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 inline int has_pushable_tasks(struct rq *rq)
 128 {
 129         return !plist_head_empty(&rq->rt.pushable_tasks);
 130 }
 131
 132 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 133 {
 134         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 135         plist_node_init(&p->pushable_tasks, p->prio);
 136         plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
 137
 138         /* Update the highest prio pushable task */
 139         if (p->prio < rq->rt.highest_prio.next)
 140                 rq->rt.highest_prio.next = p->prio;
 141 }
 142
 143 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 144 {
 145         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 146
 147         /* Update the new highest prio pushable task */
 148         if (has_pushable_tasks(rq)) {
 149                 p = plist_first_entry(&rq->rt.pushable_tasks,
 150                                       struct task_struct, pushable_tasks);
 151                 rq->rt.highest_prio.next = p->prio;
 152         } else
 153                 rq->rt.highest_prio.next = MAX_RT_PRIO;
 154 }
 155
 156 #else
 157
 158 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 159 {
 160 }
 161
 162 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 163 {
 164 }
 165
 166 static inline
 167 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 168 {
 169 }
 170
 171 static inline
 172 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 173 {
 174 }
 175
 176 #endif /* CONFIG_SMP */
 177
 178 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
 179 {
 180         return !list_empty(&rt_se->run_list);
 181 }
 182
 183 #ifdef CONFIG_RT_GROUP_SCHED
 184
 185 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 186 {
 187         if (!rt_rq->tg)
 188                 return RUNTIME_INF;
 189
 190         return rt_rq->rt_runtime;
 191 }
 192
 193 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 194 {
 195         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
 196 }
 197
 198 typedef struct task_group *rt_rq_iter_t;
 199
 200 static inline struct task_group *next_task_group(struct task_group *tg)
 201 {
 202         do {
 203                 tg = list_entry_rcu(tg->list.next,
 204                         typeof(struct task_group), list);
 205         } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
 206
 207         if (&tg->list == &task_groups)
 208                 tg = NULL;
 209
 210         return tg;
 211 }
 212
 213 #define for_each_rt_rq(rt_rq, iter, rq)                                 \
 214         for (iter = container_of(&task_groups, typeof(*iter), list);    \
 215                 (iter = next_task_group(iter)) &&                       \
 216                 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
 217
 218 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
 219 {
 220         list_add_rcu(&rt_rq->leaf_rt_rq_list,
 221                         &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
 222 }
 223
 224 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
 225 {
 226         list_del_rcu(&rt_rq->leaf_rt_rq_list);
 227 }
 228
 229 #define for_each_leaf_rt_rq(rt_rq, rq) \
 230         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
 231
 232 #define for_each_sched_rt_entity(rt_se) \
 233         for (; rt_se; rt_se = rt_se->parent)
 234
 235 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 236 {
 237         return rt_se->my_q;
 238 }
 239
 240 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
 241 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
 242
 243 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 244 {
 245         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
 246         struct sched_rt_entity *rt_se;
 247
 248         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 249
 250         rt_se = rt_rq->tg->rt_se[cpu];
 251
 252         if (rt_rq->rt_nr_running) {
 253                 if (rt_se && !on_rt_rq(rt_se))
 254                         enqueue_rt_entity(rt_se, false);
 255                 if (rt_rq->highest_prio.curr < curr->prio)
 256                         resched_task(curr);
 257         }
 258 }
 259
 260 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 261 {
 262         struct sched_rt_entity *rt_se;
 263         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 264
 265         rt_se = rt_rq->tg->rt_se[cpu];
 266
 267         if (rt_se && on_rt_rq(rt_se))
 268                 dequeue_rt_entity(rt_se);
 269 }
 270
 271 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 272 {
 273         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
 274 }
 275
 276 static int rt_se_boosted(struct sched_rt_entity *rt_se)
 277 {
 278         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 279         struct task_struct *p;
 280
 281         if (rt_rq)
 282                 return !!rt_rq->rt_nr_boosted;
 283
 284         p = rt_task_of(rt_se);
 285         return p->prio != p->normal_prio;
 286 }
 287
 288 #ifdef CONFIG_SMP
 289 static inline const struct cpumask *sched_rt_period_mask(void)
 290 {
 291         return cpu_rq(smp_processor_id())->rd->span;
 292 }
 293 #else
 294 static inline const struct cpumask *sched_rt_period_mask(void)
 295 {
 296         return cpu_online_mask;
 297 }
 298 #endif
 299
 300 static inline
 301 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 302 {
 303         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
 304 }
 305
 306 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 307 {
 308         return &rt_rq->tg->rt_bandwidth;
 309 }
 310
 311 #else /* !CONFIG_RT_GROUP_SCHED */
 312
 313 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 314 {
 315         return rt_rq->rt_runtime;
 316 }
 317
 318 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 319 {
 320         return ktime_to_ns(def_rt_bandwidth.rt_period);
 321 }
 322
 323 typedef struct rt_rq *rt_rq_iter_t;
 324
 325 #define for_each_rt_rq(rt_rq, iter, rq) \
 326         for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 327
 328 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
 329 {
 330 }
 331
 332 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
 333 {
 334 }
 335
 336 #define for_each_leaf_rt_rq(rt_rq, rq) \
 337         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 338
 339 #define for_each_sched_rt_entity(rt_se) \
 340         for (; rt_se; rt_se = NULL)
 341
 342 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 343 {
 344         return NULL;
 345 }
 346
 347 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 348 {
 349         if (rt_rq->rt_nr_running)
 350                 resched_task(rq_of_rt_rq(rt_rq)->curr);
 351 }
 352
 353 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 354 {
 355 }
 356
 357 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 358 {
 359         return rt_rq->rt_throttled;
 360 }
 361
 362 static inline const struct cpumask *sched_rt_period_mask(void)
 363 {
 364         return cpu_online_mask;
 365 }
 366
 367 static inline
 368 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 369 {
 370         return &cpu_rq(cpu)->rt;
 371 }
 372
 373 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 374 {
 375         return &def_rt_bandwidth;
 376 }
 377
 378 #endif /* CONFIG_RT_GROUP_SCHED */
 379
 380 #ifdef CONFIG_SMP
 381 /*
 382  * We ran out of runtime, see if we can borrow some from our neighbours.
 383  */
 384 static int do_balance_runtime(struct rt_rq *rt_rq)
 385 {
 386         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 387         struct root_domain *rd = rq_of_rt_rq(rt_rq)->rd;
 388         int i, weight, more = 0;
 389         u64 rt_period;
 390
 391         weight = cpumask_weight(rd->span);
 392
 393         raw_spin_lock(&rt_b->rt_runtime_lock);
 394         rt_period = ktime_to_ns(rt_b->rt_period);
 395         for_each_cpu(i, rd->span) {
 396                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 397                 s64 diff;
 398
 399                 if (iter == rt_rq)
 400                         continue;
 401
 402                 raw_spin_lock(&iter->rt_runtime_lock);
 403                 /*
 404                  * Either all rqs have inf runtime and there's nothing to steal
 405                  * or __disable_runtime() below sets a specific rq to inf to
 406                  * indicate its been disabled and disalow stealing.
 407                  */
 408                 if (iter->rt_runtime == RUNTIME_INF)
 409                         goto next;
 410
 411                 /*
 412                  * From runqueues with spare time, take 1/n part of their
 413                  * spare time, but no more than our period.
 414                  */
 415                 diff = iter->rt_runtime - iter->rt_time;
 416                 if (diff > 0) {
 417                         diff = div_u64((u64)diff, weight);
 418                         if (rt_rq->rt_runtime + diff > rt_period)
 419                                 diff = rt_period - rt_rq->rt_runtime;
 420                         iter->rt_runtime -= diff;
 421                         rt_rq->rt_runtime += diff;
 422                         more = 1;
 423                         if (rt_rq->rt_runtime == rt_period) {
 424                                 raw_spin_unlock(&iter->rt_runtime_lock);
 425                                 break;
 426                         }
 427                 }
 428 next:
 429                 raw_spin_unlock(&iter->rt_runtime_lock);
 430         }
 431         raw_spin_unlock(&rt_b->rt_runtime_lock);
 432
 433         return more;
 434 }
 435
 436 /*
 437  * Ensure this RQ takes back all the runtime it lend to its neighbours.
 438  */
 439 static void __disable_runtime(struct rq *rq)
 440 {
 441         struct root_domain *rd = rq->rd;
 442         rt_rq_iter_t iter;
 443         struct rt_rq *rt_rq;
 444
 445         if (unlikely(!scheduler_running))
 446                 return;
 447
 448         for_each_rt_rq(rt_rq, iter, rq) {
 449                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 450                 s64 want;
 451                 int i;
 452
 453                 raw_spin_lock(&rt_b->rt_runtime_lock);
 454                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 455                 /*
 456                  * Either we're all inf and nobody needs to borrow, or we're
 457                  * already disabled and thus have nothing to do, or we have
 458                  * exactly the right amount of runtime to take out.
 459                  */
 460                 if (rt_rq->rt_runtime == RUNTIME_INF ||
 461                                 rt_rq->rt_runtime == rt_b->rt_runtime)
 462                         goto balanced;
 463                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 464
 465                 /*
 466                  * Calculate the difference between what we started out with
 467                  * and what we current have, that's the amount of runtime
 468                  * we lend and now have to reclaim.
 469                  */
 470                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
 471
 472                 /*
 473                  * Greedy reclaim, take back as much as we can.
 474                  */
 475                 for_each_cpu(i, rd->span) {
 476                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 477                         s64 diff;
 478
 479                         /*
 480                          * Can't reclaim from ourselves or disabled runqueues.
 481                          */
 482                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
 483                                 continue;
 484
 485                         raw_spin_lock(&iter->rt_runtime_lock);
 486                         if (want > 0) {
 487                                 diff = min_t(s64, iter->rt_runtime, want);
 488                                 iter->rt_runtime -= diff;
 489                                 want -= diff;
 490                         } else {
 491                                 iter->rt_runtime -= want;
 492                                 want -= want;
 493                         }
 494                         raw_spin_unlock(&iter->rt_runtime_lock);
 495
 496                         if (!want)
 497                                 break;
 498                 }
 499
 500                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 501                 /*
 502                  * We cannot be left wanting - that would mean some runtime
 503                  * leaked out of the system.
 504                  */
 505                 BUG_ON(want);
 506 balanced:
 507                 /*
 508                  * Disable all the borrow logic by pretending we have inf
 509                  * runtime - in which case borrowing doesn't make sense.
 510                  */
 511                 rt_rq->rt_runtime = RUNTIME_INF;
 512                 rt_rq->rt_throttled = 0;
 513                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 514                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 515         }
 516 }
 517
 518 static void disable_runtime(struct rq *rq)
 519 {
 520         unsigned long flags;
 521
 522         raw_spin_lock_irqsave(&rq->lock, flags);
 523         __disable_runtime(rq);
 524         raw_spin_unlock_irqrestore(&rq->lock, flags);
 525 }
 526
 527 static void __enable_runtime(struct rq *rq)
 528 {
 529         rt_rq_iter_t iter;
 530         struct rt_rq *rt_rq;
 531
 532         if (unlikely(!scheduler_running))
 533                 return;
 534
 535         /*
 536          * Reset each runqueue's bandwidth settings
 537          */
 538         for_each_rt_rq(rt_rq, iter, rq) {
 539                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 540
 541                 raw_spin_lock(&rt_b->rt_runtime_lock);
 542                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 543                 rt_rq->rt_runtime = rt_b->rt_runtime;
 544                 rt_rq->rt_time = 0;
 545                 rt_rq->rt_throttled = 0;
 546                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 547                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 548         }
 549 }
 550
 551 static void enable_runtime(struct rq *rq)
 552 {
 553         unsigned long flags;
 554
 555         raw_spin_lock_irqsave(&rq->lock, flags);
 556         __enable_runtime(rq);
 557         raw_spin_unlock_irqrestore(&rq->lock, flags);
 558 }
 559
 560 static int balance_runtime(struct rt_rq *rt_rq)
 561 {
 562         int more = 0;
 563
 564         if (!sched_feat(RT_RUNTIME_SHARE))
 565                 return more;
 566
 567         if (rt_rq->rt_time > rt_rq->rt_runtime) {
 568                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 569                 more = do_balance_runtime(rt_rq);
 570                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 571         }
 572
 573         return more;
 574 }
 575 #else /* !CONFIG_SMP */
 576 static inline int balance_runtime(struct rt_rq *rt_rq)
 577 {
 578         return 0;
 579 }
 580 #endif /* CONFIG_SMP */
 581
 582 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 583 {
 584         int i, idle = 1;
 585         const struct cpumask *span;
 586
 587         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
 588                 return 1;
 589
 590         span = sched_rt_period_mask();
 591 #ifdef CONFIG_RT_GROUP_SCHED
 592         /*
 593          * FIXME: isolated CPUs should really leave the root task group,
 594          * whether they are isolcpus or were isolated via cpusets, lest
 595          * the timer run on a CPU which does not service all runqueues,
 596          * potentially leaving other CPUs indefinitely throttled.  If
 597          * isolation is really required, the user will turn the throttle
 598          * off to kill the perturbations it causes anyway.  Meanwhile,
 599          * this maintains functionality for boot and/or troubleshooting.
 600          */
 601         if (rt_b == &root_task_group.rt_bandwidth)
 602                 span = cpu_online_mask;
 603 #endif
 604         for_each_cpu(i, span) {
 605                 int enqueue = 0;
 606                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 607                 struct rq *rq = rq_of_rt_rq(rt_rq);
 608
 609                 raw_spin_lock(&rq->lock);
 610                 if (rt_rq->rt_time) {
 611                         u64 runtime;
 612
 613                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 614                         if (rt_rq->rt_throttled)
 615                                 balance_runtime(rt_rq);
 616                         runtime = rt_rq->rt_runtime;
 617                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 618                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 619                                 rt_rq->rt_throttled = 0;
 620                                 enqueue = 1;
 621
 622                                 /*
 623                                  * Force a clock update if the CPU was idle,
 624                                  * lest wakeup -> unthrottle time accumulate.
 625                                  */
 626                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
 627                                         rq->skip_clock_update = -1;
 628                         }
 629                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
 630                                 idle = 0;
 631                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 632                 } else if (rt_rq->rt_nr_running) {
 633                         idle = 0;
 634                         if (!rt_rq_throttled(rt_rq))
 635                                 enqueue = 1;
 636                 }
 637
 638                 if (enqueue)
 639                         sched_rt_rq_enqueue(rt_rq);
 640                 raw_spin_unlock(&rq->lock);
 641         }
 642
 643         return idle;
 644 }
 645
 646 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 647 {
 648 #ifdef CONFIG_RT_GROUP_SCHED
 649         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 650
 651         if (rt_rq)
 652                 return rt_rq->highest_prio.curr;
 653 #endif
 654
 655         return rt_task_of(rt_se)->prio;
 656 }
 657
 658 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 659 {
 660         u64 runtime = sched_rt_runtime(rt_rq);
 661
 662         if (rt_rq->rt_throttled)
 663                 return rt_rq_throttled(rt_rq);
 664
 665         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
 666                 return 0;
 667
 668         balance_runtime(rt_rq);
 669         runtime = sched_rt_runtime(rt_rq);
 670         if (runtime == RUNTIME_INF)
 671                 return 0;
 672
 673         if (rt_rq->rt_time > runtime) {
 674                 rt_rq->rt_throttled = 1;
 675                 printk_once(KERN_WARNING "sched: RT throttling activated\n");
 676                 if (rt_rq_throttled(rt_rq)) {
 677                         sched_rt_rq_dequeue(rt_rq);
 678                         return 1;
 679                 }
 680         }
 681
 682         return 0;
 683 }
 684
 685 /*
 686  * Update the current task's runtime statistics. Skip current tasks that
 687  * are not in our scheduling class.
 688  */
 689 static void update_curr_rt(struct rq *rq)
 690 {
 691         struct task_struct *curr = rq->curr;
 692         struct sched_rt_entity *rt_se = &curr->rt;
 693         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 694         u64 delta_exec;
 695
 696         if (curr->sched_class != &rt_sched_class)
 697                 return;
 698
 699         delta_exec = rq->clock_task - curr->se.exec_start;
 700         if (unlikely((s64)delta_exec < 0))
 701                 delta_exec = 0;
 702
 703         schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
 704
 705         curr->se.sum_exec_runtime += delta_exec;
 706         account_group_exec_runtime(curr, delta_exec);
 707
 708         curr->se.exec_start = rq->clock_task;
 709         cpuacct_charge(curr, delta_exec);
 710
 711         sched_rt_avg_update(rq, delta_exec);
 712
 713         if (!rt_bandwidth_enabled())
 714                 return;
 715
 716         for_each_sched_rt_entity(rt_se) {
 717                 rt_rq = rt_rq_of_se(rt_se);
 718
 719                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 720                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 721                         rt_rq->rt_time += delta_exec;
 722                         if (sched_rt_runtime_exceeded(rt_rq))
 723                                 resched_task(curr);
 724                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 725                 }
 726         }
 727 }
 728
 729 #if defined CONFIG_SMP
 730
 731 static void
 732 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 733 {
 734         struct rq *rq = rq_of_rt_rq(rt_rq);
 735
 736 #ifdef CONFIG_RT_GROUP_SCHED
 737         /*
 738          * Change rq's cpupri only if rt_rq is the top queue.
 739          */
 740         if (&rq->rt != rt_rq)
 741                 return;
 742 #endif
 743         if (rq->online && prio < prev_prio)
 744                 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
 745 }
 746
 747 static void
 748 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 749 {
 750         struct rq *rq = rq_of_rt_rq(rt_rq);
 751
 752 #ifdef CONFIG_RT_GROUP_SCHED
 753         /*
 754          * Change rq's cpupri only if rt_rq is the top queue.
 755          */
 756         if (&rq->rt != rt_rq)
 757                 return;
 758 #endif
 759         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
 760                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
 761 }
 762
 763 #else /* CONFIG_SMP */
 764
 765 static inline
 766 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 767 static inline
 768 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 769
 770 #endif /* CONFIG_SMP */
 771
 772 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 773 static void
 774 inc_rt_prio(struct rt_rq *rt_rq, int prio)
 775 {
 776         int prev_prio = rt_rq->highest_prio.curr;
 777
 778         if (prio < prev_prio)
 779                 rt_rq->highest_prio.curr = prio;
 780
 781         inc_rt_prio_smp(rt_rq, prio, prev_prio);
 782 }
 783
 784 static void
 785 dec_rt_prio(struct rt_rq *rt_rq, int prio)
 786 {
 787         int prev_prio = rt_rq->highest_prio.curr;
 788
 789         if (rt_rq->rt_nr_running) {
 790
 791                 WARN_ON(prio < prev_prio);
 792
 793                 /*
 794                  * This may have been our highest task, and therefore
 795                  * we may have some recomputation to do
 796                  */
 797                 if (prio == prev_prio) {
 798                         struct rt_prio_array *array = &rt_rq->active;
 799
 800                         rt_rq->highest_prio.curr =
 801                                 sched_find_first_bit(array->bitmap);
 802                 }
 803
 804         } else
 805                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
 806
 807         dec_rt_prio_smp(rt_rq, prio, prev_prio);
 808 }
 809
 810 #else
 811
 812 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
 813 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
 814
 815 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
 816
 817 #ifdef CONFIG_RT_GROUP_SCHED
 818
 819 static void
 820 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 821 {
 822         if (rt_se_boosted(rt_se))
 823                 rt_rq->rt_nr_boosted++;
 824
 825         if (rt_rq->tg)
 826                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
 827 }
 828
 829 static void
 830 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 831 {
 832         if (rt_se_boosted(rt_se))
 833                 rt_rq->rt_nr_boosted--;
 834
 835         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
 836 }
 837
 838 #else /* CONFIG_RT_GROUP_SCHED */
 839
 840 static void
 841 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 842 {
 843         start_rt_bandwidth(&def_rt_bandwidth);
 844 }
 845
 846 static inline
 847 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
 848
 849 #endif /* CONFIG_RT_GROUP_SCHED */
 850
 851 static inline
 852 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 853 {
 854         int prio = rt_se_prio(rt_se);
 855
 856         WARN_ON(!rt_prio(prio));
 857         rt_rq->rt_nr_running++;
 858
 859         inc_rt_prio(rt_rq, prio);
 860         inc_rt_migration(rt_se, rt_rq);
 861         inc_rt_group(rt_se, rt_rq);
 862 }
 863
 864 static inline
 865 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 866 {
 867         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 868         WARN_ON(!rt_rq->rt_nr_running);
 869         rt_rq->rt_nr_running--;
 870
 871         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
 872         dec_rt_migration(rt_se, rt_rq);
 873         dec_rt_group(rt_se, rt_rq);
 874 }
 875
 876 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 877 {
 878         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 879         struct rt_prio_array *array = &rt_rq->active;
 880         struct rt_rq *group_rq = group_rt_rq(rt_se);
 881         struct list_head *queue = array->queue + rt_se_prio(rt_se);
 882
 883         /*
 884          * Don't enqueue the group if its throttled, or when empty.
 885          * The latter is a consequence of the former when a child group
 886          * get throttled and the current group doesn't have any other
 887          * active members.
 888          */
 889         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 890                 return;
 891
 892         if (!rt_rq->rt_nr_running)
 893                 list_add_leaf_rt_rq(rt_rq);
 894
 895         if (head)
 896                 list_add(&rt_se->run_list, queue);
 897         else
 898                 list_add_tail(&rt_se->run_list, queue);
 899         __set_bit(rt_se_prio(rt_se), array->bitmap);
 900
 901         inc_rt_tasks(rt_se, rt_rq);
 902 }
 903
 904 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
 905 {
 906         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 907         struct rt_prio_array *array = &rt_rq->active;
 908
 909         list_del_init(&rt_se->run_list);
 910         if (list_empty(array->queue + rt_se_prio(rt_se)))
 911                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
 912
 913         dec_rt_tasks(rt_se, rt_rq);
 914         if (!rt_rq->rt_nr_running)
 915                 list_del_leaf_rt_rq(rt_rq);
 916 }
 917
 918 /*
 919  * Because the prio of an upper entry depends on the lower
 920  * entries, we must remove entries top - down.
 921  */
 922 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 923 {
 924         struct sched_rt_entity *back = NULL;
 925
 926         for_each_sched_rt_entity(rt_se) {
 927                 rt_se->back = back;
 928                 back = rt_se;
 929         }
 930
 931         for (rt_se = back; rt_se; rt_se = rt_se->back) {
 932                 if (on_rt_rq(rt_se))
 933                         __dequeue_rt_entity(rt_se);
 934         }
 935 }
 936
 937 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 938 {
 939         dequeue_rt_stack(rt_se);
 940         for_each_sched_rt_entity(rt_se)
 941                 __enqueue_rt_entity(rt_se, head);
 942 }
 943
 944 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 945 {
 946         dequeue_rt_stack(rt_se);
 947
 948         for_each_sched_rt_entity(rt_se) {
 949                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
 950
 951                 if (rt_rq && rt_rq->rt_nr_running)
 952                         __enqueue_rt_entity(rt_se, false);
 953         }
 954 }
 955
 956 /*
 957  * Adding/removing a task to/from a priority array:
 958  */
 959 static void
 960 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 961 {
 962         struct sched_rt_entity *rt_se = &p->rt;
 963
 964         if (flags & ENQUEUE_WAKEUP)
 965                 rt_se->timeout = 0;
 966
 967         enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
 968
 969         if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
 970                 enqueue_pushable_task(rq, p);
 971
 972         inc_nr_running(rq);
 973 }
 974
 975 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 976 {
 977         struct sched_rt_entity *rt_se = &p->rt;
 978
 979         update_curr_rt(rq);
 980         dequeue_rt_entity(rt_se);
 981
 982         dequeue_pushable_task(rq, p);
 983
 984         dec_nr_running(rq);
 985 }
 986
 987 /*
 988  * Put task to the end of the run list without the overhead of dequeue
 989  * followed by enqueue.
 990  */
 991 static void
 992 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
 993 {
 994         if (on_rt_rq(rt_se)) {
 995                 struct rt_prio_array *array = &rt_rq->active;
 996                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
 997
 998                 if (head)
 999                         list_move(&rt_se->run_list, queue);
1000                 else
1001                         list_move_tail(&rt_se->run_list, queue);
1002         }
1003 }
1004
1005 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
1006 {
1007         struct sched_rt_entity *rt_se = &p->rt;
1008         struct rt_rq *rt_rq;
1009
1010         for_each_sched_rt_entity(rt_se) {
1011                 rt_rq = rt_rq_of_se(rt_se);
1012                 requeue_rt_entity(rt_rq, rt_se, head);
1013         }
1014 }
1015
1016 static void yield_task_rt(struct rq *rq)
1017 {
1018         requeue_task_rt(rq, rq->curr, 0);
1019 }
1020
1021 #ifdef CONFIG_SMP
1022 static int find_lowest_rq(struct task_struct *task);
1023
1024 static int
1025 select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
1026 {
1027         struct task_struct *curr;
1028         struct rq *rq;
1029         int cpu;
1030
1031         cpu = task_cpu(p);
1032
1033         /* For anything but wake ups, just return the task_cpu */
1034         if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1035                 goto out;
1036
1037         rq = cpu_rq(cpu);
1038
1039         rcu_read_lock();
1040         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1041
1042         /*
1043          * If the current task on @p's runqueue is an RT task, then
1044          * try to see if we can wake this RT task up on another
1045          * runqueue. Otherwise simply start this RT task
1046          * on its current runqueue.
1047          *
1048          * We want to avoid overloading runqueues. If the woken
1049          * task is a higher priority, then it will stay on this CPU
1050          * and the lower prio task should be moved to another CPU.
1051          * Even though this will probably make the lower prio task
1052          * lose its cache, we do not want to bounce a higher task
1053          * around just because it gave up its CPU, perhaps for a
1054          * lock?
1055          *
1056          * For equal prio tasks, we just let the scheduler sort it out.
1057          *
1058          * Otherwise, just let it ride on the affined RQ and the
1059          * post-schedule router will push the preempted task away
1060          *
1061          * This test is optimistic, if we get it wrong the load-balancer
1062          * will have to sort it out.
1063          */
1064         if (curr && unlikely(rt_task(curr)) &&
1065             (curr->rt.nr_cpus_allowed < 2 ||
1066              curr->prio <= p->prio) &&
1067             (p->rt.nr_cpus_allowed > 1)) {
1068                 int target = find_lowest_rq(p);
1069
1070                 if (target != -1)
1071                         cpu = target;
1072         }
1073         rcu_read_unlock();
1074
1075 out:
1076         return cpu;
1077 }
1078
1079 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1080 {
1081         if (rq->curr->rt.nr_cpus_allowed == 1)
1082                 return;
1083
1084         if (p->rt.nr_cpus_allowed != 1
1085             && cpupri_find(&rq->rd->cpupri, p, NULL))
1086                 return;
1087
1088         if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1089                 return;
1090
1091         /*
1092          * There appears to be other cpus that can accept
1093          * current and none to run 'p', so lets reschedule
1094          * to try and push current away:
1095          */
1096         requeue_task_rt(rq, p, 1);
1097         resched_task(rq->curr);
1098 }
1099
1100 #endif /* CONFIG_SMP */
1101
1102 /*
1103  * Preempt the current task with a newly woken task if needed:
1104  */
1105 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1106 {
1107         if (p->prio < rq->curr->prio) {
1108                 resched_task(rq->curr);
1109                 return;
1110         }
1111
1112 #ifdef CONFIG_SMP
1113         /*
1114          * If:
1115          *
1116          * - the newly woken task is of equal priority to the current task
1117          * - the newly woken task is non-migratable while current is migratable
1118          * - current will be preempted on the next reschedule
1119          *
1120          * we should check to see if current can readily move to a different
1121          * cpu.  If so, we will reschedule to allow the push logic to try
1122          * to move current somewhere else, making room for our non-migratable
1123          * task.
1124          */
1125         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1126                 check_preempt_equal_prio(rq, p);
1127 #endif
1128 }
1129
1130 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1131                                                    struct rt_rq *rt_rq)
1132 {
1133         struct rt_prio_array *array = &rt_rq->active;
1134         struct sched_rt_entity *next = NULL;
1135         struct list_head *queue;
1136         int idx;
1137
1138         idx = sched_find_first_bit(array->bitmap);
1139         BUG_ON(idx >= MAX_RT_PRIO);
1140
1141         queue = array->queue + idx;
1142         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1143
1144         return next;
1145 }
1146
1147 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1148 {
1149         struct sched_rt_entity *rt_se;
1150         struct task_struct *p;
1151         struct rt_rq *rt_rq;
1152
1153         rt_rq = &rq->rt;
1154
1155         if (!rt_rq->rt_nr_running)
1156                 return NULL;
1157
1158         if (rt_rq_throttled(rt_rq))
1159                 return NULL;
1160
1161         do {
1162                 rt_se = pick_next_rt_entity(rq, rt_rq);
1163                 BUG_ON(!rt_se);
1164                 rt_rq = group_rt_rq(rt_se);
1165         } while (rt_rq);
1166
1167         p = rt_task_of(rt_se);
1168         p->se.exec_start = rq->clock_task;
1169
1170         return p;
1171 }
1172
1173 static struct task_struct *pick_next_task_rt(struct rq *rq)
1174 {
1175         struct task_struct *p = _pick_next_task_rt(rq);
1176
1177         /* The running task is never eligible for pushing */
1178         if (p)
1179                 dequeue_pushable_task(rq, p);
1180
1181 #ifdef CONFIG_SMP
1182         /*
1183          * We detect this state here so that we can avoid taking the RQ
1184          * lock again later if there is no need to push
1185          */
1186         rq->post_schedule = has_pushable_tasks(rq);
1187 #endif
1188
1189         return p;
1190 }
1191
1192 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1193 {
1194         update_curr_rt(rq);
1195
1196         /*
1197          * The previous task needs to be made eligible for pushing
1198          * if it is still active
1199          */
1200         if (on_rt_rq(&p->rt) && p->rt.nr_cpus_allowed > 1)
1201                 enqueue_pushable_task(rq, p);
1202 }
1203
1204 #ifdef CONFIG_SMP
1205
1206 /* Only try algorithms three times */
1207 #define RT_MAX_TRIES 3
1208
1209 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
1210
1211 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1212 {
1213         if (!task_running(rq, p) &&
1214             (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
1215             (p->rt.nr_cpus_allowed > 1))
1216                 return 1;
1217         return 0;
1218 }
1219
1220 /* Return the second highest RT task, NULL otherwise */
1221 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
1222 {
1223         struct task_struct *next = NULL;
1224         struct sched_rt_entity *rt_se;
1225         struct rt_prio_array *array;
1226         struct rt_rq *rt_rq;
1227         int idx;
1228
1229         for_each_leaf_rt_rq(rt_rq, rq) {
1230                 array = &rt_rq->active;
1231                 idx = sched_find_first_bit(array->bitmap);
1232 next_idx:
1233                 if (idx >= MAX_RT_PRIO)
1234                         continue;
1235                 if (next && next->prio < idx)
1236                         continue;
1237                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
1238                         struct task_struct *p;
1239
1240                         if (!rt_entity_is_task(rt_se))
1241                                 continue;
1242
1243                         p = rt_task_of(rt_se);
1244                         if (pick_rt_task(rq, p, cpu)) {
1245                                 next = p;
1246                                 break;
1247                         }
1248                 }
1249                 if (!next) {
1250                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
1251                         goto next_idx;
1252                 }
1253         }
1254
1255         return next;
1256 }
1257
1258 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1259
1260 static int find_lowest_rq(struct task_struct *task)
1261 {
1262         struct sched_domain *sd;
1263         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1264         int this_cpu = smp_processor_id();
1265         int cpu      = task_cpu(task);
1266
1267         /* Make sure the mask is initialized first */
1268         if (unlikely(!lowest_mask))
1269                 return -1;
1270
1271         if (task->rt.nr_cpus_allowed == 1)
1272                 return -1; /* No other targets possible */
1273
1274         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1275                 return -1; /* No targets found */
1276
1277         /*
1278          * At this point we have built a mask of cpus representing the
1279          * lowest priority tasks in the system.  Now we want to elect
1280          * the best one based on our affinity and topology.
1281          *
1282          * We prioritize the last cpu that the task executed on since
1283          * it is most likely cache-hot in that location.
1284          */
1285         if (cpumask_test_cpu(cpu, lowest_mask))
1286                 return cpu;
1287
1288         /*
1289          * Otherwise, we consult the sched_domains span maps to figure
1290          * out which cpu is logically closest to our hot cache data.
1291          */
1292         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1293                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1294
1295         rcu_read_lock();
1296         for_each_domain(cpu, sd) {
1297                 if (sd->flags & SD_WAKE_AFFINE) {
1298                         int best_cpu;
1299
1300                         /*
1301                          * "this_cpu" is cheaper to preempt than a
1302                          * remote processor.
1303                          */
1304                         if (this_cpu != -1 &&
1305                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1306                                 rcu_read_unlock();
1307                                 return this_cpu;
1308                         }
1309
1310                         best_cpu = cpumask_first_and(lowest_mask,
1311                                                      sched_domain_span(sd));
1312                         if (best_cpu < nr_cpu_ids) {
1313                                 rcu_read_unlock();
1314                                 return best_cpu;
1315                         }
1316                 }
1317         }
1318         rcu_read_unlock();
1319
1320         /*
1321          * And finally, if there were no matches within the domains
1322          * just give the caller *something* to work with from the compatible
1323          * locations.
1324          */
1325         if (this_cpu != -1)
1326                 return this_cpu;
1327
1328         cpu = cpumask_any(lowest_mask);
1329         if (cpu < nr_cpu_ids)
1330                 return cpu;
1331         return -1;
1332 }
1333
1334 /* Will lock the rq it finds */
1335 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1336 {
1337         struct rq *lowest_rq = NULL;
1338         int tries;
1339         int cpu;
1340
1341         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1342                 cpu = find_lowest_rq(task);
1343
1344                 if ((cpu == -1) || (cpu == rq->cpu))
1345                         break;
1346
1347                 lowest_rq = cpu_rq(cpu);
1348
1349                 /* if the prio of this runqueue changed, try again */
1350                 if (double_lock_balance(rq, lowest_rq)) {
1351                         /*
1352                          * We had to unlock the run queue. In
1353                          * the mean time, task could have
1354                          * migrated already or had its affinity changed.
1355                          * Also make sure that it wasn't scheduled on its rq.
1356                          */
1357                         if (unlikely(task_rq(task) != rq ||
1358                                      !cpumask_test_cpu(lowest_rq->cpu,
1359                                                        tsk_cpus_allowed(task)) ||
1360                                      task_running(rq, task) ||
1361                                      !task->on_rq)) {
1362
1363                                 raw_spin_unlock(&lowest_rq->lock);
1364                                 lowest_rq = NULL;
1365                                 break;
1366                         }
1367                 }
1368
1369                 /* If this rq is still suitable use it. */
1370                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1371                         break;
1372
1373                 /* try again */
1374                 double_unlock_balance(rq, lowest_rq);
1375                 lowest_rq = NULL;
1376         }
1377
1378         return lowest_rq;
1379 }
1380
1381 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1382 {
1383         struct task_struct *p;
1384
1385         if (!has_pushable_tasks(rq))
1386                 return NULL;
1387
1388         p = plist_first_entry(&rq->rt.pushable_tasks,
1389                               struct task_struct, pushable_tasks);
1390
1391         BUG_ON(rq->cpu != task_cpu(p));
1392         BUG_ON(task_current(rq, p));
1393         BUG_ON(p->rt.nr_cpus_allowed <= 1);
1394
1395         BUG_ON(!p->on_rq);
1396         BUG_ON(!rt_task(p));
1397
1398         return p;
1399 }
1400
1401 /*
1402  * If the current CPU has more than one RT task, see if the non
1403  * running task can migrate over to a CPU that is running a task
1404  * of lesser priority.
1405  */
1406 static int push_rt_task(struct rq *rq)
1407 {
1408         struct task_struct *next_task;
1409         struct rq *lowest_rq;
1410         int ret = 0;
1411
1412         if (!rq->rt.overloaded)
1413                 return 0;
1414
1415         next_task = pick_next_pushable_task(rq);
1416         if (!next_task)
1417                 return 0;
1418
1419 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1420        if (unlikely(task_running(rq, next_task)))
1421                return 0;
1422 #endif
1423
1424 retry:
1425         if (unlikely(next_task == rq->curr)) {
1426                 WARN_ON(1);
1427                 return 0;
1428         }
1429
1430         /*
1431          * It's possible that the next_task slipped in of
1432          * higher priority than current. If that's the case
1433          * just reschedule current.
1434          */
1435         if (unlikely(next_task->prio < rq->curr->prio)) {
1436                 resched_task(rq->curr);
1437                 return 0;
1438         }
1439
1440         /* We might release rq lock */
1441         get_task_struct(next_task);
1442
1443         /* find_lock_lowest_rq locks the rq if found */
1444         lowest_rq = find_lock_lowest_rq(next_task, rq);
1445         if (!lowest_rq) {
1446                 struct task_struct *task;
1447                 /*
1448                  * find_lock_lowest_rq releases rq->lock
1449                  * so it is possible that next_task has migrated.
1450                  *
1451                  * We need to make sure that the task is still on the same
1452                  * run-queue and is also still the next task eligible for
1453                  * pushing.
1454                  */
1455                 task = pick_next_pushable_task(rq);
1456                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1457                         /*
1458                          * The task hasn't migrated, and is still the next
1459                          * eligible task, but we failed to find a run-queue
1460                          * to push it to.  Do not retry in this case, since
1461                          * other cpus will pull from us when ready.
1462                          */
1463                         goto out;
1464                 }
1465
1466                 if (!task)
1467                         /* No more tasks, just exit */
1468                         goto out;
1469
1470                 /*
1471                  * Something has shifted, try again.
1472                  */
1473                 put_task_struct(next_task);
1474                 next_task = task;
1475                 goto retry;
1476         }
1477
1478         deactivate_task(rq, next_task, 0);
1479         set_task_cpu(next_task, lowest_rq->cpu);
1480         activate_task(lowest_rq, next_task, 0);
1481         ret = 1;
1482
1483         resched_task(lowest_rq->curr);
1484
1485         double_unlock_balance(rq, lowest_rq);
1486
1487 out:
1488         put_task_struct(next_task);
1489
1490         return ret;
1491 }
1492
1493 static void push_rt_tasks(struct rq *rq)
1494 {
1495         /* push_rt_task will return true if it moved an RT */
1496         while (push_rt_task(rq))
1497                 ;
1498 }
1499
1500 static int pull_rt_task(struct rq *this_rq)
1501 {
1502         int this_cpu = this_rq->cpu, ret = 0, cpu;
1503         struct task_struct *p;
1504         struct rq *src_rq;
1505
1506         if (likely(!rt_overloaded(this_rq)))
1507                 return 0;
1508
1509         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1510                 if (this_cpu == cpu)
1511                         continue;
1512
1513                 src_rq = cpu_rq(cpu);
1514
1515                 /*
1516                  * Don't bother taking the src_rq->lock if the next highest
1517                  * task is known to be lower-priority than our current task.
1518                  * This may look racy, but if this value is about to go
1519                  * logically higher, the src_rq will push this task away.
1520                  * And if its going logically lower, we do not care
1521                  */
1522                 if (src_rq->rt.highest_prio.next >=
1523                     this_rq->rt.highest_prio.curr)
1524                         continue;
1525
1526                 /*
1527                  * We can potentially drop this_rq's lock in
1528                  * double_lock_balance, and another CPU could
1529                  * alter this_rq
1530                  */
1531                 double_lock_balance(this_rq, src_rq);
1532
1533                 /*
1534                  * Are there still pullable RT tasks?
1535                  */
1536                 if (src_rq->rt.rt_nr_running <= 1)
1537                         goto skip;
1538
1539                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1540
1541                 /*
1542                  * Do we have an RT task that preempts
1543                  * the to-be-scheduled task?
1544                  */
1545                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1546                         WARN_ON(p == src_rq->curr);
1547                         WARN_ON(!p->on_rq);
1548
1549                         /*
1550                          * There's a chance that p is higher in priority
1551                          * than what's currently running on its cpu.
1552                          * This is just that p is wakeing up and hasn't
1553                          * had a chance to schedule. We only pull
1554                          * p if it is lower in priority than the
1555                          * current task on the run queue
1556                          */
1557                         if (p->prio < src_rq->curr->prio)
1558                                 goto skip;
1559
1560                         ret = 1;
1561
1562                         deactivate_task(src_rq, p, 0);
1563                         set_task_cpu(p, this_cpu);
1564                         activate_task(this_rq, p, 0);
1565                         /*
1566                          * We continue with the search, just in
1567                          * case there's an even higher prio task
1568                          * in another runqueue. (low likelihood
1569                          * but possible)
1570                          */
1571                 }
1572 skip:
1573                 double_unlock_balance(this_rq, src_rq);
1574         }
1575
1576         return ret;
1577 }
1578
1579 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1580 {
1581         /* Try to pull RT tasks here if we lower this rq's prio */
1582         if (rq->rt.highest_prio.curr > prev->prio)
1583                 pull_rt_task(rq);
1584 }
1585
1586 static void post_schedule_rt(struct rq *rq)
1587 {
1588         push_rt_tasks(rq);
1589 }
1590
1591 /*
1592  * If we are not running and we are not going to reschedule soon, we should
1593  * try to push tasks away now
1594  */
1595 static void task_woken_rt(struct rq *rq, struct task_struct *p)
1596 {
1597         if (!task_running(rq, p) &&
1598             !test_tsk_need_resched(rq->curr) &&
1599             has_pushable_tasks(rq) &&
1600             p->rt.nr_cpus_allowed > 1 &&
1601             rt_task(rq->curr) &&
1602             (rq->curr->rt.nr_cpus_allowed < 2 ||
1603              rq->curr->prio <= p->prio))
1604                 push_rt_tasks(rq);
1605 }
1606
1607 static void set_cpus_allowed_rt(struct task_struct *p,
1608                                 const struct cpumask *new_mask)
1609 {
1610         int weight = cpumask_weight(new_mask);
1611
1612         BUG_ON(!rt_task(p));
1613
1614         /*
1615          * Update the migration status of the RQ if we have an RT task
1616          * which is running AND changing its weight value.
1617          */
1618         if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
1619                 struct rq *rq = task_rq(p);
1620
1621                 if (!task_current(rq, p)) {
1622                         /*
1623                          * Make sure we dequeue this task from the pushable list
1624                          * before going further.  It will either remain off of
1625                          * the list because we are no longer pushable, or it
1626                          * will be requeued.
1627                          */
1628                         if (p->rt.nr_cpus_allowed > 1)
1629                                 dequeue_pushable_task(rq, p);
1630
1631                         /*
1632                          * Requeue if our weight is changing and still > 1
1633                          */
1634                         if (weight > 1)
1635                                 enqueue_pushable_task(rq, p);
1636
1637                 }
1638
1639                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1640                         rq->rt.rt_nr_migratory++;
1641                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1642                         BUG_ON(!rq->rt.rt_nr_migratory);
1643                         rq->rt.rt_nr_migratory--;
1644                 }
1645
1646                 update_rt_migration(&rq->rt);
1647         }
1648 }
1649
1650 /* Assumes rq->lock is held */
1651 static void rq_online_rt(struct rq *rq)
1652 {
1653         if (rq->rt.overloaded)
1654                 rt_set_overload(rq);
1655
1656         __enable_runtime(rq);
1657
1658         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1659 }
1660
1661 /* Assumes rq->lock is held */
1662 static void rq_offline_rt(struct rq *rq)
1663 {
1664         if (rq->rt.overloaded)
1665                 rt_clear_overload(rq);
1666
1667         __disable_runtime(rq);
1668
1669         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1670 }
1671
1672 /*
1673  * When switch from the rt queue, we bring ourselves to a position
1674  * that we might want to pull RT tasks from other runqueues.
1675  */
1676 static void switched_from_rt(struct rq *rq, struct task_struct *p)
1677 {
1678         /*
1679          * If there are other RT tasks then we will reschedule
1680          * and the scheduling of the other RT tasks will handle
1681          * the balancing. But if we are the last RT task
1682          * we may need to handle the pulling of RT tasks
1683          * now.
1684          */
1685         if (p->on_rq && !rq->rt.rt_nr_running)
1686                 pull_rt_task(rq);
1687 }
1688
1689 static inline void init_sched_rt_class(void)
1690 {
1691         unsigned int i;
1692
1693         for_each_possible_cpu(i)
1694                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1695                                         GFP_KERNEL, cpu_to_node(i));
1696 }
1697 #endif /* CONFIG_SMP */
1698
1699 /*
1700  * When switching a task to RT, we may overload the runqueue
1701  * with RT tasks. In this case we try to push them off to
1702  * other runqueues.
1703  */
1704 static void switched_to_rt(struct rq *rq, struct task_struct *p)
1705 {
1706         int check_resched = 1;
1707
1708         /*
1709          * If we are already running, then there's nothing
1710          * that needs to be done. But if we are not running
1711          * we may need to preempt the current running task.
1712          * If that current running task is also an RT task
1713          * then see if we can move to another run queue.
1714          */
1715         if (p->on_rq && rq->curr != p) {
1716 #ifdef CONFIG_SMP
1717                 if (rq->rt.overloaded && push_rt_task(rq) &&
1718                     /* Don't resched if we changed runqueues */
1719                     rq != task_rq(p))
1720                         check_resched = 0;
1721 #endif /* CONFIG_SMP */
1722                 if (check_resched && p->prio < rq->curr->prio)
1723                         resched_task(rq->curr);
1724         }
1725 }
1726
1727 /*
1728  * Priority of the task has changed. This may cause
1729  * us to initiate a push or pull.
1730  */
1731 static void
1732 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1733 {
1734         if (!p->on_rq)
1735                 return;
1736
1737         if (rq->curr == p) {
1738 #ifdef CONFIG_SMP
1739                 /*
1740                  * If our priority decreases while running, we
1741                  * may need to pull tasks to this runqueue.
1742                  */
1743                 if (oldprio < p->prio)
1744                         pull_rt_task(rq);
1745                 /*
1746                  * If there's a higher priority task waiting to run
1747                  * then reschedule. Note, the above pull_rt_task
1748                  * can release the rq lock and p could migrate.
1749                  * Only reschedule if p is still on the same runqueue.
1750                  */
1751                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1752                         resched_task(p);
1753 #else
1754                 /* For UP simply resched on drop of prio */
1755                 if (oldprio < p->prio)
1756                         resched_task(p);
1757 #endif /* CONFIG_SMP */
1758         } else {
1759                 /*
1760                  * This task is not running, but if it is
1761                  * greater than the current running task
1762                  * then reschedule.
1763                  */
1764                 if (p->prio < rq->curr->prio)
1765                         resched_task(rq->curr);
1766         }
1767 }
1768
1769 static void watchdog(struct rq *rq, struct task_struct *p)
1770 {
1771         unsigned long soft, hard;
1772
1773         /* max may change after cur was read, this will be fixed next tick */
1774         soft = task_rlimit(p, RLIMIT_RTTIME);
1775         hard = task_rlimit_max(p, RLIMIT_RTTIME);
1776
1777         if (soft != RLIM_INFINITY) {
1778                 unsigned long next;
1779
1780                 if (p->rt.watchdog_stamp != jiffies) {
1781                         p->rt.timeout++;
1782                         p->rt.watchdog_stamp = jiffies;
1783                 }
1784
1785                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1786                 if (p->rt.timeout > next)
1787                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1788         }
1789 }
1790
1791 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1792 {
1793         struct sched_rt_entity *rt_se = &p->rt;
1794
1795         update_curr_rt(rq);
1796
1797         watchdog(rq, p);
1798
1799         /*
1800          * RR tasks need a special form of timeslice management.
1801          * FIFO tasks have no timeslices.
1802          */
1803         if (p->policy != SCHED_RR)
1804                 return;
1805
1806         if (--p->rt.time_slice)
1807                 return;
1808
1809         p->rt.time_slice = DEF_TIMESLICE;
1810
1811         /*
1812          * Requeue to the end of queue if we (and all of our ancestors) are the
1813          * only element on the queue
1814          */
1815         for_each_sched_rt_entity(rt_se) {
1816                 if (rt_se->run_list.prev != rt_se->run_list.next) {
1817                         requeue_task_rt(rq, p, 0);
1818                         set_tsk_need_resched(p);
1819                         return;
1820                 }
1821         }
1822 }
1823
1824 static void set_curr_task_rt(struct rq *rq)
1825 {
1826         struct task_struct *p = rq->curr;
1827
1828         p->se.exec_start = rq->clock_task;
1829
1830         /* The running task is never eligible for pushing */
1831         dequeue_pushable_task(rq, p);
1832 }
1833
1834 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
1835 {
1836         /*
1837          * Time slice is 0 for SCHED_FIFO tasks
1838          */
1839         if (task->policy == SCHED_RR)
1840                 return DEF_TIMESLICE;
1841         else
1842                 return 0;
1843 }
1844
1845 static const struct sched_class rt_sched_class = {
1846         .next                   = &fair_sched_class,
1847         .enqueue_task           = enqueue_task_rt,
1848         .dequeue_task           = dequeue_task_rt,
1849         .yield_task             = yield_task_rt,
1850
1851         .check_preempt_curr     = check_preempt_curr_rt,
1852
1853         .pick_next_task         = pick_next_task_rt,
1854         .put_prev_task          = put_prev_task_rt,
1855
1856 #ifdef CONFIG_SMP
1857         .select_task_rq         = select_task_rq_rt,
1858
1859         .set_cpus_allowed       = set_cpus_allowed_rt,
1860         .rq_online              = rq_online_rt,
1861         .rq_offline             = rq_offline_rt,
1862         .pre_schedule           = pre_schedule_rt,
1863         .post_schedule          = post_schedule_rt,
1864         .task_woken             = task_woken_rt,
1865         .switched_from          = switched_from_rt,
1866 #endif
1867
1868         .set_curr_task          = set_curr_task_rt,
1869         .task_tick              = task_tick_rt,
1870
1871         .get_rr_interval        = get_rr_interval_rt,
1872
1873         .prio_changed           = prio_changed_rt,
1874         .switched_to            = switched_to_rt,
1875 };
1876
1877 #ifdef CONFIG_SCHED_DEBUG
1878 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1879
1880 static void print_rt_stats(struct seq_file *m, int cpu)
1881 {
1882         rt_rq_iter_t iter;
1883         struct rt_rq *rt_rq;
1884
1885         rcu_read_lock();
1886         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1887                 print_rt_rq(m, cpu, rt_rq);
1888         rcu_read_unlock();
1889 }
1890 #endif /* CONFIG_SCHED_DEBUG */