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 = cpu_rq(smp_processor_id())->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                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 513                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 514         }
 515 }
 516
 517 static void disable_runtime(struct rq *rq)
 518 {
 519         unsigned long flags;
 520
 521         raw_spin_lock_irqsave(&rq->lock, flags);
 522         __disable_runtime(rq);
 523         raw_spin_unlock_irqrestore(&rq->lock, flags);
 524 }
 525
 526 static void __enable_runtime(struct rq *rq)
 527 {
 528         rt_rq_iter_t iter;
 529         struct rt_rq *rt_rq;
 530
 531         if (unlikely(!scheduler_running))
 532                 return;
 533
 534         /*
 535          * Reset each runqueue's bandwidth settings
 536          */
 537         for_each_rt_rq(rt_rq, iter, rq) {
 538                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 539
 540                 raw_spin_lock(&rt_b->rt_runtime_lock);
 541                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 542                 rt_rq->rt_runtime = rt_b->rt_runtime;
 543                 rt_rq->rt_time = 0;
 544                 rt_rq->rt_throttled = 0;
 545                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 546                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 547         }
 548 }
 549
 550 static void enable_runtime(struct rq *rq)
 551 {
 552         unsigned long flags;
 553
 554         raw_spin_lock_irqsave(&rq->lock, flags);
 555         __enable_runtime(rq);
 556         raw_spin_unlock_irqrestore(&rq->lock, flags);
 557 }
 558
 559 static int balance_runtime(struct rt_rq *rt_rq)
 560 {
 561         int more = 0;
 562
 563         if (rt_rq->rt_time > rt_rq->rt_runtime) {
 564                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 565                 more = do_balance_runtime(rt_rq);
 566                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 567         }
 568
 569         return more;
 570 }
 571 #else /* !CONFIG_SMP */
 572 static inline int balance_runtime(struct rt_rq *rt_rq)
 573 {
 574         return 0;
 575 }
 576 #endif /* CONFIG_SMP */
 577
 578 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 579 {
 580         int i, idle = 1;
 581         const struct cpumask *span;
 582
 583         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
 584                 return 1;
 585
 586         span = sched_rt_period_mask();
 587         for_each_cpu(i, span) {
 588                 int enqueue = 0;
 589                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 590                 struct rq *rq = rq_of_rt_rq(rt_rq);
 591
 592                 raw_spin_lock(&rq->lock);
 593                 if (rt_rq->rt_time) {
 594                         u64 runtime;
 595
 596                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 597                         if (rt_rq->rt_throttled)
 598                                 balance_runtime(rt_rq);
 599                         runtime = rt_rq->rt_runtime;
 600                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 601                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 602                                 rt_rq->rt_throttled = 0;
 603                                 enqueue = 1;
 604
 605                                 /*
 606                                  * Force a clock update if the CPU was idle,
 607                                  * lest wakeup -> unthrottle time accumulate.
 608                                  */
 609                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
 610                                         rq->skip_clock_update = -1;
 611                         }
 612                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
 613                                 idle = 0;
 614                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 615                 } else if (rt_rq->rt_nr_running) {
 616                         idle = 0;
 617                         if (!rt_rq_throttled(rt_rq))
 618                                 enqueue = 1;
 619                 }
 620
 621                 if (enqueue)
 622                         sched_rt_rq_enqueue(rt_rq);
 623                 raw_spin_unlock(&rq->lock);
 624         }
 625
 626         return idle;
 627 }
 628
 629 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 630 {
 631 #ifdef CONFIG_RT_GROUP_SCHED
 632         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 633
 634         if (rt_rq)
 635                 return rt_rq->highest_prio.curr;
 636 #endif
 637
 638         return rt_task_of(rt_se)->prio;
 639 }
 640
 641 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 642 {
 643         u64 runtime = sched_rt_runtime(rt_rq);
 644
 645         if (rt_rq->rt_throttled)
 646                 return rt_rq_throttled(rt_rq);
 647
 648         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
 649                 return 0;
 650
 651         balance_runtime(rt_rq);
 652         runtime = sched_rt_runtime(rt_rq);
 653         if (runtime == RUNTIME_INF)
 654                 return 0;
 655
 656         if (rt_rq->rt_time > runtime) {
 657                 rt_rq->rt_throttled = 1;
 658                 printk_once(KERN_WARNING "sched: RT throttling activated\n");
 659                 if (rt_rq_throttled(rt_rq)) {
 660                         sched_rt_rq_dequeue(rt_rq);
 661                         return 1;
 662                 }
 663         }
 664
 665         return 0;
 666 }
 667
 668 /*
 669  * Update the current task's runtime statistics. Skip current tasks that
 670  * are not in our scheduling class.
 671  */
 672 static void update_curr_rt(struct rq *rq)
 673 {
 674         struct task_struct *curr = rq->curr;
 675         struct sched_rt_entity *rt_se = &curr->rt;
 676         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 677         u64 delta_exec;
 678
 679         if (curr->sched_class != &rt_sched_class)
 680                 return;
 681
 682         delta_exec = rq->clock_task - curr->se.exec_start;
 683         if (unlikely((s64)delta_exec < 0))
 684                 delta_exec = 0;
 685
 686         schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
 687
 688         curr->se.sum_exec_runtime += delta_exec;
 689         account_group_exec_runtime(curr, delta_exec);
 690
 691         curr->se.exec_start = rq->clock_task;
 692         cpuacct_charge(curr, delta_exec);
 693
 694         sched_rt_avg_update(rq, delta_exec);
 695
 696         if (!rt_bandwidth_enabled())
 697                 return;
 698
 699         for_each_sched_rt_entity(rt_se) {
 700                 rt_rq = rt_rq_of_se(rt_se);
 701
 702                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 703                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 704                         rt_rq->rt_time += delta_exec;
 705                         if (sched_rt_runtime_exceeded(rt_rq))
 706                                 resched_task(curr);
 707                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 708                 }
 709         }
 710 }
 711
 712 #if defined CONFIG_SMP
 713
 714 static void
 715 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 716 {
 717         struct rq *rq = rq_of_rt_rq(rt_rq);
 718
 719         if (rq->online && prio < prev_prio)
 720                 cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
 721 }
 722
 723 static void
 724 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 725 {
 726         struct rq *rq = rq_of_rt_rq(rt_rq);
 727
 728         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
 729                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
 730 }
 731
 732 #else /* CONFIG_SMP */
 733
 734 static inline
 735 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 736 static inline
 737 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 738
 739 #endif /* CONFIG_SMP */
 740
 741 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 742 static void
 743 inc_rt_prio(struct rt_rq *rt_rq, int prio)
 744 {
 745         int prev_prio = rt_rq->highest_prio.curr;
 746
 747         if (prio < prev_prio)
 748                 rt_rq->highest_prio.curr = prio;
 749
 750         inc_rt_prio_smp(rt_rq, prio, prev_prio);
 751 }
 752
 753 static void
 754 dec_rt_prio(struct rt_rq *rt_rq, int prio)
 755 {
 756         int prev_prio = rt_rq->highest_prio.curr;
 757
 758         if (rt_rq->rt_nr_running) {
 759
 760                 WARN_ON(prio < prev_prio);
 761
 762                 /*
 763                  * This may have been our highest task, and therefore
 764                  * we may have some recomputation to do
 765                  */
 766                 if (prio == prev_prio) {
 767                         struct rt_prio_array *array = &rt_rq->active;
 768
 769                         rt_rq->highest_prio.curr =
 770                                 sched_find_first_bit(array->bitmap);
 771                 }
 772
 773         } else
 774                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
 775
 776         dec_rt_prio_smp(rt_rq, prio, prev_prio);
 777 }
 778
 779 #else
 780
 781 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
 782 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
 783
 784 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
 785
 786 #ifdef CONFIG_RT_GROUP_SCHED
 787
 788 static void
 789 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 790 {
 791         if (rt_se_boosted(rt_se))
 792                 rt_rq->rt_nr_boosted++;
 793
 794         if (rt_rq->tg)
 795                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
 796 }
 797
 798 static void
 799 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 800 {
 801         if (rt_se_boosted(rt_se))
 802                 rt_rq->rt_nr_boosted--;
 803
 804         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
 805 }
 806
 807 #else /* CONFIG_RT_GROUP_SCHED */
 808
 809 static void
 810 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 811 {
 812         start_rt_bandwidth(&def_rt_bandwidth);
 813 }
 814
 815 static inline
 816 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
 817
 818 #endif /* CONFIG_RT_GROUP_SCHED */
 819
 820 static inline
 821 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 822 {
 823         int prio = rt_se_prio(rt_se);
 824
 825         WARN_ON(!rt_prio(prio));
 826         rt_rq->rt_nr_running++;
 827
 828         inc_rt_prio(rt_rq, prio);
 829         inc_rt_migration(rt_se, rt_rq);
 830         inc_rt_group(rt_se, rt_rq);
 831 }
 832
 833 static inline
 834 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 835 {
 836         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 837         WARN_ON(!rt_rq->rt_nr_running);
 838         rt_rq->rt_nr_running--;
 839
 840         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
 841         dec_rt_migration(rt_se, rt_rq);
 842         dec_rt_group(rt_se, rt_rq);
 843 }
 844
 845 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 846 {
 847         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 848         struct rt_prio_array *array = &rt_rq->active;
 849         struct rt_rq *group_rq = group_rt_rq(rt_se);
 850         struct list_head *queue = array->queue + rt_se_prio(rt_se);
 851
 852         /*
 853          * Don't enqueue the group if its throttled, or when empty.
 854          * The latter is a consequence of the former when a child group
 855          * get throttled and the current group doesn't have any other
 856          * active members.
 857          */
 858         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 859                 return;
 860
 861         if (!rt_rq->rt_nr_running)
 862                 list_add_leaf_rt_rq(rt_rq);
 863
 864         if (head)
 865                 list_add(&rt_se->run_list, queue);
 866         else
 867                 list_add_tail(&rt_se->run_list, queue);
 868         __set_bit(rt_se_prio(rt_se), array->bitmap);
 869
 870         inc_rt_tasks(rt_se, rt_rq);
 871 }
 872
 873 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
 874 {
 875         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 876         struct rt_prio_array *array = &rt_rq->active;
 877
 878         list_del_init(&rt_se->run_list);
 879         if (list_empty(array->queue + rt_se_prio(rt_se)))
 880                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
 881
 882         dec_rt_tasks(rt_se, rt_rq);
 883         if (!rt_rq->rt_nr_running)
 884                 list_del_leaf_rt_rq(rt_rq);
 885 }
 886
 887 /*
 888  * Because the prio of an upper entry depends on the lower
 889  * entries, we must remove entries top - down.
 890  */
 891 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 892 {
 893         struct sched_rt_entity *back = NULL;
 894
 895         for_each_sched_rt_entity(rt_se) {
 896                 rt_se->back = back;
 897                 back = rt_se;
 898         }
 899
 900         for (rt_se = back; rt_se; rt_se = rt_se->back) {
 901                 if (on_rt_rq(rt_se))
 902                         __dequeue_rt_entity(rt_se);
 903         }
 904 }
 905
 906 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 907 {
 908         dequeue_rt_stack(rt_se);
 909         for_each_sched_rt_entity(rt_se)
 910                 __enqueue_rt_entity(rt_se, head);
 911 }
 912
 913 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 914 {
 915         dequeue_rt_stack(rt_se);
 916
 917         for_each_sched_rt_entity(rt_se) {
 918                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
 919
 920                 if (rt_rq && rt_rq->rt_nr_running)
 921                         __enqueue_rt_entity(rt_se, false);
 922         }
 923 }
 924
 925 /*
 926  * Adding/removing a task to/from a priority array:
 927  */
 928 static void
 929 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 930 {
 931         struct sched_rt_entity *rt_se = &p->rt;
 932
 933         if (flags & ENQUEUE_WAKEUP)
 934                 rt_se->timeout = 0;
 935
 936         enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
 937
 938         if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
 939                 enqueue_pushable_task(rq, p);
 940
 941         inc_nr_running(rq);
 942 }
 943
 944 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 945 {
 946         struct sched_rt_entity *rt_se = &p->rt;
 947
 948         update_curr_rt(rq);
 949         dequeue_rt_entity(rt_se);
 950
 951         dequeue_pushable_task(rq, p);
 952
 953         dec_nr_running(rq);
 954 }
 955
 956 /*
 957  * Put task to the end of the run list without the overhead of dequeue
 958  * followed by enqueue.
 959  */
 960 static void
 961 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
 962 {
 963         if (on_rt_rq(rt_se)) {
 964                 struct rt_prio_array *array = &rt_rq->active;
 965                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
 966
 967                 if (head)
 968                         list_move(&rt_se->run_list, queue);
 969                 else
 970                         list_move_tail(&rt_se->run_list, queue);
 971         }
 972 }
 973
 974 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
 975 {
 976         struct sched_rt_entity *rt_se = &p->rt;
 977         struct rt_rq *rt_rq;
 978
 979         for_each_sched_rt_entity(rt_se) {
 980                 rt_rq = rt_rq_of_se(rt_se);
 981                 requeue_rt_entity(rt_rq, rt_se, head);
 982         }
 983 }
 984
 985 static void yield_task_rt(struct rq *rq)
 986 {
 987         requeue_task_rt(rq, rq->curr, 0);
 988 }
 989
 990 #ifdef CONFIG_SMP
 991 static int find_lowest_rq(struct task_struct *task);
 992
 993 static int
 994 select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
 995 {
 996         struct task_struct *curr;
 997         struct rq *rq;
 998         int cpu;
 999
1000         cpu = task_cpu(p);
1001
1002         /* For anything but wake ups, just return the task_cpu */
1003         if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
1004                 goto out;
1005
1006         rq = cpu_rq(cpu);
1007
1008         rcu_read_lock();
1009         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1010
1011         /*
1012          * If the current task on @p's runqueue is an RT task, then
1013          * try to see if we can wake this RT task up on another
1014          * runqueue. Otherwise simply start this RT task
1015          * on its current runqueue.
1016          *
1017          * We want to avoid overloading runqueues. If the woken
1018          * task is a higher priority, then it will stay on this CPU
1019          * and the lower prio task should be moved to another CPU.
1020          * Even though this will probably make the lower prio task
1021          * lose its cache, we do not want to bounce a higher task
1022          * around just because it gave up its CPU, perhaps for a
1023          * lock?
1024          *
1025          * For equal prio tasks, we just let the scheduler sort it out.
1026          *
1027          * Otherwise, just let it ride on the affined RQ and the
1028          * post-schedule router will push the preempted task away
1029          *
1030          * This test is optimistic, if we get it wrong the load-balancer
1031          * will have to sort it out.
1032          */
1033         if (curr && unlikely(rt_task(curr)) &&
1034             (curr->rt.nr_cpus_allowed < 2 ||
1035              curr->prio <= p->prio) &&
1036             (p->rt.nr_cpus_allowed > 1)) {
1037                 int target = find_lowest_rq(p);
1038
1039                 if (target != -1)
1040                         cpu = target;
1041         }
1042         rcu_read_unlock();
1043
1044 out:
1045         return cpu;
1046 }
1047
1048 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1049 {
1050         if (rq->curr->rt.nr_cpus_allowed == 1)
1051                 return;
1052
1053         if (p->rt.nr_cpus_allowed != 1
1054             && cpupri_find(&rq->rd->cpupri, p, NULL))
1055                 return;
1056
1057         if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1058                 return;
1059
1060         /*
1061          * There appears to be other cpus that can accept
1062          * current and none to run 'p', so lets reschedule
1063          * to try and push current away:
1064          */
1065         requeue_task_rt(rq, p, 1);
1066         resched_task(rq->curr);
1067 }
1068
1069 #endif /* CONFIG_SMP */
1070
1071 /*
1072  * Preempt the current task with a newly woken task if needed:
1073  */
1074 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1075 {
1076         if (p->prio < rq->curr->prio) {
1077                 resched_task(rq->curr);
1078                 return;
1079         }
1080
1081 #ifdef CONFIG_SMP
1082         /*
1083          * If:
1084          *
1085          * - the newly woken task is of equal priority to the current task
1086          * - the newly woken task is non-migratable while current is migratable
1087          * - current will be preempted on the next reschedule
1088          *
1089          * we should check to see if current can readily move to a different
1090          * cpu.  If so, we will reschedule to allow the push logic to try
1091          * to move current somewhere else, making room for our non-migratable
1092          * task.
1093          */
1094         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1095                 check_preempt_equal_prio(rq, p);
1096 #endif
1097 }
1098
1099 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1100                                                    struct rt_rq *rt_rq)
1101 {
1102         struct rt_prio_array *array = &rt_rq->active;
1103         struct sched_rt_entity *next = NULL;
1104         struct list_head *queue;
1105         int idx;
1106
1107         idx = sched_find_first_bit(array->bitmap);
1108         BUG_ON(idx >= MAX_RT_PRIO);
1109
1110         queue = array->queue + idx;
1111         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1112
1113         return next;
1114 }
1115
1116 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1117 {
1118         struct sched_rt_entity *rt_se;
1119         struct task_struct *p;
1120         struct rt_rq *rt_rq;
1121
1122         rt_rq = &rq->rt;
1123
1124         if (!rt_rq->rt_nr_running)
1125                 return NULL;
1126
1127         if (rt_rq_throttled(rt_rq))
1128                 return NULL;
1129
1130         do {
1131                 rt_se = pick_next_rt_entity(rq, rt_rq);
1132                 BUG_ON(!rt_se);
1133                 rt_rq = group_rt_rq(rt_se);
1134         } while (rt_rq);
1135
1136         p = rt_task_of(rt_se);
1137         p->se.exec_start = rq->clock_task;
1138
1139         return p;
1140 }
1141
1142 static struct task_struct *pick_next_task_rt(struct rq *rq)
1143 {
1144         struct task_struct *p = _pick_next_task_rt(rq);
1145
1146         /* The running task is never eligible for pushing */
1147         if (p)
1148                 dequeue_pushable_task(rq, p);
1149
1150 #ifdef CONFIG_SMP
1151         /*
1152          * We detect this state here so that we can avoid taking the RQ
1153          * lock again later if there is no need to push
1154          */
1155         rq->post_schedule = has_pushable_tasks(rq);
1156 #endif
1157
1158         return p;
1159 }
1160
1161 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1162 {
1163         update_curr_rt(rq);
1164
1165         /*
1166          * The previous task needs to be made eligible for pushing
1167          * if it is still active
1168          */
1169         if (on_rt_rq(&p->rt) && p->rt.nr_cpus_allowed > 1)
1170                 enqueue_pushable_task(rq, p);
1171 }
1172
1173 #ifdef CONFIG_SMP
1174
1175 /* Only try algorithms three times */
1176 #define RT_MAX_TRIES 3
1177
1178 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
1179
1180 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1181 {
1182         if (!task_running(rq, p) &&
1183             (cpu < 0 || cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) &&
1184             (p->rt.nr_cpus_allowed > 1))
1185                 return 1;
1186         return 0;
1187 }
1188
1189 /* Return the second highest RT task, NULL otherwise */
1190 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
1191 {
1192         struct task_struct *next = NULL;
1193         struct sched_rt_entity *rt_se;
1194         struct rt_prio_array *array;
1195         struct rt_rq *rt_rq;
1196         int idx;
1197
1198         for_each_leaf_rt_rq(rt_rq, rq) {
1199                 array = &rt_rq->active;
1200                 idx = sched_find_first_bit(array->bitmap);
1201 next_idx:
1202                 if (idx >= MAX_RT_PRIO)
1203                         continue;
1204                 if (next && next->prio < idx)
1205                         continue;
1206                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
1207                         struct task_struct *p;
1208
1209                         if (!rt_entity_is_task(rt_se))
1210                                 continue;
1211
1212                         p = rt_task_of(rt_se);
1213                         if (pick_rt_task(rq, p, cpu)) {
1214                                 next = p;
1215                                 break;
1216                         }
1217                 }
1218                 if (!next) {
1219                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
1220                         goto next_idx;
1221                 }
1222         }
1223
1224         return next;
1225 }
1226
1227 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1228
1229 static int find_lowest_rq(struct task_struct *task)
1230 {
1231         struct sched_domain *sd;
1232         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1233         int this_cpu = smp_processor_id();
1234         int cpu      = task_cpu(task);
1235
1236         /* Make sure the mask is initialized first */
1237         if (unlikely(!lowest_mask))
1238                 return -1;
1239
1240         if (task->rt.nr_cpus_allowed == 1)
1241                 return -1; /* No other targets possible */
1242
1243         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1244                 return -1; /* No targets found */
1245
1246         /*
1247          * At this point we have built a mask of cpus representing the
1248          * lowest priority tasks in the system.  Now we want to elect
1249          * the best one based on our affinity and topology.
1250          *
1251          * We prioritize the last cpu that the task executed on since
1252          * it is most likely cache-hot in that location.
1253          */
1254         if (cpumask_test_cpu(cpu, lowest_mask))
1255                 return cpu;
1256
1257         /*
1258          * Otherwise, we consult the sched_domains span maps to figure
1259          * out which cpu is logically closest to our hot cache data.
1260          */
1261         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1262                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1263
1264         rcu_read_lock();
1265         for_each_domain(cpu, sd) {
1266                 if (sd->flags & SD_WAKE_AFFINE) {
1267                         int best_cpu;
1268
1269                         /*
1270                          * "this_cpu" is cheaper to preempt than a
1271                          * remote processor.
1272                          */
1273                         if (this_cpu != -1 &&
1274                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1275                                 rcu_read_unlock();
1276                                 return this_cpu;
1277                         }
1278
1279                         best_cpu = cpumask_first_and(lowest_mask,
1280                                                      sched_domain_span(sd));
1281                         if (best_cpu < nr_cpu_ids) {
1282                                 rcu_read_unlock();
1283                                 return best_cpu;
1284                         }
1285                 }
1286         }
1287         rcu_read_unlock();
1288
1289         /*
1290          * And finally, if there were no matches within the domains
1291          * just give the caller *something* to work with from the compatible
1292          * locations.
1293          */
1294         if (this_cpu != -1)
1295                 return this_cpu;
1296
1297         cpu = cpumask_any(lowest_mask);
1298         if (cpu < nr_cpu_ids)
1299                 return cpu;
1300         return -1;
1301 }
1302
1303 /* Will lock the rq it finds */
1304 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1305 {
1306         struct rq *lowest_rq = NULL;
1307         int tries;
1308         int cpu;
1309
1310         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1311                 cpu = find_lowest_rq(task);
1312
1313                 if ((cpu == -1) || (cpu == rq->cpu))
1314                         break;
1315
1316                 lowest_rq = cpu_rq(cpu);
1317
1318                 /* if the prio of this runqueue changed, try again */
1319                 if (double_lock_balance(rq, lowest_rq)) {
1320                         /*
1321                          * We had to unlock the run queue. In
1322                          * the mean time, task could have
1323                          * migrated already or had its affinity changed.
1324                          * Also make sure that it wasn't scheduled on its rq.
1325                          */
1326                         if (unlikely(task_rq(task) != rq ||
1327                                      !cpumask_test_cpu(lowest_rq->cpu,
1328                                                        tsk_cpus_allowed(task)) ||
1329                                      task_running(rq, task) ||
1330                                      !task->on_rq)) {
1331
1332                                 raw_spin_unlock(&lowest_rq->lock);
1333                                 lowest_rq = NULL;
1334                                 break;
1335                         }
1336                 }
1337
1338                 /* If this rq is still suitable use it. */
1339                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1340                         break;
1341
1342                 /* try again */
1343                 double_unlock_balance(rq, lowest_rq);
1344                 lowest_rq = NULL;
1345         }
1346
1347         return lowest_rq;
1348 }
1349
1350 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1351 {
1352         struct task_struct *p;
1353
1354         if (!has_pushable_tasks(rq))
1355                 return NULL;
1356
1357         p = plist_first_entry(&rq->rt.pushable_tasks,
1358                               struct task_struct, pushable_tasks);
1359
1360         BUG_ON(rq->cpu != task_cpu(p));
1361         BUG_ON(task_current(rq, p));
1362         BUG_ON(p->rt.nr_cpus_allowed <= 1);
1363
1364         BUG_ON(!p->on_rq);
1365         BUG_ON(!rt_task(p));
1366
1367         return p;
1368 }
1369
1370 /*
1371  * If the current CPU has more than one RT task, see if the non
1372  * running task can migrate over to a CPU that is running a task
1373  * of lesser priority.
1374  */
1375 static int push_rt_task(struct rq *rq)
1376 {
1377         struct task_struct *next_task;
1378         struct rq *lowest_rq;
1379         int ret = 0;
1380
1381         if (!rq->rt.overloaded)
1382                 return 0;
1383
1384         next_task = pick_next_pushable_task(rq);
1385         if (!next_task)
1386                 return 0;
1387
1388 retry:
1389         if (unlikely(next_task == rq->curr)) {
1390                 WARN_ON(1);
1391                 return 0;
1392         }
1393
1394         /*
1395          * It's possible that the next_task slipped in of
1396          * higher priority than current. If that's the case
1397          * just reschedule current.
1398          */
1399         if (unlikely(next_task->prio < rq->curr->prio)) {
1400                 resched_task(rq->curr);
1401                 return 0;
1402         }
1403
1404         /* We might release rq lock */
1405         get_task_struct(next_task);
1406
1407         /* find_lock_lowest_rq locks the rq if found */
1408         lowest_rq = find_lock_lowest_rq(next_task, rq);
1409         if (!lowest_rq) {
1410                 struct task_struct *task;
1411                 /*
1412                  * find_lock_lowest_rq releases rq->lock
1413                  * so it is possible that next_task has migrated.
1414                  *
1415                  * We need to make sure that the task is still on the same
1416                  * run-queue and is also still the next task eligible for
1417                  * pushing.
1418                  */
1419                 task = pick_next_pushable_task(rq);
1420                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1421                         /*
1422                          * The task hasn't migrated, and is still the next
1423                          * eligible task, but we failed to find a run-queue
1424                          * to push it to.  Do not retry in this case, since
1425                          * other cpus will pull from us when ready.
1426                          */
1427                         goto out;
1428                 }
1429
1430                 if (!task)
1431                         /* No more tasks, just exit */
1432                         goto out;
1433
1434                 /*
1435                  * Something has shifted, try again.
1436                  */
1437                 put_task_struct(next_task);
1438                 next_task = task;
1439                 goto retry;
1440         }
1441
1442         deactivate_task(rq, next_task, 0);
1443         set_task_cpu(next_task, lowest_rq->cpu);
1444         activate_task(lowest_rq, next_task, 0);
1445         ret = 1;
1446
1447         resched_task(lowest_rq->curr);
1448
1449         double_unlock_balance(rq, lowest_rq);
1450
1451 out:
1452         put_task_struct(next_task);
1453
1454         return ret;
1455 }
1456
1457 static void push_rt_tasks(struct rq *rq)
1458 {
1459         /* push_rt_task will return true if it moved an RT */
1460         while (push_rt_task(rq))
1461                 ;
1462 }
1463
1464 static int pull_rt_task(struct rq *this_rq)
1465 {
1466         int this_cpu = this_rq->cpu, ret = 0, cpu;
1467         struct task_struct *p;
1468         struct rq *src_rq;
1469
1470         if (likely(!rt_overloaded(this_rq)))
1471                 return 0;
1472
1473         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1474                 if (this_cpu == cpu)
1475                         continue;
1476
1477                 src_rq = cpu_rq(cpu);
1478
1479                 /*
1480                  * Don't bother taking the src_rq->lock if the next highest
1481                  * task is known to be lower-priority than our current task.
1482                  * This may look racy, but if this value is about to go
1483                  * logically higher, the src_rq will push this task away.
1484                  * And if its going logically lower, we do not care
1485                  */
1486                 if (src_rq->rt.highest_prio.next >=
1487                     this_rq->rt.highest_prio.curr)
1488                         continue;
1489
1490                 /*
1491                  * We can potentially drop this_rq's lock in
1492                  * double_lock_balance, and another CPU could
1493                  * alter this_rq
1494                  */
1495                 double_lock_balance(this_rq, src_rq);
1496
1497                 /*
1498                  * Are there still pullable RT tasks?
1499                  */
1500                 if (src_rq->rt.rt_nr_running <= 1)
1501                         goto skip;
1502
1503                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1504
1505                 /*
1506                  * Do we have an RT task that preempts
1507                  * the to-be-scheduled task?
1508                  */
1509                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1510                         WARN_ON(p == src_rq->curr);
1511                         WARN_ON(!p->on_rq);
1512
1513                         /*
1514                          * There's a chance that p is higher in priority
1515                          * than what's currently running on its cpu.
1516                          * This is just that p is wakeing up and hasn't
1517                          * had a chance to schedule. We only pull
1518                          * p if it is lower in priority than the
1519                          * current task on the run queue
1520                          */
1521                         if (p->prio < src_rq->curr->prio)
1522                                 goto skip;
1523
1524                         ret = 1;
1525
1526                         deactivate_task(src_rq, p, 0);
1527                         set_task_cpu(p, this_cpu);
1528                         activate_task(this_rq, p, 0);
1529                         /*
1530                          * We continue with the search, just in
1531                          * case there's an even higher prio task
1532                          * in another runqueue. (low likelihood
1533                          * but possible)
1534                          */
1535                 }
1536 skip:
1537                 double_unlock_balance(this_rq, src_rq);
1538         }
1539
1540         return ret;
1541 }
1542
1543 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1544 {
1545         /* Try to pull RT tasks here if we lower this rq's prio */
1546         if (rq->rt.highest_prio.curr > prev->prio)
1547                 pull_rt_task(rq);
1548 }
1549
1550 static void post_schedule_rt(struct rq *rq)
1551 {
1552         push_rt_tasks(rq);
1553 }
1554
1555 /*
1556  * If we are not running and we are not going to reschedule soon, we should
1557  * try to push tasks away now
1558  */
1559 static void task_woken_rt(struct rq *rq, struct task_struct *p)
1560 {
1561         if (!task_running(rq, p) &&
1562             !test_tsk_need_resched(rq->curr) &&
1563             has_pushable_tasks(rq) &&
1564             p->rt.nr_cpus_allowed > 1 &&
1565             rt_task(rq->curr) &&
1566             (rq->curr->rt.nr_cpus_allowed < 2 ||
1567              rq->curr->prio <= p->prio))
1568                 push_rt_tasks(rq);
1569 }
1570
1571 static void set_cpus_allowed_rt(struct task_struct *p,
1572                                 const struct cpumask *new_mask)
1573 {
1574         int weight = cpumask_weight(new_mask);
1575
1576         BUG_ON(!rt_task(p));
1577
1578         /*
1579          * Update the migration status of the RQ if we have an RT task
1580          * which is running AND changing its weight value.
1581          */
1582         if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
1583                 struct rq *rq = task_rq(p);
1584
1585                 if (!task_current(rq, p)) {
1586                         /*
1587                          * Make sure we dequeue this task from the pushable list
1588                          * before going further.  It will either remain off of
1589                          * the list because we are no longer pushable, or it
1590                          * will be requeued.
1591                          */
1592                         if (p->rt.nr_cpus_allowed > 1)
1593                                 dequeue_pushable_task(rq, p);
1594
1595                         /*
1596                          * Requeue if our weight is changing and still > 1
1597                          */
1598                         if (weight > 1)
1599                                 enqueue_pushable_task(rq, p);
1600
1601                 }
1602
1603                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1604                         rq->rt.rt_nr_migratory++;
1605                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1606                         BUG_ON(!rq->rt.rt_nr_migratory);
1607                         rq->rt.rt_nr_migratory--;
1608                 }
1609
1610                 update_rt_migration(&rq->rt);
1611         }
1612 }
1613
1614 /* Assumes rq->lock is held */
1615 static void rq_online_rt(struct rq *rq)
1616 {
1617         if (rq->rt.overloaded)
1618                 rt_set_overload(rq);
1619
1620         __enable_runtime(rq);
1621
1622         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1623 }
1624
1625 /* Assumes rq->lock is held */
1626 static void rq_offline_rt(struct rq *rq)
1627 {
1628         if (rq->rt.overloaded)
1629                 rt_clear_overload(rq);
1630
1631         __disable_runtime(rq);
1632
1633         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1634 }
1635
1636 /*
1637  * When switch from the rt queue, we bring ourselves to a position
1638  * that we might want to pull RT tasks from other runqueues.
1639  */
1640 static void switched_from_rt(struct rq *rq, struct task_struct *p)
1641 {
1642         /*
1643          * If there are other RT tasks then we will reschedule
1644          * and the scheduling of the other RT tasks will handle
1645          * the balancing. But if we are the last RT task
1646          * we may need to handle the pulling of RT tasks
1647          * now.
1648          */
1649         if (p->on_rq && !rq->rt.rt_nr_running)
1650                 pull_rt_task(rq);
1651 }
1652
1653 static inline void init_sched_rt_class(void)
1654 {
1655         unsigned int i;
1656
1657         for_each_possible_cpu(i)
1658                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1659                                         GFP_KERNEL, cpu_to_node(i));
1660 }
1661 #endif /* CONFIG_SMP */
1662
1663 /*
1664  * When switching a task to RT, we may overload the runqueue
1665  * with RT tasks. In this case we try to push them off to
1666  * other runqueues.
1667  */
1668 static void switched_to_rt(struct rq *rq, struct task_struct *p)
1669 {
1670         int check_resched = 1;
1671
1672         /*
1673          * If we are already running, then there's nothing
1674          * that needs to be done. But if we are not running
1675          * we may need to preempt the current running task.
1676          * If that current running task is also an RT task
1677          * then see if we can move to another run queue.
1678          */
1679         if (p->on_rq && rq->curr != p) {
1680 #ifdef CONFIG_SMP
1681                 if (rq->rt.overloaded && push_rt_task(rq) &&
1682                     /* Don't resched if we changed runqueues */
1683                     rq != task_rq(p))
1684                         check_resched = 0;
1685 #endif /* CONFIG_SMP */
1686                 if (check_resched && p->prio < rq->curr->prio)
1687                         resched_task(rq->curr);
1688         }
1689 }
1690
1691 /*
1692  * Priority of the task has changed. This may cause
1693  * us to initiate a push or pull.
1694  */
1695 static void
1696 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1697 {
1698         if (!p->on_rq)
1699                 return;
1700
1701         if (rq->curr == p) {
1702 #ifdef CONFIG_SMP
1703                 /*
1704                  * If our priority decreases while running, we
1705                  * may need to pull tasks to this runqueue.
1706                  */
1707                 if (oldprio < p->prio)
1708                         pull_rt_task(rq);
1709                 /*
1710                  * If there's a higher priority task waiting to run
1711                  * then reschedule. Note, the above pull_rt_task
1712                  * can release the rq lock and p could migrate.
1713                  * Only reschedule if p is still on the same runqueue.
1714                  */
1715                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1716                         resched_task(p);
1717 #else
1718                 /* For UP simply resched on drop of prio */
1719                 if (oldprio < p->prio)
1720                         resched_task(p);
1721 #endif /* CONFIG_SMP */
1722         } else {
1723                 /*
1724                  * This task is not running, but if it is
1725                  * greater than the current running task
1726                  * then reschedule.
1727                  */
1728                 if (p->prio < rq->curr->prio)
1729                         resched_task(rq->curr);
1730         }
1731 }
1732
1733 static void watchdog(struct rq *rq, struct task_struct *p)
1734 {
1735         unsigned long soft, hard;
1736
1737         /* max may change after cur was read, this will be fixed next tick */
1738         soft = task_rlimit(p, RLIMIT_RTTIME);
1739         hard = task_rlimit_max(p, RLIMIT_RTTIME);
1740
1741         if (soft != RLIM_INFINITY) {
1742                 unsigned long next;
1743
1744                 p->rt.timeout++;
1745                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1746                 if (p->rt.timeout > next)
1747                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1748         }
1749 }
1750
1751 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1752 {
1753         update_curr_rt(rq);
1754
1755         watchdog(rq, p);
1756
1757         /*
1758          * RR tasks need a special form of timeslice management.
1759          * FIFO tasks have no timeslices.
1760          */
1761         if (p->policy != SCHED_RR)
1762                 return;
1763
1764         if (--p->rt.time_slice)
1765                 return;
1766
1767         p->rt.time_slice = DEF_TIMESLICE;
1768
1769         /*
1770          * Requeue to the end of queue if we are not the only element
1771          * on the queue:
1772          */
1773         if (p->rt.run_list.prev != p->rt.run_list.next) {
1774                 requeue_task_rt(rq, p, 0);
1775                 set_tsk_need_resched(p);
1776         }
1777 }
1778
1779 static void set_curr_task_rt(struct rq *rq)
1780 {
1781         struct task_struct *p = rq->curr;
1782
1783         p->se.exec_start = rq->clock_task;
1784
1785         /* The running task is never eligible for pushing */
1786         dequeue_pushable_task(rq, p);
1787 }
1788
1789 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
1790 {
1791         /*
1792          * Time slice is 0 for SCHED_FIFO tasks
1793          */
1794         if (task->policy == SCHED_RR)
1795                 return DEF_TIMESLICE;
1796         else
1797                 return 0;
1798 }
1799
1800 static const struct sched_class rt_sched_class = {
1801         .next                   = &fair_sched_class,
1802         .enqueue_task           = enqueue_task_rt,
1803         .dequeue_task           = dequeue_task_rt,
1804         .yield_task             = yield_task_rt,
1805
1806         .check_preempt_curr     = check_preempt_curr_rt,
1807
1808         .pick_next_task         = pick_next_task_rt,
1809         .put_prev_task          = put_prev_task_rt,
1810
1811 #ifdef CONFIG_SMP
1812         .select_task_rq         = select_task_rq_rt,
1813
1814         .set_cpus_allowed       = set_cpus_allowed_rt,
1815         .rq_online              = rq_online_rt,
1816         .rq_offline             = rq_offline_rt,
1817         .pre_schedule           = pre_schedule_rt,
1818         .post_schedule          = post_schedule_rt,
1819         .task_woken             = task_woken_rt,
1820         .switched_from          = switched_from_rt,
1821 #endif
1822
1823         .set_curr_task          = set_curr_task_rt,
1824         .task_tick              = task_tick_rt,
1825
1826         .get_rr_interval        = get_rr_interval_rt,
1827
1828         .prio_changed           = prio_changed_rt,
1829         .switched_to            = switched_to_rt,
1830 };
1831
1832 #ifdef CONFIG_SCHED_DEBUG
1833 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1834
1835 static void print_rt_stats(struct seq_file *m, int cpu)
1836 {
1837         rt_rq_iter_t iter;
1838         struct rt_rq *rt_rq;
1839
1840         rcu_read_lock();
1841         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1842                 print_rt_rq(m, cpu, rt_rq);
1843         rcu_read_unlock();
1844 }
1845 #endif /* CONFIG_SCHED_DEBUG */