sched: add some comments to the bandwidth code
[linux-2.6.git] / kernel / sched_rt.c
1 /*
2  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
3  * policies)
4  */
5
6 #ifdef CONFIG_SMP
7
8 static inline int rt_overloaded(struct rq *rq)
9 {
10         return atomic_read(&rq->rd->rto_count);
11 }
12
13 static inline void rt_set_overload(struct rq *rq)
14 {
15         if (!rq->online)
16                 return;
17
18         cpu_set(rq->cpu, rq->rd->rto_mask);
19         /*
20          * Make sure the mask is visible before we set
21          * the overload count. That is checked to determine
22          * if we should look at the mask. It would be a shame
23          * if we looked at the mask, but the mask was not
24          * updated yet.
25          */
26         wmb();
27         atomic_inc(&rq->rd->rto_count);
28 }
29
30 static inline void rt_clear_overload(struct rq *rq)
31 {
32         if (!rq->online)
33                 return;
34
35         /* the order here really doesn't matter */
36         atomic_dec(&rq->rd->rto_count);
37         cpu_clear(rq->cpu, rq->rd->rto_mask);
38 }
39
40 static void update_rt_migration(struct rq *rq)
41 {
42         if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
43                 if (!rq->rt.overloaded) {
44                         rt_set_overload(rq);
45                         rq->rt.overloaded = 1;
46                 }
47         } else if (rq->rt.overloaded) {
48                 rt_clear_overload(rq);
49                 rq->rt.overloaded = 0;
50         }
51 }
52 #endif /* CONFIG_SMP */
53
54 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
55 {
56         return container_of(rt_se, struct task_struct, rt);
57 }
58
59 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
60 {
61         return !list_empty(&rt_se->run_list);
62 }
63
64 #ifdef CONFIG_RT_GROUP_SCHED
65
66 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
67 {
68         if (!rt_rq->tg)
69                 return RUNTIME_INF;
70
71         return rt_rq->rt_runtime;
72 }
73
74 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
75 {
76         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
77 }
78
79 #define for_each_leaf_rt_rq(rt_rq, rq) \
80         list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
81
82 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
83 {
84         return rt_rq->rq;
85 }
86
87 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
88 {
89         return rt_se->rt_rq;
90 }
91
92 #define for_each_sched_rt_entity(rt_se) \
93         for (; rt_se; rt_se = rt_se->parent)
94
95 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
96 {
97         return rt_se->my_q;
98 }
99
100 static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
101 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
102
103 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
104 {
105         struct sched_rt_entity *rt_se = rt_rq->rt_se;
106
107         if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
108                 struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
109
110                 enqueue_rt_entity(rt_se);
111                 if (rt_rq->highest_prio < curr->prio)
112                         resched_task(curr);
113         }
114 }
115
116 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
117 {
118         struct sched_rt_entity *rt_se = rt_rq->rt_se;
119
120         if (rt_se && on_rt_rq(rt_se))
121                 dequeue_rt_entity(rt_se);
122 }
123
124 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
125 {
126         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
127 }
128
129 static int rt_se_boosted(struct sched_rt_entity *rt_se)
130 {
131         struct rt_rq *rt_rq = group_rt_rq(rt_se);
132         struct task_struct *p;
133
134         if (rt_rq)
135                 return !!rt_rq->rt_nr_boosted;
136
137         p = rt_task_of(rt_se);
138         return p->prio != p->normal_prio;
139 }
140
141 #ifdef CONFIG_SMP
142 static inline cpumask_t sched_rt_period_mask(void)
143 {
144         return cpu_rq(smp_processor_id())->rd->span;
145 }
146 #else
147 static inline cpumask_t sched_rt_period_mask(void)
148 {
149         return cpu_online_map;
150 }
151 #endif
152
153 static inline
154 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
155 {
156         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
157 }
158
159 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
160 {
161         return &rt_rq->tg->rt_bandwidth;
162 }
163
164 #else /* !CONFIG_RT_GROUP_SCHED */
165
166 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
167 {
168         return rt_rq->rt_runtime;
169 }
170
171 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
172 {
173         return ktime_to_ns(def_rt_bandwidth.rt_period);
174 }
175
176 #define for_each_leaf_rt_rq(rt_rq, rq) \
177         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
178
179 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
180 {
181         return container_of(rt_rq, struct rq, rt);
182 }
183
184 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
185 {
186         struct task_struct *p = rt_task_of(rt_se);
187         struct rq *rq = task_rq(p);
188
189         return &rq->rt;
190 }
191
192 #define for_each_sched_rt_entity(rt_se) \
193         for (; rt_se; rt_se = NULL)
194
195 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
196 {
197         return NULL;
198 }
199
200 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
201 {
202         if (rt_rq->rt_nr_running)
203                 resched_task(rq_of_rt_rq(rt_rq)->curr);
204 }
205
206 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
207 {
208 }
209
210 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
211 {
212         return rt_rq->rt_throttled;
213 }
214
215 static inline cpumask_t sched_rt_period_mask(void)
216 {
217         return cpu_online_map;
218 }
219
220 static inline
221 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
222 {
223         return &cpu_rq(cpu)->rt;
224 }
225
226 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
227 {
228         return &def_rt_bandwidth;
229 }
230
231 #endif /* CONFIG_RT_GROUP_SCHED */
232
233 #ifdef CONFIG_SMP
234 /*
235  * We ran out of runtime, see if we can borrow some from our neighbours.
236  */
237 static int do_balance_runtime(struct rt_rq *rt_rq)
238 {
239         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
240         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
241         int i, weight, more = 0;
242         u64 rt_period;
243
244         weight = cpus_weight(rd->span);
245
246         spin_lock(&rt_b->rt_runtime_lock);
247         rt_period = ktime_to_ns(rt_b->rt_period);
248         for_each_cpu_mask_nr(i, rd->span) {
249                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
250                 s64 diff;
251
252                 if (iter == rt_rq)
253                         continue;
254
255                 spin_lock(&iter->rt_runtime_lock);
256                 /*
257                  * Either all rqs have inf runtime and there's nothing to steal
258                  * or __disable_runtime() below sets a specific rq to inf to
259                  * indicate its been disabled and disalow stealing.
260                  */
261                 if (iter->rt_runtime == RUNTIME_INF)
262                         goto next;
263
264                 /*
265                  * From runqueues with spare time, take 1/n part of their
266                  * spare time, but no more than our period.
267                  */
268                 diff = iter->rt_runtime - iter->rt_time;
269                 if (diff > 0) {
270                         diff = div_u64((u64)diff, weight);
271                         if (rt_rq->rt_runtime + diff > rt_period)
272                                 diff = rt_period - rt_rq->rt_runtime;
273                         iter->rt_runtime -= diff;
274                         rt_rq->rt_runtime += diff;
275                         more = 1;
276                         if (rt_rq->rt_runtime == rt_period) {
277                                 spin_unlock(&iter->rt_runtime_lock);
278                                 break;
279                         }
280                 }
281 next:
282                 spin_unlock(&iter->rt_runtime_lock);
283         }
284         spin_unlock(&rt_b->rt_runtime_lock);
285
286         return more;
287 }
288
289 /*
290  * Ensure this RQ takes back all the runtime it lend to its neighbours.
291  */
292 static void __disable_runtime(struct rq *rq)
293 {
294         struct root_domain *rd = rq->rd;
295         struct rt_rq *rt_rq;
296
297         if (unlikely(!scheduler_running))
298                 return;
299
300         for_each_leaf_rt_rq(rt_rq, rq) {
301                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
302                 s64 want;
303                 int i;
304
305                 spin_lock(&rt_b->rt_runtime_lock);
306                 spin_lock(&rt_rq->rt_runtime_lock);
307                 /*
308                  * Either we're all inf and nobody needs to borrow, or we're
309                  * already disabled and thus have nothing to do, or we have
310                  * exactly the right amount of runtime to take out.
311                  */
312                 if (rt_rq->rt_runtime == RUNTIME_INF ||
313                                 rt_rq->rt_runtime == rt_b->rt_runtime)
314                         goto balanced;
315                 spin_unlock(&rt_rq->rt_runtime_lock);
316
317                 /*
318                  * Calculate the difference between what we started out with
319                  * and what we current have, that's the amount of runtime
320                  * we lend and now have to reclaim.
321                  */
322                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
323
324                 /*
325                  * Greedy reclaim, take back as much as we can.
326                  */
327                 for_each_cpu_mask(i, rd->span) {
328                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
329                         s64 diff;
330
331                         /*
332                          * Can't reclaim from ourselves or disabled runqueues.
333                          */
334                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
335                                 continue;
336
337                         spin_lock(&iter->rt_runtime_lock);
338                         if (want > 0) {
339                                 diff = min_t(s64, iter->rt_runtime, want);
340                                 iter->rt_runtime -= diff;
341                                 want -= diff;
342                         } else {
343                                 iter->rt_runtime -= want;
344                                 want -= want;
345                         }
346                         spin_unlock(&iter->rt_runtime_lock);
347
348                         if (!want)
349                                 break;
350                 }
351
352                 spin_lock(&rt_rq->rt_runtime_lock);
353                 /*
354                  * We cannot be left wanting - that would mean some runtime
355                  * leaked out of the system.
356                  */
357                 BUG_ON(want);
358 balanced:
359                 /*
360                  * Disable all the borrow logic by pretending we have inf
361                  * runtime - in which case borrowing doesn't make sense.
362                  */
363                 rt_rq->rt_runtime = RUNTIME_INF;
364                 spin_unlock(&rt_rq->rt_runtime_lock);
365                 spin_unlock(&rt_b->rt_runtime_lock);
366         }
367 }
368
369 static void disable_runtime(struct rq *rq)
370 {
371         unsigned long flags;
372
373         spin_lock_irqsave(&rq->lock, flags);
374         __disable_runtime(rq);
375         spin_unlock_irqrestore(&rq->lock, flags);
376 }
377
378 static void __enable_runtime(struct rq *rq)
379 {
380         struct rt_rq *rt_rq;
381
382         if (unlikely(!scheduler_running))
383                 return;
384
385         /*
386          * Reset each runqueue's bandwidth settings
387          */
388         for_each_leaf_rt_rq(rt_rq, rq) {
389                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
390
391                 spin_lock(&rt_b->rt_runtime_lock);
392                 spin_lock(&rt_rq->rt_runtime_lock);
393                 rt_rq->rt_runtime = rt_b->rt_runtime;
394                 rt_rq->rt_time = 0;
395                 rt_rq->rt_throttled = 0;
396                 spin_unlock(&rt_rq->rt_runtime_lock);
397                 spin_unlock(&rt_b->rt_runtime_lock);
398         }
399 }
400
401 static void enable_runtime(struct rq *rq)
402 {
403         unsigned long flags;
404
405         spin_lock_irqsave(&rq->lock, flags);
406         __enable_runtime(rq);
407         spin_unlock_irqrestore(&rq->lock, flags);
408 }
409
410 static int balance_runtime(struct rt_rq *rt_rq)
411 {
412         int more = 0;
413
414         if (rt_rq->rt_time > rt_rq->rt_runtime) {
415                 spin_unlock(&rt_rq->rt_runtime_lock);
416                 more = do_balance_runtime(rt_rq);
417                 spin_lock(&rt_rq->rt_runtime_lock);
418         }
419
420         return more;
421 }
422 #else /* !CONFIG_SMP */
423 static inline int balance_runtime(struct rt_rq *rt_rq)
424 {
425         return 0;
426 }
427 #endif /* CONFIG_SMP */
428
429 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
430 {
431         int i, idle = 1;
432         cpumask_t span;
433
434         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
435                 return 1;
436
437         span = sched_rt_period_mask();
438         for_each_cpu_mask(i, span) {
439                 int enqueue = 0;
440                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
441                 struct rq *rq = rq_of_rt_rq(rt_rq);
442
443                 spin_lock(&rq->lock);
444                 if (rt_rq->rt_time) {
445                         u64 runtime;
446
447                         spin_lock(&rt_rq->rt_runtime_lock);
448                         if (rt_rq->rt_throttled)
449                                 balance_runtime(rt_rq);
450                         runtime = rt_rq->rt_runtime;
451                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
452                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
453                                 rt_rq->rt_throttled = 0;
454                                 enqueue = 1;
455                         }
456                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
457                                 idle = 0;
458                         spin_unlock(&rt_rq->rt_runtime_lock);
459                 } else if (rt_rq->rt_nr_running)
460                         idle = 0;
461
462                 if (enqueue)
463                         sched_rt_rq_enqueue(rt_rq);
464                 spin_unlock(&rq->lock);
465         }
466
467         return idle;
468 }
469
470 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
471 {
472 #ifdef CONFIG_RT_GROUP_SCHED
473         struct rt_rq *rt_rq = group_rt_rq(rt_se);
474
475         if (rt_rq)
476                 return rt_rq->highest_prio;
477 #endif
478
479         return rt_task_of(rt_se)->prio;
480 }
481
482 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
483 {
484         u64 runtime = sched_rt_runtime(rt_rq);
485
486         if (rt_rq->rt_throttled)
487                 return rt_rq_throttled(rt_rq);
488
489         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
490                 return 0;
491
492         balance_runtime(rt_rq);
493         runtime = sched_rt_runtime(rt_rq);
494         if (runtime == RUNTIME_INF)
495                 return 0;
496
497         if (rt_rq->rt_time > runtime) {
498                 rt_rq->rt_throttled = 1;
499                 if (rt_rq_throttled(rt_rq)) {
500                         sched_rt_rq_dequeue(rt_rq);
501                         return 1;
502                 }
503         }
504
505         return 0;
506 }
507
508 /*
509  * Update the current task's runtime statistics. Skip current tasks that
510  * are not in our scheduling class.
511  */
512 static void update_curr_rt(struct rq *rq)
513 {
514         struct task_struct *curr = rq->curr;
515         struct sched_rt_entity *rt_se = &curr->rt;
516         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
517         u64 delta_exec;
518
519         if (!task_has_rt_policy(curr))
520                 return;
521
522         delta_exec = rq->clock - curr->se.exec_start;
523         if (unlikely((s64)delta_exec < 0))
524                 delta_exec = 0;
525
526         schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
527
528         curr->se.sum_exec_runtime += delta_exec;
529         curr->se.exec_start = rq->clock;
530         cpuacct_charge(curr, delta_exec);
531
532         if (!rt_bandwidth_enabled())
533                 return;
534
535         for_each_sched_rt_entity(rt_se) {
536                 rt_rq = rt_rq_of_se(rt_se);
537
538                 spin_lock(&rt_rq->rt_runtime_lock);
539                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
540                         rt_rq->rt_time += delta_exec;
541                         if (sched_rt_runtime_exceeded(rt_rq))
542                                 resched_task(curr);
543                 }
544                 spin_unlock(&rt_rq->rt_runtime_lock);
545         }
546 }
547
548 static inline
549 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
550 {
551         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
552         rt_rq->rt_nr_running++;
553 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
554         if (rt_se_prio(rt_se) < rt_rq->highest_prio) {
555 #ifdef CONFIG_SMP
556                 struct rq *rq = rq_of_rt_rq(rt_rq);
557 #endif
558
559                 rt_rq->highest_prio = rt_se_prio(rt_se);
560 #ifdef CONFIG_SMP
561                 if (rq->online)
562                         cpupri_set(&rq->rd->cpupri, rq->cpu,
563                                    rt_se_prio(rt_se));
564 #endif
565         }
566 #endif
567 #ifdef CONFIG_SMP
568         if (rt_se->nr_cpus_allowed > 1) {
569                 struct rq *rq = rq_of_rt_rq(rt_rq);
570
571                 rq->rt.rt_nr_migratory++;
572         }
573
574         update_rt_migration(rq_of_rt_rq(rt_rq));
575 #endif
576 #ifdef CONFIG_RT_GROUP_SCHED
577         if (rt_se_boosted(rt_se))
578                 rt_rq->rt_nr_boosted++;
579
580         if (rt_rq->tg)
581                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
582 #else
583         start_rt_bandwidth(&def_rt_bandwidth);
584 #endif
585 }
586
587 static inline
588 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
589 {
590 #ifdef CONFIG_SMP
591         int highest_prio = rt_rq->highest_prio;
592 #endif
593
594         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
595         WARN_ON(!rt_rq->rt_nr_running);
596         rt_rq->rt_nr_running--;
597 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
598         if (rt_rq->rt_nr_running) {
599                 struct rt_prio_array *array;
600
601                 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
602                 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
603                         /* recalculate */
604                         array = &rt_rq->active;
605                         rt_rq->highest_prio =
606                                 sched_find_first_bit(array->bitmap);
607                 } /* otherwise leave rq->highest prio alone */
608         } else
609                 rt_rq->highest_prio = MAX_RT_PRIO;
610 #endif
611 #ifdef CONFIG_SMP
612         if (rt_se->nr_cpus_allowed > 1) {
613                 struct rq *rq = rq_of_rt_rq(rt_rq);
614                 rq->rt.rt_nr_migratory--;
615         }
616
617         if (rt_rq->highest_prio != highest_prio) {
618                 struct rq *rq = rq_of_rt_rq(rt_rq);
619
620                 if (rq->online)
621                         cpupri_set(&rq->rd->cpupri, rq->cpu,
622                                    rt_rq->highest_prio);
623         }
624
625         update_rt_migration(rq_of_rt_rq(rt_rq));
626 #endif /* CONFIG_SMP */
627 #ifdef CONFIG_RT_GROUP_SCHED
628         if (rt_se_boosted(rt_se))
629                 rt_rq->rt_nr_boosted--;
630
631         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
632 #endif
633 }
634
635 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
636 {
637         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
638         struct rt_prio_array *array = &rt_rq->active;
639         struct rt_rq *group_rq = group_rt_rq(rt_se);
640         struct list_head *queue = array->queue + rt_se_prio(rt_se);
641
642         /*
643          * Don't enqueue the group if its throttled, or when empty.
644          * The latter is a consequence of the former when a child group
645          * get throttled and the current group doesn't have any other
646          * active members.
647          */
648         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
649                 return;
650
651         list_add_tail(&rt_se->run_list, queue);
652         __set_bit(rt_se_prio(rt_se), array->bitmap);
653
654         inc_rt_tasks(rt_se, rt_rq);
655 }
656
657 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
658 {
659         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
660         struct rt_prio_array *array = &rt_rq->active;
661
662         list_del_init(&rt_se->run_list);
663         if (list_empty(array->queue + rt_se_prio(rt_se)))
664                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
665
666         dec_rt_tasks(rt_se, rt_rq);
667 }
668
669 /*
670  * Because the prio of an upper entry depends on the lower
671  * entries, we must remove entries top - down.
672  */
673 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
674 {
675         struct sched_rt_entity *back = NULL;
676
677         for_each_sched_rt_entity(rt_se) {
678                 rt_se->back = back;
679                 back = rt_se;
680         }
681
682         for (rt_se = back; rt_se; rt_se = rt_se->back) {
683                 if (on_rt_rq(rt_se))
684                         __dequeue_rt_entity(rt_se);
685         }
686 }
687
688 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
689 {
690         dequeue_rt_stack(rt_se);
691         for_each_sched_rt_entity(rt_se)
692                 __enqueue_rt_entity(rt_se);
693 }
694
695 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
696 {
697         dequeue_rt_stack(rt_se);
698
699         for_each_sched_rt_entity(rt_se) {
700                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
701
702                 if (rt_rq && rt_rq->rt_nr_running)
703                         __enqueue_rt_entity(rt_se);
704         }
705 }
706
707 /*
708  * Adding/removing a task to/from a priority array:
709  */
710 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
711 {
712         struct sched_rt_entity *rt_se = &p->rt;
713
714         if (wakeup)
715                 rt_se->timeout = 0;
716
717         enqueue_rt_entity(rt_se);
718
719         inc_cpu_load(rq, p->se.load.weight);
720 }
721
722 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
723 {
724         struct sched_rt_entity *rt_se = &p->rt;
725
726         update_curr_rt(rq);
727         dequeue_rt_entity(rt_se);
728
729         dec_cpu_load(rq, p->se.load.weight);
730 }
731
732 /*
733  * Put task to the end of the run list without the overhead of dequeue
734  * followed by enqueue.
735  */
736 static void
737 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
738 {
739         if (on_rt_rq(rt_se)) {
740                 struct rt_prio_array *array = &rt_rq->active;
741                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
742
743                 if (head)
744                         list_move(&rt_se->run_list, queue);
745                 else
746                         list_move_tail(&rt_se->run_list, queue);
747         }
748 }
749
750 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
751 {
752         struct sched_rt_entity *rt_se = &p->rt;
753         struct rt_rq *rt_rq;
754
755         for_each_sched_rt_entity(rt_se) {
756                 rt_rq = rt_rq_of_se(rt_se);
757                 requeue_rt_entity(rt_rq, rt_se, head);
758         }
759 }
760
761 static void yield_task_rt(struct rq *rq)
762 {
763         requeue_task_rt(rq, rq->curr, 0);
764 }
765
766 #ifdef CONFIG_SMP
767 static int find_lowest_rq(struct task_struct *task);
768
769 static int select_task_rq_rt(struct task_struct *p, int sync)
770 {
771         struct rq *rq = task_rq(p);
772
773         /*
774          * If the current task is an RT task, then
775          * try to see if we can wake this RT task up on another
776          * runqueue. Otherwise simply start this RT task
777          * on its current runqueue.
778          *
779          * We want to avoid overloading runqueues. Even if
780          * the RT task is of higher priority than the current RT task.
781          * RT tasks behave differently than other tasks. If
782          * one gets preempted, we try to push it off to another queue.
783          * So trying to keep a preempting RT task on the same
784          * cache hot CPU will force the running RT task to
785          * a cold CPU. So we waste all the cache for the lower
786          * RT task in hopes of saving some of a RT task
787          * that is just being woken and probably will have
788          * cold cache anyway.
789          */
790         if (unlikely(rt_task(rq->curr)) &&
791             (p->rt.nr_cpus_allowed > 1)) {
792                 int cpu = find_lowest_rq(p);
793
794                 return (cpu == -1) ? task_cpu(p) : cpu;
795         }
796
797         /*
798          * Otherwise, just let it ride on the affined RQ and the
799          * post-schedule router will push the preempted task away
800          */
801         return task_cpu(p);
802 }
803
804 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
805 {
806         cpumask_t mask;
807
808         if (rq->curr->rt.nr_cpus_allowed == 1)
809                 return;
810
811         if (p->rt.nr_cpus_allowed != 1
812             && cpupri_find(&rq->rd->cpupri, p, &mask))
813                 return;
814
815         if (!cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
816                 return;
817
818         /*
819          * There appears to be other cpus that can accept
820          * current and none to run 'p', so lets reschedule
821          * to try and push current away:
822          */
823         requeue_task_rt(rq, p, 1);
824         resched_task(rq->curr);
825 }
826
827 #endif /* CONFIG_SMP */
828
829 /*
830  * Preempt the current task with a newly woken task if needed:
831  */
832 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync)
833 {
834         if (p->prio < rq->curr->prio) {
835                 resched_task(rq->curr);
836                 return;
837         }
838
839 #ifdef CONFIG_SMP
840         /*
841          * If:
842          *
843          * - the newly woken task is of equal priority to the current task
844          * - the newly woken task is non-migratable while current is migratable
845          * - current will be preempted on the next reschedule
846          *
847          * we should check to see if current can readily move to a different
848          * cpu.  If so, we will reschedule to allow the push logic to try
849          * to move current somewhere else, making room for our non-migratable
850          * task.
851          */
852         if (p->prio == rq->curr->prio && !need_resched())
853                 check_preempt_equal_prio(rq, p);
854 #endif
855 }
856
857 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
858                                                    struct rt_rq *rt_rq)
859 {
860         struct rt_prio_array *array = &rt_rq->active;
861         struct sched_rt_entity *next = NULL;
862         struct list_head *queue;
863         int idx;
864
865         idx = sched_find_first_bit(array->bitmap);
866         BUG_ON(idx >= MAX_RT_PRIO);
867
868         queue = array->queue + idx;
869         next = list_entry(queue->next, struct sched_rt_entity, run_list);
870
871         return next;
872 }
873
874 static struct task_struct *pick_next_task_rt(struct rq *rq)
875 {
876         struct sched_rt_entity *rt_se;
877         struct task_struct *p;
878         struct rt_rq *rt_rq;
879
880         rt_rq = &rq->rt;
881
882         if (unlikely(!rt_rq->rt_nr_running))
883                 return NULL;
884
885         if (rt_rq_throttled(rt_rq))
886                 return NULL;
887
888         do {
889                 rt_se = pick_next_rt_entity(rq, rt_rq);
890                 BUG_ON(!rt_se);
891                 rt_rq = group_rt_rq(rt_se);
892         } while (rt_rq);
893
894         p = rt_task_of(rt_se);
895         p->se.exec_start = rq->clock;
896         return p;
897 }
898
899 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
900 {
901         update_curr_rt(rq);
902         p->se.exec_start = 0;
903 }
904
905 #ifdef CONFIG_SMP
906
907 /* Only try algorithms three times */
908 #define RT_MAX_TRIES 3
909
910 static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
911 static void double_unlock_balance(struct rq *this_rq, struct rq *busiest);
912
913 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
914
915 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
916 {
917         if (!task_running(rq, p) &&
918             (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
919             (p->rt.nr_cpus_allowed > 1))
920                 return 1;
921         return 0;
922 }
923
924 /* Return the second highest RT task, NULL otherwise */
925 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
926 {
927         struct task_struct *next = NULL;
928         struct sched_rt_entity *rt_se;
929         struct rt_prio_array *array;
930         struct rt_rq *rt_rq;
931         int idx;
932
933         for_each_leaf_rt_rq(rt_rq, rq) {
934                 array = &rt_rq->active;
935                 idx = sched_find_first_bit(array->bitmap);
936  next_idx:
937                 if (idx >= MAX_RT_PRIO)
938                         continue;
939                 if (next && next->prio < idx)
940                         continue;
941                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
942                         struct task_struct *p = rt_task_of(rt_se);
943                         if (pick_rt_task(rq, p, cpu)) {
944                                 next = p;
945                                 break;
946                         }
947                 }
948                 if (!next) {
949                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
950                         goto next_idx;
951                 }
952         }
953
954         return next;
955 }
956
957 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
958
959 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
960 {
961         int first;
962
963         /* "this_cpu" is cheaper to preempt than a remote processor */
964         if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
965                 return this_cpu;
966
967         first = first_cpu(*mask);
968         if (first != NR_CPUS)
969                 return first;
970
971         return -1;
972 }
973
974 static int find_lowest_rq(struct task_struct *task)
975 {
976         struct sched_domain *sd;
977         cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
978         int this_cpu = smp_processor_id();
979         int cpu      = task_cpu(task);
980
981         if (task->rt.nr_cpus_allowed == 1)
982                 return -1; /* No other targets possible */
983
984         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
985                 return -1; /* No targets found */
986
987         /*
988          * Only consider CPUs that are usable for migration.
989          * I guess we might want to change cpupri_find() to ignore those
990          * in the first place.
991          */
992         cpus_and(*lowest_mask, *lowest_mask, cpu_active_map);
993
994         /*
995          * At this point we have built a mask of cpus representing the
996          * lowest priority tasks in the system.  Now we want to elect
997          * the best one based on our affinity and topology.
998          *
999          * We prioritize the last cpu that the task executed on since
1000          * it is most likely cache-hot in that location.
1001          */
1002         if (cpu_isset(cpu, *lowest_mask))
1003                 return cpu;
1004
1005         /*
1006          * Otherwise, we consult the sched_domains span maps to figure
1007          * out which cpu is logically closest to our hot cache data.
1008          */
1009         if (this_cpu == cpu)
1010                 this_cpu = -1; /* Skip this_cpu opt if the same */
1011
1012         for_each_domain(cpu, sd) {
1013                 if (sd->flags & SD_WAKE_AFFINE) {
1014                         cpumask_t domain_mask;
1015                         int       best_cpu;
1016
1017                         cpus_and(domain_mask, sd->span, *lowest_mask);
1018
1019                         best_cpu = pick_optimal_cpu(this_cpu,
1020                                                     &domain_mask);
1021                         if (best_cpu != -1)
1022                                 return best_cpu;
1023                 }
1024         }
1025
1026         /*
1027          * And finally, if there were no matches within the domains
1028          * just give the caller *something* to work with from the compatible
1029          * locations.
1030          */
1031         return pick_optimal_cpu(this_cpu, lowest_mask);
1032 }
1033
1034 /* Will lock the rq it finds */
1035 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1036 {
1037         struct rq *lowest_rq = NULL;
1038         int tries;
1039         int cpu;
1040
1041         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1042                 cpu = find_lowest_rq(task);
1043
1044                 if ((cpu == -1) || (cpu == rq->cpu))
1045                         break;
1046
1047                 lowest_rq = cpu_rq(cpu);
1048
1049                 /* if the prio of this runqueue changed, try again */
1050                 if (double_lock_balance(rq, lowest_rq)) {
1051                         /*
1052                          * We had to unlock the run queue. In
1053                          * the mean time, task could have
1054                          * migrated already or had its affinity changed.
1055                          * Also make sure that it wasn't scheduled on its rq.
1056                          */
1057                         if (unlikely(task_rq(task) != rq ||
1058                                      !cpu_isset(lowest_rq->cpu,
1059                                                 task->cpus_allowed) ||
1060                                      task_running(rq, task) ||
1061                                      !task->se.on_rq)) {
1062
1063                                 spin_unlock(&lowest_rq->lock);
1064                                 lowest_rq = NULL;
1065                                 break;
1066                         }
1067                 }
1068
1069                 /* If this rq is still suitable use it. */
1070                 if (lowest_rq->rt.highest_prio > task->prio)
1071                         break;
1072
1073                 /* try again */
1074                 double_unlock_balance(rq, lowest_rq);
1075                 lowest_rq = NULL;
1076         }
1077
1078         return lowest_rq;
1079 }
1080
1081 /*
1082  * If the current CPU has more than one RT task, see if the non
1083  * running task can migrate over to a CPU that is running a task
1084  * of lesser priority.
1085  */
1086 static int push_rt_task(struct rq *rq)
1087 {
1088         struct task_struct *next_task;
1089         struct rq *lowest_rq;
1090         int ret = 0;
1091         int paranoid = RT_MAX_TRIES;
1092
1093         if (!rq->rt.overloaded)
1094                 return 0;
1095
1096         next_task = pick_next_highest_task_rt(rq, -1);
1097         if (!next_task)
1098                 return 0;
1099
1100  retry:
1101         if (unlikely(next_task == rq->curr)) {
1102                 WARN_ON(1);
1103                 return 0;
1104         }
1105
1106         /*
1107          * It's possible that the next_task slipped in of
1108          * higher priority than current. If that's the case
1109          * just reschedule current.
1110          */
1111         if (unlikely(next_task->prio < rq->curr->prio)) {
1112                 resched_task(rq->curr);
1113                 return 0;
1114         }
1115
1116         /* We might release rq lock */
1117         get_task_struct(next_task);
1118
1119         /* find_lock_lowest_rq locks the rq if found */
1120         lowest_rq = find_lock_lowest_rq(next_task, rq);
1121         if (!lowest_rq) {
1122                 struct task_struct *task;
1123                 /*
1124                  * find lock_lowest_rq releases rq->lock
1125                  * so it is possible that next_task has changed.
1126                  * If it has, then try again.
1127                  */
1128                 task = pick_next_highest_task_rt(rq, -1);
1129                 if (unlikely(task != next_task) && task && paranoid--) {
1130                         put_task_struct(next_task);
1131                         next_task = task;
1132                         goto retry;
1133                 }
1134                 goto out;
1135         }
1136
1137         deactivate_task(rq, next_task, 0);
1138         set_task_cpu(next_task, lowest_rq->cpu);
1139         activate_task(lowest_rq, next_task, 0);
1140
1141         resched_task(lowest_rq->curr);
1142
1143         double_unlock_balance(rq, lowest_rq);
1144
1145         ret = 1;
1146 out:
1147         put_task_struct(next_task);
1148
1149         return ret;
1150 }
1151
1152 /*
1153  * TODO: Currently we just use the second highest prio task on
1154  *       the queue, and stop when it can't migrate (or there's
1155  *       no more RT tasks).  There may be a case where a lower
1156  *       priority RT task has a different affinity than the
1157  *       higher RT task. In this case the lower RT task could
1158  *       possibly be able to migrate where as the higher priority
1159  *       RT task could not.  We currently ignore this issue.
1160  *       Enhancements are welcome!
1161  */
1162 static void push_rt_tasks(struct rq *rq)
1163 {
1164         /* push_rt_task will return true if it moved an RT */
1165         while (push_rt_task(rq))
1166                 ;
1167 }
1168
1169 static int pull_rt_task(struct rq *this_rq)
1170 {
1171         int this_cpu = this_rq->cpu, ret = 0, cpu;
1172         struct task_struct *p, *next;
1173         struct rq *src_rq;
1174
1175         if (likely(!rt_overloaded(this_rq)))
1176                 return 0;
1177
1178         next = pick_next_task_rt(this_rq);
1179
1180         for_each_cpu_mask_nr(cpu, this_rq->rd->rto_mask) {
1181                 if (this_cpu == cpu)
1182                         continue;
1183
1184                 src_rq = cpu_rq(cpu);
1185                 /*
1186                  * We can potentially drop this_rq's lock in
1187                  * double_lock_balance, and another CPU could
1188                  * steal our next task - hence we must cause
1189                  * the caller to recalculate the next task
1190                  * in that case:
1191                  */
1192                 if (double_lock_balance(this_rq, src_rq)) {
1193                         struct task_struct *old_next = next;
1194
1195                         next = pick_next_task_rt(this_rq);
1196                         if (next != old_next)
1197                                 ret = 1;
1198                 }
1199
1200                 /*
1201                  * Are there still pullable RT tasks?
1202                  */
1203                 if (src_rq->rt.rt_nr_running <= 1)
1204                         goto skip;
1205
1206                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1207
1208                 /*
1209                  * Do we have an RT task that preempts
1210                  * the to-be-scheduled task?
1211                  */
1212                 if (p && (!next || (p->prio < next->prio))) {
1213                         WARN_ON(p == src_rq->curr);
1214                         WARN_ON(!p->se.on_rq);
1215
1216                         /*
1217                          * There's a chance that p is higher in priority
1218                          * than what's currently running on its cpu.
1219                          * This is just that p is wakeing up and hasn't
1220                          * had a chance to schedule. We only pull
1221                          * p if it is lower in priority than the
1222                          * current task on the run queue or
1223                          * this_rq next task is lower in prio than
1224                          * the current task on that rq.
1225                          */
1226                         if (p->prio < src_rq->curr->prio ||
1227                             (next && next->prio < src_rq->curr->prio))
1228                                 goto skip;
1229
1230                         ret = 1;
1231
1232                         deactivate_task(src_rq, p, 0);
1233                         set_task_cpu(p, this_cpu);
1234                         activate_task(this_rq, p, 0);
1235                         /*
1236                          * We continue with the search, just in
1237                          * case there's an even higher prio task
1238                          * in another runqueue. (low likelyhood
1239                          * but possible)
1240                          *
1241                          * Update next so that we won't pick a task
1242                          * on another cpu with a priority lower (or equal)
1243                          * than the one we just picked.
1244                          */
1245                         next = p;
1246
1247                 }
1248  skip:
1249                 double_unlock_balance(this_rq, src_rq);
1250         }
1251
1252         return ret;
1253 }
1254
1255 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1256 {
1257         /* Try to pull RT tasks here if we lower this rq's prio */
1258         if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
1259                 pull_rt_task(rq);
1260 }
1261
1262 static void post_schedule_rt(struct rq *rq)
1263 {
1264         /*
1265          * If we have more than one rt_task queued, then
1266          * see if we can push the other rt_tasks off to other CPUS.
1267          * Note we may release the rq lock, and since
1268          * the lock was owned by prev, we need to release it
1269          * first via finish_lock_switch and then reaquire it here.
1270          */
1271         if (unlikely(rq->rt.overloaded)) {
1272                 spin_lock_irq(&rq->lock);
1273                 push_rt_tasks(rq);
1274                 spin_unlock_irq(&rq->lock);
1275         }
1276 }
1277
1278 /*
1279  * If we are not running and we are not going to reschedule soon, we should
1280  * try to push tasks away now
1281  */
1282 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1283 {
1284         if (!task_running(rq, p) &&
1285             !test_tsk_need_resched(rq->curr) &&
1286             rq->rt.overloaded)
1287                 push_rt_tasks(rq);
1288 }
1289
1290 static unsigned long
1291 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1292                 unsigned long max_load_move,
1293                 struct sched_domain *sd, enum cpu_idle_type idle,
1294                 int *all_pinned, int *this_best_prio)
1295 {
1296         /* don't touch RT tasks */
1297         return 0;
1298 }
1299
1300 static int
1301 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1302                  struct sched_domain *sd, enum cpu_idle_type idle)
1303 {
1304         /* don't touch RT tasks */
1305         return 0;
1306 }
1307
1308 static void set_cpus_allowed_rt(struct task_struct *p,
1309                                 const cpumask_t *new_mask)
1310 {
1311         int weight = cpus_weight(*new_mask);
1312
1313         BUG_ON(!rt_task(p));
1314
1315         /*
1316          * Update the migration status of the RQ if we have an RT task
1317          * which is running AND changing its weight value.
1318          */
1319         if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1320                 struct rq *rq = task_rq(p);
1321
1322                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1323                         rq->rt.rt_nr_migratory++;
1324                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1325                         BUG_ON(!rq->rt.rt_nr_migratory);
1326                         rq->rt.rt_nr_migratory--;
1327                 }
1328
1329                 update_rt_migration(rq);
1330         }
1331
1332         p->cpus_allowed    = *new_mask;
1333         p->rt.nr_cpus_allowed = weight;
1334 }
1335
1336 /* Assumes rq->lock is held */
1337 static void rq_online_rt(struct rq *rq)
1338 {
1339         if (rq->rt.overloaded)
1340                 rt_set_overload(rq);
1341
1342         __enable_runtime(rq);
1343
1344         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
1345 }
1346
1347 /* Assumes rq->lock is held */
1348 static void rq_offline_rt(struct rq *rq)
1349 {
1350         if (rq->rt.overloaded)
1351                 rt_clear_overload(rq);
1352
1353         __disable_runtime(rq);
1354
1355         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1356 }
1357
1358 /*
1359  * When switch from the rt queue, we bring ourselves to a position
1360  * that we might want to pull RT tasks from other runqueues.
1361  */
1362 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1363                            int running)
1364 {
1365         /*
1366          * If there are other RT tasks then we will reschedule
1367          * and the scheduling of the other RT tasks will handle
1368          * the balancing. But if we are the last RT task
1369          * we may need to handle the pulling of RT tasks
1370          * now.
1371          */
1372         if (!rq->rt.rt_nr_running)
1373                 pull_rt_task(rq);
1374 }
1375 #endif /* CONFIG_SMP */
1376
1377 /*
1378  * When switching a task to RT, we may overload the runqueue
1379  * with RT tasks. In this case we try to push them off to
1380  * other runqueues.
1381  */
1382 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1383                            int running)
1384 {
1385         int check_resched = 1;
1386
1387         /*
1388          * If we are already running, then there's nothing
1389          * that needs to be done. But if we are not running
1390          * we may need to preempt the current running task.
1391          * If that current running task is also an RT task
1392          * then see if we can move to another run queue.
1393          */
1394         if (!running) {
1395 #ifdef CONFIG_SMP
1396                 if (rq->rt.overloaded && push_rt_task(rq) &&
1397                     /* Don't resched if we changed runqueues */
1398                     rq != task_rq(p))
1399                         check_resched = 0;
1400 #endif /* CONFIG_SMP */
1401                 if (check_resched && p->prio < rq->curr->prio)
1402                         resched_task(rq->curr);
1403         }
1404 }
1405
1406 /*
1407  * Priority of the task has changed. This may cause
1408  * us to initiate a push or pull.
1409  */
1410 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1411                             int oldprio, int running)
1412 {
1413         if (running) {
1414 #ifdef CONFIG_SMP
1415                 /*
1416                  * If our priority decreases while running, we
1417                  * may need to pull tasks to this runqueue.
1418                  */
1419                 if (oldprio < p->prio)
1420                         pull_rt_task(rq);
1421                 /*
1422                  * If there's a higher priority task waiting to run
1423                  * then reschedule. Note, the above pull_rt_task
1424                  * can release the rq lock and p could migrate.
1425                  * Only reschedule if p is still on the same runqueue.
1426                  */
1427                 if (p->prio > rq->rt.highest_prio && rq->curr == p)
1428                         resched_task(p);
1429 #else
1430                 /* For UP simply resched on drop of prio */
1431                 if (oldprio < p->prio)
1432                         resched_task(p);
1433 #endif /* CONFIG_SMP */
1434         } else {
1435                 /*
1436                  * This task is not running, but if it is
1437                  * greater than the current running task
1438                  * then reschedule.
1439                  */
1440                 if (p->prio < rq->curr->prio)
1441                         resched_task(rq->curr);
1442         }
1443 }
1444
1445 static void watchdog(struct rq *rq, struct task_struct *p)
1446 {
1447         unsigned long soft, hard;
1448
1449         if (!p->signal)
1450                 return;
1451
1452         soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1453         hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1454
1455         if (soft != RLIM_INFINITY) {
1456                 unsigned long next;
1457
1458                 p->rt.timeout++;
1459                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1460                 if (p->rt.timeout > next)
1461                         p->it_sched_expires = p->se.sum_exec_runtime;
1462         }
1463 }
1464
1465 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1466 {
1467         update_curr_rt(rq);
1468
1469         watchdog(rq, p);
1470
1471         /*
1472          * RR tasks need a special form of timeslice management.
1473          * FIFO tasks have no timeslices.
1474          */
1475         if (p->policy != SCHED_RR)
1476                 return;
1477
1478         if (--p->rt.time_slice)
1479                 return;
1480
1481         p->rt.time_slice = DEF_TIMESLICE;
1482
1483         /*
1484          * Requeue to the end of queue if we are not the only element
1485          * on the queue:
1486          */
1487         if (p->rt.run_list.prev != p->rt.run_list.next) {
1488                 requeue_task_rt(rq, p, 0);
1489                 set_tsk_need_resched(p);
1490         }
1491 }
1492
1493 static void set_curr_task_rt(struct rq *rq)
1494 {
1495         struct task_struct *p = rq->curr;
1496
1497         p->se.exec_start = rq->clock;
1498 }
1499
1500 static const struct sched_class rt_sched_class = {
1501         .next                   = &fair_sched_class,
1502         .enqueue_task           = enqueue_task_rt,
1503         .dequeue_task           = dequeue_task_rt,
1504         .yield_task             = yield_task_rt,
1505 #ifdef CONFIG_SMP
1506         .select_task_rq         = select_task_rq_rt,
1507 #endif /* CONFIG_SMP */
1508
1509         .check_preempt_curr     = check_preempt_curr_rt,
1510
1511         .pick_next_task         = pick_next_task_rt,
1512         .put_prev_task          = put_prev_task_rt,
1513
1514 #ifdef CONFIG_SMP
1515         .load_balance           = load_balance_rt,
1516         .move_one_task          = move_one_task_rt,
1517         .set_cpus_allowed       = set_cpus_allowed_rt,
1518         .rq_online              = rq_online_rt,
1519         .rq_offline             = rq_offline_rt,
1520         .pre_schedule           = pre_schedule_rt,
1521         .post_schedule          = post_schedule_rt,
1522         .task_wake_up           = task_wake_up_rt,
1523         .switched_from          = switched_from_rt,
1524 #endif
1525
1526         .set_curr_task          = set_curr_task_rt,
1527         .task_tick              = task_tick_rt,
1528
1529         .prio_changed           = prio_changed_rt,
1530         .switched_to            = switched_to_rt,
1531 };
1532
1533 #ifdef CONFIG_SCHED_DEBUG
1534 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1535
1536 static void print_rt_stats(struct seq_file *m, int cpu)
1537 {
1538         struct rt_rq *rt_rq;
1539
1540         rcu_read_lock();
1541         for_each_leaf_rt_rq(rt_rq, cpu_rq(cpu))
1542                 print_rt_rq(m, cpu, rt_rq);
1543         rcu_read_unlock();
1544 }
1545 #endif /* CONFIG_SCHED_DEBUG */