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Linux/kernel/sched/deadline.c

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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 
 21 struct dl_bandwidth def_dl_bandwidth;
 22 
 23 static 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 
 28 static inline struct rq *rq_of_dl_rq(struct dl_rq *dl_rq)
 29 {
 30         return container_of(dl_rq, struct rq, dl);
 31 }
 32 
 33 static 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 
 41 static inline int on_dl_rq(struct sched_dl_entity *dl_se)
 42 {
 43         return !RB_EMPTY_NODE(&dl_se->rb_node);
 44 }
 45 
 46 static 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 
 53 void 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 
 60 void 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 
 72 void init_dl_rq(struct dl_rq *dl_rq, struct rq *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 
 90 static inline int dl_overloaded(struct rq *rq)
 91 {
 92         return atomic_read(&rq->rd->dlo_count);
 93 }
 94 
 95 static 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 
111 static 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 
120 static 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 
133 static 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 (p->nr_cpus_allowed > 1)
138                 dl_rq->dl_nr_migratory++;
139 
140         update_dl_migration(dl_rq);
141 }
142 
143 static 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 (p->nr_cpus_allowed > 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  */
157 static 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 
182         rb_link_node(&p->pushable_dl_tasks, parent, link);
183         rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
184 }
185 
186 static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
187 {
188         struct dl_rq *dl_rq = &rq->dl;
189 
190         if (RB_EMPTY_NODE(&p->pushable_dl_tasks))
191                 return;
192 
193         if (dl_rq->pushable_dl_tasks_leftmost == &p->pushable_dl_tasks) {
194                 struct rb_node *next_node;
195 
196                 next_node = rb_next(&p->pushable_dl_tasks);
197                 dl_rq->pushable_dl_tasks_leftmost = next_node;
198         }
199 
200         rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
201         RB_CLEAR_NODE(&p->pushable_dl_tasks);
202 }
203 
204 static inline int has_pushable_dl_tasks(struct rq *rq)
205 {
206         return !RB_EMPTY_ROOT(&rq->dl.pushable_dl_tasks_root);
207 }
208 
209 static int push_dl_task(struct rq *rq);
210 
211 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
212 {
213         return dl_task(prev);
214 }
215 
216 static inline void set_post_schedule(struct rq *rq)
217 {
218         rq->post_schedule = has_pushable_dl_tasks(rq);
219 }
220 
221 #else
222 
223 static inline
224 void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
225 {
226 }
227 
228 static inline
229 void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)
230 {
231 }
232 
233 static inline
234 void inc_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
235 {
236 }
237 
238 static inline
239 void dec_dl_migration(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
240 {
241 }
242 
243 static inline bool need_pull_dl_task(struct rq *rq, struct task_struct *prev)
244 {
245         return false;
246 }
247 
248 static inline int pull_dl_task(struct rq *rq)
249 {
250         return 0;
251 }
252 
253 static inline void set_post_schedule(struct rq *rq)
254 {
255 }
256 #endif /* CONFIG_SMP */
257 
258 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags);
259 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags);
260 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
261                                   int flags);
262 
263 /*
264  * We are being explicitly informed that a new instance is starting,
265  * and this means that:
266  *  - the absolute deadline of the entity has to be placed at
267  *    current time + relative deadline;
268  *  - the runtime of the entity has to be set to the maximum value.
269  *
270  * The capability of specifying such event is useful whenever a -deadline
271  * entity wants to (try to!) synchronize its behaviour with the scheduler's
272  * one, and to (try to!) reconcile itself with its own scheduling
273  * parameters.
274  */
275 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se,
276                                        struct sched_dl_entity *pi_se)
277 {
278         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
279         struct rq *rq = rq_of_dl_rq(dl_rq);
280 
281         WARN_ON(!dl_se->dl_new || dl_se->dl_throttled);
282 
283         /*
284          * We use the regular wall clock time to set deadlines in the
285          * future; in fact, we must consider execution overheads (time
286          * spent on hardirq context, etc.).
287          */
288         dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
289         dl_se->runtime = pi_se->dl_runtime;
290         dl_se->dl_new = 0;
291 }
292 
293 /*
294  * Pure Earliest Deadline First (EDF) scheduling does not deal with the
295  * possibility of a entity lasting more than what it declared, and thus
296  * exhausting its runtime.
297  *
298  * Here we are interested in making runtime overrun possible, but we do
299  * not want a entity which is misbehaving to affect the scheduling of all
300  * other entities.
301  * Therefore, a budgeting strategy called Constant Bandwidth Server (CBS)
302  * is used, in order to confine each entity within its own bandwidth.
303  *
304  * This function deals exactly with that, and ensures that when the runtime
305  * of a entity is replenished, its deadline is also postponed. That ensures
306  * the overrunning entity can't interfere with other entity in the system and
307  * can't make them miss their deadlines. Reasons why this kind of overruns
308  * could happen are, typically, a entity voluntarily trying to overcome its
309  * runtime, or it just underestimated it during sched_setattr().
310  */
311 static void replenish_dl_entity(struct sched_dl_entity *dl_se,
312                                 struct sched_dl_entity *pi_se)
313 {
314         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
315         struct rq *rq = rq_of_dl_rq(dl_rq);
316 
317         BUG_ON(pi_se->dl_runtime <= 0);
318 
319         /*
320          * This could be the case for a !-dl task that is boosted.
321          * Just go with full inherited parameters.
322          */
323         if (dl_se->dl_deadline == 0) {
324                 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
325                 dl_se->runtime = pi_se->dl_runtime;
326         }
327 
328         /*
329          * We keep moving the deadline away until we get some
330          * available runtime for the entity. This ensures correct
331          * handling of situations where the runtime overrun is
332          * arbitrary large.
333          */
334         while (dl_se->runtime <= 0) {
335                 dl_se->deadline += pi_se->dl_period;
336                 dl_se->runtime += pi_se->dl_runtime;
337         }
338 
339         /*
340          * At this point, the deadline really should be "in
341          * the future" with respect to rq->clock. If it's
342          * not, we are, for some reason, lagging too much!
343          * Anyway, after having warn userspace abut that,
344          * we still try to keep the things running by
345          * resetting the deadline and the budget of the
346          * entity.
347          */
348         if (dl_time_before(dl_se->deadline, rq_clock(rq))) {
349                 printk_deferred_once("sched: DL replenish lagged to much\n");
350                 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
351                 dl_se->runtime = pi_se->dl_runtime;
352         }
353 
354         if (dl_se->dl_yielded)
355                 dl_se->dl_yielded = 0;
356         if (dl_se->dl_throttled)
357                 dl_se->dl_throttled = 0;
358 }
359 
360 /*
361  * Here we check if --at time t-- an entity (which is probably being
362  * [re]activated or, in general, enqueued) can use its remaining runtime
363  * and its current deadline _without_ exceeding the bandwidth it is
364  * assigned (function returns true if it can't). We are in fact applying
365  * one of the CBS rules: when a task wakes up, if the residual runtime
366  * over residual deadline fits within the allocated bandwidth, then we
367  * can keep the current (absolute) deadline and residual budget without
368  * disrupting the schedulability of the system. Otherwise, we should
369  * refill the runtime and set the deadline a period in the future,
370  * because keeping the current (absolute) deadline of the task would
371  * result in breaking guarantees promised to other tasks (refer to
372  * Documentation/scheduler/sched-deadline.txt for more informations).
373  *
374  * This function returns true if:
375  *
376  *   runtime / (deadline - t) > dl_runtime / dl_period ,
377  *
378  * IOW we can't recycle current parameters.
379  *
380  * Notice that the bandwidth check is done against the period. For
381  * task with deadline equal to period this is the same of using
382  * dl_deadline instead of dl_period in the equation above.
383  */
384 static bool dl_entity_overflow(struct sched_dl_entity *dl_se,
385                                struct sched_dl_entity *pi_se, u64 t)
386 {
387         u64 left, right;
388 
389         /*
390          * left and right are the two sides of the equation above,
391          * after a bit of shuffling to use multiplications instead
392          * of divisions.
393          *
394          * Note that none of the time values involved in the two
395          * multiplications are absolute: dl_deadline and dl_runtime
396          * are the relative deadline and the maximum runtime of each
397          * instance, runtime is the runtime left for the last instance
398          * and (deadline - t), since t is rq->clock, is the time left
399          * to the (absolute) deadline. Even if overflowing the u64 type
400          * is very unlikely to occur in both cases, here we scale down
401          * as we want to avoid that risk at all. Scaling down by 10
402          * means that we reduce granularity to 1us. We are fine with it,
403          * since this is only a true/false check and, anyway, thinking
404          * of anything below microseconds resolution is actually fiction
405          * (but still we want to give the user that illusion >;).
406          */
407         left = (pi_se->dl_period >> DL_SCALE) * (dl_se->runtime >> DL_SCALE);
408         right = ((dl_se->deadline - t) >> DL_SCALE) *
409                 (pi_se->dl_runtime >> DL_SCALE);
410 
411         return dl_time_before(right, left);
412 }
413 
414 /*
415  * When a -deadline entity is queued back on the runqueue, its runtime and
416  * deadline might need updating.
417  *
418  * The policy here is that we update the deadline of the entity only if:
419  *  - the current deadline is in the past,
420  *  - using the remaining runtime with the current deadline would make
421  *    the entity exceed its bandwidth.
422  */
423 static void update_dl_entity(struct sched_dl_entity *dl_se,
424                              struct sched_dl_entity *pi_se)
425 {
426         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
427         struct rq *rq = rq_of_dl_rq(dl_rq);
428 
429         /*
430          * The arrival of a new instance needs special treatment, i.e.,
431          * the actual scheduling parameters have to be "renewed".
432          */
433         if (dl_se->dl_new) {
434                 setup_new_dl_entity(dl_se, pi_se);
435                 return;
436         }
437 
438         if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
439             dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
440                 dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
441                 dl_se->runtime = pi_se->dl_runtime;
442         }
443 }
444 
445 /*
446  * If the entity depleted all its runtime, and if we want it to sleep
447  * while waiting for some new execution time to become available, we
448  * set the bandwidth enforcement timer to the replenishment instant
449  * and try to activate it.
450  *
451  * Notice that it is important for the caller to know if the timer
452  * actually started or not (i.e., the replenishment instant is in
453  * the future or in the past).
454  */
455 static int start_dl_timer(struct sched_dl_entity *dl_se, bool boosted)
456 {
457         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
458         struct rq *rq = rq_of_dl_rq(dl_rq);
459         ktime_t now, act;
460         ktime_t soft, hard;
461         unsigned long range;
462         s64 delta;
463 
464         if (boosted)
465                 return 0;
466         /*
467          * We want the timer to fire at the deadline, but considering
468          * that it is actually coming from rq->clock and not from
469          * hrtimer's time base reading.
470          */
471         act = ns_to_ktime(dl_se->deadline);
472         now = hrtimer_cb_get_time(&dl_se->dl_timer);
473         delta = ktime_to_ns(now) - rq_clock(rq);
474         act = ktime_add_ns(act, delta);
475 
476         /*
477          * If the expiry time already passed, e.g., because the value
478          * chosen as the deadline is too small, don't even try to
479          * start the timer in the past!
480          */
481         if (ktime_us_delta(act, now) < 0)
482                 return 0;
483 
484         hrtimer_set_expires(&dl_se->dl_timer, act);
485 
486         soft = hrtimer_get_softexpires(&dl_se->dl_timer);
487         hard = hrtimer_get_expires(&dl_se->dl_timer);
488         range = ktime_to_ns(ktime_sub(hard, soft));
489         __hrtimer_start_range_ns(&dl_se->dl_timer, soft,
490                                  range, HRTIMER_MODE_ABS, 0);
491 
492         return hrtimer_active(&dl_se->dl_timer);
493 }
494 
495 /*
496  * This is the bandwidth enforcement timer callback. If here, we know
497  * a task is not on its dl_rq, since the fact that the timer was running
498  * means the task is throttled and needs a runtime replenishment.
499  *
500  * However, what we actually do depends on the fact the task is active,
501  * (it is on its rq) or has been removed from there by a call to
502  * dequeue_task_dl(). In the former case we must issue the runtime
503  * replenishment and add the task back to the dl_rq; in the latter, we just
504  * do nothing but clearing dl_throttled, so that runtime and deadline
505  * updating (and the queueing back to dl_rq) will be done by the
506  * next call to enqueue_task_dl().
507  */
508 static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
509 {
510         struct sched_dl_entity *dl_se = container_of(timer,
511                                                      struct sched_dl_entity,
512                                                      dl_timer);
513         struct task_struct *p = dl_task_of(dl_se);
514         unsigned long flags;
515         struct rq *rq;
516 
517         rq = task_rq_lock(p, &flags);
518 
519         /*
520          * We need to take care of several possible races here:
521          *
522          *   - the task might have changed its scheduling policy
523          *     to something different than SCHED_DEADLINE
524          *   - the task might have changed its reservation parameters
525          *     (through sched_setattr())
526          *   - the task might have been boosted by someone else and
527          *     might be in the boosting/deboosting path
528          *
529          * In all this cases we bail out, as the task is already
530          * in the runqueue or is going to be enqueued back anyway.
531          */
532         if (!dl_task(p) || dl_se->dl_new ||
533             dl_se->dl_boosted || !dl_se->dl_throttled)
534                 goto unlock;
535 
536         sched_clock_tick();
537         update_rq_clock(rq);
538 
539         /*
540          * If the throttle happened during sched-out; like:
541          *
542          *   schedule()
543          *     deactivate_task()
544          *       dequeue_task_dl()
545          *         update_curr_dl()
546          *           start_dl_timer()
547          *         __dequeue_task_dl()
548          *     prev->on_rq = 0;
549          *
550          * We can be both throttled and !queued. Replenish the counter
551          * but do not enqueue -- wait for our wakeup to do that.
552          */
553         if (!task_on_rq_queued(p)) {
554                 replenish_dl_entity(dl_se, dl_se);
555                 goto unlock;
556         }
557 
558         enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
559         if (dl_task(rq->curr))
560                 check_preempt_curr_dl(rq, p, 0);
561         else
562                 resched_curr(rq);
563 #ifdef CONFIG_SMP
564         /*
565          * Queueing this task back might have overloaded rq,
566          * check if we need to kick someone away.
567          */
568         if (has_pushable_dl_tasks(rq))
569                 push_dl_task(rq);
570 #endif
571 unlock:
572         task_rq_unlock(rq, p, &flags);
573 
574         return HRTIMER_NORESTART;
575 }
576 
577 void init_dl_task_timer(struct sched_dl_entity *dl_se)
578 {
579         struct hrtimer *timer = &dl_se->dl_timer;
580 
581         hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
582         timer->function = dl_task_timer;
583 }
584 
585 static
586 int dl_runtime_exceeded(struct rq *rq, struct sched_dl_entity *dl_se)
587 {
588         return (dl_se->runtime <= 0);
589 }
590 
591 extern bool sched_rt_bandwidth_account(struct rt_rq *rt_rq);
592 
593 /*
594  * Update the current task's runtime statistics (provided it is still
595  * a -deadline task and has not been removed from the dl_rq).
596  */
597 static void update_curr_dl(struct rq *rq)
598 {
599         struct task_struct *curr = rq->curr;
600         struct sched_dl_entity *dl_se = &curr->dl;
601         u64 delta_exec;
602 
603         if (!dl_task(curr) || !on_dl_rq(dl_se))
604                 return;
605 
606         /*
607          * Consumed budget is computed considering the time as
608          * observed by schedulable tasks (excluding time spent
609          * in hardirq context, etc.). Deadlines are instead
610          * computed using hard walltime. This seems to be the more
611          * natural solution, but the full ramifications of this
612          * approach need further study.
613          */
614         delta_exec = rq_clock_task(rq) - curr->se.exec_start;
615         if (unlikely((s64)delta_exec <= 0))
616                 return;
617 
618         schedstat_set(curr->se.statistics.exec_max,
619                       max(curr->se.statistics.exec_max, delta_exec));
620 
621         curr->se.sum_exec_runtime += delta_exec;
622         account_group_exec_runtime(curr, delta_exec);
623 
624         curr->se.exec_start = rq_clock_task(rq);
625         cpuacct_charge(curr, delta_exec);
626 
627         sched_rt_avg_update(rq, delta_exec);
628 
629         dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec;
630         if (dl_runtime_exceeded(rq, dl_se)) {
631                 dl_se->dl_throttled = 1;
632                 __dequeue_task_dl(rq, curr, 0);
633                 if (unlikely(!start_dl_timer(dl_se, curr->dl.dl_boosted)))
634                         enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);
635 
636                 if (!is_leftmost(curr, &rq->dl))
637                         resched_curr(rq);
638         }
639 
640         /*
641          * Because -- for now -- we share the rt bandwidth, we need to
642          * account our runtime there too, otherwise actual rt tasks
643          * would be able to exceed the shared quota.
644          *
645          * Account to the root rt group for now.
646          *
647          * The solution we're working towards is having the RT groups scheduled
648          * using deadline servers -- however there's a few nasties to figure
649          * out before that can happen.
650          */
651         if (rt_bandwidth_enabled()) {
652                 struct rt_rq *rt_rq = &rq->rt;
653 
654                 raw_spin_lock(&rt_rq->rt_runtime_lock);
655                 /*
656                  * We'll let actual RT tasks worry about the overflow here, we
657                  * have our own CBS to keep us inline; only account when RT
658                  * bandwidth is relevant.
659                  */
660                 if (sched_rt_bandwidth_account(rt_rq))
661                         rt_rq->rt_time += delta_exec;
662                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
663         }
664 }
665 
666 #ifdef CONFIG_SMP
667 
668 static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
669 
670 static inline u64 next_deadline(struct rq *rq)
671 {
672         struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
673 
674         if (next && dl_prio(next->prio))
675                 return next->dl.deadline;
676         else
677                 return 0;
678 }
679 
680 static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
681 {
682         struct rq *rq = rq_of_dl_rq(dl_rq);
683 
684         if (dl_rq->earliest_dl.curr == 0 ||
685             dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
686                 /*
687                  * If the dl_rq had no -deadline tasks, or if the new task
688                  * has shorter deadline than the current one on dl_rq, we
689                  * know that the previous earliest becomes our next earliest,
690                  * as the new task becomes the earliest itself.
691                  */
692                 dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
693                 dl_rq->earliest_dl.curr = deadline;
694                 cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
695         } else if (dl_rq->earliest_dl.next == 0 ||
696                    dl_time_before(deadline, dl_rq->earliest_dl.next)) {
697                 /*
698                  * On the other hand, if the new -deadline task has a
699                  * a later deadline than the earliest one on dl_rq, but
700                  * it is earlier than the next (if any), we must
701                  * recompute the next-earliest.
702                  */
703                 dl_rq->earliest_dl.next = next_deadline(rq);
704         }
705 }
706 
707 static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
708 {
709         struct rq *rq = rq_of_dl_rq(dl_rq);
710 
711         /*
712          * Since we may have removed our earliest (and/or next earliest)
713          * task we must recompute them.
714          */
715         if (!dl_rq->dl_nr_running) {
716                 dl_rq->earliest_dl.curr = 0;
717                 dl_rq->earliest_dl.next = 0;
718                 cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
719         } else {
720                 struct rb_node *leftmost = dl_rq->rb_leftmost;
721                 struct sched_dl_entity *entry;
722 
723                 entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
724                 dl_rq->earliest_dl.curr = entry->deadline;
725                 dl_rq->earliest_dl.next = next_deadline(rq);
726                 cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
727         }
728 }
729 
730 #else
731 
732 static inline void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
733 static inline void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline) {}
734 
735 #endif /* CONFIG_SMP */
736 
737 static inline
738 void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
739 {
740         int prio = dl_task_of(dl_se)->prio;
741         u64 deadline = dl_se->deadline;
742 
743         WARN_ON(!dl_prio(prio));
744         dl_rq->dl_nr_running++;
745         add_nr_running(rq_of_dl_rq(dl_rq), 1);
746 
747         inc_dl_deadline(dl_rq, deadline);
748         inc_dl_migration(dl_se, dl_rq);
749 }
750 
751 static inline
752 void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
753 {
754         int prio = dl_task_of(dl_se)->prio;
755 
756         WARN_ON(!dl_prio(prio));
757         WARN_ON(!dl_rq->dl_nr_running);
758         dl_rq->dl_nr_running--;
759         sub_nr_running(rq_of_dl_rq(dl_rq), 1);
760 
761         dec_dl_deadline(dl_rq, dl_se->deadline);
762         dec_dl_migration(dl_se, dl_rq);
763 }
764 
765 static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
766 {
767         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
768         struct rb_node **link = &dl_rq->rb_root.rb_node;
769         struct rb_node *parent = NULL;
770         struct sched_dl_entity *entry;
771         int leftmost = 1;
772 
773         BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
774 
775         while (*link) {
776                 parent = *link;
777                 entry = rb_entry(parent, struct sched_dl_entity, rb_node);
778                 if (dl_time_before(dl_se->deadline, entry->deadline))
779                         link = &parent->rb_left;
780                 else {
781                         link = &parent->rb_right;
782                         leftmost = 0;
783                 }
784         }
785 
786         if (leftmost)
787                 dl_rq->rb_leftmost = &dl_se->rb_node;
788 
789         rb_link_node(&dl_se->rb_node, parent, link);
790         rb_insert_color(&dl_se->rb_node, &dl_rq->rb_root);
791 
792         inc_dl_tasks(dl_se, dl_rq);
793 }
794 
795 static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
796 {
797         struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
798 
799         if (RB_EMPTY_NODE(&dl_se->rb_node))
800                 return;
801 
802         if (dl_rq->rb_leftmost == &dl_se->rb_node) {
803                 struct rb_node *next_node;
804 
805                 next_node = rb_next(&dl_se->rb_node);
806                 dl_rq->rb_leftmost = next_node;
807         }
808 
809         rb_erase(&dl_se->rb_node, &dl_rq->rb_root);
810         RB_CLEAR_NODE(&dl_se->rb_node);
811 
812         dec_dl_tasks(dl_se, dl_rq);
813 }
814 
815 static void
816 enqueue_dl_entity(struct sched_dl_entity *dl_se,
817                   struct sched_dl_entity *pi_se, int flags)
818 {
819         BUG_ON(on_dl_rq(dl_se));
820 
821         /*
822          * If this is a wakeup or a new instance, the scheduling
823          * parameters of the task might need updating. Otherwise,
824          * we want a replenishment of its runtime.
825          */
826         if (dl_se->dl_new || flags & ENQUEUE_WAKEUP)
827                 update_dl_entity(dl_se, pi_se);
828         else if (flags & ENQUEUE_REPLENISH)
829                 replenish_dl_entity(dl_se, pi_se);
830 
831         __enqueue_dl_entity(dl_se);
832 }
833 
834 static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
835 {
836         __dequeue_dl_entity(dl_se);
837 }
838 
839 static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
840 {
841         struct task_struct *pi_task = rt_mutex_get_top_task(p);
842         struct sched_dl_entity *pi_se = &p->dl;
843 
844         /*
845          * Use the scheduling parameters of the top pi-waiter
846          * task if we have one and its (relative) deadline is
847          * smaller than our one... OTW we keep our runtime and
848          * deadline.
849          */
850         if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio)) {
851                 pi_se = &pi_task->dl;
852         } else if (!dl_prio(p->normal_prio)) {
853                 /*
854                  * Special case in which we have a !SCHED_DEADLINE task
855                  * that is going to be deboosted, but exceedes its
856                  * runtime while doing so. No point in replenishing
857                  * it, as it's going to return back to its original
858                  * scheduling class after this.
859                  */
860                 BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
861                 return;
862         }
863 
864         /*
865          * If p is throttled, we do nothing. In fact, if it exhausted
866          * its budget it needs a replenishment and, since it now is on
867          * its rq, the bandwidth timer callback (which clearly has not
868          * run yet) will take care of this.
869          */
870         if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))
871                 return;
872 
873         enqueue_dl_entity(&p->dl, pi_se, flags);
874 
875         if (!task_current(rq, p) && p->nr_cpus_allowed > 1)
876                 enqueue_pushable_dl_task(rq, p);
877 }
878 
879 static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
880 {
881         dequeue_dl_entity(&p->dl);
882         dequeue_pushable_dl_task(rq, p);
883 }
884 
885 static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
886 {
887         update_curr_dl(rq);
888         __dequeue_task_dl(rq, p, flags);
889 }
890 
891 /*
892  * Yield task semantic for -deadline tasks is:
893  *
894  *   get off from the CPU until our next instance, with
895  *   a new runtime. This is of little use now, since we
896  *   don't have a bandwidth reclaiming mechanism. Anyway,
897  *   bandwidth reclaiming is planned for the future, and
898  *   yield_task_dl will indicate that some spare budget
899  *   is available for other task instances to use it.
900  */
901 static void yield_task_dl(struct rq *rq)
902 {
903         struct task_struct *p = rq->curr;
904 
905         /*
906          * We make the task go to sleep until its current deadline by
907          * forcing its runtime to zero. This way, update_curr_dl() stops
908          * it and the bandwidth timer will wake it up and will give it
909          * new scheduling parameters (thanks to dl_yielded=1).
910          */
911         if (p->dl.runtime > 0) {
912                 rq->curr->dl.dl_yielded = 1;
913                 p->dl.runtime = 0;
914         }
915         update_rq_clock(rq);
916         update_curr_dl(rq);
917 }
918 
919 #ifdef CONFIG_SMP
920 
921 static int find_later_rq(struct task_struct *task);
922 
923 static int
924 select_task_rq_dl(struct task_struct *p, int cpu, int sd_flag, int flags)
925 {
926         struct task_struct *curr;
927         struct rq *rq;
928 
929         if (sd_flag != SD_BALANCE_WAKE)
930                 goto out;
931 
932         rq = cpu_rq(cpu);
933 
934         rcu_read_lock();
935         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
936 
937         /*
938          * If we are dealing with a -deadline task, we must
939          * decide where to wake it up.
940          * If it has a later deadline and the current task
941          * on this rq can't move (provided the waking task
942          * can!) we prefer to send it somewhere else. On the
943          * other hand, if it has a shorter deadline, we
944          * try to make it stay here, it might be important.
945          */
946         if (unlikely(dl_task(curr)) &&
947             (curr->nr_cpus_allowed < 2 ||
948              !dl_entity_preempt(&p->dl, &curr->dl)) &&
949             (p->nr_cpus_allowed > 1)) {
950                 int target = find_later_rq(p);
951 
952                 if (target != -1)
953                         cpu = target;
954         }
955         rcu_read_unlock();
956 
957 out:
958         return cpu;
959 }
960 
961 static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
962 {
963         /*
964          * Current can't be migrated, useless to reschedule,
965          * let's hope p can move out.
966          */
967         if (rq->curr->nr_cpus_allowed == 1 ||
968             cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
969                 return;
970 
971         /*
972          * p is migratable, so let's not schedule it and
973          * see if it is pushed or pulled somewhere else.
974          */
975         if (p->nr_cpus_allowed != 1 &&
976             cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
977                 return;
978 
979         resched_curr(rq);
980 }
981 
982 static int pull_dl_task(struct rq *this_rq);
983 
984 #endif /* CONFIG_SMP */
985 
986 /*
987  * Only called when both the current and waking task are -deadline
988  * tasks.
989  */
990 static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
991                                   int flags)
992 {
993         if (dl_entity_preempt(&p->dl, &rq->curr->dl)) {
994                 resched_curr(rq);
995                 return;
996         }
997 
998 #ifdef CONFIG_SMP
999         /*
1000          * In the unlikely case current and p have the same deadline
1001          * let us try to decide what's the best thing to do...
1002          */
1003         if ((p->dl.deadline == rq->curr->dl.deadline) &&
1004             !test_tsk_need_resched(rq->curr))
1005                 check_preempt_equal_dl(rq, p);
1006 #endif /* CONFIG_SMP */
1007 }
1008 
1009 #ifdef CONFIG_SCHED_HRTICK
1010 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1011 {
1012         hrtick_start(rq, p->dl.runtime);
1013 }
1014 #else /* !CONFIG_SCHED_HRTICK */
1015 static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
1016 {
1017 }
1018 #endif
1019 
1020 static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
1021                                                    struct dl_rq *dl_rq)
1022 {
1023         struct rb_node *left = dl_rq->rb_leftmost;
1024 
1025         if (!left)
1026                 return NULL;
1027 
1028         return rb_entry(left, struct sched_dl_entity, rb_node);
1029 }
1030 
1031 struct task_struct *pick_next_task_dl(struct rq *rq, struct task_struct *prev)
1032 {
1033         struct sched_dl_entity *dl_se;
1034         struct task_struct *p;
1035         struct dl_rq *dl_rq;
1036 
1037         dl_rq = &rq->dl;
1038 
1039         if (need_pull_dl_task(rq, prev)) {
1040                 pull_dl_task(rq);
1041                 /*
1042                  * pull_rt_task() can drop (and re-acquire) rq->lock; this
1043                  * means a stop task can slip in, in which case we need to
1044                  * re-start task selection.
1045                  */
1046                 if (rq->stop && task_on_rq_queued(rq->stop))
1047                         return RETRY_TASK;
1048         }
1049 
1050         /*
1051          * When prev is DL, we may throttle it in put_prev_task().
1052          * So, we update time before we check for dl_nr_running.
1053          */
1054         if (prev->sched_class == &dl_sched_class)
1055                 update_curr_dl(rq);
1056 
1057         if (unlikely(!dl_rq->dl_nr_running))
1058                 return NULL;
1059 
1060         put_prev_task(rq, prev);
1061 
1062         dl_se = pick_next_dl_entity(rq, dl_rq);
1063         BUG_ON(!dl_se);
1064 
1065         p = dl_task_of(dl_se);
1066         p->se.exec_start = rq_clock_task(rq);
1067 
1068         /* Running task will never be pushed. */
1069        dequeue_pushable_dl_task(rq, p);
1070 
1071         if (hrtick_enabled(rq))
1072                 start_hrtick_dl(rq, p);
1073 
1074         set_post_schedule(rq);
1075 
1076         return p;
1077 }
1078 
1079 static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
1080 {
1081         update_curr_dl(rq);
1082 
1083         if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
1084                 enqueue_pushable_dl_task(rq, p);
1085 }
1086 
1087 static void task_tick_dl(struct rq *rq, struct task_struct *p, int queued)
1088 {
1089         update_curr_dl(rq);
1090 
1091         /*
1092          * Even when we have runtime, update_curr_dl() might have resulted in us
1093          * not being the leftmost task anymore. In that case NEED_RESCHED will
1094          * be set and schedule() will start a new hrtick for the next task.
1095          */
1096         if (hrtick_enabled(rq) && queued && p->dl.runtime > 0 &&
1097             is_leftmost(p, &rq->dl))
1098                 start_hrtick_dl(rq, p);
1099 }
1100 
1101 static void task_fork_dl(struct task_struct *p)
1102 {
1103         /*
1104          * SCHED_DEADLINE tasks cannot fork and this is achieved through
1105          * sched_fork()
1106          */
1107 }
1108 
1109 static void task_dead_dl(struct task_struct *p)
1110 {
1111         struct hrtimer *timer = &p->dl.dl_timer;
1112         struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
1113 
1114         /*
1115          * Since we are TASK_DEAD we won't slip out of the domain!
1116          */
1117         raw_spin_lock_irq(&dl_b->lock);
1118         /* XXX we should retain the bw until 0-lag */
1119         dl_b->total_bw -= p->dl.dl_bw;
1120         raw_spin_unlock_irq(&dl_b->lock);
1121 
1122         hrtimer_cancel(timer);
1123 }
1124 
1125 static void set_curr_task_dl(struct rq *rq)
1126 {
1127         struct task_struct *p = rq->curr;
1128 
1129         p->se.exec_start = rq_clock_task(rq);
1130 
1131         /* You can't push away the running task */
1132         dequeue_pushable_dl_task(rq, p);
1133 }
1134 
1135 #ifdef CONFIG_SMP
1136 
1137 /* Only try algorithms three times */
1138 #define DL_MAX_TRIES 3
1139 
1140 static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
1141 {
1142         if (!task_running(rq, p) &&
1143             cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
1144                 return 1;
1145         return 0;
1146 }
1147 
1148 /* Returns the second earliest -deadline task, NULL otherwise */
1149 static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
1150 {
1151         struct rb_node *next_node = rq->dl.rb_leftmost;
1152         struct sched_dl_entity *dl_se;
1153         struct task_struct *p = NULL;
1154 
1155 next_node:
1156         next_node = rb_next(next_node);
1157         if (next_node) {
1158                 dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
1159                 p = dl_task_of(dl_se);
1160 
1161                 if (pick_dl_task(rq, p, cpu))
1162                         return p;
1163 
1164                 goto next_node;
1165         }
1166 
1167         return NULL;
1168 }
1169 
1170 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
1171 
1172 static int find_later_rq(struct task_struct *task)
1173 {
1174         struct sched_domain *sd;
1175         struct cpumask *later_mask = this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
1176         int this_cpu = smp_processor_id();
1177         int best_cpu, cpu = task_cpu(task);
1178 
1179         /* Make sure the mask is initialized first */
1180         if (unlikely(!later_mask))
1181                 return -1;
1182 
1183         if (task->nr_cpus_allowed == 1)
1184                 return -1;
1185 
1186         /*
1187          * We have to consider system topology and task affinity
1188          * first, then we can look for a suitable cpu.
1189          */
1190         best_cpu = cpudl_find(&task_rq(task)->rd->cpudl,
1191                         task, later_mask);
1192         if (best_cpu == -1)
1193                 return -1;
1194 
1195         /*
1196          * If we are here, some target has been found,
1197          * the most suitable of which is cached in best_cpu.
1198          * This is, among the runqueues where the current tasks
1199          * have later deadlines than the task's one, the rq
1200          * with the latest possible one.
1201          *
1202          * Now we check how well this matches with task's
1203          * affinity and system topology.
1204          *
1205          * The last cpu where the task run is our first
1206          * guess, since it is most likely cache-hot there.
1207          */
1208         if (cpumask_test_cpu(cpu, later_mask))
1209                 return cpu;
1210         /*
1211          * Check if this_cpu is to be skipped (i.e., it is
1212          * not in the mask) or not.
1213          */
1214         if (!cpumask_test_cpu(this_cpu, later_mask))
1215                 this_cpu = -1;
1216 
1217         rcu_read_lock();
1218         for_each_domain(cpu, sd) {
1219                 if (sd->flags & SD_WAKE_AFFINE) {
1220 
1221                         /*
1222                          * If possible, preempting this_cpu is
1223                          * cheaper than migrating.
1224                          */
1225                         if (this_cpu != -1 &&
1226                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1227                                 rcu_read_unlock();
1228                                 return this_cpu;
1229                         }
1230 
1231                         /*
1232                          * Last chance: if best_cpu is valid and is
1233                          * in the mask, that becomes our choice.
1234                          */
1235                         if (best_cpu < nr_cpu_ids &&
1236                             cpumask_test_cpu(best_cpu, sched_domain_span(sd))) {
1237                                 rcu_read_unlock();
1238                                 return best_cpu;
1239                         }
1240                 }
1241         }
1242         rcu_read_unlock();
1243 
1244         /*
1245          * At this point, all our guesses failed, we just return
1246          * 'something', and let the caller sort the things out.
1247          */
1248         if (this_cpu != -1)
1249                 return this_cpu;
1250 
1251         cpu = cpumask_any(later_mask);
1252         if (cpu < nr_cpu_ids)
1253                 return cpu;
1254 
1255         return -1;
1256 }
1257 
1258 /* Locks the rq it finds */
1259 static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
1260 {
1261         struct rq *later_rq = NULL;
1262         int tries;
1263         int cpu;
1264 
1265         for (tries = 0; tries < DL_MAX_TRIES; tries++) {
1266                 cpu = find_later_rq(task);
1267 
1268                 if ((cpu == -1) || (cpu == rq->cpu))
1269                         break;
1270 
1271                 later_rq = cpu_rq(cpu);
1272 
1273                 /* Retry if something changed. */
1274                 if (double_lock_balance(rq, later_rq)) {
1275                         if (unlikely(task_rq(task) != rq ||
1276                                      !cpumask_test_cpu(later_rq->cpu,
1277                                                        &task->cpus_allowed) ||
1278                                      task_running(rq, task) ||
1279                                      !task_on_rq_queued(task))) {
1280                                 double_unlock_balance(rq, later_rq);
1281                                 later_rq = NULL;
1282                                 break;
1283                         }
1284                 }
1285 
1286                 /*
1287                  * If the rq we found has no -deadline task, or
1288                  * its earliest one has a later deadline than our
1289                  * task, the rq is a good one.
1290                  */
1291                 if (!later_rq->dl.dl_nr_running ||
1292                     dl_time_before(task->dl.deadline,
1293                                    later_rq->dl.earliest_dl.curr))
1294                         break;
1295 
1296                 /* Otherwise we try again. */
1297                 double_unlock_balance(rq, later_rq);
1298                 later_rq = NULL;
1299         }
1300 
1301         return later_rq;
1302 }
1303 
1304 static struct task_struct *pick_next_pushable_dl_task(struct rq *rq)
1305 {
1306         struct task_struct *p;
1307 
1308         if (!has_pushable_dl_tasks(rq))
1309                 return NULL;
1310 
1311         p = rb_entry(rq->dl.pushable_dl_tasks_leftmost,
1312                      struct task_struct, pushable_dl_tasks);
1313 
1314         BUG_ON(rq->cpu != task_cpu(p));
1315         BUG_ON(task_current(rq, p));
1316         BUG_ON(p->nr_cpus_allowed <= 1);
1317 
1318         BUG_ON(!task_on_rq_queued(p));
1319         BUG_ON(!dl_task(p));
1320 
1321         return p;
1322 }
1323 
1324 /*
1325  * See if the non running -deadline tasks on this rq
1326  * can be sent to some other CPU where they can preempt
1327  * and start executing.
1328  */
1329 static int push_dl_task(struct rq *rq)
1330 {
1331         struct task_struct *next_task;
1332         struct rq *later_rq;
1333         int ret = 0;
1334 
1335         if (!rq->dl.overloaded)
1336                 return 0;
1337 
1338         next_task = pick_next_pushable_dl_task(rq);
1339         if (!next_task)
1340                 return 0;
1341 
1342 retry:
1343         if (unlikely(next_task == rq->curr)) {
1344                 WARN_ON(1);
1345                 return 0;
1346         }
1347 
1348         /*
1349          * If next_task preempts rq->curr, and rq->curr
1350          * can move away, it makes sense to just reschedule
1351          * without going further in pushing next_task.
1352          */
1353         if (dl_task(rq->curr) &&
1354             dl_time_before(next_task->dl.deadline, rq->curr->dl.deadline) &&
1355             rq->curr->nr_cpus_allowed > 1) {
1356                 resched_curr(rq);
1357                 return 0;
1358         }
1359 
1360         /* We might release rq lock */
1361         get_task_struct(next_task);
1362 
1363         /* Will lock the rq it'll find */
1364         later_rq = find_lock_later_rq(next_task, rq);
1365         if (!later_rq) {
1366                 struct task_struct *task;
1367 
1368                 /*
1369                  * We must check all this again, since
1370                  * find_lock_later_rq releases rq->lock and it is
1371                  * then possible that next_task has migrated.
1372                  */
1373                 task = pick_next_pushable_dl_task(rq);
1374                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1375                         /*
1376                          * The task is still there. We don't try
1377                          * again, some other cpu will pull it when ready.
1378                          */
1379                         goto out;
1380                 }
1381 
1382                 if (!task)
1383                         /* No more tasks */
1384                         goto out;
1385 
1386                 put_task_struct(next_task);
1387                 next_task = task;
1388                 goto retry;
1389         }
1390 
1391         deactivate_task(rq, next_task, 0);
1392         set_task_cpu(next_task, later_rq->cpu);
1393         activate_task(later_rq, next_task, 0);
1394         ret = 1;
1395 
1396         resched_curr(later_rq);
1397 
1398         double_unlock_balance(rq, later_rq);
1399 
1400 out:
1401         put_task_struct(next_task);
1402 
1403         return ret;
1404 }
1405 
1406 static void push_dl_tasks(struct rq *rq)
1407 {
1408         /* Terminates as it moves a -deadline task */
1409         while (push_dl_task(rq))
1410                 ;
1411 }
1412 
1413 static int pull_dl_task(struct rq *this_rq)
1414 {
1415         int this_cpu = this_rq->cpu, ret = 0, cpu;
1416         struct task_struct *p;
1417         struct rq *src_rq;
1418         u64 dmin = LONG_MAX;
1419 
1420         if (likely(!dl_overloaded(this_rq)))
1421                 return 0;
1422 
1423         /*
1424          * Match the barrier from dl_set_overloaded; this guarantees that if we
1425          * see overloaded we must also see the dlo_mask bit.
1426          */
1427         smp_rmb();
1428 
1429         for_each_cpu(cpu, this_rq->rd->dlo_mask) {
1430                 if (this_cpu == cpu)
1431                         continue;
1432 
1433                 src_rq = cpu_rq(cpu);
1434 
1435                 /*
1436                  * It looks racy, abd it is! However, as in sched_rt.c,
1437                  * we are fine with this.
1438                  */
1439                 if (this_rq->dl.dl_nr_running &&
1440                     dl_time_before(this_rq->dl.earliest_dl.curr,
1441                                    src_rq->dl.earliest_dl.next))
1442                         continue;
1443 
1444                 /* Might drop this_rq->lock */
1445                 double_lock_balance(this_rq, src_rq);
1446 
1447                 /*
1448                  * If there are no more pullable tasks on the
1449                  * rq, we're done with it.
1450                  */
1451                 if (src_rq->dl.dl_nr_running <= 1)
1452                         goto skip;
1453 
1454                 p = pick_next_earliest_dl_task(src_rq, this_cpu);
1455 
1456                 /*
1457                  * We found a task to be pulled if:
1458                  *  - it preempts our current (if there's one),
1459                  *  - it will preempt the last one we pulled (if any).
1460                  */
1461                 if (p && dl_time_before(p->dl.deadline, dmin) &&
1462                     (!this_rq->dl.dl_nr_running ||
1463                      dl_time_before(p->dl.deadline,
1464                                     this_rq->dl.earliest_dl.curr))) {
1465                         WARN_ON(p == src_rq->curr);
1466                         WARN_ON(!task_on_rq_queued(p));
1467 
1468                         /*
1469                          * Then we pull iff p has actually an earlier
1470                          * deadline than the current task of its runqueue.
1471                          */
1472                         if (dl_time_before(p->dl.deadline,
1473                                            src_rq->curr->dl.deadline))
1474                                 goto skip;
1475 
1476                         ret = 1;
1477 
1478                         deactivate_task(src_rq, p, 0);
1479                         set_task_cpu(p, this_cpu);
1480                         activate_task(this_rq, p, 0);
1481                         dmin = p->dl.deadline;
1482 
1483                         /* Is there any other task even earlier? */
1484                 }
1485 skip:
1486                 double_unlock_balance(this_rq, src_rq);
1487         }
1488 
1489         return ret;
1490 }
1491 
1492 static void post_schedule_dl(struct rq *rq)
1493 {
1494         push_dl_tasks(rq);
1495 }
1496 
1497 /*
1498  * Since the task is not running and a reschedule is not going to happen
1499  * anytime soon on its runqueue, we try pushing it away now.
1500  */
1501 static void task_woken_dl(struct rq *rq, struct task_struct *p)
1502 {
1503         if (!task_running(rq, p) &&
1504             !test_tsk_need_resched(rq->curr) &&
1505             has_pushable_dl_tasks(rq) &&
1506             p->nr_cpus_allowed > 1 &&
1507             dl_task(rq->curr) &&
1508             (rq->curr->nr_cpus_allowed < 2 ||
1509              !dl_entity_preempt(&p->dl, &rq->curr->dl))) {
1510                 push_dl_tasks(rq);
1511         }
1512 }
1513 
1514 static void set_cpus_allowed_dl(struct task_struct *p,
1515                                 const struct cpumask *new_mask)
1516 {
1517         struct rq *rq;
1518         struct root_domain *src_rd;
1519         int weight;
1520 
1521         BUG_ON(!dl_task(p));
1522 
1523         rq = task_rq(p);
1524         src_rd = rq->rd;
1525         /*
1526          * Migrating a SCHED_DEADLINE task between exclusive
1527          * cpusets (different root_domains) entails a bandwidth
1528          * update. We already made space for us in the destination
1529          * domain (see cpuset_can_attach()).
1530          */
1531         if (!cpumask_intersects(src_rd->span, new_mask)) {
1532                 struct dl_bw *src_dl_b;
1533 
1534                 src_dl_b = dl_bw_of(cpu_of(rq));
1535                 /*
1536                  * We now free resources of the root_domain we are migrating
1537                  * off. In the worst case, sched_setattr() may temporary fail
1538                  * until we complete the update.
1539                  */
1540                 raw_spin_lock(&src_dl_b->lock);
1541                 __dl_clear(src_dl_b, p->dl.dl_bw);
1542                 raw_spin_unlock(&src_dl_b->lock);
1543         }
1544 
1545         /*
1546          * Update only if the task is actually running (i.e.,
1547          * it is on the rq AND it is not throttled).
1548          */
1549         if (!on_dl_rq(&p->dl))
1550                 return;
1551 
1552         weight = cpumask_weight(new_mask);
1553 
1554         /*
1555          * Only update if the process changes its state from whether it
1556          * can migrate or not.
1557          */
1558         if ((p->nr_cpus_allowed > 1) == (weight > 1))
1559                 return;
1560 
1561         /*
1562          * The process used to be able to migrate OR it can now migrate
1563          */
1564         if (weight <= 1) {
1565                 if (!task_current(rq, p))
1566                         dequeue_pushable_dl_task(rq, p);
1567                 BUG_ON(!rq->dl.dl_nr_migratory);
1568                 rq->dl.dl_nr_migratory--;
1569         } else {
1570                 if (!task_current(rq, p))
1571                         enqueue_pushable_dl_task(rq, p);
1572                 rq->dl.dl_nr_migratory++;
1573         }
1574 
1575         update_dl_migration(&rq->dl);
1576 }
1577 
1578 /* Assumes rq->lock is held */
1579 static void rq_online_dl(struct rq *rq)
1580 {
1581         if (rq->dl.overloaded)
1582                 dl_set_overload(rq);
1583 
1584         cpudl_set_freecpu(&rq->rd->cpudl, rq->cpu);
1585         if (rq->dl.dl_nr_running > 0)
1586                 cpudl_set(&rq->rd->cpudl, rq->cpu, rq->dl.earliest_dl.curr, 1);
1587 }
1588 
1589 /* Assumes rq->lock is held */
1590 static void rq_offline_dl(struct rq *rq)
1591 {
1592         if (rq->dl.overloaded)
1593                 dl_clear_overload(rq);
1594 
1595         cpudl_set(&rq->rd->cpudl, rq->cpu, 0, 0);
1596         cpudl_clear_freecpu(&rq->rd->cpudl, rq->cpu);
1597 }
1598 
1599 void init_sched_dl_class(void)
1600 {
1601         unsigned int i;
1602 
1603         for_each_possible_cpu(i)
1604                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask_dl, i),
1605                                         GFP_KERNEL, cpu_to_node(i));
1606 }
1607 
1608 #endif /* CONFIG_SMP */
1609 
1610 /*
1611  *  Ensure p's dl_timer is cancelled. May drop rq->lock for a while.
1612  */
1613 static void cancel_dl_timer(struct rq *rq, struct task_struct *p)
1614 {
1615         struct hrtimer *dl_timer = &p->dl.dl_timer;
1616 
1617         /* Nobody will change task's class if pi_lock is held */
1618         lockdep_assert_held(&p->pi_lock);
1619 
1620         if (hrtimer_active(dl_timer)) {
1621                 int ret = hrtimer_try_to_cancel(dl_timer);
1622 
1623                 if (unlikely(ret == -1)) {
1624                         /*
1625                          * Note, p may migrate OR new deadline tasks
1626                          * may appear in rq when we are unlocking it.
1627                          * A caller of us must be fine with that.
1628                          */
1629                         raw_spin_unlock(&rq->lock);
1630                         hrtimer_cancel(dl_timer);
1631                         raw_spin_lock(&rq->lock);
1632                 }
1633         }
1634 }
1635 
1636 static void switched_from_dl(struct rq *rq, struct task_struct *p)
1637 {
1638         /* XXX we should retain the bw until 0-lag */
1639         cancel_dl_timer(rq, p);
1640         __dl_clear_params(p);
1641 
1642         /*
1643          * Since this might be the only -deadline task on the rq,
1644          * this is the right place to try to pull some other one
1645          * from an overloaded cpu, if any.
1646          */
1647         if (!task_on_rq_queued(p) || rq->dl.dl_nr_running)
1648                 return;
1649 
1650         if (pull_dl_task(rq))
1651                 resched_curr(rq);
1652 }
1653 
1654 /*
1655  * When switching to -deadline, we may overload the rq, then
1656  * we try to push someone off, if possible.
1657  */
1658 static void switched_to_dl(struct rq *rq, struct task_struct *p)
1659 {
1660         int check_resched = 1;
1661 
1662         /*
1663          * If p is throttled, don't consider the possibility
1664          * of preempting rq->curr, the check will be done right
1665          * after its runtime will get replenished.
1666          */
1667         if (unlikely(p->dl.dl_throttled))
1668                 return;
1669 
1670         if (task_on_rq_queued(p) && rq->curr != p) {
1671 #ifdef CONFIG_SMP
1672                 if (p->nr_cpus_allowed > 1 && rq->dl.overloaded &&
1673                         push_dl_task(rq) && rq != task_rq(p))
1674                         /* Only reschedule if pushing failed */
1675                         check_resched = 0;
1676 #endif /* CONFIG_SMP */
1677                 if (check_resched) {
1678                         if (dl_task(rq->curr))
1679                                 check_preempt_curr_dl(rq, p, 0);
1680                         else
1681                                 resched_curr(rq);
1682                 }
1683         }
1684 }
1685 
1686 /*
1687  * If the scheduling parameters of a -deadline task changed,
1688  * a push or pull operation might be needed.
1689  */
1690 static void prio_changed_dl(struct rq *rq, struct task_struct *p,
1691                             int oldprio)
1692 {
1693         if (task_on_rq_queued(p) || rq->curr == p) {
1694 #ifdef CONFIG_SMP
1695                 /*
1696                  * This might be too much, but unfortunately
1697                  * we don't have the old deadline value, and
1698                  * we can't argue if the task is increasing
1699                  * or lowering its prio, so...
1700                  */
1701                 if (!rq->dl.overloaded)
1702                         pull_dl_task(rq);
1703 
1704                 /*
1705                  * If we now have a earlier deadline task than p,
1706                  * then reschedule, provided p is still on this
1707                  * runqueue.
1708                  */
1709                 if (dl_time_before(rq->dl.earliest_dl.curr, p->dl.deadline) &&
1710                     rq->curr == p)
1711                         resched_curr(rq);
1712 #else
1713                 /*
1714                  * Again, we don't know if p has a earlier
1715                  * or later deadline, so let's blindly set a
1716                  * (maybe not needed) rescheduling point.
1717                  */
1718                 resched_curr(rq);
1719 #endif /* CONFIG_SMP */
1720         } else
1721                 switched_to_dl(rq, p);
1722 }
1723 
1724 const struct sched_class dl_sched_class = {
1725         .next                   = &rt_sched_class,
1726         .enqueue_task           = enqueue_task_dl,
1727         .dequeue_task           = dequeue_task_dl,
1728         .yield_task             = yield_task_dl,
1729 
1730         .check_preempt_curr     = check_preempt_curr_dl,
1731 
1732         .pick_next_task         = pick_next_task_dl,
1733         .put_prev_task          = put_prev_task_dl,
1734 
1735 #ifdef CONFIG_SMP
1736         .select_task_rq         = select_task_rq_dl,
1737         .set_cpus_allowed       = set_cpus_allowed_dl,
1738         .rq_online              = rq_online_dl,
1739         .rq_offline             = rq_offline_dl,
1740         .post_schedule          = post_schedule_dl,
1741         .task_woken             = task_woken_dl,
1742 #endif
1743 
1744         .set_curr_task          = set_curr_task_dl,
1745         .task_tick              = task_tick_dl,
1746         .task_fork              = task_fork_dl,
1747         .task_dead              = task_dead_dl,
1748 
1749         .prio_changed           = prio_changed_dl,
1750         .switched_from          = switched_from_dl,
1751         .switched_to            = switched_to_dl,
1752 
1753         .update_curr            = update_curr_dl,
1754 };
1755 
1756 #ifdef CONFIG_SCHED_DEBUG
1757 extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq);
1758 
1759 void print_dl_stats(struct seq_file *m, int cpu)
1760 {
1761         print_dl_rq(m, cpu, &cpu_rq(cpu)->dl);
1762 }
1763 #endif /* CONFIG_SCHED_DEBUG */
1764 

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