printk: Fix log_buf_copy termination.
[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_RT_GROUP_SCHED
7
8 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
9
10 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
11 {
12 #ifdef CONFIG_SCHED_DEBUG
13         WARN_ON_ONCE(!rt_entity_is_task(rt_se));
14 #endif
15         return container_of(rt_se, struct task_struct, rt);
16 }
17
18 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
19 {
20         return rt_rq->rq;
21 }
22
23 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
24 {
25         return rt_se->rt_rq;
26 }
27
28 #else /* CONFIG_RT_GROUP_SCHED */
29
30 #define rt_entity_is_task(rt_se) (1)
31
32 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
33 {
34         return container_of(rt_se, struct task_struct, rt);
35 }
36
37 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
38 {
39         return container_of(rt_rq, struct rq, rt);
40 }
41
42 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
43 {
44         struct task_struct *p = rt_task_of(rt_se);
45         struct rq *rq = task_rq(p);
46
47         return &rq->rt;
48 }
49
50 #endif /* CONFIG_RT_GROUP_SCHED */
51
52 #ifdef CONFIG_SMP
53
54 static inline int rt_overloaded(struct rq *rq)
55 {
56         return atomic_read(&rq->rd->rto_count);
57 }
58
59 static inline void rt_set_overload(struct rq *rq)
60 {
61         if (!rq->online)
62                 return;
63
64         cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
65         /*
66          * Make sure the mask is visible before we set
67          * the overload count. That is checked to determine
68          * if we should look at the mask. It would be a shame
69          * if we looked at the mask, but the mask was not
70          * updated yet.
71          */
72         wmb();
73         atomic_inc(&rq->rd->rto_count);
74 }
75
76 static inline void rt_clear_overload(struct rq *rq)
77 {
78         if (!rq->online)
79                 return;
80
81         /* the order here really doesn't matter */
82         atomic_dec(&rq->rd->rto_count);
83         cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
84 }
85
86 static void update_rt_migration(struct rt_rq *rt_rq)
87 {
88         if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
89                 if (!rt_rq->overloaded) {
90                         rt_set_overload(rq_of_rt_rq(rt_rq));
91                         rt_rq->overloaded = 1;
92                 }
93         } else if (rt_rq->overloaded) {
94                 rt_clear_overload(rq_of_rt_rq(rt_rq));
95                 rt_rq->overloaded = 0;
96         }
97 }
98
99 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
100 {
101         if (!rt_entity_is_task(rt_se))
102                 return;
103
104         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
105
106         rt_rq->rt_nr_total++;
107         if (rt_se->nr_cpus_allowed > 1)
108                 rt_rq->rt_nr_migratory++;
109
110         update_rt_migration(rt_rq);
111 }
112
113 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
114 {
115         if (!rt_entity_is_task(rt_se))
116                 return;
117
118         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
119
120         rt_rq->rt_nr_total--;
121         if (rt_se->nr_cpus_allowed > 1)
122                 rt_rq->rt_nr_migratory--;
123
124         update_rt_migration(rt_rq);
125 }
126
127 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
128 {
129         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
130         plist_node_init(&p->pushable_tasks, p->prio);
131         plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
132 }
133
134 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
135 {
136         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
137 }
138
139 static inline int has_pushable_tasks(struct rq *rq)
140 {
141         return !plist_head_empty(&rq->rt.pushable_tasks);
142 }
143
144 #else
145
146 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
147 {
148 }
149
150 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
151 {
152 }
153
154 static inline
155 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
156 {
157 }
158
159 static inline
160 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
161 {
162 }
163
164 #endif /* CONFIG_SMP */
165
166 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
167 {
168         return !list_empty(&rt_se->run_list);
169 }
170
171 #ifdef CONFIG_RT_GROUP_SCHED
172
173 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
174 {
175         if (!rt_rq->tg)
176                 return RUNTIME_INF;
177
178         return rt_rq->rt_runtime;
179 }
180
181 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
182 {
183         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
184 }
185
186 typedef struct task_group *rt_rq_iter_t;
187
188 static inline struct task_group *next_task_group(struct task_group *tg)
189 {
190         do {
191                 tg = list_entry_rcu(tg->list.next,
192                         typeof(struct task_group), list);
193         } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
194
195         if (&tg->list == &task_groups)
196                 tg = NULL;
197
198         return tg;
199 }
200
201 #define for_each_rt_rq(rt_rq, iter, rq)                                 \
202         for (iter = container_of(&task_groups, typeof(*iter), list);    \
203                 (iter = next_task_group(iter)) &&                       \
204                 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
205
206 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
207 {
208         list_add_rcu(&rt_rq->leaf_rt_rq_list,
209                         &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
210 }
211
212 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
213 {
214         list_del_rcu(&rt_rq->leaf_rt_rq_list);
215 }
216
217 #define for_each_leaf_rt_rq(rt_rq, rq) \
218         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
219
220 #define for_each_sched_rt_entity(rt_se) \
221         for (; rt_se; rt_se = rt_se->parent)
222
223 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
224 {
225         return rt_se->my_q;
226 }
227
228 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
229 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
230
231 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
232 {
233         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
234         struct sched_rt_entity *rt_se;
235
236         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
237
238         rt_se = rt_rq->tg->rt_se[cpu];
239
240         if (rt_rq->rt_nr_running) {
241                 if (rt_se && !on_rt_rq(rt_se))
242                         enqueue_rt_entity(rt_se, false);
243                 if (rt_rq->highest_prio.curr < curr->prio)
244                         resched_task(curr);
245         }
246 }
247
248 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
249 {
250         struct sched_rt_entity *rt_se;
251         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
252
253         rt_se = rt_rq->tg->rt_se[cpu];
254
255         if (rt_se && on_rt_rq(rt_se))
256                 dequeue_rt_entity(rt_se);
257 }
258
259 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
260 {
261         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
262 }
263
264 static int rt_se_boosted(struct sched_rt_entity *rt_se)
265 {
266         struct rt_rq *rt_rq = group_rt_rq(rt_se);
267         struct task_struct *p;
268
269         if (rt_rq)
270                 return !!rt_rq->rt_nr_boosted;
271
272         p = rt_task_of(rt_se);
273         return p->prio != p->normal_prio;
274 }
275
276 #ifdef CONFIG_SMP
277 static inline const struct cpumask *sched_rt_period_mask(void)
278 {
279         return cpu_rq(smp_processor_id())->rd->span;
280 }
281 #else
282 static inline const struct cpumask *sched_rt_period_mask(void)
283 {
284         return cpu_online_mask;
285 }
286 #endif
287
288 static inline
289 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
290 {
291         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
292 }
293
294 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
295 {
296         return &rt_rq->tg->rt_bandwidth;
297 }
298
299 #else /* !CONFIG_RT_GROUP_SCHED */
300
301 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
302 {
303         return rt_rq->rt_runtime;
304 }
305
306 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
307 {
308         return ktime_to_ns(def_rt_bandwidth.rt_period);
309 }
310
311 typedef struct rt_rq *rt_rq_iter_t;
312
313 #define for_each_rt_rq(rt_rq, iter, rq) \
314         for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
315
316 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
317 {
318 }
319
320 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
321 {
322 }
323
324 #define for_each_leaf_rt_rq(rt_rq, rq) \
325         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
326
327 #define for_each_sched_rt_entity(rt_se) \
328         for (; rt_se; rt_se = NULL)
329
330 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
331 {
332         return NULL;
333 }
334
335 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
336 {
337         if (rt_rq->rt_nr_running)
338                 resched_task(rq_of_rt_rq(rt_rq)->curr);
339 }
340
341 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
342 {
343 }
344
345 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
346 {
347         return rt_rq->rt_throttled;
348 }
349
350 static inline const struct cpumask *sched_rt_period_mask(void)
351 {
352         return cpu_online_mask;
353 }
354
355 static inline
356 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
357 {
358         return &cpu_rq(cpu)->rt;
359 }
360
361 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
362 {
363         return &def_rt_bandwidth;
364 }
365
366 #endif /* CONFIG_RT_GROUP_SCHED */
367
368 #ifdef CONFIG_SMP
369 /*
370  * We ran out of runtime, see if we can borrow some from our neighbours.
371  */
372 static int do_balance_runtime(struct rt_rq *rt_rq)
373 {
374         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
375         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
376         int i, weight, more = 0;
377         u64 rt_period;
378
379         weight = cpumask_weight(rd->span);
380
381         raw_spin_lock(&rt_b->rt_runtime_lock);
382         rt_period = ktime_to_ns(rt_b->rt_period);
383         for_each_cpu(i, rd->span) {
384                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
385                 s64 diff;
386
387                 if (iter == rt_rq)
388                         continue;
389
390                 raw_spin_lock(&iter->rt_runtime_lock);
391                 /*
392                  * Either all rqs have inf runtime and there's nothing to steal
393                  * or __disable_runtime() below sets a specific rq to inf to
394                  * indicate its been disabled and disalow stealing.
395                  */
396                 if (iter->rt_runtime == RUNTIME_INF)
397                         goto next;
398
399                 /*
400                  * From runqueues with spare time, take 1/n part of their
401                  * spare time, but no more than our period.
402                  */
403                 diff = iter->rt_runtime - iter->rt_time;
404                 if (diff > 0) {
405                         diff = div_u64((u64)diff, weight);
406                         if (rt_rq->rt_runtime + diff > rt_period)
407                                 diff = rt_period - rt_rq->rt_runtime;
408                         iter->rt_runtime -= diff;
409                         rt_rq->rt_runtime += diff;
410                         more = 1;
411                         if (rt_rq->rt_runtime == rt_period) {
412                                 raw_spin_unlock(&iter->rt_runtime_lock);
413                                 break;
414                         }
415                 }
416 next:
417                 raw_spin_unlock(&iter->rt_runtime_lock);
418         }
419         raw_spin_unlock(&rt_b->rt_runtime_lock);
420
421         return more;
422 }
423
424 /*
425  * Ensure this RQ takes back all the runtime it lend to its neighbours.
426  */
427 static void __disable_runtime(struct rq *rq)
428 {
429         struct root_domain *rd = rq->rd;
430         rt_rq_iter_t iter;
431         struct rt_rq *rt_rq;
432
433         if (unlikely(!scheduler_running))
434                 return;
435
436         for_each_rt_rq(rt_rq, iter, rq) {
437                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
438                 s64 want;
439                 int i;
440
441                 raw_spin_lock(&rt_b->rt_runtime_lock);
442                 raw_spin_lock(&rt_rq->rt_runtime_lock);
443                 /*
444                  * Either we're all inf and nobody needs to borrow, or we're
445                  * already disabled and thus have nothing to do, or we have
446                  * exactly the right amount of runtime to take out.
447                  */
448                 if (rt_rq->rt_runtime == RUNTIME_INF ||
449                                 rt_rq->rt_runtime == rt_b->rt_runtime)
450                         goto balanced;
451                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
452
453                 /*
454                  * Calculate the difference between what we started out with
455                  * and what we current have, that's the amount of runtime
456                  * we lend and now have to reclaim.
457                  */
458                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
459
460                 /*
461                  * Greedy reclaim, take back as much as we can.
462                  */
463                 for_each_cpu(i, rd->span) {
464                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
465                         s64 diff;
466
467                         /*
468                          * Can't reclaim from ourselves or disabled runqueues.
469                          */
470                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
471                                 continue;
472
473                         raw_spin_lock(&iter->rt_runtime_lock);
474                         if (want > 0) {
475                                 diff = min_t(s64, iter->rt_runtime, want);
476                                 iter->rt_runtime -= diff;
477                                 want -= diff;
478                         } else {
479                                 iter->rt_runtime -= want;
480                                 want -= want;
481                         }
482                         raw_spin_unlock(&iter->rt_runtime_lock);
483
484                         if (!want)
485                                 break;
486                 }
487
488                 raw_spin_lock(&rt_rq->rt_runtime_lock);
489                 /*
490                  * We cannot be left wanting - that would mean some runtime
491                  * leaked out of the system.
492                  */
493                 BUG_ON(want);
494 balanced:
495                 /*
496                  * Disable all the borrow logic by pretending we have inf
497                  * runtime - in which case borrowing doesn't make sense.
498                  */
499                 rt_rq->rt_runtime = RUNTIME_INF;
500                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
501                 raw_spin_unlock(&rt_b->rt_runtime_lock);
502         }
503 }
504
505 static void disable_runtime(struct rq *rq)
506 {
507         unsigned long flags;
508
509         raw_spin_lock_irqsave(&rq->lock, flags);
510         __disable_runtime(rq);
511         raw_spin_unlock_irqrestore(&rq->lock, flags);
512 }
513
514 static void __enable_runtime(struct rq *rq)
515 {
516         rt_rq_iter_t iter;
517         struct rt_rq *rt_rq;
518
519         if (unlikely(!scheduler_running))
520                 return;
521
522         /*
523          * Reset each runqueue's bandwidth settings
524          */
525         for_each_rt_rq(rt_rq, iter, rq) {
526                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
527
528                 raw_spin_lock(&rt_b->rt_runtime_lock);
529                 raw_spin_lock(&rt_rq->rt_runtime_lock);
530                 rt_rq->rt_runtime = rt_b->rt_runtime;
531                 rt_rq->rt_time = 0;
532                 rt_rq->rt_throttled = 0;
533                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
534                 raw_spin_unlock(&rt_b->rt_runtime_lock);
535         }
536 }
537
538 static void enable_runtime(struct rq *rq)
539 {
540         unsigned long flags;
541
542         raw_spin_lock_irqsave(&rq->lock, flags);
543         __enable_runtime(rq);
544         raw_spin_unlock_irqrestore(&rq->lock, flags);
545 }
546
547 static int balance_runtime(struct rt_rq *rt_rq)
548 {
549         int more = 0;
550
551         if (rt_rq->rt_time > rt_rq->rt_runtime) {
552                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
553                 more = do_balance_runtime(rt_rq);
554                 raw_spin_lock(&rt_rq->rt_runtime_lock);
555         }
556
557         return more;
558 }
559 #else /* !CONFIG_SMP */
560 static inline int balance_runtime(struct rt_rq *rt_rq)
561 {
562         return 0;
563 }
564 #endif /* CONFIG_SMP */
565
566 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
567 {
568         int i, idle = 1;
569         const struct cpumask *span;
570
571         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
572                 return 1;
573
574         span = sched_rt_period_mask();
575         for_each_cpu(i, span) {
576                 int enqueue = 0;
577                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
578                 struct rq *rq = rq_of_rt_rq(rt_rq);
579
580                 raw_spin_lock(&rq->lock);
581                 if (rt_rq->rt_time) {
582                         u64 runtime;
583
584                         raw_spin_lock(&rt_rq->rt_runtime_lock);
585                         if (rt_rq->rt_throttled)
586                                 balance_runtime(rt_rq);
587                         runtime = rt_rq->rt_runtime;
588                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
589                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
590                                 rt_rq->rt_throttled = 0;
591                                 enqueue = 1;
592
593                                 /*
594                                  * Force a clock update if the CPU was idle,
595                                  * lest wakeup -> unthrottle time accumulate.
596                                  */
597                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
598                                         rq->skip_clock_update = -1;
599                         }
600                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
601                                 idle = 0;
602                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
603                 } else if (rt_rq->rt_nr_running) {
604                         idle = 0;
605                         if (!rt_rq_throttled(rt_rq))
606                                 enqueue = 1;
607                 }
608
609                 if (enqueue)
610                         sched_rt_rq_enqueue(rt_rq);
611                 raw_spin_unlock(&rq->lock);
612         }
613
614         return idle;
615 }
616
617 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
618 {
619 #ifdef CONFIG_RT_GROUP_SCHED
620         struct rt_rq *rt_rq = group_rt_rq(rt_se);
621
622         if (rt_rq)
623                 return rt_rq->highest_prio.curr;
624 #endif
625
626         return rt_task_of(rt_se)->prio;
627 }
628
629 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
630 {
631         u64 runtime = sched_rt_runtime(rt_rq);
632
633         if (rt_rq->rt_throttled)
634                 return rt_rq_throttled(rt_rq);
635
636         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
637                 return 0;
638
639         balance_runtime(rt_rq);
640         runtime = sched_rt_runtime(rt_rq);
641         if (runtime == RUNTIME_INF)
642                 return 0;
643
644         if (rt_rq->rt_time > runtime) {
645                 rt_rq->rt_throttled = 1;
646                 if (rt_rq_throttled(rt_rq)) {
647                         sched_rt_rq_dequeue(rt_rq);
648                         return 1;
649                 }
650         }
651
652         return 0;
653 }
654
655 /*
656  * Update the current task's runtime statistics. Skip current tasks that
657  * are not in our scheduling class.
658  */
659 static void update_curr_rt(struct rq *rq)
660 {
661         struct task_struct *curr = rq->curr;
662         struct sched_rt_entity *rt_se = &curr->rt;
663         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
664         u64 delta_exec;
665
666         if (curr->sched_class != &rt_sched_class)
667                 return;
668
669         delta_exec = rq->clock_task - curr->se.exec_start;
670         if (unlikely((s64)delta_exec < 0))
671                 delta_exec = 0;
672
673         schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
674
675         curr->se.sum_exec_runtime += delta_exec;
676         account_group_exec_runtime(curr, delta_exec);
677
678         curr->se.exec_start = rq->clock_task;
679         cpuacct_charge(curr, delta_exec);
680
681         sched_rt_avg_update(rq, delta_exec);
682
683         if (!rt_bandwidth_enabled())
684                 return;
685
686         for_each_sched_rt_entity(rt_se) {
687                 rt_rq = rt_rq_of_se(rt_se);
688
689                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
690                         raw_spin_lock(&rt_rq->rt_runtime_lock);
691                         rt_rq->rt_time += delta_exec;
692                         if (sched_rt_runtime_exceeded(rt_rq))
693                                 resched_task(curr);
694                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
695                 }
696         }
697 }
698
699 #if defined CONFIG_SMP
700
701 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu);
702
703 static inline int next_prio(struct rq *rq)
704 {
705         struct task_struct *next = pick_next_highest_task_rt(rq, rq->cpu);
706
707         if (next && rt_prio(next->prio))
708                 return next->prio;
709         else
710                 return MAX_RT_PRIO;
711 }
712
713 static void
714 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
715 {
716         struct rq *rq = rq_of_rt_rq(rt_rq);
717
718         if (prio < prev_prio) {
719
720                 /*
721                  * If the new task is higher in priority than anything on the
722                  * run-queue, we know that the previous high becomes our
723                  * next-highest.
724                  */
725                 rt_rq->highest_prio.next = prev_prio;
726
727                 if (rq->online)
728                         cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
729
730         } else if (prio == rt_rq->highest_prio.curr)
731                 /*
732                  * If the next task is equal in priority to the highest on
733                  * the run-queue, then we implicitly know that the next highest
734                  * task cannot be any lower than current
735                  */
736                 rt_rq->highest_prio.next = prio;
737         else if (prio < rt_rq->highest_prio.next)
738                 /*
739                  * Otherwise, we need to recompute next-highest
740                  */
741                 rt_rq->highest_prio.next = next_prio(rq);
742 }
743
744 static void
745 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
746 {
747         struct rq *rq = rq_of_rt_rq(rt_rq);
748
749         if (rt_rq->rt_nr_running && (prio <= rt_rq->highest_prio.next))
750                 rt_rq->highest_prio.next = next_prio(rq);
751
752         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
753                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
754 }
755
756 #else /* CONFIG_SMP */
757
758 static inline
759 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
760 static inline
761 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
762
763 #endif /* CONFIG_SMP */
764
765 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
766 static void
767 inc_rt_prio(struct rt_rq *rt_rq, int prio)
768 {
769         int prev_prio = rt_rq->highest_prio.curr;
770
771         if (prio < prev_prio)
772                 rt_rq->highest_prio.curr = prio;
773
774         inc_rt_prio_smp(rt_rq, prio, prev_prio);
775 }
776
777 static void
778 dec_rt_prio(struct rt_rq *rt_rq, int prio)
779 {
780         int prev_prio = rt_rq->highest_prio.curr;
781
782         if (rt_rq->rt_nr_running) {
783
784                 WARN_ON(prio < prev_prio);
785
786                 /*
787                  * This may have been our highest task, and therefore
788                  * we may have some recomputation to do
789                  */
790                 if (prio == prev_prio) {
791                         struct rt_prio_array *array = &rt_rq->active;
792
793                         rt_rq->highest_prio.curr =
794                                 sched_find_first_bit(array->bitmap);
795                 }
796
797         } else
798                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
799
800         dec_rt_prio_smp(rt_rq, prio, prev_prio);
801 }
802
803 #else
804
805 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
806 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
807
808 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
809
810 #ifdef CONFIG_RT_GROUP_SCHED
811
812 static void
813 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
814 {
815         if (rt_se_boosted(rt_se))
816                 rt_rq->rt_nr_boosted++;
817
818         if (rt_rq->tg)
819                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
820 }
821
822 static void
823 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
824 {
825         if (rt_se_boosted(rt_se))
826                 rt_rq->rt_nr_boosted--;
827
828         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
829 }
830
831 #else /* CONFIG_RT_GROUP_SCHED */
832
833 static void
834 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
835 {
836         start_rt_bandwidth(&def_rt_bandwidth);
837 }
838
839 static inline
840 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
841
842 #endif /* CONFIG_RT_GROUP_SCHED */
843
844 static inline
845 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
846 {
847         int prio = rt_se_prio(rt_se);
848
849         WARN_ON(!rt_prio(prio));
850         rt_rq->rt_nr_running++;
851
852         inc_rt_prio(rt_rq, prio);
853         inc_rt_migration(rt_se, rt_rq);
854         inc_rt_group(rt_se, rt_rq);
855 }
856
857 static inline
858 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
859 {
860         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
861         WARN_ON(!rt_rq->rt_nr_running);
862         rt_rq->rt_nr_running--;
863
864         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
865         dec_rt_migration(rt_se, rt_rq);
866         dec_rt_group(rt_se, rt_rq);
867 }
868
869 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
870 {
871         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
872         struct rt_prio_array *array = &rt_rq->active;
873         struct rt_rq *group_rq = group_rt_rq(rt_se);
874         struct list_head *queue = array->queue + rt_se_prio(rt_se);
875
876         /*
877          * Don't enqueue the group if its throttled, or when empty.
878          * The latter is a consequence of the former when a child group
879          * get throttled and the current group doesn't have any other
880          * active members.
881          */
882         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
883                 return;
884
885         if (!rt_rq->rt_nr_running)
886                 list_add_leaf_rt_rq(rt_rq);
887
888         if (head)
889                 list_add(&rt_se->run_list, queue);
890         else
891                 list_add_tail(&rt_se->run_list, queue);
892         __set_bit(rt_se_prio(rt_se), array->bitmap);
893
894         inc_rt_tasks(rt_se, rt_rq);
895 }
896
897 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
898 {
899         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
900         struct rt_prio_array *array = &rt_rq->active;
901
902         list_del_init(&rt_se->run_list);
903         if (list_empty(array->queue + rt_se_prio(rt_se)))
904                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
905
906         dec_rt_tasks(rt_se, rt_rq);
907         if (!rt_rq->rt_nr_running)
908                 list_del_leaf_rt_rq(rt_rq);
909 }
910
911 /*
912  * Because the prio of an upper entry depends on the lower
913  * entries, we must remove entries top - down.
914  */
915 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
916 {
917         struct sched_rt_entity *back = NULL;
918
919         for_each_sched_rt_entity(rt_se) {
920                 rt_se->back = back;
921                 back = rt_se;
922         }
923
924         for (rt_se = back; rt_se; rt_se = rt_se->back) {
925                 if (on_rt_rq(rt_se))
926                         __dequeue_rt_entity(rt_se);
927         }
928 }
929
930 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
931 {
932         dequeue_rt_stack(rt_se);
933         for_each_sched_rt_entity(rt_se)
934                 __enqueue_rt_entity(rt_se, head);
935 }
936
937 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
938 {
939         dequeue_rt_stack(rt_se);
940
941         for_each_sched_rt_entity(rt_se) {
942                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
943
944                 if (rt_rq && rt_rq->rt_nr_running)
945                         __enqueue_rt_entity(rt_se, false);
946         }
947 }
948
949 /*
950  * Adding/removing a task to/from a priority array:
951  */
952 static void
953 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
954 {
955         struct sched_rt_entity *rt_se = &p->rt;
956
957         if (flags & ENQUEUE_WAKEUP)
958                 rt_se->timeout = 0;
959
960         enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
961
962         if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
963                 enqueue_pushable_task(rq, p);
964 }
965
966 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
967 {
968         struct sched_rt_entity *rt_se = &p->rt;
969
970         update_curr_rt(rq);
971         dequeue_rt_entity(rt_se);
972
973         dequeue_pushable_task(rq, p);
974 }
975
976 /*
977  * Put task to the end of the run list without the overhead of dequeue
978  * followed by enqueue.
979  */
980 static void
981 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
982 {
983         if (on_rt_rq(rt_se)) {
984                 struct rt_prio_array *array = &rt_rq->active;
985                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
986
987                 if (head)
988                         list_move(&rt_se->run_list, queue);
989                 else
990                         list_move_tail(&rt_se->run_list, queue);
991         }
992 }
993
994 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
995 {
996         struct sched_rt_entity *rt_se = &p->rt;
997         struct rt_rq *rt_rq;
998
999         for_each_sched_rt_entity(rt_se) {
1000                 rt_rq = rt_rq_of_se(rt_se);
1001                 requeue_rt_entity(rt_rq, rt_se, head);
1002         }
1003 }
1004
1005 static void yield_task_rt(struct rq *rq)
1006 {
1007         requeue_task_rt(rq, rq->curr, 0);
1008 }
1009
1010 #ifdef CONFIG_SMP
1011 static int find_lowest_rq(struct task_struct *task);
1012
1013 static int
1014 select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
1015 {
1016         struct task_struct *curr;
1017         struct rq *rq;
1018         int cpu;
1019
1020         if (sd_flag != SD_BALANCE_WAKE)
1021                 return smp_processor_id();
1022
1023         cpu = task_cpu(p);
1024         rq = cpu_rq(cpu);
1025
1026         rcu_read_lock();
1027         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1028
1029         /*
1030          * If the current task on @p's runqueue is an RT task, then
1031          * try to see if we can wake this RT task up on another
1032          * runqueue. Otherwise simply start this RT task
1033          * on its current runqueue.
1034          *
1035          * We want to avoid overloading runqueues. If the woken
1036          * task is a higher priority, then it will stay on this CPU
1037          * and the lower prio task should be moved to another CPU.
1038          * Even though this will probably make the lower prio task
1039          * lose its cache, we do not want to bounce a higher task
1040          * around just because it gave up its CPU, perhaps for a
1041          * lock?
1042          *
1043          * For equal prio tasks, we just let the scheduler sort it out.
1044          *
1045          * Otherwise, just let it ride on the affined RQ and the
1046          * post-schedule router will push the preempted task away
1047          *
1048          * This test is optimistic, if we get it wrong the load-balancer
1049          * will have to sort it out.
1050          */
1051         if (curr && unlikely(rt_task(curr)) &&
1052             (curr->rt.nr_cpus_allowed < 2 ||
1053              curr->prio <= p->prio) &&
1054             (p->rt.nr_cpus_allowed > 1)) {
1055                 int target = find_lowest_rq(p);
1056
1057                 if (target != -1)
1058                         cpu = target;
1059         }
1060         rcu_read_unlock();
1061
1062         return cpu;
1063 }
1064
1065 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1066 {
1067         if (rq->curr->rt.nr_cpus_allowed == 1)
1068                 return;
1069
1070         if (p->rt.nr_cpus_allowed != 1
1071             && cpupri_find(&rq->rd->cpupri, p, NULL))
1072                 return;
1073
1074         if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1075                 return;
1076
1077         /*
1078          * There appears to be other cpus that can accept
1079          * current and none to run 'p', so lets reschedule
1080          * to try and push current away:
1081          */
1082         requeue_task_rt(rq, p, 1);
1083         resched_task(rq->curr);
1084 }
1085
1086 #endif /* CONFIG_SMP */
1087
1088 /*
1089  * Preempt the current task with a newly woken task if needed:
1090  */
1091 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1092 {
1093         if (p->prio < rq->curr->prio) {
1094                 resched_task(rq->curr);
1095                 return;
1096         }
1097
1098 #ifdef CONFIG_SMP
1099         /*
1100          * If:
1101          *
1102          * - the newly woken task is of equal priority to the current task
1103          * - the newly woken task is non-migratable while current is migratable
1104          * - current will be preempted on the next reschedule
1105          *
1106          * we should check to see if current can readily move to a different
1107          * cpu.  If so, we will reschedule to allow the push logic to try
1108          * to move current somewhere else, making room for our non-migratable
1109          * task.
1110          */
1111         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1112                 check_preempt_equal_prio(rq, p);
1113 #endif
1114 }
1115
1116 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1117                                                    struct rt_rq *rt_rq)
1118 {
1119         struct rt_prio_array *array = &rt_rq->active;
1120         struct sched_rt_entity *next = NULL;
1121         struct list_head *queue;
1122         int idx;
1123
1124         idx = sched_find_first_bit(array->bitmap);
1125         BUG_ON(idx >= MAX_RT_PRIO);
1126
1127         queue = array->queue + idx;
1128         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1129
1130         return next;
1131 }
1132
1133 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1134 {
1135         struct sched_rt_entity *rt_se;
1136         struct task_struct *p;
1137         struct rt_rq *rt_rq;
1138
1139         rt_rq = &rq->rt;
1140
1141         if (!rt_rq->rt_nr_running)
1142                 return NULL;
1143
1144         if (rt_rq_throttled(rt_rq))
1145                 return NULL;
1146
1147         do {
1148                 rt_se = pick_next_rt_entity(rq, rt_rq);
1149                 BUG_ON(!rt_se);
1150                 rt_rq = group_rt_rq(rt_se);
1151         } while (rt_rq);
1152
1153         p = rt_task_of(rt_se);
1154         p->se.exec_start = rq->clock_task;
1155
1156         return p;
1157 }
1158
1159 static struct task_struct *pick_next_task_rt(struct rq *rq)
1160 {
1161         struct task_struct *p = _pick_next_task_rt(rq);
1162
1163         /* The running task is never eligible for pushing */
1164         if (p)
1165                 dequeue_pushable_task(rq, p);
1166
1167 #ifdef CONFIG_SMP
1168         /*
1169          * We detect this state here so that we can avoid taking the RQ
1170          * lock again later if there is no need to push
1171          */
1172         rq->post_schedule = has_pushable_tasks(rq);
1173 #endif
1174
1175         return p;
1176 }
1177
1178 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1179 {
1180         update_curr_rt(rq);
1181         p->se.exec_start = 0;
1182
1183         /*
1184          * The previous task needs to be made eligible for pushing
1185          * if it is still active
1186          */
1187         if (on_rt_rq(&p->rt) && p->rt.nr_cpus_allowed > 1)
1188                 enqueue_pushable_task(rq, p);
1189 }
1190
1191 #ifdef CONFIG_SMP
1192
1193 /* Only try algorithms three times */
1194 #define RT_MAX_TRIES 3
1195
1196 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
1197
1198 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1199 {
1200         if (!task_running(rq, p) &&
1201             (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
1202             (p->rt.nr_cpus_allowed > 1))
1203                 return 1;
1204         return 0;
1205 }
1206
1207 /* Return the second highest RT task, NULL otherwise */
1208 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
1209 {
1210         struct task_struct *next = NULL;
1211         struct sched_rt_entity *rt_se;
1212         struct rt_prio_array *array;
1213         struct rt_rq *rt_rq;
1214         int idx;
1215
1216         for_each_leaf_rt_rq(rt_rq, rq) {
1217                 array = &rt_rq->active;
1218                 idx = sched_find_first_bit(array->bitmap);
1219 next_idx:
1220                 if (idx >= MAX_RT_PRIO)
1221                         continue;
1222                 if (next && next->prio < idx)
1223                         continue;
1224                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
1225                         struct task_struct *p;
1226
1227                         if (!rt_entity_is_task(rt_se))
1228                                 continue;
1229
1230                         p = rt_task_of(rt_se);
1231                         if (pick_rt_task(rq, p, cpu)) {
1232                                 next = p;
1233                                 break;
1234                         }
1235                 }
1236                 if (!next) {
1237                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
1238                         goto next_idx;
1239                 }
1240         }
1241
1242         return next;
1243 }
1244
1245 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1246
1247 static int find_lowest_rq(struct task_struct *task)
1248 {
1249         struct sched_domain *sd;
1250         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1251         int this_cpu = smp_processor_id();
1252         int cpu      = task_cpu(task);
1253
1254         /* Make sure the mask is initialized first */
1255         if (unlikely(!lowest_mask))
1256                 return -1;
1257
1258         if (task->rt.nr_cpus_allowed == 1)
1259                 return -1; /* No other targets possible */
1260
1261         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1262                 return -1; /* No targets found */
1263
1264         /*
1265          * At this point we have built a mask of cpus representing the
1266          * lowest priority tasks in the system.  Now we want to elect
1267          * the best one based on our affinity and topology.
1268          *
1269          * We prioritize the last cpu that the task executed on since
1270          * it is most likely cache-hot in that location.
1271          */
1272         if (cpumask_test_cpu(cpu, lowest_mask))
1273                 return cpu;
1274
1275         /*
1276          * Otherwise, we consult the sched_domains span maps to figure
1277          * out which cpu is logically closest to our hot cache data.
1278          */
1279         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1280                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1281
1282         rcu_read_lock();
1283         for_each_domain(cpu, sd) {
1284                 if (sd->flags & SD_WAKE_AFFINE) {
1285                         int best_cpu;
1286
1287                         /*
1288                          * "this_cpu" is cheaper to preempt than a
1289                          * remote processor.
1290                          */
1291                         if (this_cpu != -1 &&
1292                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1293                                 rcu_read_unlock();
1294                                 return this_cpu;
1295                         }
1296
1297                         best_cpu = cpumask_first_and(lowest_mask,
1298                                                      sched_domain_span(sd));
1299                         if (best_cpu < nr_cpu_ids) {
1300                                 rcu_read_unlock();
1301                                 return best_cpu;
1302                         }
1303                 }
1304         }
1305         rcu_read_unlock();
1306
1307         /*
1308          * And finally, if there were no matches within the domains
1309          * just give the caller *something* to work with from the compatible
1310          * locations.
1311          */
1312         if (this_cpu != -1)
1313                 return this_cpu;
1314
1315         cpu = cpumask_any(lowest_mask);
1316         if (cpu < nr_cpu_ids)
1317                 return cpu;
1318         return -1;
1319 }
1320
1321 /* Will lock the rq it finds */
1322 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1323 {
1324         struct rq *lowest_rq = NULL;
1325         int tries;
1326         int cpu;
1327
1328         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1329                 cpu = find_lowest_rq(task);
1330
1331                 if ((cpu == -1) || (cpu == rq->cpu))
1332                         break;
1333
1334                 lowest_rq = cpu_rq(cpu);
1335
1336                 /* if the prio of this runqueue changed, try again */
1337                 if (double_lock_balance(rq, lowest_rq)) {
1338                         /*
1339                          * We had to unlock the run queue. In
1340                          * the mean time, task could have
1341                          * migrated already or had its affinity changed.
1342                          * Also make sure that it wasn't scheduled on its rq.
1343                          */
1344                         if (unlikely(task_rq(task) != rq ||
1345                                      !cpumask_test_cpu(lowest_rq->cpu,
1346                                                        &task->cpus_allowed) ||
1347                                      task_running(rq, task) ||
1348                                      !task->on_rq)) {
1349
1350                                 raw_spin_unlock(&lowest_rq->lock);
1351                                 lowest_rq = NULL;
1352                                 break;
1353                         }
1354                 }
1355
1356                 /* If this rq is still suitable use it. */
1357                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1358                         break;
1359
1360                 /* try again */
1361                 double_unlock_balance(rq, lowest_rq);
1362                 lowest_rq = NULL;
1363         }
1364
1365         return lowest_rq;
1366 }
1367
1368 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1369 {
1370         struct task_struct *p;
1371
1372         if (!has_pushable_tasks(rq))
1373                 return NULL;
1374
1375         p = plist_first_entry(&rq->rt.pushable_tasks,
1376                               struct task_struct, pushable_tasks);
1377
1378         BUG_ON(rq->cpu != task_cpu(p));
1379         BUG_ON(task_current(rq, p));
1380         BUG_ON(p->rt.nr_cpus_allowed <= 1);
1381
1382         BUG_ON(!p->on_rq);
1383         BUG_ON(!rt_task(p));
1384
1385         return p;
1386 }
1387
1388 /*
1389  * If the current CPU has more than one RT task, see if the non
1390  * running task can migrate over to a CPU that is running a task
1391  * of lesser priority.
1392  */
1393 static int push_rt_task(struct rq *rq)
1394 {
1395         struct task_struct *next_task;
1396         struct rq *lowest_rq;
1397
1398         if (!rq->rt.overloaded)
1399                 return 0;
1400
1401         next_task = pick_next_pushable_task(rq);
1402         if (!next_task)
1403                 return 0;
1404
1405 retry:
1406         if (unlikely(next_task == rq->curr)) {
1407                 WARN_ON(1);
1408                 return 0;
1409         }
1410
1411         /*
1412          * It's possible that the next_task slipped in of
1413          * higher priority than current. If that's the case
1414          * just reschedule current.
1415          */
1416         if (unlikely(next_task->prio < rq->curr->prio)) {
1417                 resched_task(rq->curr);
1418                 return 0;
1419         }
1420
1421         /* We might release rq lock */
1422         get_task_struct(next_task);
1423
1424         /* find_lock_lowest_rq locks the rq if found */
1425         lowest_rq = find_lock_lowest_rq(next_task, rq);
1426         if (!lowest_rq) {
1427                 struct task_struct *task;
1428                 /*
1429                  * find lock_lowest_rq releases rq->lock
1430                  * so it is possible that next_task has migrated.
1431                  *
1432                  * We need to make sure that the task is still on the same
1433                  * run-queue and is also still the next task eligible for
1434                  * pushing.
1435                  */
1436                 task = pick_next_pushable_task(rq);
1437                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1438                         /*
1439                          * If we get here, the task hasn't moved at all, but
1440                          * it has failed to push.  We will not try again,
1441                          * since the other cpus will pull from us when they
1442                          * are ready.
1443                          */
1444                         dequeue_pushable_task(rq, next_task);
1445                         goto out;
1446                 }
1447
1448                 if (!task)
1449                         /* No more tasks, just exit */
1450                         goto out;
1451
1452                 /*
1453                  * Something has shifted, try again.
1454                  */
1455                 put_task_struct(next_task);
1456                 next_task = task;
1457                 goto retry;
1458         }
1459
1460         deactivate_task(rq, next_task, 0);
1461         set_task_cpu(next_task, lowest_rq->cpu);
1462         activate_task(lowest_rq, next_task, 0);
1463
1464         resched_task(lowest_rq->curr);
1465
1466         double_unlock_balance(rq, lowest_rq);
1467
1468 out:
1469         put_task_struct(next_task);
1470
1471         return 1;
1472 }
1473
1474 static void push_rt_tasks(struct rq *rq)
1475 {
1476         /* push_rt_task will return true if it moved an RT */
1477         while (push_rt_task(rq))
1478                 ;
1479 }
1480
1481 static int pull_rt_task(struct rq *this_rq)
1482 {
1483         int this_cpu = this_rq->cpu, ret = 0, cpu;
1484         struct task_struct *p;
1485         struct rq *src_rq;
1486
1487         if (likely(!rt_overloaded(this_rq)))
1488                 return 0;
1489
1490         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1491                 if (this_cpu == cpu)
1492                         continue;
1493
1494                 src_rq = cpu_rq(cpu);
1495
1496                 /*
1497                  * Don't bother taking the src_rq->lock if the next highest
1498                  * task is known to be lower-priority than our current task.
1499                  * This may look racy, but if this value is about to go
1500                  * logically higher, the src_rq will push this task away.
1501                  * And if its going logically lower, we do not care
1502                  */
1503                 if (src_rq->rt.highest_prio.next >=
1504                     this_rq->rt.highest_prio.curr)
1505                         continue;
1506
1507                 /*
1508                  * We can potentially drop this_rq's lock in
1509                  * double_lock_balance, and another CPU could
1510                  * alter this_rq
1511                  */
1512                 double_lock_balance(this_rq, src_rq);
1513
1514                 /*
1515                  * Are there still pullable RT tasks?
1516                  */
1517                 if (src_rq->rt.rt_nr_running <= 1)
1518                         goto skip;
1519
1520                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1521
1522                 /*
1523                  * Do we have an RT task that preempts
1524                  * the to-be-scheduled task?
1525                  */
1526                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1527                         WARN_ON(p == src_rq->curr);
1528                         WARN_ON(!p->on_rq);
1529
1530                         /*
1531                          * There's a chance that p is higher in priority
1532                          * than what's currently running on its cpu.
1533                          * This is just that p is wakeing up and hasn't
1534                          * had a chance to schedule. We only pull
1535                          * p if it is lower in priority than the
1536                          * current task on the run queue
1537                          */
1538                         if (p->prio < src_rq->curr->prio)
1539                                 goto skip;
1540
1541                         ret = 1;
1542
1543                         deactivate_task(src_rq, p, 0);
1544                         set_task_cpu(p, this_cpu);
1545                         activate_task(this_rq, p, 0);
1546                         /*
1547                          * We continue with the search, just in
1548                          * case there's an even higher prio task
1549                          * in another runqueue. (low likelihood
1550                          * but possible)
1551                          */
1552                 }
1553 skip:
1554                 double_unlock_balance(this_rq, src_rq);
1555         }
1556
1557         return ret;
1558 }
1559
1560 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1561 {
1562         /* Try to pull RT tasks here if we lower this rq's prio */
1563         if (rq->rt.highest_prio.curr > prev->prio)
1564                 pull_rt_task(rq);
1565 }
1566
1567 static void post_schedule_rt(struct rq *rq)
1568 {
1569         push_rt_tasks(rq);
1570 }
1571
1572 /*
1573  * If we are not running and we are not going to reschedule soon, we should
1574  * try to push tasks away now
1575  */
1576 static void task_woken_rt(struct rq *rq, struct task_struct *p)
1577 {
1578         if (!task_running(rq, p) &&
1579             !test_tsk_need_resched(rq->curr) &&
1580             has_pushable_tasks(rq) &&
1581             p->rt.nr_cpus_allowed > 1 &&
1582             rt_task(rq->curr) &&
1583             (rq->curr->rt.nr_cpus_allowed < 2 ||
1584              rq->curr->prio <= p->prio))
1585                 push_rt_tasks(rq);
1586 }
1587
1588 static void set_cpus_allowed_rt(struct task_struct *p,
1589                                 const struct cpumask *new_mask)
1590 {
1591         int weight = cpumask_weight(new_mask);
1592
1593         BUG_ON(!rt_task(p));
1594
1595         /*
1596          * Update the migration status of the RQ if we have an RT task
1597          * which is running AND changing its weight value.
1598          */
1599         if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
1600                 struct rq *rq = task_rq(p);
1601
1602                 if (!task_current(rq, p)) {
1603                         /*
1604                          * Make sure we dequeue this task from the pushable list
1605                          * before going further.  It will either remain off of
1606                          * the list because we are no longer pushable, or it
1607                          * will be requeued.
1608                          */
1609                         if (p->rt.nr_cpus_allowed > 1)
1610                                 dequeue_pushable_task(rq, p);
1611
1612                         /*
1613                          * Requeue if our weight is changing and still > 1
1614                          */
1615                         if (weight > 1)
1616                                 enqueue_pushable_task(rq, p);
1617
1618                 }
1619
1620                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1621                         rq->rt.rt_nr_migratory++;
1622                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1623                         BUG_ON(!rq->rt.rt_nr_migratory);
1624                         rq->rt.rt_nr_migratory--;
1625                 }
1626
1627                 update_rt_migration(&rq->rt);
1628         }
1629
1630         cpumask_copy(&p->cpus_allowed, new_mask);
1631         p->rt.nr_cpus_allowed = weight;
1632 }
1633
1634 /* Assumes rq->lock is held */
1635 static void rq_online_rt(struct rq *rq)
1636 {
1637         if (rq->rt.overloaded)
1638                 rt_set_overload(rq);
1639
1640         __enable_runtime(rq);
1641
1642         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1643 }
1644
1645 /* Assumes rq->lock is held */
1646 static void rq_offline_rt(struct rq *rq)
1647 {
1648         if (rq->rt.overloaded)
1649                 rt_clear_overload(rq);
1650
1651         __disable_runtime(rq);
1652
1653         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1654 }
1655
1656 /*
1657  * When switch from the rt queue, we bring ourselves to a position
1658  * that we might want to pull RT tasks from other runqueues.
1659  */
1660 static void switched_from_rt(struct rq *rq, struct task_struct *p)
1661 {
1662         /*
1663          * If there are other RT tasks then we will reschedule
1664          * and the scheduling of the other RT tasks will handle
1665          * the balancing. But if we are the last RT task
1666          * we may need to handle the pulling of RT tasks
1667          * now.
1668          */
1669         if (p->on_rq && !rq->rt.rt_nr_running)
1670                 pull_rt_task(rq);
1671 }
1672
1673 static inline void init_sched_rt_class(void)
1674 {
1675         unsigned int i;
1676
1677         for_each_possible_cpu(i)
1678                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1679                                         GFP_KERNEL, cpu_to_node(i));
1680 }
1681 #endif /* CONFIG_SMP */
1682
1683 /*
1684  * When switching a task to RT, we may overload the runqueue
1685  * with RT tasks. In this case we try to push them off to
1686  * other runqueues.
1687  */
1688 static void switched_to_rt(struct rq *rq, struct task_struct *p)
1689 {
1690         int check_resched = 1;
1691
1692         /*
1693          * If we are already running, then there's nothing
1694          * that needs to be done. But if we are not running
1695          * we may need to preempt the current running task.
1696          * If that current running task is also an RT task
1697          * then see if we can move to another run queue.
1698          */
1699         if (p->on_rq && rq->curr != p) {
1700 #ifdef CONFIG_SMP
1701                 if (rq->rt.overloaded && push_rt_task(rq) &&
1702                     /* Don't resched if we changed runqueues */
1703                     rq != task_rq(p))
1704                         check_resched = 0;
1705 #endif /* CONFIG_SMP */
1706                 if (check_resched && p->prio < rq->curr->prio)
1707                         resched_task(rq->curr);
1708         }
1709 }
1710
1711 /*
1712  * Priority of the task has changed. This may cause
1713  * us to initiate a push or pull.
1714  */
1715 static void
1716 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1717 {
1718         if (!p->on_rq)
1719                 return;
1720
1721         if (rq->curr == p) {
1722 #ifdef CONFIG_SMP
1723                 /*
1724                  * If our priority decreases while running, we
1725                  * may need to pull tasks to this runqueue.
1726                  */
1727                 if (oldprio < p->prio)
1728                         pull_rt_task(rq);
1729                 /*
1730                  * If there's a higher priority task waiting to run
1731                  * then reschedule. Note, the above pull_rt_task
1732                  * can release the rq lock and p could migrate.
1733                  * Only reschedule if p is still on the same runqueue.
1734                  */
1735                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1736                         resched_task(p);
1737 #else
1738                 /* For UP simply resched on drop of prio */
1739                 if (oldprio < p->prio)
1740                         resched_task(p);
1741 #endif /* CONFIG_SMP */
1742         } else {
1743                 /*
1744                  * This task is not running, but if it is
1745                  * greater than the current running task
1746                  * then reschedule.
1747                  */
1748                 if (p->prio < rq->curr->prio)
1749                         resched_task(rq->curr);
1750         }
1751 }
1752
1753 static void watchdog(struct rq *rq, struct task_struct *p)
1754 {
1755         unsigned long soft, hard;
1756
1757         /* max may change after cur was read, this will be fixed next tick */
1758         soft = task_rlimit(p, RLIMIT_RTTIME);
1759         hard = task_rlimit_max(p, RLIMIT_RTTIME);
1760
1761         if (soft != RLIM_INFINITY) {
1762                 unsigned long next;
1763
1764                 p->rt.timeout++;
1765                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1766                 if (p->rt.timeout > next)
1767                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1768         }
1769 }
1770
1771 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1772 {
1773         update_curr_rt(rq);
1774
1775         watchdog(rq, p);
1776
1777         /*
1778          * RR tasks need a special form of timeslice management.
1779          * FIFO tasks have no timeslices.
1780          */
1781         if (p->policy != SCHED_RR)
1782                 return;
1783
1784         if (--p->rt.time_slice)
1785                 return;
1786
1787         p->rt.time_slice = DEF_TIMESLICE;
1788
1789         /*
1790          * Requeue to the end of queue if we are not the only element
1791          * on the queue:
1792          */
1793         if (p->rt.run_list.prev != p->rt.run_list.next) {
1794                 requeue_task_rt(rq, p, 0);
1795                 set_tsk_need_resched(p);
1796         }
1797 }
1798
1799 static void set_curr_task_rt(struct rq *rq)
1800 {
1801         struct task_struct *p = rq->curr;
1802
1803         p->se.exec_start = rq->clock_task;
1804
1805         /* The running task is never eligible for pushing */
1806         dequeue_pushable_task(rq, p);
1807 }
1808
1809 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
1810 {
1811         /*
1812          * Time slice is 0 for SCHED_FIFO tasks
1813          */
1814         if (task->policy == SCHED_RR)
1815                 return DEF_TIMESLICE;
1816         else
1817                 return 0;
1818 }
1819
1820 static const struct sched_class rt_sched_class = {
1821         .next                   = &fair_sched_class,
1822         .enqueue_task           = enqueue_task_rt,
1823         .dequeue_task           = dequeue_task_rt,
1824         .yield_task             = yield_task_rt,
1825
1826         .check_preempt_curr     = check_preempt_curr_rt,
1827
1828         .pick_next_task         = pick_next_task_rt,
1829         .put_prev_task          = put_prev_task_rt,
1830
1831 #ifdef CONFIG_SMP
1832         .select_task_rq         = select_task_rq_rt,
1833
1834         .set_cpus_allowed       = set_cpus_allowed_rt,
1835         .rq_online              = rq_online_rt,
1836         .rq_offline             = rq_offline_rt,
1837         .pre_schedule           = pre_schedule_rt,
1838         .post_schedule          = post_schedule_rt,
1839         .task_woken             = task_woken_rt,
1840         .switched_from          = switched_from_rt,
1841 #endif
1842
1843         .set_curr_task          = set_curr_task_rt,
1844         .task_tick              = task_tick_rt,
1845
1846         .get_rr_interval        = get_rr_interval_rt,
1847
1848         .prio_changed           = prio_changed_rt,
1849         .switched_to            = switched_to_rt,
1850 };
1851
1852 #ifdef CONFIG_SCHED_DEBUG
1853 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1854
1855 static void print_rt_stats(struct seq_file *m, int cpu)
1856 {
1857         rt_rq_iter_t iter;
1858         struct rt_rq *rt_rq;
1859
1860         rcu_read_lock();
1861         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1862                 print_rt_rq(m, cpu, rt_rq);
1863         rcu_read_unlock();
1864 }
1865 #endif /* CONFIG_SCHED_DEBUG */
1866