if (flags & ENQUEUE_REPLENISH) {
1514 replenish_dl_entity(dl_se);
1515 } else if ((flags & ENQUEUE_RESTORE) &&
1516 dl_time_before(dl_se->deadline,
1517 rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
1518 setup_new_dl_entity(dl_se);
1519 }
1520
1521 __enqueue_dl_entity(dl_se);
1522}
1523
1524static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
1525{
1526 __dequeue_dl_entity(dl_se);
1527}
1528
1529static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1530{
1531 if (is_dl_boosted(&p->dl)) {
1532 /*
1533 * Because of delays in the detection of the overrun of a
1534 * thread's runtime, it might be the case that a thread
1535 * goes to sleep in a rt mutex with negative runtime. As
1536 * a consequence, the thread will be throttled.
1537 *
1538 * While waiting for the mutex, this thread can also be
1539 * boosted via PI, resulting in a thread that is throttled
1540 * and boosted at the same time.
1541 *
1542 * In this case, the boost overrides the throttle.
1543 */
1544 if (p->dl.dl_throttled) {
1545 /*
1546 * The replenish timer needs to be canceled. No
1547 * problem if it fires concurrently: boosted threads
1548 * are ignored in dl_task_timer().
1549 */
1550 hrtimer_try_to_cancel(&p->dl.dl_timer);
1551 p->dl.dl_throttled = 0;
1552 }
1553 } else if (!dl_prio(p->normal_prio)) {
1554 /*
1555 * Special case in which we have a !SCHED_DEADLINE task that is going
1556 * to be deboosted, but exceeds its runtime while doing so. No point in
1557 * replenishing it, as it's going to return back to its original
1558 * scheduling class after this. If it has been throttled, we need to
1559 * clear the flag, otherwise the task may wake up as throttled after
1560 * being boosted again with no means to replenish the runtime and clear
1561 * the throttle.
1562 */
1563 p->dl.dl_throttled = 0;
1564 BUG_ON(!is_dl_boosted(&p->dl) || flags != ENQUEUE_REPLENISH);
1565 return;
1566 }
1567
1568 /*
1569 * Check if a constrained deadline task was activated
1570 * after the deadline but before the next period.
1571 * If that is the case, the task will be throttled and
1572 * the replenishment timer will be set to the next period.
1573 */
1574 if (!p->dl.dl_throttled && !dl_is_implicit(&p->dl))
1575 dl_check_constrained_dl(&p->dl);
1576
1577 if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & ENQUEUE_RESTORE) {
1578 add_rq_bw(&p->dl, &rq->dl);
1579 add_running_bw(&p->dl, &rq->dl);
1580 }
1581
1582 /*
1583 * If p is throttled, we do not enqueue it. In fact, if it exhausted
1584 * its budget it needs a replenishment and, since it now is on
1585 * its rq, the bandwidth timer callback (which clearly has not
1586 * run yet) will take care of this.
1587 * However, the active utilization does not depend on the fact
1588 * that the task is on the runqueue or not (but depends on the
1589 * task's state - in GRUB parlance, "inactive" vs "active contending").
1590 * In other words, even if a task is throttled its utilization must
1591 * be counted in the active utilization; hence, we need to call
1592 * add_running_bw().
1593 */
1594 if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
1595 if (flags & ENQUEUE_WAKEUP)
1596 task_contending(&p->dl, flags);
1597
1598 return;
1599 }
1600
1601 enqueue_dl_entity(&p->dl, flags);
1602
1603 if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
1604 enqueue_pushable_dl_task(rq, p);
1605}
1606
1607static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1608{
1609 dequeue_dl_entity(&p->dl);
1610 dequeue_pushable_dl_task(rq, p);
1611}
1612
1613static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
1614{
1615 update_curr_dl(rq);
1616 __dequeue_task_dl(rq, p, flags);
1617
1618 if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
1619 sub_running_bw(&p->dl, &rq->dl);
1620 sub_rq_bw(&p->dl, &rq->dl);
1621 }
1622
1623 /*
1624 * This check allows to start the inactive timer (or to immediately
1625 * decrease the active utilization, if needed) in two cases:
1626 * when the task blocks and when it is terminating
1627 * (p->state == TASK_DEAD). We can handle the two cases in the same
1628 * way, because from GRUB's point of view the same thing is happening
1629 * (the task moves from "active contending" to "active non contending"
1630 * or "inactive")
1631 */
1632 if (flags & DEQUEUE_SLEEP)
1633 task_non_contending(p);
1634}
1635
1636/*
1637 * Yield task semantic for -deadline tasks is:
1638 *
1639 * get off from the CPU until our next instance, with
1640 * a new runtime. This is of little use now, since we
1641 * don't have a bandwidth reclaiming mechanism. Anyway,
1642 * bandwidth reclaiming is planned for the future, and
1643 * yield_task_dl will indicate that some spare budget
1644 * is available for other task instances to use it.
1645 */
1646static void yield_task_dl(struct rq *rq)
1647{
1648 /*
1649 * We make the task go to sleep until its current deadline by
1650 * forcing its runtime to zero. This way, update_curr_dl() stops
1651 * it and the bandwidth timer will wake it up and will give it
1652 * new scheduling parameters (thanks to dl_yielded=1).
1653 */
1654 rq->curr->dl.dl_yielded = 1;
1655
1656 update_rq_clock(rq);
1657 update_curr_dl(rq);
1658 /*
1659 * Tell update_rq_clock() that we've just updated,
1660 * so we don't do microscopic update in schedule()
1661 * and double the fastpath cost.
1662 */
1663 rq_clock_skip_update(rq);
1664}
1665
1666#ifdef CONFIG_SMP
1667
1668static int find_later_rq(struct task_struct *task);
1669
1670static int
1671select_task_rq_dl(struct task_struct *p, int cpu, int flags)
1672{
1673 struct task_struct *curr;
1674 bool select_rq;
1675 struct rq *rq;
1676
1677 if (!(flags & WF_TTWU))
1678 goto out;
1679
1680 rq = cpu_rq(cpu);
1681
1682 rcu_read_lock();
1683 curr = READ_ONCE(rq->curr); /* unlocked access */
1684
1685 /*
1686 * If we are dealing with a -deadline task, we must
1687 * decide where to wake it up.
1688 * If it has a later deadline and the current task
1689 * on this rq can't move (provided the waking task
1690 * can!) we prefer to send it somewhere else. On the
1691 * other hand, if it has a shorter deadline, we
1692 * try to make it stay here, it might be important.
1693 */
1694 select_rq = unlikely(dl_task(curr)) &&
1695 (curr->nr_cpus_allowed < 2 ||
1696 !dl_entity_preempt(&p->dl, &curr->dl)) &&
1697 p->nr_cpus_allowed > 1;
1698
1699 /*
1700 * Take the capacity of the CPU into account to
1701 * ensure it fits the requirement of the task.
1702 */
1703 if (static_branch_unlikely(&sched_asym_cpucapacity))
1704 select_rq |= !dl_task_fits_capacity(p, cpu);
1705
1706 if (select_rq) {
1707 int target = find_later_rq(p);
1708
1709 if (target != -1 &&
1710 (dl_time_before(p->dl.deadline,
1711 cpu_rq(target)->dl.earliest_dl.curr) ||
1712 (cpu_rq(target)->dl.dl_nr_running == 0)))
1713 cpu = target;
1714 }
1715 rcu_read_unlock();
1716
1717out:
1718 return cpu;
1719}
1720
1721static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused)
1722{
1723 struct rq *rq;
1724
1725 if (READ_ONCE(p->__state) != TASK_WAKING)
1726 return;
1727
1728 rq = task_rq(p);
1729 /*
1730 * Since p->state == TASK_WAKING, set_task_cpu() has been called
1731 * from try_to_wake_up(). Hence, p->pi_lock is locked, but
1732 * rq->lock is not... So, lock it
1733 */
1734 raw_spin_rq_lock(rq);
1735 if (p->dl.dl_non_contending) {
1736 update_rq_clock(rq);
1737 sub_running_bw(&p->dl, &rq->dl);
1738 p->dl.dl_non_contending = 0;
1739 /*
1740 * If the timer handler is currently running and the
1741 * timer cannot be canceled, inactive_task_timer()
1742 * will see that dl_not_contending is not set, and
1743 * will not touch the rq's active utilization,
1744 * so we are still safe.
1745 */
1746 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
1747 put_task_struct(p);
1748 }
1749 sub_rq_bw(&p->dl, &rq->dl);
1750 raw_spin_rq_unlock(rq);
1751}
1752
1753static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
1754{
1755 /*
1756 * Current can't be migrated, useless to reschedule,
1757 * let's hope p can move out.
1758 */
1759 if (rq->curr->nr_cpus_allowed == 1 ||
1760 !cpudl_find(&rq->rd->cpudl, rq->curr, NULL))
1761 return;
1762
1763 /*
1764 * p is migratable, so let's not schedule it and
1765 * see if it is pushed or pulled somewhere else.
1766 */
1767 if (p->nr_cpus_allowed != 1 &&
1768 cpudl_find(&rq->rd->cpudl, p, NULL))
1769 return;
1770
1771 resched_curr(rq);
1772}
1773
1774static int balance_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
1775{
1776 if (!on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
1777 /*
1778 * This is OK, because current is on_cpu, which avoids it being
1779 * picked for load-balance and preemption/IRQs are still
1780 * disabled avoiding further scheduler activity on it and we've
1781 * not yet started the picking loop.
1782 */
1783 rq_unpin_lock(rq, rf);
1784 pull_dl_task(rq);
1785 rq_repin_lock(rq, rf);
1786 }
1787
1788 return sched_stop_runnable(rq) || sched_dl_runnable(rq);
1789}
1790#endif /* CONFIG_SMP */
1791
1792/*
1793 * Only called when both the current and waking task are -deadline
1794 * tasks.
1795 */
1796static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
1797 int flags)
1798{
1799 if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
1800 resched_curr(rq);
1801 return;
1802 }
1803
1804#ifdef CONFIG_SMP
1805 /*
1806 * In the unlikely case current and p have the same deadline
1807 * let us try to decide what's the best thing to do...
1808 */
1809 if ((p->dl.deadline == rq->curr->dl.deadline) &&
1810 !test_tsk_need_resched(rq->curr))
1811 check_preempt_equal_dl(rq, p);
1812#endif /* CONFIG_SMP */
1813}
1814
1815#ifdef CONFIG_SCHED_HRTICK
1816static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1817{
1818 hrtick_start(rq, p->dl.runtime);
1819}
1820#else /* !CONFIG_SCHED_HRTICK */
1821static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1822{
1823}
1824#endif
1825
1826static void set_next_task_dl(struct rq *rq, struct task_struct *p, bool first)
1827{
1828 p->se.exec_start = rq_clock_task(rq);
1829
1830 /* You can't push away the running task */
1831 dequeue_pushable_dl_task(rq, p);
1832
1833 if (!first)
1834 return;
1835
1836 if (hrtick_enabled_dl(rq))
1837 start_hrtick_dl(rq, p);
1838
1839 if (rq->curr->sched_class != &dl_sched_class)
1840 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
1841
1842 deadline_queue_push_tasks(rq);
1843}
1844
1845static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
1846 struct dl_rq *dl_rq)
1847{
1848 struct rb_node *left = rb_first_cached(&dl_rq->root);
1849
1850 if (!left)
1851 return NULL;
1852
1853 return rb_entry(left, struct sched_dl_entity, rb_node);
1854}
1855
1856static struct task_struct *pick_task_dl(struct rq *rq)
1857{
1858 struct sched_dl_entity *dl_se;
1859 struct dl_rq *dl_rq = &rq->dl;
1860 struct task_struct *p;
1861
1862 if (!sched_dl_runnable(rq))
1863 return NULL;
1864
1865 dl_se = pick_next_dl_entity(rq, dl_rq);
1866 BUG_ON(!dl_se);
1867 p = dl_task_of(dl_se);
1868
1869 return p;
1870}
1871
1872static struct task_struct *pick_next_task_dl(struct rq *rq)
1873{
1874 struct task_struct *p;
1875
1876 p = pick_task_dl(rq);
1877 if (p)
1878 set_next_task_dl(rq, p, true);
1879
1880 return p;
1881}
1882
1883static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
1884{
1885 update_curr_dl(rq);
1886
1887 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1888 if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
1889 enqueue_pushable_dl_task(rq, p);
1890}
1891
1892/*
1893 * scheduler tick hitting a task of our scheduling class.
1894 *
1895 * NOTE: This function can be called remotely by the tick offload that
1896 * goes along full dynticks. Therefore no local assumption can be made
1897 * and everything must be accessed through the @rq and @curr passed in
1898 * parameters.
1899 */
1900static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
1901{
1902 update_curr_dl(rq);
1903
1904 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
1905 /*
1906 * Even when we have runtime, update_curr_dl() might have resulted in us
1907 * not being the leftmost task anymore. In that case NEED_RESCHED will
1908 * be set and schedule() will start a new hrtick for the next task.
1909 */
1910 if (hrtick_enabled_dl(rq) && queued && p->dl.runtime > 0 &&
1911 is_leftmost(p, &rq->dl))
1912 start_hrtick_dl(rq, p);
1913}
1914
1915static void task_fork_dl(struct task_struct *p)
1916{
1917 /*
1918 * SCHED_DEADLINE tasks cannot fork and this is achieved through
1919 * sched_fork()
1920 */
1921}
1922
1923#ifdef CONFIG_SMP
1924
1925/* Only try algorithms three times */
1926#define DL_MAX_TRIES 3
1927
1928static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
1929{
1930 if (!task_running(rq, p) &&
1931 cpumask_test_cpu(cpu, &p->cpus_mask))
1932 return 1;
1933 return 0;
1934}
1935
1936/*
1937 * Return the earliest pushable rq's task, which is suitable to be executed
1938 * on the CPU, NULL otherwise:
1939 */
1940static struct task_struct *pick_earliest_pushable_dl_task(struct rq *rq, int cpu)
1941{
1942 struct rb_node *next_node = rq->dl.pushable_dl_tasks_root.rb_leftmost;
1943 struct task_struct *p = NULL;
1944
1945 if (!has_pushable_dl_tasks(rq))
1946 return NULL;
1947
1948next_node:
1949 if (next_node) {
1950 p = rb_entry(next_node, struct task_struct, pushable_dl_tasks);
1951
1952 if (pick_dl_task(rq, p, cpu))
1953 return p;
1954
1955 next_node = rb_next(next_node);
1956 goto next_node;
1957 }
1958
1959 return NULL;
1960}
1961
1962static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
1963
1964static int find_later_rq(struct task_struct *task)
1965{
1966 struct sched_domain *sd;
1967 struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
1968 int this_cpu = smp_processor_id();
1969 int cpu = task_cpu(task);
1970
1971 /* Make sure the mask is initialized first */
1972 if (unlikely(!later_mask))
1973 return -1;
1974
1975 if (task->nr_cpus_allowed == 1)
1976 return -1;
1977
1978 /*
1979 * We have to consider system topology and task affinity
1980 * first, then we can look for a suitable CPU.
1981 */
1982 if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
1983 return -1;
1984
1985 /*
1986 * If we are here, some targets have been found, including
1987 * the most suitable which is, among the runqueues where the
1988 * current tasks have later deadlines than the task's one, the
1989 * rq with the latest possible one.
1990 *
1991 * Now we check how well this matches with task's
1992 * affinity and system topology.
1993 *
1994 * The last CPU where the task run is our first
1995 * guess, since it is most likely cache-hot there.
1996 */
1997 if (cpumask_test_cpu(cpu, later_mask))
1998 return cpu;
1999 /*
2000 * Check if this_cpu is to be skipped (i.e., it is
2001 * not in the mask) or not.
2002 */
2003 if (!cpumask_test_cpu(this_cpu, later_mask))
2004 this_cpu = -1;
2005
2006 rcu_read_lock();
2007 for_each_domain(cpu, sd) {
2008 if (sd->flags & SD_WAKE_AFFINE) {
2009 int best_cpu;
2010
2011 /*
2012 * If possible, preempting this_cpu is
2013 * cheaper than migrating.
2014 */
2015 if (this_cpu != -1 &&
2016 cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
2017 rcu_read_unlock();
2018 return this_cpu;
2019 }
2020
2021 best_cpu = cpumask_any_and_distribute(later_mask,
2022 sched_domain_span(sd));
2023 /*
2024 * Last chance: if a CPU being in both later_mask
2025 * and current sd span is valid, that becomes our
2026 * choice. Of course, the latest possible CPU is
2027 * already under consideration through later_mask.
2028 */
2029 if (best_cpu < nr_cpu_ids) {
2030 rcu_read_unlock();
2031 return best_cpu;
2032 }
2033 }
2034 }
2035 rcu_read_unlock();
2036
2037 /*
2038 * At this point, all our guesses failed, we just return
2039 * 'something', and let the caller sort the things out.
2040 */
2041 if (this_cpu != -1)
2042 return this_cpu;
2043
2044 cpu = cpumask_any_distribute(later_mask);
2045 if (cpu < nr_cpu_ids)
2046 return cpu;
2047
2048 return -1;
2049}
2050
2051/* Locks the rq it finds */
2052static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
2053{
2054 struct rq *later_rq = NULL;
2055 int tries;
2056 int cpu;
2057
2058 for (tries = 0; tries < DL_MAX_TRIES; tries++) {
2059 cpu = find_later_rq(task);
2060
2061 if ((cpu == -1) || (cpu == rq->cpu))
2062 break;
2063
2064 later_rq = cpu_rq(cpu);
2065
2066 if (later_rq->dl.dl_nr_running &&
2067 !dl_time_before(task->dl.deadline,
2068 later_rq->dl.earliest_dl.curr)) {
2069 /*
2070 * Target rq has tasks of equal or earlier deadline,
2071 * retrying does not release any lock and is unlikely
2072 * to yield a different result.
2073 */
2074 later_rq = NULL;
2075 break;
2076 }
2077
2078 /* Retry if something changed. */
2079 if (double_lock_balance(rq, later_rq)) {
2080 if (unlikely(task_rq(task) != rq ||
2081 !cpumask_test_cpu(later_rq->cpu, &task->cpus_mask) ||
2082 task_running(rq, task) ||
2083 !dl_task(task) ||
2084 !task_on_rq_queued(task))) {
2085 double_unlock_balance(rq, later_rq);
2086 later_rq = NULL;
2087 break;
2088 }
2089 }
2090
2091 /*
2092 * If the rq we found has no -deadline task, or
2093 * its earliest one has a later deadline than our
2094 * task, the rq is a good one.
2095 */
2096 if (!later_rq->dl.dl_nr_running ||
2097 dl_time_before(task->dl.deadline,
2098 later_rq->dl.earliest_dl.curr))
2099 break;
2100
2101 /* Otherwise we try again. */
2102 double_unlock_balance(rq, later_rq);
2103 later_rq = NULL;
2104 }
2105
2106 return later_rq;
2107}
2108
2109static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
2110{
2111 struct task_struct *p;
2112
2113 if (!has_pushable_dl_tasks(rq))
2114 return NULL;
2115
2116 p = rb_entry(rq->dl.pushable_dl_tasks_root.rb_leftmost,
2117 struct task_struct, pushable_dl_tasks);
2118
2119 BUG_ON(rq->cpu != task_cpu(p));
2120 BUG_ON(task_current(rq, p));
2121 BUG_ON(p->nr_cpus_allowed <= 1);
2122
2123 BUG_ON(!task_on_rq_queued(p));
2124 BUG_ON(!dl_task(p));
2125
2126 return p;
2127}
2128
2129/*
2130 * See if the non running -deadline tasks on this rq
2131 * can be sent to some other CPU where they can preempt
2132 * and start executing.
2133 */
2134static int push_dl_task(struct rq *rq)
2135{
2136 struct task_struct *next_task;
2137 struct rq *later_rq;
2138 int ret = 0;
2139
2140 if (!rq->dl.overloaded)
2141 return 0;
2142
2143 next_task = pick_next_pushable_dl_task(rq);
2144 if (!next_task)
2145 return 0;
2146
2147retry:
2148 if (is_migration_disabled(next_task))
2149 return 0;
2150
2151 if (WARN_ON(next_task == rq->curr))
2152 return 0;
2153
2154 /*
2155 * If next_task preempts rq->curr, and rq->curr
2156 * can move away, it makes sense to just reschedule
2157 * without going further in pushing next_task.
2158 */
2159 if (dl_task(rq->curr) &&
2160 dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
2161 rq->curr->nr_cpus_allowed > 1) {
2162 resched_curr(rq);
2163 return 0;
2164 }
2165
2166 /* We might release rq lock */
2167 get_task_struct(next_task);
2168
2169 /* Will lock the rq it'll find */
2170 later_rq = find_lock_later_rq(next_task, rq);
2171 if (!later_rq) {
2172 struct task_struct *task;
2173
2174 /*
2175 * We must check all this again, since
2176 * find_lock_later_rq releases rq->lock and it is
2177 * then possible that next_task has migrated.
2178 */
2179 task = pick_next_pushable_dl_task(rq);
2180 if (task == next_task) {
2181 /*
2182 * The task is still there. We don't try
2183 * again, some other CPU will pull it when ready.
2184 */
2185 goto out;
2186 }
2187
2188 if (!task)
2189 /* No more tasks */
2190 goto out;
2191
2192 put_task_struct(next_task);
2193 next_task = task;
2194 goto retry;
2195 }
2196
2197 deactivate_task(rq, next_task, 0);
2198 set_task_cpu(next_task, later_rq->cpu);
2199
2200 /*
2201 * Update the later_rq clock here, because the clock is used
2202 * by the cpufreq_update_util() inside __add_running_bw().
2203 */
2204 update_rq_clock(later_rq);
2205 activate_task(later_rq, next_task, ENQUEUE_NOCLOCK);
2206 ret = 1;
2207
2208 resched_curr(later_rq);
2209
2210 double_unlock_balance(rq, later_rq);
2211
2212out:
2213 put_task_struct(next_task);
2214
2215 return ret;
2216}
2217
2218static void push_dl_tasks(struct rq *rq)
2219{
2220 /* push_dl_task() will return true if it moved a -deadline task */
2221 while (push_dl_task(rq))
2222 ;
2223}
2224
2225static void pull_dl_task(struct rq *this_rq)
2226{
2227 int this_cpu = this_rq->cpu, cpu;
2228 struct task_struct *p, *push_task;
2229 bool resched = false;
2230 struct rq *src_rq;
2231 u64 dmin = LONG_MAX;
2232
2233 if (likely(!dl_overloaded(this_rq)))
2234 return;
2235
2236 /*
2237 * Match the barrier from dl_set_overloaded; this guarantees that if we
2238 * see overloaded we must also see the dlo_mask bit.
2239 */
2240 smp_rmb();
2241
2242 for_each_cpu(cpu, this_rq->rd->dlo_mask) {
2243 if (this_cpu == cpu)
2244 continue;
2245
2246 src_rq = cpu_rq(cpu);
2247
2248 /*
2249 * It looks racy, abd it is! However, as in sched_rt.c,
2250 * we are fine with this.
2251 */
2252 if (this_rq->dl.dl_nr_running &&
2253 dl_time_before(this_rq->dl.earliest_dl.curr,
2254 src_rq->dl.earliest_dl.next))
2255 continue;
2256
2257 /* Might drop this_rq->lock */
2258 push_task = NULL;
2259 double_lock_balance(this_rq, src_rq);
2260
2261 /*
2262 * If there are no more pullable tasks on the
2263 * rq, we're done with it.
2264 */
2265 if (src_rq->dl.dl_nr_running <= 1)
2266 goto skip;
2267
2268 p = pick_earliest_pushable_dl_task(src_rq, this_cpu);
2269
2270 /*
2271 * We found a task to be pulled if:
2272 * - it preempts our current (if there's one),
2273 * - it will preempt the last one we pulled (if any).
2274 */
2275 if (p && dl_time_before(p->dl.deadline, dmin) &&
2276 (!this_rq->dl.dl_nr_running ||
2277 dl_time_before(p->dl.deadline,
2278 this_rq->dl.earliest_dl.curr))) {
2279 WARN_ON(p == src_rq->curr);
2280 WARN_ON(!task_on_rq_queued(p));
2281
2282 /*
2283 * Then we pull iff p has actually an earlier
2284 * deadline than the current task of its runqueue.
2285 */
2286 if (dl_time_before(p->dl.deadline,
2287 src_rq->curr->dl.deadline))
2288 goto skip;
2289
2290 if (is_migration_disabled(p)) {
2291 push_task = get_push_task(src_rq);
2292 } else {
2293 deactivate_task(src_rq, p, 0);
2294 set_task_cpu(p, this_cpu);
2295 activate_task(this_rq, p, 0);
2296 dmin = p->dl.deadline;
2297 resched = true;
2298 }
2299
2300 /* Is there any other task even earlier? */
2301 }
2302skip:
2303 double_unlock_balance(this_rq, src_rq);
2304
2305 if (push_task) {
2306 raw_spin_rq_unlock(this_rq);
2307 stop_one_cpu_nowait(src_rq->cpu, push_cpu_stop,
2308 push_task, &src_rq->push_work);
2309 raw_spin_rq_lock(this_rq);
2310 }
2311 }
2312
2313 if (resched)
2314 resched_curr(this_rq);
2315}
2316
2317/*
2318 * Since the task is not running and a reschedule is not going to happen
2319 * anytime soon on its runqueue, we try pushing it away now.
2320 */
2321static void task_woken_dl(struct rq *rq, struct task_struct *p)
2322{
2323 if (!task_running(rq, p) &&
2324 !test_tsk_need_resched(rq->curr) &&
2325 p->nr_cpus_allowed > 1 &&
2326 dl_task(rq->curr) &&
2327 (rq->curr->nr_cpus_allowed < 2 ||
2328 !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
2329 push_dl_tasks(rq);
2330 }
2331}
2332
2333static void set_cpus_allowed_dl(struct task_struct *p,
2334 const struct cpumask *new_mask,
2335 u32 flags)
2336{
2337 struct root_domain *src_rd;
2338 struct rq *rq;
2339
2340 BUG_ON(!dl_task(p));
2341
2342 rq = task_rq(p);
2343 src_rd = rq->rd;
2344 /*
2345 * Migrating a SCHED_DEADLINE task between exclusive
2346 * cpusets (different root_domains) entails a bandwidth
2347 * update. We already made space for us in the destination
2348 * domain (see cpuset_can_attach()).
2349 */
2350 if (!cpumask_intersects(src_rd->span, new_mask)) {
2351 struct dl_bw *src_dl_b;
2352
2353 src_dl_b = dl_bw_of(cpu_of(rq));
2354 /*
2355 * We now free resources of the root_domain we are migrating
2356 * off. In the worst case, sched_setattr() may temporary fail
2357 * until we complete the update.
2358 */
2359 raw_spin_lock(&src_dl_b->lock);
2360 __dl_sub(src_dl_b, p->dl.dl_bw, dl_bw_cpus(task_cpu(p)));
2361 raw_spin_unlock(&src_dl_b->lock);
2362 }
2363
2364 set_cpus_allowed_common(p, new_mask, flags);
2365}
2366
2367/* Assumes rq->lock is held */
2368static void rq_online_dl(struct rq *rq)
2369{
2370 if (rq->dl.overloaded)
2371 dl_set_overload(rq);
2372
2373 cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
2374 if (rq->dl.dl_nr_running > 0)
2375 cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr);
2376}
2377
2378/* Assumes rq->lock is held */
2379static void rq_offline_dl(struct rq *rq)
2380{
2381 if (rq->dl.overloaded)
2382 dl_clear_overload(rq);
2383
2384 cpudl_clear(&rq->rd->cpudl, rq->cpu);
2385 cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
2386}
2387
2388void __init init_sched_dl_class(void)
2389{
2390 unsigned int i;
2391
2392 for_each_possible_cpu(i)
2393 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
2394 GFP_KERNEL, cpu_to_node(i));
2395}
2396
2397void dl_add_task_root_domain(struct task_struct *p)
2398{
2399 struct rq_flags rf;
2400 struct rq *rq;
2401 struct dl_bw *dl_b;
2402
2403 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2404 if (!dl_task(p)) {
2405 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
2406 return;
2407 }
2408
2409 rq = __task_rq_lock(p, &rf);
2410
2411 dl_b = &rq->rd->dl_bw;
2412 raw_spin_lock(&dl_b->lock);
2413
2414 __dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
2415
2416 raw_spin_unlock(&dl_b->lock);
2417
2418 task_rq_unlock(rq, p, &rf);
2419}
2420
2421void dl_clear_root_domain(struct root_domain *rd)
2422{
2423 unsigned long flags;
2424
2425 raw_spin_lock_irqsave(&rd->dl_bw.lock, flags);
2426 rd->dl_bw.total_bw = 0;
2427 raw_spin_unlock_irqrestore(&rd->dl_bw.lock, flags);
2428}
2429
2430#endif /* CONFIG_SMP */
2431
2432static void switched_from_dl(struct rq *rq, struct task_struct *p)
2433{
2434 /*
2435 * task_non_contending() can start the "inactive timer" (if the 0-lag
2436 * time is in the future). If the task switches back to dl before
2437 * the "inactive timer" fires, it can continue to consume its current
2438 * runtime using its current deadline. If it stays outside of
2439 * SCHED_DEADLINE until the 0-lag time passes, inactive_task_timer()
2440 * will reset the task parameters.
2441 */
2442 if (task_on_rq_queued(p) && p->dl.dl_runtime)
2443 task_non_contending(p);
2444
2445 if (!task_on_rq_queued(p)) {
2446 /*
2447 * Inactive timer is armed. However, p is leaving DEADLINE and
2448 * might migrate away from this rq while continuing to run on
2449 * some other class. We need to remove its contribution from
2450 * this rq running_bw now, or sub_rq_bw (below) will complain.
2451 */
2452 if (p->dl.dl_non_contending)
2453 sub_running_bw(&p->dl, &rq->dl);
2454 sub_rq_bw(&p->dl, &rq->dl);
2455 }
2456
2457 /*
2458 * We cannot use inactive_task_timer() to invoke sub_running_bw()
2459 * at the 0-lag time, because the task could have been migrated
2460 * while SCHED_OTHER in the meanwhile.
2461 */
2462 if (p->dl.dl_non_contending)
2463 p->dl.dl_non_contending = 0;
2464
2465 /*
2466 * Since this might be the only -deadline task on the rq,
2467 * this is the right place to try to pull some other one
2468 * from an overloaded CPU, if any.
2469 */
2470 if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
2471 return;
2472
2473 deadline_queue_pull_task(rq);
2474}
2475
2476/*
2477 * When switching to -deadline, we may overload the rq, then
2478 * we try to push someone off, if possible.
2479 */
2480static void switched_to_dl(struct rq *rq, struct task_struct *p)
2481{
2482 if (hrtimer_try_to_cancel(&p->dl.inactive_timer) == 1)
2483 put_task_struct(p);
2484
2485 /* If p is not queued we will update its parameters at next wakeup. */
2486 if (!task_on_rq_queued(p)) {
2487 add_rq_bw(&p->dl, &rq->dl);
2488
2489 return;
2490 }
2491
2492 if (rq->curr != p) {
2493#ifdef CONFIG_SMP
2494 if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
2495 deadline_queue_push_tasks(rq);
2496#endif
2497 if (dl_task(rq->curr))
2498 check_preempt_curr_dl(rq, p, 0);
2499 else
2500 resched_curr(rq);
2501 } else {
2502 update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
2503 }
2504}
2505
2506/*
2507 * If the scheduling parameters of a -deadline task changed,
2508 * a push or pull operation might be needed.
2509 */
2510static void prio_changed_dl(struct rq *rq, struct task_struct *p,
2511 int oldprio)
2512{
2513 if (task_on_rq_queued(p) || task_current(rq, p)) {
2514#ifdef CONFIG_SMP
2515 /*
2516 * This might be too much, but unfortunately
2517 * we don't have the old deadline value, and
2518 * we can't argue if the task is increasing
2519 * or lowering its prio, so...
2520 */
2521 if (!rq->dl.overloaded)
2522 deadline_queue_pull_task(rq);
2523
2524 /*
2525 * If we now have a earlier deadline task than p,
2526 * then reschedule, provided p is still on this
2527 * runqueue.
2528 */
2529 if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline))
2530 resched_curr(rq);
2531#else
2532 /*
2533 * Again, we don't know if p has a earlier
2534 * or later deadline, so let's blindly set a
2535 * (maybe not needed) rescheduling point.
2536 */
2537 resched_curr(rq);
2538#endif /* CONFIG_SMP */
2539 }
2540}
2541
2542DEFINE_SCHED_CLASS(dl) = {
2543
2544 .enqueue_task = enqueue_task_dl,
2545 .dequeue_task = dequeue_task_dl,
2546 .yield_task = yield_task_dl,
2547
2548 .check_preempt_curr = check_preempt_curr_dl,
2549
2550 .pick_next_task = pick_next_task_dl,
2551 .put_prev_task = put_prev_task_dl,
2552 .set_next_task = set_next_task_dl,
2553
2554#ifdef CONFIG_SMP
2555 .balance = balance_dl,
2556 .pick_task = pick_task_dl,
2557 .select_task_rq = select_task_rq_dl,
2558 .migrate_task_rq = migrate_task_rq_dl,
2559 .set_cpus_allowed = set_cpus_allowed_dl,
2560 .rq_online = rq_online_dl,
2561 .rq_offline = rq_offline_dl,
2562 .task_woken = task_woken_dl,
2563 .find_lock_rq = find_lock_later_rq,
2564#endif
2565
2566 .task_tick = task_tick_dl,
2567 .task_fork = task_fork_dl,
2568
2569 .prio_changed = prio_changed_dl,
2570 .switched_from = switched_from_dl,
2571 .switched_to = switched_to_dl,
2572
2573 .update_curr = update_curr_dl,
2574};
2575
2576/* Used for dl_bw check and update, used under sched_rt_handler()::mutex */
2577static u64 dl_generation;
2578
2579int sched_dl_global_validate(void)
2580{
2581 u64 runtime = global_rt_runtime();
2582 u64 period = global_rt_period();
2583 u64 new_bw = to_ratio(period, runtime);
2584 u64 gen = ++dl_generation;
2585 struct dl_bw *dl_b;
2586 int cpu, cpus, ret = 0;
2587 unsigned long flags;
2588
2589 /*
2590 * Here we want to check the bandwidth not being set to some
2591 * value smaller than the currently allocated bandwidth in
2592 * any of the root_domains.
2593 */
2594 for_each_possible_cpu(cpu) {
2595 rcu_read_lock_sched();
2596
2597 if (dl_bw_visited(cpu, gen))
2598 goto next;
2599
2600 dl_b = dl_bw_of(cpu);
2601 cpus = dl_bw_cpus(cpu);
2602
2603 raw_spin_lock_irqsave(&dl_b->lock, flags);
2604 if (new_bw * cpus < dl_b->total_bw)
2605 ret = -EBUSY;
2606 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2607
2608next:
2609 rcu_read_unlock_sched();
2610
2611 if (ret)
2612 break;
2613 }
2614
2615 return ret;
2616}
2617
2618static void init_dl_rq_bw_ratio(struct dl_rq *dl_rq)
2619{
2620 if (global_rt_runtime() == RUNTIME_INF) {
2621 dl_rq->bw_ratio = 1 << RATIO_SHIFT;
2622 dl_rq->extra_bw = 1 << BW_SHIFT;
2623 } else {
2624 dl_rq->bw_ratio = to_ratio(global_rt_runtime(),
2625 global_rt_period()) >> (BW_SHIFT - RATIO_SHIFT);
2626 dl_rq->extra_bw = to_ratio(global_rt_period(),
2627 global_rt_runtime());
2628 }
2629}
2630
2631void sched_dl_do_global(void)
2632{
2633 u64 new_bw = -1;
2634 u64 gen = ++dl_generation;
2635 struct dl_bw *dl_b;
2636 int cpu;
2637 unsigned long flags;
2638
2639 def_dl_bandwidth.dl_period = global_rt_period();
2640 def_dl_bandwidth.dl_runtime = global_rt_runtime();
2641
2642 if (global_rt_runtime() != RUNTIME_INF)
2643 new_bw = to_ratio(global_rt_period(), global_rt_runtime());
2644
2645 for_each_possible_cpu(cpu) {
2646 rcu_read_lock_sched();
2647
2648 if (dl_bw_visited(cpu, gen)) {
2649 rcu_read_unlock_sched();
2650 continue;
2651 }
2652
2653 dl_b = dl_bw_of(cpu);
2654
2655 raw_spin_lock_irqsave(&dl_b->lock, flags);
2656 dl_b->bw = new_bw;
2657 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2658
2659 rcu_read_unlock_sched();
2660 init_dl_rq_bw_ratio(&cpu_rq(cpu)->dl);
2661 }
2662}
2663
2664/*
2665 * We must be sure that accepting a new task (or allowing changing the
2666 * parameters of an existing one) is consistent with the bandwidth
2667 * constraints. If yes, this function also accordingly updates the currently
2668 * allocated bandwidth to reflect the new situation.
2669 *
2670 * This function is called while holding p's rq->lock.
2671 */
2672int sched_dl_overflow(struct task_struct *p, int policy,
2673 const struct sched_attr *attr)
2674{
2675 u64 period = attr->sched_period ?: attr->sched_deadline;
2676 u64 runtime = attr->sched_runtime;
2677 u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
2678 int cpus, err = -1, cpu = task_cpu(p);
2679 struct dl_bw *dl_b = dl_bw_of(cpu);
2680 unsigned long cap;
2681
2682 if (attr->sched_flags & SCHED_FLAG_SUGOV)
2683 return 0;
2684
2685 /* !deadline task may carry old deadline bandwidth */
2686 if (new_bw == p->dl.dl_bw && task_has_dl_policy(p))
2687 return 0;
2688
2689 /*
2690 * Either if a task, enters, leave, or stays -deadline but changes
2691 * its parameters, we may need to update accordingly the total
2692 * allocated bandwidth of the container.
2693 */
2694 raw_spin_lock(&dl_b->lock);
2695 cpus = dl_bw_cpus(cpu);
2696 cap = dl_bw_capacity(cpu);
2697
2698 if (dl_policy(policy) && !task_has_dl_policy(p) &&
2699 !__dl_overflow(dl_b, cap, 0, new_bw)) {
2700 if (hrtimer_active(&p->dl.inactive_timer))
2701 __dl_sub(dl_b, p->dl.dl_bw, cpus);
2702 __dl_add(dl_b, new_bw, cpus);
2703 err = 0;
2704 } else if (dl_policy(policy) && task_has_dl_policy(p) &&
2705 !__dl_overflow(dl_b, cap, p->dl.dl_bw, new_bw)) {
2706 /*
2707 * XXX this is slightly incorrect: when the task
2708 * utilization decreases, we should delay the total
2709 * utilization change until the task's 0-lag point.
2710 * But this would require to set the task's "inactive
2711 * timer" when the task is not inactive.
2712 */
2713 __dl_sub(dl_b, p->dl.dl_bw, cpus);
2714 __dl_add(dl_b, new_bw, cpus);
2715 dl_change_utilization(p, new_bw);
2716 err = 0;
2717 } else if (!dl_policy(policy) && task_has_dl_policy(p)) {
2718 /*
2719 * Do not decrease the total deadline utilization here,
2720 * switched_from_dl() will take care to do it at the correct
2721 * (0-lag) time.
2722 */
2723 err = 0;
2724 }
2725 raw_spin_unlock(&dl_b->lock);
2726
2727 return err;
2728}
2729
2730/*
2731 * This function initializes the sched_dl_entity of a newly becoming
2732 * SCHED_DEADLINE task.
2733 *
2734 * Only the static values are considered here, the actual runtime and the
2735 * absolute deadline will be properly calculated when the task is enqueued
2736 * for the first time with its new policy.
2737 */
2738void __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
2739{
2740 struct sched_dl_entity *dl_se = &p->dl;
2741
2742 dl_se->dl_runtime = attr->sched_runtime;
2743 dl_se->dl_deadline = attr->sched_deadline;
2744 dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
2745 dl_se->flags = attr->sched_flags & SCHED_DL_FLAGS;
2746 dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
2747 dl_se->dl_density = to_ratio(dl_se->dl_deadline, dl_se->dl_runtime);
2748}
2749
2750void __getparam_dl(struct task_struct *p, struct sched_attr *attr)
2751{
2752 struct sched_dl_entity *dl_se = &p->dl;
2753
2754 attr->sched_priority = p->rt_priority;
2755 attr->sched_runtime = dl_se->dl_runtime;
2756 attr->sched_deadline = dl_se->dl_deadline;
2757 attr->sched_period = dl_se->dl_period;
2758 attr->sched_flags &= ~SCHED_DL_FLAGS;
2759 attr->sched_flags |= dl_se->flags;
2760}
2761
2762/*
2763 * Default limits for DL period; on the top end we guard against small util
2764 * tasks still getting ridiculously long effective runtimes, on the bottom end we
2765 * guard against timer DoS.
2766 */
2767unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */
2768unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */
2769
2770/*
2771 * This function validates the new parameters of a -deadline task.
2772 * We ask for the deadline not being zero, and greater or equal
2773 * than the runtime, as well as the period of being zero or
2774 * greater than deadline. Furthermore, we have to be sure that
2775 * user parameters are above the internal resolution of 1us (we
2776 * check sched_runtime only since it is always the smaller one) and
2777 * below 2^63 ns (we have to check both sched_deadline and
2778 * sched_period, as the latter can be zero).
2779 */
2780bool __checkparam_dl(const struct sched_attr *attr)
2781{
2782 u64 period, max, min;
2783
2784 /* special dl tasks don't actually use any parameter */
2785 if (attr->sched_flags & SCHED_FLAG_SUGOV)
2786 return true;
2787
2788 /* deadline != 0 */
2789 if (attr->sched_deadline == 0)
2790 return false;
2791
2792 /*
2793 * Since we truncate DL_SCALE bits, make sure we're at least
2794 * that big.
2795 */
2796 if (attr->sched_runtime < (1ULL << DL_SCALE))
2797 return false;
2798
2799 /*
2800 * Since we use the MSB for wrap-around and sign issues, make
2801 * sure it's not set (mind that period can be equal to zero).
2802 */
2803 if (attr->sched_deadline & (1ULL << 63) ||
2804 attr->sched_period & (1ULL << 63))
2805 return false;
2806
2807 period = attr->sched_period;
2808 if (!period)
2809 period = attr->sched_deadline;
2810
2811 /* runtime <= deadline <= period (if period != 0) */
2812 if (period < attr->sched_deadline ||
2813 attr->sched_deadline < attr->sched_runtime)
2814 return false;
2815
2816 max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC;
2817 min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC;
2818
2819 if (period < min || period > max)
2820 return false;
2821
2822 return true;
2823}
2824
2825/*
2826 * This function clears the sched_dl_entity static params.
2827 */
2828void __dl_clear_params(struct task_struct *p)
2829{
2830 struct sched_dl_entity *dl_se = &p->dl;
2831
2832 dl_se->dl_runtime = 0;
2833 dl_se->dl_deadline = 0;
2834 dl_se->dl_period = 0;
2835 dl_se->flags = 0;
2836 dl_se->dl_bw = 0;
2837 dl_se->dl_density = 0;
2838
2839 dl_se->dl_throttled = 0;
2840 dl_se->dl_yielded = 0;
2841 dl_se->dl_non_contending = 0;
2842 dl_se->dl_overrun = 0;
2843
2844#ifdef CONFIG_RT_MUTEXES
2845 dl_se->pi_se = dl_se;
2846#endif
2847}
2848
2849bool dl_param_changed(struct task_struct *p, const struct sched_attr *attr)
2850{
2851 struct sched_dl_entity *dl_se = &p->dl;
2852
2853 if (dl_se->dl_runtime != attr->sched_runtime ||
2854 dl_se->dl_deadline != attr->sched_deadline ||
2855 dl_se->dl_period != attr->sched_period ||
2856 dl_se->flags != (attr->sched_flags & SCHED_DL_FLAGS))
2857 return true;
2858
2859 return false;
2860}
2861
2862#ifdef CONFIG_SMP
2863int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed)
2864{
2865 unsigned long flags, cap;
2866 unsigned int dest_cpu;
2867 struct dl_bw *dl_b;
2868 bool overflow;
2869 int ret;
2870
2871 dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
2872
2873 rcu_read_lock_sched();
2874 dl_b = dl_bw_of(dest_cpu);
2875 raw_spin_lock_irqsave(&dl_b->lock, flags);
2876 cap = dl_bw_capacity(dest_cpu);
2877 overflow = __dl_overflow(dl_b, cap, 0, p->dl.dl_bw);
2878 if (overflow) {
2879 ret = -EBUSY;
2880 } else {
2881 /*
2882 * We reserve space for this task in the destination
2883 * root_domain, as we can't fail after this point.
2884 * We will free resources in the source root_domain
2885 * later on (see set_cpus_allowed_dl()).
2886 */
2887 int cpus = dl_bw_cpus(dest_cpu);
2888
2889 __dl_add(dl_b, p->dl.dl_bw, cpus);
2890 ret = 0;
2891 }
2892 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2893 rcu_read_unlock_sched();
2894
2895 return ret;
2896}
2897
2898int dl_cpuset_cpumask_can_shrink(const struct cpumask *cur,
2899 const struct cpumask *trial)
2900{
2901 int ret = 1, trial_cpus;
2902 struct dl_bw *cur_dl_b;
2903 unsigned long flags;
2904
2905 rcu_read_lock_sched();
2906 cur_dl_b = dl_bw_of(cpumask_any(cur));
2907 trial_cpus = cpumask_weight(trial);
2908
2909 raw_spin_lock_irqsave(&cur_dl_b->lock, flags);
2910 if (cur_dl_b->bw != -1 &&
2911 cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw)
2912 ret = 0;
2913 raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags);
2914 rcu_read_unlock_sched();
2915
2916 return ret;
2917}
2918
2919bool dl_cpu_busy(unsigned int cpu)
2920{
2921 unsigned long flags, cap;
2922 struct dl_bw *dl_b;
2923 bool overflow;
2924
2925 rcu_read_lock_sched();
2926 dl_b = dl_bw_of(cpu);
2927 raw_spin_lock_irqsave(&dl_b->lock, flags);
2928 cap = dl_bw_capacity(cpu);
2929 overflow = __dl_overflow(dl_b, cap, 0, 0);
2930 raw_spin_unlock_irqrestore(&dl_b->lock, flags);
2931 rcu_read_unlock_sched();
2932
2933 return overflow;
2934}
2935#endif
2936
2937#ifdef CONFIG_SCHED_DEBUG
2938void print_dl_stats(struct seq_file *m, int cpu)
2939{
2940 print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
2941}
2942#endif /* CONFIG_SCHED_DEBUG */