2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
8 static inline int rt_overloaded(struct rq
*rq
)
10 return atomic_read(&rq
->rd
->rto_count
);
13 static inline void rt_set_overload(struct rq
*rq
)
15 cpu_set(rq
->cpu
, rq
->rd
->rto_mask
);
17 * Make sure the mask is visible before we set
18 * the overload count. That is checked to determine
19 * if we should look at the mask. It would be a shame
20 * if we looked at the mask, but the mask was not
24 atomic_inc(&rq
->rd
->rto_count
);
27 static inline void rt_clear_overload(struct rq
*rq
)
29 /* the order here really doesn't matter */
30 atomic_dec(&rq
->rd
->rto_count
);
31 cpu_clear(rq
->cpu
, rq
->rd
->rto_mask
);
34 static void update_rt_migration(struct rq
*rq
)
36 if (rq
->rt
.rt_nr_migratory
&& (rq
->rt
.rt_nr_running
> 1)) {
37 if (!rq
->rt
.overloaded
) {
39 rq
->rt
.overloaded
= 1;
41 } else if (rq
->rt
.overloaded
) {
42 rt_clear_overload(rq
);
43 rq
->rt
.overloaded
= 0;
46 #endif /* CONFIG_SMP */
48 static inline struct task_struct
*rt_task_of(struct sched_rt_entity
*rt_se
)
50 return container_of(rt_se
, struct task_struct
, rt
);
53 static inline int on_rt_rq(struct sched_rt_entity
*rt_se
)
55 return !list_empty(&rt_se
->run_list
);
58 #ifdef CONFIG_FAIR_GROUP_SCHED
60 static inline unsigned int sched_rt_ratio(struct rt_rq
*rt_rq
)
65 return rt_rq
->tg
->rt_ratio
;
68 #define for_each_leaf_rt_rq(rt_rq, rq) \
69 list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
71 static inline struct rq
*rq_of_rt_rq(struct rt_rq
*rt_rq
)
76 static inline struct rt_rq
*rt_rq_of_se(struct sched_rt_entity
*rt_se
)
81 #define for_each_sched_rt_entity(rt_se) \
82 for (; rt_se; rt_se = rt_se->parent)
84 static inline struct rt_rq
*group_rt_rq(struct sched_rt_entity
*rt_se
)
89 static void enqueue_rt_entity(struct sched_rt_entity
*rt_se
);
90 static void dequeue_rt_entity(struct sched_rt_entity
*rt_se
);
92 static void sched_rt_ratio_enqueue(struct rt_rq
*rt_rq
)
94 struct sched_rt_entity
*rt_se
= rt_rq
->rt_se
;
96 if (rt_se
&& !on_rt_rq(rt_se
) && rt_rq
->rt_nr_running
) {
97 struct task_struct
*curr
= rq_of_rt_rq(rt_rq
)->curr
;
99 enqueue_rt_entity(rt_se
);
100 if (rt_rq
->highest_prio
< curr
->prio
)
105 static void sched_rt_ratio_dequeue(struct rt_rq
*rt_rq
)
107 struct sched_rt_entity
*rt_se
= rt_rq
->rt_se
;
109 if (rt_se
&& on_rt_rq(rt_se
))
110 dequeue_rt_entity(rt_se
);
115 static inline unsigned int sched_rt_ratio(struct rt_rq
*rt_rq
)
117 return sysctl_sched_rt_ratio
;
120 #define for_each_leaf_rt_rq(rt_rq, rq) \
121 for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
123 static inline struct rq
*rq_of_rt_rq(struct rt_rq
*rt_rq
)
125 return container_of(rt_rq
, struct rq
, rt
);
128 static inline struct rt_rq
*rt_rq_of_se(struct sched_rt_entity
*rt_se
)
130 struct task_struct
*p
= rt_task_of(rt_se
);
131 struct rq
*rq
= task_rq(p
);
136 #define for_each_sched_rt_entity(rt_se) \
137 for (; rt_se; rt_se = NULL)
139 static inline struct rt_rq
*group_rt_rq(struct sched_rt_entity
*rt_se
)
144 static inline void sched_rt_ratio_enqueue(struct rt_rq
*rt_rq
)
148 static inline void sched_rt_ratio_dequeue(struct rt_rq
*rt_rq
)
154 static inline int rt_se_prio(struct sched_rt_entity
*rt_se
)
156 #ifdef CONFIG_FAIR_GROUP_SCHED
157 struct rt_rq
*rt_rq
= group_rt_rq(rt_se
);
160 return rt_rq
->highest_prio
;
163 return rt_task_of(rt_se
)->prio
;
166 static int sched_rt_ratio_exceeded(struct rt_rq
*rt_rq
)
168 unsigned int rt_ratio
= sched_rt_ratio(rt_rq
);
171 if (rt_ratio
== SCHED_RT_FRAC
)
174 if (rt_rq
->rt_throttled
)
177 period
= (u64
)sysctl_sched_rt_period
* NSEC_PER_MSEC
;
178 ratio
= (period
* rt_ratio
) >> SCHED_RT_FRAC_SHIFT
;
180 if (rt_rq
->rt_time
> ratio
) {
181 struct rq
*rq
= rq_of_rt_rq(rt_rq
);
183 rq
->rt_throttled
= 1;
184 rt_rq
->rt_throttled
= 1;
186 sched_rt_ratio_dequeue(rt_rq
);
193 static void update_sched_rt_period(struct rq
*rq
)
198 while (rq
->clock
> rq
->rt_period_expire
) {
199 period
= (u64
)sysctl_sched_rt_period
* NSEC_PER_MSEC
;
200 rq
->rt_period_expire
+= period
;
202 for_each_leaf_rt_rq(rt_rq
, rq
) {
203 unsigned long rt_ratio
= sched_rt_ratio(rt_rq
);
204 u64 ratio
= (period
* rt_ratio
) >> SCHED_RT_FRAC_SHIFT
;
206 rt_rq
->rt_time
-= min(rt_rq
->rt_time
, ratio
);
207 if (rt_rq
->rt_throttled
) {
208 rt_rq
->rt_throttled
= 0;
209 sched_rt_ratio_enqueue(rt_rq
);
213 rq
->rt_throttled
= 0;
218 * Update the current task's runtime statistics. Skip current tasks that
219 * are not in our scheduling class.
221 static void update_curr_rt(struct rq
*rq
)
223 struct task_struct
*curr
= rq
->curr
;
224 struct sched_rt_entity
*rt_se
= &curr
->rt
;
225 struct rt_rq
*rt_rq
= rt_rq_of_se(rt_se
);
228 if (!task_has_rt_policy(curr
))
231 delta_exec
= rq
->clock
- curr
->se
.exec_start
;
232 if (unlikely((s64
)delta_exec
< 0))
235 schedstat_set(curr
->se
.exec_max
, max(curr
->se
.exec_max
, delta_exec
));
237 curr
->se
.sum_exec_runtime
+= delta_exec
;
238 curr
->se
.exec_start
= rq
->clock
;
239 cpuacct_charge(curr
, delta_exec
);
241 rt_rq
->rt_time
+= delta_exec
;
243 * might make it a tad more accurate:
245 * update_sched_rt_period(rq);
247 if (sched_rt_ratio_exceeded(rt_rq
))
252 void inc_rt_tasks(struct sched_rt_entity
*rt_se
, struct rt_rq
*rt_rq
)
254 WARN_ON(!rt_prio(rt_se_prio(rt_se
)));
255 rt_rq
->rt_nr_running
++;
256 #if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
257 if (rt_se_prio(rt_se
) < rt_rq
->highest_prio
)
258 rt_rq
->highest_prio
= rt_se_prio(rt_se
);
261 if (rt_se
->nr_cpus_allowed
> 1) {
262 struct rq
*rq
= rq_of_rt_rq(rt_rq
);
263 rq
->rt
.rt_nr_migratory
++;
266 update_rt_migration(rq_of_rt_rq(rt_rq
));
271 void dec_rt_tasks(struct sched_rt_entity
*rt_se
, struct rt_rq
*rt_rq
)
273 WARN_ON(!rt_prio(rt_se_prio(rt_se
)));
274 WARN_ON(!rt_rq
->rt_nr_running
);
275 rt_rq
->rt_nr_running
--;
276 #if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
277 if (rt_rq
->rt_nr_running
) {
278 struct rt_prio_array
*array
;
280 WARN_ON(rt_se_prio(rt_se
) < rt_rq
->highest_prio
);
281 if (rt_se_prio(rt_se
) == rt_rq
->highest_prio
) {
283 array
= &rt_rq
->active
;
284 rt_rq
->highest_prio
=
285 sched_find_first_bit(array
->bitmap
);
286 } /* otherwise leave rq->highest prio alone */
288 rt_rq
->highest_prio
= MAX_RT_PRIO
;
291 if (rt_se
->nr_cpus_allowed
> 1) {
292 struct rq
*rq
= rq_of_rt_rq(rt_rq
);
293 rq
->rt
.rt_nr_migratory
--;
296 update_rt_migration(rq_of_rt_rq(rt_rq
));
297 #endif /* CONFIG_SMP */
300 static void enqueue_rt_entity(struct sched_rt_entity
*rt_se
)
302 struct rt_rq
*rt_rq
= rt_rq_of_se(rt_se
);
303 struct rt_prio_array
*array
= &rt_rq
->active
;
304 struct rt_rq
*group_rq
= group_rt_rq(rt_se
);
306 if (group_rq
&& group_rq
->rt_throttled
)
309 list_add_tail(&rt_se
->run_list
, array
->queue
+ rt_se_prio(rt_se
));
310 __set_bit(rt_se_prio(rt_se
), array
->bitmap
);
312 inc_rt_tasks(rt_se
, rt_rq
);
315 static void dequeue_rt_entity(struct sched_rt_entity
*rt_se
)
317 struct rt_rq
*rt_rq
= rt_rq_of_se(rt_se
);
318 struct rt_prio_array
*array
= &rt_rq
->active
;
320 list_del_init(&rt_se
->run_list
);
321 if (list_empty(array
->queue
+ rt_se_prio(rt_se
)))
322 __clear_bit(rt_se_prio(rt_se
), array
->bitmap
);
324 dec_rt_tasks(rt_se
, rt_rq
);
328 * Because the prio of an upper entry depends on the lower
329 * entries, we must remove entries top - down.
331 * XXX: O(1/2 h^2) because we can only walk up, not down the chain.
332 * doesn't matter much for now, as h=2 for GROUP_SCHED.
334 static void dequeue_rt_stack(struct task_struct
*p
)
336 struct sched_rt_entity
*rt_se
, *top_se
;
339 * dequeue all, top - down.
344 for_each_sched_rt_entity(rt_se
) {
349 dequeue_rt_entity(top_se
);
354 * Adding/removing a task to/from a priority array:
356 static void enqueue_task_rt(struct rq
*rq
, struct task_struct
*p
, int wakeup
)
358 struct sched_rt_entity
*rt_se
= &p
->rt
;
366 * enqueue everybody, bottom - up.
368 for_each_sched_rt_entity(rt_se
)
369 enqueue_rt_entity(rt_se
);
371 inc_cpu_load(rq
, p
->se
.load
.weight
);
374 static void dequeue_task_rt(struct rq
*rq
, struct task_struct
*p
, int sleep
)
376 struct sched_rt_entity
*rt_se
= &p
->rt
;
384 * re-enqueue all non-empty rt_rq entities.
386 for_each_sched_rt_entity(rt_se
) {
387 rt_rq
= group_rt_rq(rt_se
);
388 if (rt_rq
&& rt_rq
->rt_nr_running
)
389 enqueue_rt_entity(rt_se
);
392 dec_cpu_load(rq
, p
->se
.load
.weight
);
396 * Put task to the end of the run list without the overhead of dequeue
397 * followed by enqueue.
400 void requeue_rt_entity(struct rt_rq
*rt_rq
, struct sched_rt_entity
*rt_se
)
402 struct rt_prio_array
*array
= &rt_rq
->active
;
404 list_move_tail(&rt_se
->run_list
, array
->queue
+ rt_se_prio(rt_se
));
407 static void requeue_task_rt(struct rq
*rq
, struct task_struct
*p
)
409 struct sched_rt_entity
*rt_se
= &p
->rt
;
412 for_each_sched_rt_entity(rt_se
) {
413 rt_rq
= rt_rq_of_se(rt_se
);
414 requeue_rt_entity(rt_rq
, rt_se
);
418 static void yield_task_rt(struct rq
*rq
)
420 requeue_task_rt(rq
, rq
->curr
);
424 static int find_lowest_rq(struct task_struct
*task
);
426 static int select_task_rq_rt(struct task_struct
*p
, int sync
)
428 struct rq
*rq
= task_rq(p
);
431 * If the current task is an RT task, then
432 * try to see if we can wake this RT task up on another
433 * runqueue. Otherwise simply start this RT task
434 * on its current runqueue.
436 * We want to avoid overloading runqueues. Even if
437 * the RT task is of higher priority than the current RT task.
438 * RT tasks behave differently than other tasks. If
439 * one gets preempted, we try to push it off to another queue.
440 * So trying to keep a preempting RT task on the same
441 * cache hot CPU will force the running RT task to
442 * a cold CPU. So we waste all the cache for the lower
443 * RT task in hopes of saving some of a RT task
444 * that is just being woken and probably will have
447 if (unlikely(rt_task(rq
->curr
)) &&
448 (p
->rt
.nr_cpus_allowed
> 1)) {
449 int cpu
= find_lowest_rq(p
);
451 return (cpu
== -1) ? task_cpu(p
) : cpu
;
455 * Otherwise, just let it ride on the affined RQ and the
456 * post-schedule router will push the preempted task away
460 #endif /* CONFIG_SMP */
463 * Preempt the current task with a newly woken task if needed:
465 static void check_preempt_curr_rt(struct rq
*rq
, struct task_struct
*p
)
467 if (p
->prio
< rq
->curr
->prio
)
468 resched_task(rq
->curr
);
471 static struct sched_rt_entity
*pick_next_rt_entity(struct rq
*rq
,
474 struct rt_prio_array
*array
= &rt_rq
->active
;
475 struct sched_rt_entity
*next
= NULL
;
476 struct list_head
*queue
;
479 if (sched_rt_ratio_exceeded(rt_rq
))
482 idx
= sched_find_first_bit(array
->bitmap
);
483 BUG_ON(idx
>= MAX_RT_PRIO
);
485 queue
= array
->queue
+ idx
;
486 next
= list_entry(queue
->next
, struct sched_rt_entity
, run_list
);
491 static struct task_struct
*pick_next_task_rt(struct rq
*rq
)
493 struct sched_rt_entity
*rt_se
;
494 struct task_struct
*p
;
500 if (unlikely(!rt_rq
->rt_nr_running
))
503 if (sched_rt_ratio_exceeded(rt_rq
))
507 rt_se
= pick_next_rt_entity(rq
, rt_rq
);
508 if (unlikely(!rt_se
))
510 rt_rq
= group_rt_rq(rt_se
);
513 p
= rt_task_of(rt_se
);
514 p
->se
.exec_start
= rq
->clock
;
518 static void put_prev_task_rt(struct rq
*rq
, struct task_struct
*p
)
521 p
->se
.exec_start
= 0;
526 /* Only try algorithms three times */
527 #define RT_MAX_TRIES 3
529 static int double_lock_balance(struct rq
*this_rq
, struct rq
*busiest
);
530 static void deactivate_task(struct rq
*rq
, struct task_struct
*p
, int sleep
);
532 static int pick_rt_task(struct rq
*rq
, struct task_struct
*p
, int cpu
)
534 if (!task_running(rq
, p
) &&
535 (cpu
< 0 || cpu_isset(cpu
, p
->cpus_allowed
)) &&
536 (p
->rt
.nr_cpus_allowed
> 1))
541 /* Return the second highest RT task, NULL otherwise */
542 static struct task_struct
*pick_next_highest_task_rt(struct rq
*rq
, int cpu
)
544 struct task_struct
*next
= NULL
;
545 struct sched_rt_entity
*rt_se
;
546 struct rt_prio_array
*array
;
550 for_each_leaf_rt_rq(rt_rq
, rq
) {
551 array
= &rt_rq
->active
;
552 idx
= sched_find_first_bit(array
->bitmap
);
554 if (idx
>= MAX_RT_PRIO
)
556 if (next
&& next
->prio
< idx
)
558 list_for_each_entry(rt_se
, array
->queue
+ idx
, run_list
) {
559 struct task_struct
*p
= rt_task_of(rt_se
);
560 if (pick_rt_task(rq
, p
, cpu
)) {
566 idx
= find_next_bit(array
->bitmap
, MAX_RT_PRIO
, idx
+1);
574 static DEFINE_PER_CPU(cpumask_t
, local_cpu_mask
);
576 static int find_lowest_cpus(struct task_struct
*task
, cpumask_t
*lowest_mask
)
578 int lowest_prio
= -1;
583 cpus_and(*lowest_mask
, task_rq(task
)->rd
->online
, task
->cpus_allowed
);
586 * Scan each rq for the lowest prio.
588 for_each_cpu_mask(cpu
, *lowest_mask
) {
589 struct rq
*rq
= cpu_rq(cpu
);
591 /* We look for lowest RT prio or non-rt CPU */
592 if (rq
->rt
.highest_prio
>= MAX_RT_PRIO
) {
594 * if we already found a low RT queue
595 * and now we found this non-rt queue
596 * clear the mask and set our bit.
597 * Otherwise just return the queue as is
598 * and the count==1 will cause the algorithm
599 * to use the first bit found.
601 if (lowest_cpu
!= -1) {
602 cpus_clear(*lowest_mask
);
603 cpu_set(rq
->cpu
, *lowest_mask
);
608 /* no locking for now */
609 if ((rq
->rt
.highest_prio
> task
->prio
)
610 && (rq
->rt
.highest_prio
>= lowest_prio
)) {
611 if (rq
->rt
.highest_prio
> lowest_prio
) {
612 /* new low - clear old data */
613 lowest_prio
= rq
->rt
.highest_prio
;
619 cpu_clear(cpu
, *lowest_mask
);
623 * Clear out all the set bits that represent
624 * runqueues that were of higher prio than
627 if (lowest_cpu
> 0) {
629 * Perhaps we could add another cpumask op to
630 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
631 * Then that could be optimized to use memset and such.
633 for_each_cpu_mask(cpu
, *lowest_mask
) {
634 if (cpu
>= lowest_cpu
)
636 cpu_clear(cpu
, *lowest_mask
);
643 static inline int pick_optimal_cpu(int this_cpu
, cpumask_t
*mask
)
647 /* "this_cpu" is cheaper to preempt than a remote processor */
648 if ((this_cpu
!= -1) && cpu_isset(this_cpu
, *mask
))
651 first
= first_cpu(*mask
);
652 if (first
!= NR_CPUS
)
658 static int find_lowest_rq(struct task_struct
*task
)
660 struct sched_domain
*sd
;
661 cpumask_t
*lowest_mask
= &__get_cpu_var(local_cpu_mask
);
662 int this_cpu
= smp_processor_id();
663 int cpu
= task_cpu(task
);
664 int count
= find_lowest_cpus(task
, lowest_mask
);
667 return -1; /* No targets found */
670 * There is no sense in performing an optimal search if only one
674 return first_cpu(*lowest_mask
);
677 * At this point we have built a mask of cpus representing the
678 * lowest priority tasks in the system. Now we want to elect
679 * the best one based on our affinity and topology.
681 * We prioritize the last cpu that the task executed on since
682 * it is most likely cache-hot in that location.
684 if (cpu_isset(cpu
, *lowest_mask
))
688 * Otherwise, we consult the sched_domains span maps to figure
689 * out which cpu is logically closest to our hot cache data.
692 this_cpu
= -1; /* Skip this_cpu opt if the same */
694 for_each_domain(cpu
, sd
) {
695 if (sd
->flags
& SD_WAKE_AFFINE
) {
696 cpumask_t domain_mask
;
699 cpus_and(domain_mask
, sd
->span
, *lowest_mask
);
701 best_cpu
= pick_optimal_cpu(this_cpu
,
709 * And finally, if there were no matches within the domains
710 * just give the caller *something* to work with from the compatible
713 return pick_optimal_cpu(this_cpu
, lowest_mask
);
716 /* Will lock the rq it finds */
717 static struct rq
*find_lock_lowest_rq(struct task_struct
*task
, struct rq
*rq
)
719 struct rq
*lowest_rq
= NULL
;
723 for (tries
= 0; tries
< RT_MAX_TRIES
; tries
++) {
724 cpu
= find_lowest_rq(task
);
726 if ((cpu
== -1) || (cpu
== rq
->cpu
))
729 lowest_rq
= cpu_rq(cpu
);
731 /* if the prio of this runqueue changed, try again */
732 if (double_lock_balance(rq
, lowest_rq
)) {
734 * We had to unlock the run queue. In
735 * the mean time, task could have
736 * migrated already or had its affinity changed.
737 * Also make sure that it wasn't scheduled on its rq.
739 if (unlikely(task_rq(task
) != rq
||
740 !cpu_isset(lowest_rq
->cpu
,
741 task
->cpus_allowed
) ||
742 task_running(rq
, task
) ||
745 spin_unlock(&lowest_rq
->lock
);
751 /* If this rq is still suitable use it. */
752 if (lowest_rq
->rt
.highest_prio
> task
->prio
)
756 spin_unlock(&lowest_rq
->lock
);
764 * If the current CPU has more than one RT task, see if the non
765 * running task can migrate over to a CPU that is running a task
766 * of lesser priority.
768 static int push_rt_task(struct rq
*rq
)
770 struct task_struct
*next_task
;
771 struct rq
*lowest_rq
;
773 int paranoid
= RT_MAX_TRIES
;
775 if (!rq
->rt
.overloaded
)
778 next_task
= pick_next_highest_task_rt(rq
, -1);
783 if (unlikely(next_task
== rq
->curr
)) {
789 * It's possible that the next_task slipped in of
790 * higher priority than current. If that's the case
791 * just reschedule current.
793 if (unlikely(next_task
->prio
< rq
->curr
->prio
)) {
794 resched_task(rq
->curr
);
798 /* We might release rq lock */
799 get_task_struct(next_task
);
801 /* find_lock_lowest_rq locks the rq if found */
802 lowest_rq
= find_lock_lowest_rq(next_task
, rq
);
804 struct task_struct
*task
;
806 * find lock_lowest_rq releases rq->lock
807 * so it is possible that next_task has changed.
808 * If it has, then try again.
810 task
= pick_next_highest_task_rt(rq
, -1);
811 if (unlikely(task
!= next_task
) && task
&& paranoid
--) {
812 put_task_struct(next_task
);
819 deactivate_task(rq
, next_task
, 0);
820 set_task_cpu(next_task
, lowest_rq
->cpu
);
821 activate_task(lowest_rq
, next_task
, 0);
823 resched_task(lowest_rq
->curr
);
825 spin_unlock(&lowest_rq
->lock
);
829 put_task_struct(next_task
);
835 * TODO: Currently we just use the second highest prio task on
836 * the queue, and stop when it can't migrate (or there's
837 * no more RT tasks). There may be a case where a lower
838 * priority RT task has a different affinity than the
839 * higher RT task. In this case the lower RT task could
840 * possibly be able to migrate where as the higher priority
841 * RT task could not. We currently ignore this issue.
842 * Enhancements are welcome!
844 static void push_rt_tasks(struct rq
*rq
)
846 /* push_rt_task will return true if it moved an RT */
847 while (push_rt_task(rq
))
851 static int pull_rt_task(struct rq
*this_rq
)
853 int this_cpu
= this_rq
->cpu
, ret
= 0, cpu
;
854 struct task_struct
*p
, *next
;
857 if (likely(!rt_overloaded(this_rq
)))
860 next
= pick_next_task_rt(this_rq
);
862 for_each_cpu_mask(cpu
, this_rq
->rd
->rto_mask
) {
866 src_rq
= cpu_rq(cpu
);
868 * We can potentially drop this_rq's lock in
869 * double_lock_balance, and another CPU could
870 * steal our next task - hence we must cause
871 * the caller to recalculate the next task
874 if (double_lock_balance(this_rq
, src_rq
)) {
875 struct task_struct
*old_next
= next
;
877 next
= pick_next_task_rt(this_rq
);
878 if (next
!= old_next
)
883 * Are there still pullable RT tasks?
885 if (src_rq
->rt
.rt_nr_running
<= 1)
888 p
= pick_next_highest_task_rt(src_rq
, this_cpu
);
891 * Do we have an RT task that preempts
892 * the to-be-scheduled task?
894 if (p
&& (!next
|| (p
->prio
< next
->prio
))) {
895 WARN_ON(p
== src_rq
->curr
);
896 WARN_ON(!p
->se
.on_rq
);
899 * There's a chance that p is higher in priority
900 * than what's currently running on its cpu.
901 * This is just that p is wakeing up and hasn't
902 * had a chance to schedule. We only pull
903 * p if it is lower in priority than the
904 * current task on the run queue or
905 * this_rq next task is lower in prio than
906 * the current task on that rq.
908 if (p
->prio
< src_rq
->curr
->prio
||
909 (next
&& next
->prio
< src_rq
->curr
->prio
))
914 deactivate_task(src_rq
, p
, 0);
915 set_task_cpu(p
, this_cpu
);
916 activate_task(this_rq
, p
, 0);
918 * We continue with the search, just in
919 * case there's an even higher prio task
920 * in another runqueue. (low likelyhood
923 * Update next so that we won't pick a task
924 * on another cpu with a priority lower (or equal)
925 * than the one we just picked.
931 spin_unlock(&src_rq
->lock
);
937 static void pre_schedule_rt(struct rq
*rq
, struct task_struct
*prev
)
939 /* Try to pull RT tasks here if we lower this rq's prio */
940 if (unlikely(rt_task(prev
)) && rq
->rt
.highest_prio
> prev
->prio
)
944 static void post_schedule_rt(struct rq
*rq
)
947 * If we have more than one rt_task queued, then
948 * see if we can push the other rt_tasks off to other CPUS.
949 * Note we may release the rq lock, and since
950 * the lock was owned by prev, we need to release it
951 * first via finish_lock_switch and then reaquire it here.
953 if (unlikely(rq
->rt
.overloaded
)) {
954 spin_lock_irq(&rq
->lock
);
956 spin_unlock_irq(&rq
->lock
);
961 static void task_wake_up_rt(struct rq
*rq
, struct task_struct
*p
)
963 if (!task_running(rq
, p
) &&
964 (p
->prio
>= rq
->rt
.highest_prio
) &&
970 load_balance_rt(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
971 unsigned long max_load_move
,
972 struct sched_domain
*sd
, enum cpu_idle_type idle
,
973 int *all_pinned
, int *this_best_prio
)
975 /* don't touch RT tasks */
980 move_one_task_rt(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
981 struct sched_domain
*sd
, enum cpu_idle_type idle
)
983 /* don't touch RT tasks */
987 static void set_cpus_allowed_rt(struct task_struct
*p
, cpumask_t
*new_mask
)
989 int weight
= cpus_weight(*new_mask
);
994 * Update the migration status of the RQ if we have an RT task
995 * which is running AND changing its weight value.
997 if (p
->se
.on_rq
&& (weight
!= p
->rt
.nr_cpus_allowed
)) {
998 struct rq
*rq
= task_rq(p
);
1000 if ((p
->rt
.nr_cpus_allowed
<= 1) && (weight
> 1)) {
1001 rq
->rt
.rt_nr_migratory
++;
1002 } else if ((p
->rt
.nr_cpus_allowed
> 1) && (weight
<= 1)) {
1003 BUG_ON(!rq
->rt
.rt_nr_migratory
);
1004 rq
->rt
.rt_nr_migratory
--;
1007 update_rt_migration(rq
);
1010 p
->cpus_allowed
= *new_mask
;
1011 p
->rt
.nr_cpus_allowed
= weight
;
1014 /* Assumes rq->lock is held */
1015 static void join_domain_rt(struct rq
*rq
)
1017 if (rq
->rt
.overloaded
)
1018 rt_set_overload(rq
);
1021 /* Assumes rq->lock is held */
1022 static void leave_domain_rt(struct rq
*rq
)
1024 if (rq
->rt
.overloaded
)
1025 rt_clear_overload(rq
);
1029 * When switch from the rt queue, we bring ourselves to a position
1030 * that we might want to pull RT tasks from other runqueues.
1032 static void switched_from_rt(struct rq
*rq
, struct task_struct
*p
,
1036 * If there are other RT tasks then we will reschedule
1037 * and the scheduling of the other RT tasks will handle
1038 * the balancing. But if we are the last RT task
1039 * we may need to handle the pulling of RT tasks
1042 if (!rq
->rt
.rt_nr_running
)
1045 #endif /* CONFIG_SMP */
1048 * When switching a task to RT, we may overload the runqueue
1049 * with RT tasks. In this case we try to push them off to
1052 static void switched_to_rt(struct rq
*rq
, struct task_struct
*p
,
1055 int check_resched
= 1;
1058 * If we are already running, then there's nothing
1059 * that needs to be done. But if we are not running
1060 * we may need to preempt the current running task.
1061 * If that current running task is also an RT task
1062 * then see if we can move to another run queue.
1066 if (rq
->rt
.overloaded
&& push_rt_task(rq
) &&
1067 /* Don't resched if we changed runqueues */
1070 #endif /* CONFIG_SMP */
1071 if (check_resched
&& p
->prio
< rq
->curr
->prio
)
1072 resched_task(rq
->curr
);
1077 * Priority of the task has changed. This may cause
1078 * us to initiate a push or pull.
1080 static void prio_changed_rt(struct rq
*rq
, struct task_struct
*p
,
1081 int oldprio
, int running
)
1086 * If our priority decreases while running, we
1087 * may need to pull tasks to this runqueue.
1089 if (oldprio
< p
->prio
)
1092 * If there's a higher priority task waiting to run
1095 if (p
->prio
> rq
->rt
.highest_prio
)
1098 /* For UP simply resched on drop of prio */
1099 if (oldprio
< p
->prio
)
1101 #endif /* CONFIG_SMP */
1104 * This task is not running, but if it is
1105 * greater than the current running task
1108 if (p
->prio
< rq
->curr
->prio
)
1109 resched_task(rq
->curr
);
1113 static void watchdog(struct rq
*rq
, struct task_struct
*p
)
1115 unsigned long soft
, hard
;
1120 soft
= p
->signal
->rlim
[RLIMIT_RTTIME
].rlim_cur
;
1121 hard
= p
->signal
->rlim
[RLIMIT_RTTIME
].rlim_max
;
1123 if (soft
!= RLIM_INFINITY
) {
1127 next
= DIV_ROUND_UP(min(soft
, hard
), USEC_PER_SEC
/HZ
);
1128 if (p
->rt
.timeout
> next
)
1129 p
->it_sched_expires
= p
->se
.sum_exec_runtime
;
1133 static void task_tick_rt(struct rq
*rq
, struct task_struct
*p
, int queued
)
1140 * RR tasks need a special form of timeslice management.
1141 * FIFO tasks have no timeslices.
1143 if (p
->policy
!= SCHED_RR
)
1146 if (--p
->rt
.time_slice
)
1149 p
->rt
.time_slice
= DEF_TIMESLICE
;
1152 * Requeue to the end of queue if we are not the only element
1155 if (p
->rt
.run_list
.prev
!= p
->rt
.run_list
.next
) {
1156 requeue_task_rt(rq
, p
);
1157 set_tsk_need_resched(p
);
1161 static void set_curr_task_rt(struct rq
*rq
)
1163 struct task_struct
*p
= rq
->curr
;
1165 p
->se
.exec_start
= rq
->clock
;
1168 const struct sched_class rt_sched_class
= {
1169 .next
= &fair_sched_class
,
1170 .enqueue_task
= enqueue_task_rt
,
1171 .dequeue_task
= dequeue_task_rt
,
1172 .yield_task
= yield_task_rt
,
1174 .select_task_rq
= select_task_rq_rt
,
1175 #endif /* CONFIG_SMP */
1177 .check_preempt_curr
= check_preempt_curr_rt
,
1179 .pick_next_task
= pick_next_task_rt
,
1180 .put_prev_task
= put_prev_task_rt
,
1183 .load_balance
= load_balance_rt
,
1184 .move_one_task
= move_one_task_rt
,
1185 .set_cpus_allowed
= set_cpus_allowed_rt
,
1186 .join_domain
= join_domain_rt
,
1187 .leave_domain
= leave_domain_rt
,
1188 .pre_schedule
= pre_schedule_rt
,
1189 .post_schedule
= post_schedule_rt
,
1190 .task_wake_up
= task_wake_up_rt
,
1191 .switched_from
= switched_from_rt
,
1194 .set_curr_task
= set_curr_task_rt
,
1195 .task_tick
= task_tick_rt
,
1197 .prio_changed
= prio_changed_rt
,
1198 .switched_to
= switched_to_rt
,