[SCSI] advansys: Fix bug in AdvLoadMicrocode
[linux-2.6/mini2440.git] / kernel / sched_rt.c
blob76e828517541b742c960de0b48bd503ea88f99d6
1 /*
2 * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
3 * policies)
4 */
6 #ifdef CONFIG_SMP
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
21 * updated yet.
23 wmb();
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) {
38 rt_set_overload(rq);
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_RT_GROUP_SCHED
60 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
62 if (!rt_rq->tg)
63 return RUNTIME_INF;
65 return rt_rq->tg->rt_runtime;
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)
73 return rt_rq->rq;
76 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
78 return rt_se->rt_rq;
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)
86 return rt_se->my_q;
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_rq_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)
101 resched_task(curr);
105 static void sched_rt_rq_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);
113 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
115 return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
118 static int rt_se_boosted(struct sched_rt_entity *rt_se)
120 struct rt_rq *rt_rq = group_rt_rq(rt_se);
121 struct task_struct *p;
123 if (rt_rq)
124 return !!rt_rq->rt_nr_boosted;
126 p = rt_task_of(rt_se);
127 return p->prio != p->normal_prio;
130 #else
132 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
134 if (sysctl_sched_rt_runtime == -1)
135 return RUNTIME_INF;
137 return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
140 #define for_each_leaf_rt_rq(rt_rq, rq) \
141 for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
143 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
145 return container_of(rt_rq, struct rq, rt);
148 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
150 struct task_struct *p = rt_task_of(rt_se);
151 struct rq *rq = task_rq(p);
153 return &rq->rt;
156 #define for_each_sched_rt_entity(rt_se) \
157 for (; rt_se; rt_se = NULL)
159 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
161 return NULL;
164 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
168 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
172 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
174 return rt_rq->rt_throttled;
176 #endif
178 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
180 #ifdef CONFIG_RT_GROUP_SCHED
181 struct rt_rq *rt_rq = group_rt_rq(rt_se);
183 if (rt_rq)
184 return rt_rq->highest_prio;
185 #endif
187 return rt_task_of(rt_se)->prio;
190 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
192 u64 runtime = sched_rt_runtime(rt_rq);
194 if (runtime == RUNTIME_INF)
195 return 0;
197 if (rt_rq->rt_throttled)
198 return rt_rq_throttled(rt_rq);
200 if (rt_rq->rt_time > runtime) {
201 struct rq *rq = rq_of_rt_rq(rt_rq);
203 rq->rt_throttled = 1;
204 rt_rq->rt_throttled = 1;
206 if (rt_rq_throttled(rt_rq)) {
207 sched_rt_rq_dequeue(rt_rq);
208 return 1;
212 return 0;
215 static void update_sched_rt_period(struct rq *rq)
217 struct rt_rq *rt_rq;
218 u64 period;
220 while (rq->clock > rq->rt_period_expire) {
221 period = (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
222 rq->rt_period_expire += period;
224 for_each_leaf_rt_rq(rt_rq, rq) {
225 u64 runtime = sched_rt_runtime(rt_rq);
227 rt_rq->rt_time -= min(rt_rq->rt_time, runtime);
228 if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
229 rt_rq->rt_throttled = 0;
230 sched_rt_rq_enqueue(rt_rq);
234 rq->rt_throttled = 0;
239 * Update the current task's runtime statistics. Skip current tasks that
240 * are not in our scheduling class.
242 static void update_curr_rt(struct rq *rq)
244 struct task_struct *curr = rq->curr;
245 struct sched_rt_entity *rt_se = &curr->rt;
246 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
247 u64 delta_exec;
249 if (!task_has_rt_policy(curr))
250 return;
252 delta_exec = rq->clock - curr->se.exec_start;
253 if (unlikely((s64)delta_exec < 0))
254 delta_exec = 0;
256 schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
258 curr->se.sum_exec_runtime += delta_exec;
259 curr->se.exec_start = rq->clock;
260 cpuacct_charge(curr, delta_exec);
262 rt_rq->rt_time += delta_exec;
263 if (sched_rt_runtime_exceeded(rt_rq))
264 resched_task(curr);
267 static inline
268 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
270 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
271 rt_rq->rt_nr_running++;
272 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
273 if (rt_se_prio(rt_se) < rt_rq->highest_prio)
274 rt_rq->highest_prio = rt_se_prio(rt_se);
275 #endif
276 #ifdef CONFIG_SMP
277 if (rt_se->nr_cpus_allowed > 1) {
278 struct rq *rq = rq_of_rt_rq(rt_rq);
279 rq->rt.rt_nr_migratory++;
282 update_rt_migration(rq_of_rt_rq(rt_rq));
283 #endif
284 #ifdef CONFIG_RT_GROUP_SCHED
285 if (rt_se_boosted(rt_se))
286 rt_rq->rt_nr_boosted++;
287 #endif
290 static inline
291 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
293 WARN_ON(!rt_prio(rt_se_prio(rt_se)));
294 WARN_ON(!rt_rq->rt_nr_running);
295 rt_rq->rt_nr_running--;
296 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
297 if (rt_rq->rt_nr_running) {
298 struct rt_prio_array *array;
300 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
301 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
302 /* recalculate */
303 array = &rt_rq->active;
304 rt_rq->highest_prio =
305 sched_find_first_bit(array->bitmap);
306 } /* otherwise leave rq->highest prio alone */
307 } else
308 rt_rq->highest_prio = MAX_RT_PRIO;
309 #endif
310 #ifdef CONFIG_SMP
311 if (rt_se->nr_cpus_allowed > 1) {
312 struct rq *rq = rq_of_rt_rq(rt_rq);
313 rq->rt.rt_nr_migratory--;
316 update_rt_migration(rq_of_rt_rq(rt_rq));
317 #endif /* CONFIG_SMP */
318 #ifdef CONFIG_RT_GROUP_SCHED
319 if (rt_se_boosted(rt_se))
320 rt_rq->rt_nr_boosted--;
322 WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
323 #endif
326 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
328 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
329 struct rt_prio_array *array = &rt_rq->active;
330 struct rt_rq *group_rq = group_rt_rq(rt_se);
332 if (group_rq && rt_rq_throttled(group_rq))
333 return;
335 list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
336 __set_bit(rt_se_prio(rt_se), array->bitmap);
338 inc_rt_tasks(rt_se, rt_rq);
341 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
343 struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
344 struct rt_prio_array *array = &rt_rq->active;
346 list_del_init(&rt_se->run_list);
347 if (list_empty(array->queue + rt_se_prio(rt_se)))
348 __clear_bit(rt_se_prio(rt_se), array->bitmap);
350 dec_rt_tasks(rt_se, rt_rq);
354 * Because the prio of an upper entry depends on the lower
355 * entries, we must remove entries top - down.
357 * XXX: O(1/2 h^2) because we can only walk up, not down the chain.
358 * doesn't matter much for now, as h=2 for GROUP_SCHED.
360 static void dequeue_rt_stack(struct task_struct *p)
362 struct sched_rt_entity *rt_se, *top_se;
365 * dequeue all, top - down.
367 do {
368 rt_se = &p->rt;
369 top_se = NULL;
370 for_each_sched_rt_entity(rt_se) {
371 if (on_rt_rq(rt_se))
372 top_se = rt_se;
374 if (top_se)
375 dequeue_rt_entity(top_se);
376 } while (top_se);
380 * Adding/removing a task to/from a priority array:
382 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
384 struct sched_rt_entity *rt_se = &p->rt;
386 if (wakeup)
387 rt_se->timeout = 0;
389 dequeue_rt_stack(p);
392 * enqueue everybody, bottom - up.
394 for_each_sched_rt_entity(rt_se)
395 enqueue_rt_entity(rt_se);
398 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
400 struct sched_rt_entity *rt_se = &p->rt;
401 struct rt_rq *rt_rq;
403 update_curr_rt(rq);
405 dequeue_rt_stack(p);
408 * re-enqueue all non-empty rt_rq entities.
410 for_each_sched_rt_entity(rt_se) {
411 rt_rq = group_rt_rq(rt_se);
412 if (rt_rq && rt_rq->rt_nr_running)
413 enqueue_rt_entity(rt_se);
418 * Put task to the end of the run list without the overhead of dequeue
419 * followed by enqueue.
421 static
422 void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
424 struct rt_prio_array *array = &rt_rq->active;
426 list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
429 static void requeue_task_rt(struct rq *rq, struct task_struct *p)
431 struct sched_rt_entity *rt_se = &p->rt;
432 struct rt_rq *rt_rq;
434 for_each_sched_rt_entity(rt_se) {
435 rt_rq = rt_rq_of_se(rt_se);
436 requeue_rt_entity(rt_rq, rt_se);
440 static void yield_task_rt(struct rq *rq)
442 requeue_task_rt(rq, rq->curr);
445 #ifdef CONFIG_SMP
446 static int find_lowest_rq(struct task_struct *task);
448 static int select_task_rq_rt(struct task_struct *p, int sync)
450 struct rq *rq = task_rq(p);
453 * If the current task is an RT task, then
454 * try to see if we can wake this RT task up on another
455 * runqueue. Otherwise simply start this RT task
456 * on its current runqueue.
458 * We want to avoid overloading runqueues. Even if
459 * the RT task is of higher priority than the current RT task.
460 * RT tasks behave differently than other tasks. If
461 * one gets preempted, we try to push it off to another queue.
462 * So trying to keep a preempting RT task on the same
463 * cache hot CPU will force the running RT task to
464 * a cold CPU. So we waste all the cache for the lower
465 * RT task in hopes of saving some of a RT task
466 * that is just being woken and probably will have
467 * cold cache anyway.
469 if (unlikely(rt_task(rq->curr)) &&
470 (p->rt.nr_cpus_allowed > 1)) {
471 int cpu = find_lowest_rq(p);
473 return (cpu == -1) ? task_cpu(p) : cpu;
477 * Otherwise, just let it ride on the affined RQ and the
478 * post-schedule router will push the preempted task away
480 return task_cpu(p);
482 #endif /* CONFIG_SMP */
485 * Preempt the current task with a newly woken task if needed:
487 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
489 if (p->prio < rq->curr->prio)
490 resched_task(rq->curr);
493 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
494 struct rt_rq *rt_rq)
496 struct rt_prio_array *array = &rt_rq->active;
497 struct sched_rt_entity *next = NULL;
498 struct list_head *queue;
499 int idx;
501 idx = sched_find_first_bit(array->bitmap);
502 BUG_ON(idx >= MAX_RT_PRIO);
504 queue = array->queue + idx;
505 next = list_entry(queue->next, struct sched_rt_entity, run_list);
507 return next;
510 static struct task_struct *pick_next_task_rt(struct rq *rq)
512 struct sched_rt_entity *rt_se;
513 struct task_struct *p;
514 struct rt_rq *rt_rq;
516 rt_rq = &rq->rt;
518 if (unlikely(!rt_rq->rt_nr_running))
519 return NULL;
521 if (rt_rq_throttled(rt_rq))
522 return NULL;
524 do {
525 rt_se = pick_next_rt_entity(rq, rt_rq);
526 BUG_ON(!rt_se);
527 rt_rq = group_rt_rq(rt_se);
528 } while (rt_rq);
530 p = rt_task_of(rt_se);
531 p->se.exec_start = rq->clock;
532 return p;
535 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
537 update_curr_rt(rq);
538 p->se.exec_start = 0;
541 #ifdef CONFIG_SMP
543 /* Only try algorithms three times */
544 #define RT_MAX_TRIES 3
546 static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
547 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
549 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
551 if (!task_running(rq, p) &&
552 (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
553 (p->rt.nr_cpus_allowed > 1))
554 return 1;
555 return 0;
558 /* Return the second highest RT task, NULL otherwise */
559 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
561 struct task_struct *next = NULL;
562 struct sched_rt_entity *rt_se;
563 struct rt_prio_array *array;
564 struct rt_rq *rt_rq;
565 int idx;
567 for_each_leaf_rt_rq(rt_rq, rq) {
568 array = &rt_rq->active;
569 idx = sched_find_first_bit(array->bitmap);
570 next_idx:
571 if (idx >= MAX_RT_PRIO)
572 continue;
573 if (next && next->prio < idx)
574 continue;
575 list_for_each_entry(rt_se, array->queue + idx, run_list) {
576 struct task_struct *p = rt_task_of(rt_se);
577 if (pick_rt_task(rq, p, cpu)) {
578 next = p;
579 break;
582 if (!next) {
583 idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
584 goto next_idx;
588 return next;
591 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
593 static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
595 int lowest_prio = -1;
596 int lowest_cpu = -1;
597 int count = 0;
598 int cpu;
600 cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
603 * Scan each rq for the lowest prio.
605 for_each_cpu_mask(cpu, *lowest_mask) {
606 struct rq *rq = cpu_rq(cpu);
608 /* We look for lowest RT prio or non-rt CPU */
609 if (rq->rt.highest_prio >= MAX_RT_PRIO) {
611 * if we already found a low RT queue
612 * and now we found this non-rt queue
613 * clear the mask and set our bit.
614 * Otherwise just return the queue as is
615 * and the count==1 will cause the algorithm
616 * to use the first bit found.
618 if (lowest_cpu != -1) {
619 cpus_clear(*lowest_mask);
620 cpu_set(rq->cpu, *lowest_mask);
622 return 1;
625 /* no locking for now */
626 if ((rq->rt.highest_prio > task->prio)
627 && (rq->rt.highest_prio >= lowest_prio)) {
628 if (rq->rt.highest_prio > lowest_prio) {
629 /* new low - clear old data */
630 lowest_prio = rq->rt.highest_prio;
631 lowest_cpu = cpu;
632 count = 0;
634 count++;
635 } else
636 cpu_clear(cpu, *lowest_mask);
640 * Clear out all the set bits that represent
641 * runqueues that were of higher prio than
642 * the lowest_prio.
644 if (lowest_cpu > 0) {
646 * Perhaps we could add another cpumask op to
647 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
648 * Then that could be optimized to use memset and such.
650 for_each_cpu_mask(cpu, *lowest_mask) {
651 if (cpu >= lowest_cpu)
652 break;
653 cpu_clear(cpu, *lowest_mask);
657 return count;
660 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
662 int first;
664 /* "this_cpu" is cheaper to preempt than a remote processor */
665 if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
666 return this_cpu;
668 first = first_cpu(*mask);
669 if (first != NR_CPUS)
670 return first;
672 return -1;
675 static int find_lowest_rq(struct task_struct *task)
677 struct sched_domain *sd;
678 cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
679 int this_cpu = smp_processor_id();
680 int cpu = task_cpu(task);
681 int count = find_lowest_cpus(task, lowest_mask);
683 if (!count)
684 return -1; /* No targets found */
687 * There is no sense in performing an optimal search if only one
688 * target is found.
690 if (count == 1)
691 return first_cpu(*lowest_mask);
694 * At this point we have built a mask of cpus representing the
695 * lowest priority tasks in the system. Now we want to elect
696 * the best one based on our affinity and topology.
698 * We prioritize the last cpu that the task executed on since
699 * it is most likely cache-hot in that location.
701 if (cpu_isset(cpu, *lowest_mask))
702 return cpu;
705 * Otherwise, we consult the sched_domains span maps to figure
706 * out which cpu is logically closest to our hot cache data.
708 if (this_cpu == cpu)
709 this_cpu = -1; /* Skip this_cpu opt if the same */
711 for_each_domain(cpu, sd) {
712 if (sd->flags & SD_WAKE_AFFINE) {
713 cpumask_t domain_mask;
714 int best_cpu;
716 cpus_and(domain_mask, sd->span, *lowest_mask);
718 best_cpu = pick_optimal_cpu(this_cpu,
719 &domain_mask);
720 if (best_cpu != -1)
721 return best_cpu;
726 * And finally, if there were no matches within the domains
727 * just give the caller *something* to work with from the compatible
728 * locations.
730 return pick_optimal_cpu(this_cpu, lowest_mask);
733 /* Will lock the rq it finds */
734 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
736 struct rq *lowest_rq = NULL;
737 int tries;
738 int cpu;
740 for (tries = 0; tries < RT_MAX_TRIES; tries++) {
741 cpu = find_lowest_rq(task);
743 if ((cpu == -1) || (cpu == rq->cpu))
744 break;
746 lowest_rq = cpu_rq(cpu);
748 /* if the prio of this runqueue changed, try again */
749 if (double_lock_balance(rq, lowest_rq)) {
751 * We had to unlock the run queue. In
752 * the mean time, task could have
753 * migrated already or had its affinity changed.
754 * Also make sure that it wasn't scheduled on its rq.
756 if (unlikely(task_rq(task) != rq ||
757 !cpu_isset(lowest_rq->cpu,
758 task->cpus_allowed) ||
759 task_running(rq, task) ||
760 !task->se.on_rq)) {
762 spin_unlock(&lowest_rq->lock);
763 lowest_rq = NULL;
764 break;
768 /* If this rq is still suitable use it. */
769 if (lowest_rq->rt.highest_prio > task->prio)
770 break;
772 /* try again */
773 spin_unlock(&lowest_rq->lock);
774 lowest_rq = NULL;
777 return lowest_rq;
781 * If the current CPU has more than one RT task, see if the non
782 * running task can migrate over to a CPU that is running a task
783 * of lesser priority.
785 static int push_rt_task(struct rq *rq)
787 struct task_struct *next_task;
788 struct rq *lowest_rq;
789 int ret = 0;
790 int paranoid = RT_MAX_TRIES;
792 if (!rq->rt.overloaded)
793 return 0;
795 next_task = pick_next_highest_task_rt(rq, -1);
796 if (!next_task)
797 return 0;
799 retry:
800 if (unlikely(next_task == rq->curr)) {
801 WARN_ON(1);
802 return 0;
806 * It's possible that the next_task slipped in of
807 * higher priority than current. If that's the case
808 * just reschedule current.
810 if (unlikely(next_task->prio < rq->curr->prio)) {
811 resched_task(rq->curr);
812 return 0;
815 /* We might release rq lock */
816 get_task_struct(next_task);
818 /* find_lock_lowest_rq locks the rq if found */
819 lowest_rq = find_lock_lowest_rq(next_task, rq);
820 if (!lowest_rq) {
821 struct task_struct *task;
823 * find lock_lowest_rq releases rq->lock
824 * so it is possible that next_task has changed.
825 * If it has, then try again.
827 task = pick_next_highest_task_rt(rq, -1);
828 if (unlikely(task != next_task) && task && paranoid--) {
829 put_task_struct(next_task);
830 next_task = task;
831 goto retry;
833 goto out;
836 deactivate_task(rq, next_task, 0);
837 set_task_cpu(next_task, lowest_rq->cpu);
838 activate_task(lowest_rq, next_task, 0);
840 resched_task(lowest_rq->curr);
842 spin_unlock(&lowest_rq->lock);
844 ret = 1;
845 out:
846 put_task_struct(next_task);
848 return ret;
852 * TODO: Currently we just use the second highest prio task on
853 * the queue, and stop when it can't migrate (or there's
854 * no more RT tasks). There may be a case where a lower
855 * priority RT task has a different affinity than the
856 * higher RT task. In this case the lower RT task could
857 * possibly be able to migrate where as the higher priority
858 * RT task could not. We currently ignore this issue.
859 * Enhancements are welcome!
861 static void push_rt_tasks(struct rq *rq)
863 /* push_rt_task will return true if it moved an RT */
864 while (push_rt_task(rq))
868 static int pull_rt_task(struct rq *this_rq)
870 int this_cpu = this_rq->cpu, ret = 0, cpu;
871 struct task_struct *p, *next;
872 struct rq *src_rq;
874 if (likely(!rt_overloaded(this_rq)))
875 return 0;
877 next = pick_next_task_rt(this_rq);
879 for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
880 if (this_cpu == cpu)
881 continue;
883 src_rq = cpu_rq(cpu);
885 * We can potentially drop this_rq's lock in
886 * double_lock_balance, and another CPU could
887 * steal our next task - hence we must cause
888 * the caller to recalculate the next task
889 * in that case:
891 if (double_lock_balance(this_rq, src_rq)) {
892 struct task_struct *old_next = next;
894 next = pick_next_task_rt(this_rq);
895 if (next != old_next)
896 ret = 1;
900 * Are there still pullable RT tasks?
902 if (src_rq->rt.rt_nr_running <= 1)
903 goto skip;
905 p = pick_next_highest_task_rt(src_rq, this_cpu);
908 * Do we have an RT task that preempts
909 * the to-be-scheduled task?
911 if (p && (!next || (p->prio < next->prio))) {
912 WARN_ON(p == src_rq->curr);
913 WARN_ON(!p->se.on_rq);
916 * There's a chance that p is higher in priority
917 * than what's currently running on its cpu.
918 * This is just that p is wakeing up and hasn't
919 * had a chance to schedule. We only pull
920 * p if it is lower in priority than the
921 * current task on the run queue or
922 * this_rq next task is lower in prio than
923 * the current task on that rq.
925 if (p->prio < src_rq->curr->prio ||
926 (next && next->prio < src_rq->curr->prio))
927 goto skip;
929 ret = 1;
931 deactivate_task(src_rq, p, 0);
932 set_task_cpu(p, this_cpu);
933 activate_task(this_rq, p, 0);
935 * We continue with the search, just in
936 * case there's an even higher prio task
937 * in another runqueue. (low likelyhood
938 * but possible)
940 * Update next so that we won't pick a task
941 * on another cpu with a priority lower (or equal)
942 * than the one we just picked.
944 next = p;
947 skip:
948 spin_unlock(&src_rq->lock);
951 return ret;
954 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
956 /* Try to pull RT tasks here if we lower this rq's prio */
957 if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
958 pull_rt_task(rq);
961 static void post_schedule_rt(struct rq *rq)
964 * If we have more than one rt_task queued, then
965 * see if we can push the other rt_tasks off to other CPUS.
966 * Note we may release the rq lock, and since
967 * the lock was owned by prev, we need to release it
968 * first via finish_lock_switch and then reaquire it here.
970 if (unlikely(rq->rt.overloaded)) {
971 spin_lock_irq(&rq->lock);
972 push_rt_tasks(rq);
973 spin_unlock_irq(&rq->lock);
978 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
980 if (!task_running(rq, p) &&
981 (p->prio >= rq->rt.highest_prio) &&
982 rq->rt.overloaded)
983 push_rt_tasks(rq);
986 static unsigned long
987 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
988 unsigned long max_load_move,
989 struct sched_domain *sd, enum cpu_idle_type idle,
990 int *all_pinned, int *this_best_prio)
992 /* don't touch RT tasks */
993 return 0;
996 static int
997 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
998 struct sched_domain *sd, enum cpu_idle_type idle)
1000 /* don't touch RT tasks */
1001 return 0;
1004 static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
1006 int weight = cpus_weight(*new_mask);
1008 BUG_ON(!rt_task(p));
1011 * Update the migration status of the RQ if we have an RT task
1012 * which is running AND changing its weight value.
1014 if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1015 struct rq *rq = task_rq(p);
1017 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1018 rq->rt.rt_nr_migratory++;
1019 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1020 BUG_ON(!rq->rt.rt_nr_migratory);
1021 rq->rt.rt_nr_migratory--;
1024 update_rt_migration(rq);
1027 p->cpus_allowed = *new_mask;
1028 p->rt.nr_cpus_allowed = weight;
1031 /* Assumes rq->lock is held */
1032 static void join_domain_rt(struct rq *rq)
1034 if (rq->rt.overloaded)
1035 rt_set_overload(rq);
1038 /* Assumes rq->lock is held */
1039 static void leave_domain_rt(struct rq *rq)
1041 if (rq->rt.overloaded)
1042 rt_clear_overload(rq);
1046 * When switch from the rt queue, we bring ourselves to a position
1047 * that we might want to pull RT tasks from other runqueues.
1049 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1050 int running)
1053 * If there are other RT tasks then we will reschedule
1054 * and the scheduling of the other RT tasks will handle
1055 * the balancing. But if we are the last RT task
1056 * we may need to handle the pulling of RT tasks
1057 * now.
1059 if (!rq->rt.rt_nr_running)
1060 pull_rt_task(rq);
1062 #endif /* CONFIG_SMP */
1065 * When switching a task to RT, we may overload the runqueue
1066 * with RT tasks. In this case we try to push them off to
1067 * other runqueues.
1069 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1070 int running)
1072 int check_resched = 1;
1075 * If we are already running, then there's nothing
1076 * that needs to be done. But if we are not running
1077 * we may need to preempt the current running task.
1078 * If that current running task is also an RT task
1079 * then see if we can move to another run queue.
1081 if (!running) {
1082 #ifdef CONFIG_SMP
1083 if (rq->rt.overloaded && push_rt_task(rq) &&
1084 /* Don't resched if we changed runqueues */
1085 rq != task_rq(p))
1086 check_resched = 0;
1087 #endif /* CONFIG_SMP */
1088 if (check_resched && p->prio < rq->curr->prio)
1089 resched_task(rq->curr);
1094 * Priority of the task has changed. This may cause
1095 * us to initiate a push or pull.
1097 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1098 int oldprio, int running)
1100 if (running) {
1101 #ifdef CONFIG_SMP
1103 * If our priority decreases while running, we
1104 * may need to pull tasks to this runqueue.
1106 if (oldprio < p->prio)
1107 pull_rt_task(rq);
1109 * If there's a higher priority task waiting to run
1110 * then reschedule.
1112 if (p->prio > rq->rt.highest_prio)
1113 resched_task(p);
1114 #else
1115 /* For UP simply resched on drop of prio */
1116 if (oldprio < p->prio)
1117 resched_task(p);
1118 #endif /* CONFIG_SMP */
1119 } else {
1121 * This task is not running, but if it is
1122 * greater than the current running task
1123 * then reschedule.
1125 if (p->prio < rq->curr->prio)
1126 resched_task(rq->curr);
1130 static void watchdog(struct rq *rq, struct task_struct *p)
1132 unsigned long soft, hard;
1134 if (!p->signal)
1135 return;
1137 soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1138 hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1140 if (soft != RLIM_INFINITY) {
1141 unsigned long next;
1143 p->rt.timeout++;
1144 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1145 if (p->rt.timeout > next)
1146 p->it_sched_expires = p->se.sum_exec_runtime;
1150 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1152 update_curr_rt(rq);
1154 watchdog(rq, p);
1157 * RR tasks need a special form of timeslice management.
1158 * FIFO tasks have no timeslices.
1160 if (p->policy != SCHED_RR)
1161 return;
1163 if (--p->rt.time_slice)
1164 return;
1166 p->rt.time_slice = DEF_TIMESLICE;
1169 * Requeue to the end of queue if we are not the only element
1170 * on the queue:
1172 if (p->rt.run_list.prev != p->rt.run_list.next) {
1173 requeue_task_rt(rq, p);
1174 set_tsk_need_resched(p);
1178 static void set_curr_task_rt(struct rq *rq)
1180 struct task_struct *p = rq->curr;
1182 p->se.exec_start = rq->clock;
1185 const struct sched_class rt_sched_class = {
1186 .next = &fair_sched_class,
1187 .enqueue_task = enqueue_task_rt,
1188 .dequeue_task = dequeue_task_rt,
1189 .yield_task = yield_task_rt,
1190 #ifdef CONFIG_SMP
1191 .select_task_rq = select_task_rq_rt,
1192 #endif /* CONFIG_SMP */
1194 .check_preempt_curr = check_preempt_curr_rt,
1196 .pick_next_task = pick_next_task_rt,
1197 .put_prev_task = put_prev_task_rt,
1199 #ifdef CONFIG_SMP
1200 .load_balance = load_balance_rt,
1201 .move_one_task = move_one_task_rt,
1202 .set_cpus_allowed = set_cpus_allowed_rt,
1203 .join_domain = join_domain_rt,
1204 .leave_domain = leave_domain_rt,
1205 .pre_schedule = pre_schedule_rt,
1206 .post_schedule = post_schedule_rt,
1207 .task_wake_up = task_wake_up_rt,
1208 .switched_from = switched_from_rt,
1209 #endif
1211 .set_curr_task = set_curr_task_rt,
1212 .task_tick = task_tick_rt,
1214 .prio_changed = prio_changed_rt,
1215 .switched_to = switched_to_rt,