kernel/sched_rt.c

   1 /*
   2  * Real-Time Scheduling Class (mapped to the SCHED_FIFO and SCHED_RR
   3  * policies)
   4  */
   5
   6 #ifdef CONFIG_RT_GROUP_SCHED
   7
   8 #define rt_entity_is_task(rt_se) (!(rt_se)->my_q)
   9
  10 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
  11 {
  12 #ifdef CONFIG_SCHED_DEBUG
  13         WARN_ON_ONCE(!rt_entity_is_task(rt_se));
  14 #endif
  15         return container_of(rt_se, struct task_struct, rt);
  16 }
  17
  18 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
  19 {
  20         return rt_rq->rq;
  21 }
  22
  23 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
  24 {
  25         return rt_se->rt_rq;
  26 }
  27
  28 #else /* CONFIG_RT_GROUP_SCHED */
  29
  30 #define rt_entity_is_task(rt_se) (1)
  31
  32 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
  33 {
  34         return container_of(rt_se, struct task_struct, rt);
  35 }
  36
  37 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
  38 {
  39         return container_of(rt_rq, struct rq, rt);
  40 }
  41
  42 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
  43 {
  44         struct task_struct *p = rt_task_of(rt_se);
  45         struct rq *rq = task_rq(p);
  46
  47         return &rq->rt;
  48 }
  49
  50 #endif /* CONFIG_RT_GROUP_SCHED */
  51
  52 #ifdef CONFIG_SMP
  53
  54 static inline int rt_overloaded(struct rq *rq)
  55 {
  56         return atomic_read(&rq->rd->rto_count);
  57 }
  58
  59 static inline void rt_set_overload(struct rq *rq)
  60 {
  61         if (!rq->online)
  62                 return;
  63
  64         cpumask_set_cpu(rq->cpu, rq->rd->rto_mask);
  65         /*
  66          * Make sure the mask is visible before we set
  67          * the overload count. That is checked to determine
  68          * if we should look at the mask. It would be a shame
  69          * if we looked at the mask, but the mask was not
  70          * updated yet.
  71          */
  72         wmb();
  73         atomic_inc(&rq->rd->rto_count);
  74 }
  75
  76 static inline void rt_clear_overload(struct rq *rq)
  77 {
  78         if (!rq->online)
  79                 return;
  80
  81         /* the order here really doesn't matter */
  82         atomic_dec(&rq->rd->rto_count);
  83         cpumask_clear_cpu(rq->cpu, rq->rd->rto_mask);
  84 }
  85
  86 static void update_rt_migration(struct rt_rq *rt_rq)
  87 {
  88         if (rt_rq->rt_nr_migratory && rt_rq->rt_nr_total > 1) {
  89                 if (!rt_rq->overloaded) {
  90                         rt_set_overload(rq_of_rt_rq(rt_rq));
  91                         rt_rq->overloaded = 1;
  92                 }
  93         } else if (rt_rq->overloaded) {
  94                 rt_clear_overload(rq_of_rt_rq(rt_rq));
  95                 rt_rq->overloaded = 0;
  96         }
  97 }
  98
  99 static void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 100 {
 101         if (!rt_entity_is_task(rt_se))
 102                 return;
 103
 104         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 105
 106         rt_rq->rt_nr_total++;
 107         if (rt_se->nr_cpus_allowed > 1)
 108                 rt_rq->rt_nr_migratory++;
 109
 110         update_rt_migration(rt_rq);
 111 }
 112
 113 static void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 114 {
 115         if (!rt_entity_is_task(rt_se))
 116                 return;
 117
 118         rt_rq = &rq_of_rt_rq(rt_rq)->rt;
 119
 120         rt_rq->rt_nr_total--;
 121         if (rt_se->nr_cpus_allowed > 1)
 122                 rt_rq->rt_nr_migratory--;
 123
 124         update_rt_migration(rt_rq);
 125 }
 126
 127 static void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 128 {
 129         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 130         plist_node_init(&p->pushable_tasks, p->prio);
 131         plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks);
 132 }
 133
 134 static void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 135 {
 136         plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks);
 137 }
 138
 139 static inline int has_pushable_tasks(struct rq *rq)
 140 {
 141         return !plist_head_empty(&rq->rt.pushable_tasks);
 142 }
 143
 144 #else
 145
 146 static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p)
 147 {
 148 }
 149
 150 static inline void dequeue_pushable_task(struct rq *rq, struct task_struct *p)
 151 {
 152 }
 153
 154 static inline
 155 void inc_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 156 {
 157 }
 158
 159 static inline
 160 void dec_rt_migration(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 161 {
 162 }
 163
 164 #endif /* CONFIG_SMP */
 165
 166 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
 167 {
 168         return !list_empty(&rt_se->run_list);
 169 }
 170
 171 #ifdef CONFIG_RT_GROUP_SCHED
 172
 173 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 174 {
 175         if (!rt_rq->tg)
 176                 return RUNTIME_INF;
 177
 178         return rt_rq->rt_runtime;
 179 }
 180
 181 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 182 {
 183         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
 184 }
 185
 186 typedef struct task_group *rt_rq_iter_t;
 187
 188 static inline struct task_group *next_task_group(struct task_group *tg)
 189 {
 190         do {
 191                 tg = list_entry_rcu(tg->list.next,
 192                         typeof(struct task_group), list);
 193         } while (&tg->list != &task_groups && task_group_is_autogroup(tg));
 194
 195         if (&tg->list == &task_groups)
 196                 tg = NULL;
 197
 198         return tg;
 199 }
 200
 201 #define for_each_rt_rq(rt_rq, iter, rq)                                 \
 202         for (iter = container_of(&task_groups, typeof(*iter), list);    \
 203                 (iter = next_task_group(iter)) &&                       \
 204                 (rt_rq = iter->rt_rq[cpu_of(rq)]);)
 205
 206 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
 207 {
 208         list_add_rcu(&rt_rq->leaf_rt_rq_list,
 209                         &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
 210 }
 211
 212 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
 213 {
 214         list_del_rcu(&rt_rq->leaf_rt_rq_list);
 215 }
 216
 217 #define for_each_leaf_rt_rq(rt_rq, rq) \
 218         list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
 219
 220 #define for_each_sched_rt_entity(rt_se) \
 221         for (; rt_se; rt_se = rt_se->parent)
 222
 223 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 224 {
 225         return rt_se->my_q;
 226 }
 227
 228 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head);
 229 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
 230
 231 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 232 {
 233         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
 234         struct sched_rt_entity *rt_se;
 235
 236         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 237
 238         rt_se = rt_rq->tg->rt_se[cpu];
 239
 240         if (rt_rq->rt_nr_running) {
 241                 if (rt_se && !on_rt_rq(rt_se))
 242                         enqueue_rt_entity(rt_se, false);
 243                 if (rt_rq->highest_prio.curr < curr->prio)
 244                         resched_task(curr);
 245         }
 246 }
 247
 248 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 249 {
 250         struct sched_rt_entity *rt_se;
 251         int cpu = cpu_of(rq_of_rt_rq(rt_rq));
 252
 253         rt_se = rt_rq->tg->rt_se[cpu];
 254
 255         if (rt_se && on_rt_rq(rt_se))
 256                 dequeue_rt_entity(rt_se);
 257 }
 258
 259 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 260 {
 261         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
 262 }
 263
 264 static int rt_se_boosted(struct sched_rt_entity *rt_se)
 265 {
 266         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 267         struct task_struct *p;
 268
 269         if (rt_rq)
 270                 return !!rt_rq->rt_nr_boosted;
 271
 272         p = rt_task_of(rt_se);
 273         return p->prio != p->normal_prio;
 274 }
 275
 276 #ifdef CONFIG_SMP
 277 static inline const struct cpumask *sched_rt_period_mask(void)
 278 {
 279         return cpu_rq(smp_processor_id())->rd->span;
 280 }
 281 #else
 282 static inline const struct cpumask *sched_rt_period_mask(void)
 283 {
 284         return cpu_online_mask;
 285 }
 286 #endif
 287
 288 static inline
 289 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 290 {
 291         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
 292 }
 293
 294 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 295 {
 296         return &rt_rq->tg->rt_bandwidth;
 297 }
 298
 299 #else /* !CONFIG_RT_GROUP_SCHED */
 300
 301 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 302 {
 303         return rt_rq->rt_runtime;
 304 }
 305
 306 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 307 {
 308         return ktime_to_ns(def_rt_bandwidth.rt_period);
 309 }
 310
 311 typedef struct rt_rq *rt_rq_iter_t;
 312
 313 #define for_each_rt_rq(rt_rq, iter, rq) \
 314         for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 315
 316 static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
 317 {
 318 }
 319
 320 static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
 321 {
 322 }
 323
 324 #define for_each_leaf_rt_rq(rt_rq, rq) \
 325         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 326
 327 #define for_each_sched_rt_entity(rt_se) \
 328         for (; rt_se; rt_se = NULL)
 329
 330 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 331 {
 332         return NULL;
 333 }
 334
 335 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 336 {
 337         if (rt_rq->rt_nr_running)
 338                 resched_task(rq_of_rt_rq(rt_rq)->curr);
 339 }
 340
 341 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 342 {
 343 }
 344
 345 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 346 {
 347         return rt_rq->rt_throttled;
 348 }
 349
 350 static inline const struct cpumask *sched_rt_period_mask(void)
 351 {
 352         return cpu_online_mask;
 353 }
 354
 355 static inline
 356 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 357 {
 358         return &cpu_rq(cpu)->rt;
 359 }
 360
 361 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 362 {
 363         return &def_rt_bandwidth;
 364 }
 365
 366 #endif /* CONFIG_RT_GROUP_SCHED */
 367
 368 #ifdef CONFIG_SMP
 369 /*
 370  * We ran out of runtime, see if we can borrow some from our neighbours.
 371  */
 372 static int do_balance_runtime(struct rt_rq *rt_rq)
 373 {
 374         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 375         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
 376         int i, weight, more = 0;
 377         u64 rt_period;
 378
 379         weight = cpumask_weight(rd->span);
 380
 381         raw_spin_lock(&rt_b->rt_runtime_lock);
 382         rt_period = ktime_to_ns(rt_b->rt_period);
 383         for_each_cpu(i, rd->span) {
 384                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 385                 s64 diff;
 386
 387                 if (iter == rt_rq)
 388                         continue;
 389
 390                 raw_spin_lock(&iter->rt_runtime_lock);
 391                 /*
 392                  * Either all rqs have inf runtime and there's nothing to steal
 393                  * or __disable_runtime() below sets a specific rq to inf to
 394                  * indicate its been disabled and disalow stealing.
 395                  */
 396                 if (iter->rt_runtime == RUNTIME_INF)
 397                         goto next;
 398
 399                 /*
 400                  * From runqueues with spare time, take 1/n part of their
 401                  * spare time, but no more than our period.
 402                  */
 403                 diff = iter->rt_runtime - iter->rt_time;
 404                 if (diff > 0) {
 405                         diff = div_u64((u64)diff, weight);
 406                         if (rt_rq->rt_runtime + diff > rt_period)
 407                                 diff = rt_period - rt_rq->rt_runtime;
 408                         iter->rt_runtime -= diff;
 409                         rt_rq->rt_runtime += diff;
 410                         more = 1;
 411                         if (rt_rq->rt_runtime == rt_period) {
 412                                 raw_spin_unlock(&iter->rt_runtime_lock);
 413                                 break;
 414                         }
 415                 }
 416 next:
 417                 raw_spin_unlock(&iter->rt_runtime_lock);
 418         }
 419         raw_spin_unlock(&rt_b->rt_runtime_lock);
 420
 421         return more;
 422 }
 423
 424 /*
 425  * Ensure this RQ takes back all the runtime it lend to its neighbours.
 426  */
 427 static void __disable_runtime(struct rq *rq)
 428 {
 429         struct root_domain *rd = rq->rd;
 430         rt_rq_iter_t iter;
 431         struct rt_rq *rt_rq;
 432
 433         if (unlikely(!scheduler_running))
 434                 return;
 435
 436         for_each_rt_rq(rt_rq, iter, rq) {
 437                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 438                 s64 want;
 439                 int i;
 440
 441                 raw_spin_lock(&rt_b->rt_runtime_lock);
 442                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 443                 /*
 444                  * Either we're all inf and nobody needs to borrow, or we're
 445                  * already disabled and thus have nothing to do, or we have
 446                  * exactly the right amount of runtime to take out.
 447                  */
 448                 if (rt_rq->rt_runtime == RUNTIME_INF ||
 449                                 rt_rq->rt_runtime == rt_b->rt_runtime)
 450                         goto balanced;
 451                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 452
 453                 /*
 454                  * Calculate the difference between what we started out with
 455                  * and what we current have, that's the amount of runtime
 456                  * we lend and now have to reclaim.
 457                  */
 458                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
 459
 460                 /*
 461                  * Greedy reclaim, take back as much as we can.
 462                  */
 463                 for_each_cpu(i, rd->span) {
 464                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 465                         s64 diff;
 466
 467                         /*
 468                          * Can't reclaim from ourselves or disabled runqueues.
 469                          */
 470                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
 471                                 continue;
 472
 473                         raw_spin_lock(&iter->rt_runtime_lock);
 474                         if (want > 0) {
 475                                 diff = min_t(s64, iter->rt_runtime, want);
 476                                 iter->rt_runtime -= diff;
 477                                 want -= diff;
 478                         } else {
 479                                 iter->rt_runtime -= want;
 480                                 want -= want;
 481                         }
 482                         raw_spin_unlock(&iter->rt_runtime_lock);
 483
 484                         if (!want)
 485                                 break;
 486                 }
 487
 488                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 489                 /*
 490                  * We cannot be left wanting - that would mean some runtime
 491                  * leaked out of the system.
 492                  */
 493                 BUG_ON(want);
 494 balanced:
 495                 /*
 496                  * Disable all the borrow logic by pretending we have inf
 497                  * runtime - in which case borrowing doesn't make sense.
 498                  */
 499                 rt_rq->rt_runtime = RUNTIME_INF;
 500                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 501                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 502         }
 503 }
 504
 505 static void disable_runtime(struct rq *rq)
 506 {
 507         unsigned long flags;
 508
 509         raw_spin_lock_irqsave(&rq->lock, flags);
 510         __disable_runtime(rq);
 511         raw_spin_unlock_irqrestore(&rq->lock, flags);
 512 }
 513
 514 static void __enable_runtime(struct rq *rq)
 515 {
 516         rt_rq_iter_t iter;
 517         struct rt_rq *rt_rq;
 518
 519         if (unlikely(!scheduler_running))
 520                 return;
 521
 522         /*
 523          * Reset each runqueue's bandwidth settings
 524          */
 525         for_each_rt_rq(rt_rq, iter, rq) {
 526                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 527
 528                 raw_spin_lock(&rt_b->rt_runtime_lock);
 529                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 530                 rt_rq->rt_runtime = rt_b->rt_runtime;
 531                 rt_rq->rt_time = 0;
 532                 rt_rq->rt_throttled = 0;
 533                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 534                 raw_spin_unlock(&rt_b->rt_runtime_lock);
 535         }
 536 }
 537
 538 static void enable_runtime(struct rq *rq)
 539 {
 540         unsigned long flags;
 541
 542         raw_spin_lock_irqsave(&rq->lock, flags);
 543         __enable_runtime(rq);
 544         raw_spin_unlock_irqrestore(&rq->lock, flags);
 545 }
 546
 547 static int balance_runtime(struct rt_rq *rt_rq)
 548 {
 549         int more = 0;
 550
 551         if (rt_rq->rt_time > rt_rq->rt_runtime) {
 552                 raw_spin_unlock(&rt_rq->rt_runtime_lock);
 553                 more = do_balance_runtime(rt_rq);
 554                 raw_spin_lock(&rt_rq->rt_runtime_lock);
 555         }
 556
 557         return more;
 558 }
 559 #else /* !CONFIG_SMP */
 560 static inline int balance_runtime(struct rt_rq *rt_rq)
 561 {
 562         return 0;
 563 }
 564 #endif /* CONFIG_SMP */
 565
 566 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 567 {
 568         int i, idle = 1;
 569         const struct cpumask *span;
 570
 571         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
 572                 return 1;
 573
 574         span = sched_rt_period_mask();
 575         for_each_cpu(i, span) {
 576                 int enqueue = 0;
 577                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 578                 struct rq *rq = rq_of_rt_rq(rt_rq);
 579
 580                 raw_spin_lock(&rq->lock);
 581                 if (rt_rq->rt_time) {
 582                         u64 runtime;
 583
 584                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 585                         if (rt_rq->rt_throttled)
 586                                 balance_runtime(rt_rq);
 587                         runtime = rt_rq->rt_runtime;
 588                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 589                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 590                                 rt_rq->rt_throttled = 0;
 591                                 enqueue = 1;
 592
 593                                 /*
 594                                  * Force a clock update if the CPU was idle,
 595                                  * lest wakeup -> unthrottle time accumulate.
 596                                  */
 597                                 if (rt_rq->rt_nr_running && rq->curr == rq->idle)
 598                                         rq->skip_clock_update = -1;
 599                         }
 600                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
 601                                 idle = 0;
 602                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 603                 } else if (rt_rq->rt_nr_running) {
 604                         idle = 0;
 605                         if (!rt_rq_throttled(rt_rq))
 606                                 enqueue = 1;
 607                 }
 608
 609                 if (enqueue)
 610                         sched_rt_rq_enqueue(rt_rq);
 611                 raw_spin_unlock(&rq->lock);
 612         }
 613
 614         return idle;
 615 }
 616
 617 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 618 {
 619 #ifdef CONFIG_RT_GROUP_SCHED
 620         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 621
 622         if (rt_rq)
 623                 return rt_rq->highest_prio.curr;
 624 #endif
 625
 626         return rt_task_of(rt_se)->prio;
 627 }
 628
 629 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 630 {
 631         u64 runtime = sched_rt_runtime(rt_rq);
 632
 633         if (rt_rq->rt_throttled)
 634                 return rt_rq_throttled(rt_rq);
 635
 636         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
 637                 return 0;
 638
 639         balance_runtime(rt_rq);
 640         runtime = sched_rt_runtime(rt_rq);
 641         if (runtime == RUNTIME_INF)
 642                 return 0;
 643
 644         if (rt_rq->rt_time > runtime) {
 645                 rt_rq->rt_throttled = 1;
 646                 if (rt_rq_throttled(rt_rq)) {
 647                         sched_rt_rq_dequeue(rt_rq);
 648                         return 1;
 649                 }
 650         }
 651
 652         return 0;
 653 }
 654
 655 /*
 656  * Update the current task's runtime statistics. Skip current tasks that
 657  * are not in our scheduling class.
 658  */
 659 static void update_curr_rt(struct rq *rq)
 660 {
 661         struct task_struct *curr = rq->curr;
 662         struct sched_rt_entity *rt_se = &curr->rt;
 663         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 664         u64 delta_exec;
 665
 666         if (curr->sched_class != &rt_sched_class)
 667                 return;
 668
 669         delta_exec = rq->clock_task - curr->se.exec_start;
 670         if (unlikely((s64)delta_exec < 0))
 671                 delta_exec = 0;
 672
 673         schedstat_set(curr->se.statistics.exec_max, max(curr->se.statistics.exec_max, delta_exec));
 674
 675         curr->se.sum_exec_runtime += delta_exec;
 676         account_group_exec_runtime(curr, delta_exec);
 677
 678         curr->se.exec_start = rq->clock_task;
 679         cpuacct_charge(curr, delta_exec);
 680
 681         sched_rt_avg_update(rq, delta_exec);
 682
 683         if (!rt_bandwidth_enabled())
 684                 return;
 685
 686         for_each_sched_rt_entity(rt_se) {
 687                 rt_rq = rt_rq_of_se(rt_se);
 688
 689                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 690                         raw_spin_lock(&rt_rq->rt_runtime_lock);
 691                         rt_rq->rt_time += delta_exec;
 692                         if (sched_rt_runtime_exceeded(rt_rq))
 693                                 resched_task(curr);
 694                         raw_spin_unlock(&rt_rq->rt_runtime_lock);
 695                 }
 696         }
 697 }
 698
 699 #if defined CONFIG_SMP
 700
 701 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu);
 702
 703 static inline int next_prio(struct rq *rq)
 704 {
 705         struct task_struct *next = pick_next_highest_task_rt(rq, rq->cpu);
 706
 707         if (next && rt_prio(next->prio))
 708                 return next->prio;
 709         else
 710                 return MAX_RT_PRIO;
 711 }
 712
 713 static void
 714 inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 715 {
 716         struct rq *rq = rq_of_rt_rq(rt_rq);
 717
 718         if (prio < prev_prio) {
 719
 720                 /*
 721                  * If the new task is higher in priority than anything on the
 722                  * run-queue, we know that the previous high becomes our
 723                  * next-highest.
 724                  */
 725                 rt_rq->highest_prio.next = prev_prio;
 726
 727                 if (rq->online)
 728                         cpupri_set(&rq->rd->cpupri, rq->cpu, prio);
 729
 730         } else if (prio == rt_rq->highest_prio.curr)
 731                 /*
 732                  * If the next task is equal in priority to the highest on
 733                  * the run-queue, then we implicitly know that the next highest
 734                  * task cannot be any lower than current
 735                  */
 736                 rt_rq->highest_prio.next = prio;
 737         else if (prio < rt_rq->highest_prio.next)
 738                 /*
 739                  * Otherwise, we need to recompute next-highest
 740                  */
 741                 rt_rq->highest_prio.next = next_prio(rq);
 742 }
 743
 744 static void
 745 dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio)
 746 {
 747         struct rq *rq = rq_of_rt_rq(rt_rq);
 748
 749         if (rt_rq->rt_nr_running && (prio <= rt_rq->highest_prio.next))
 750                 rt_rq->highest_prio.next = next_prio(rq);
 751
 752         if (rq->online && rt_rq->highest_prio.curr != prev_prio)
 753                 cpupri_set(&rq->rd->cpupri, rq->cpu, rt_rq->highest_prio.curr);
 754 }
 755
 756 #else /* CONFIG_SMP */
 757
 758 static inline
 759 void inc_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 760 static inline
 761 void dec_rt_prio_smp(struct rt_rq *rt_rq, int prio, int prev_prio) {}
 762
 763 #endif /* CONFIG_SMP */
 764
 765 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 766 static void
 767 inc_rt_prio(struct rt_rq *rt_rq, int prio)
 768 {
 769         int prev_prio = rt_rq->highest_prio.curr;
 770
 771         if (prio < prev_prio)
 772                 rt_rq->highest_prio.curr = prio;
 773
 774         inc_rt_prio_smp(rt_rq, prio, prev_prio);
 775 }
 776
 777 static void
 778 dec_rt_prio(struct rt_rq *rt_rq, int prio)
 779 {
 780         int prev_prio = rt_rq->highest_prio.curr;
 781
 782         if (rt_rq->rt_nr_running) {
 783
 784                 WARN_ON(prio < prev_prio);
 785
 786                 /*
 787                  * This may have been our highest task, and therefore
 788                  * we may have some recomputation to do
 789                  */
 790                 if (prio == prev_prio) {
 791                         struct rt_prio_array *array = &rt_rq->active;
 792
 793                         rt_rq->highest_prio.curr =
 794                                 sched_find_first_bit(array->bitmap);
 795                 }
 796
 797         } else
 798                 rt_rq->highest_prio.curr = MAX_RT_PRIO;
 799
 800         dec_rt_prio_smp(rt_rq, prio, prev_prio);
 801 }
 802
 803 #else
 804
 805 static inline void inc_rt_prio(struct rt_rq *rt_rq, int prio) {}
 806 static inline void dec_rt_prio(struct rt_rq *rt_rq, int prio) {}
 807
 808 #endif /* CONFIG_SMP || CONFIG_RT_GROUP_SCHED */
 809
 810 #ifdef CONFIG_RT_GROUP_SCHED
 811
 812 static void
 813 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 814 {
 815         if (rt_se_boosted(rt_se))
 816                 rt_rq->rt_nr_boosted++;
 817
 818         if (rt_rq->tg)
 819                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
 820 }
 821
 822 static void
 823 dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 824 {
 825         if (rt_se_boosted(rt_se))
 826                 rt_rq->rt_nr_boosted--;
 827
 828         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
 829 }
 830
 831 #else /* CONFIG_RT_GROUP_SCHED */
 832
 833 static void
 834 inc_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 835 {
 836         start_rt_bandwidth(&def_rt_bandwidth);
 837 }
 838
 839 static inline
 840 void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {}
 841
 842 #endif /* CONFIG_RT_GROUP_SCHED */
 843
 844 static inline
 845 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 846 {
 847         int prio = rt_se_prio(rt_se);
 848
 849         WARN_ON(!rt_prio(prio));
 850         rt_rq->rt_nr_running++;
 851
 852         inc_rt_prio(rt_rq, prio);
 853         inc_rt_migration(rt_se, rt_rq);
 854         inc_rt_group(rt_se, rt_rq);
 855 }
 856
 857 static inline
 858 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 859 {
 860         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 861         WARN_ON(!rt_rq->rt_nr_running);
 862         rt_rq->rt_nr_running--;
 863
 864         dec_rt_prio(rt_rq, rt_se_prio(rt_se));
 865         dec_rt_migration(rt_se, rt_rq);
 866         dec_rt_group(rt_se, rt_rq);
 867 }
 868
 869 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 870 {
 871         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 872         struct rt_prio_array *array = &rt_rq->active;
 873         struct rt_rq *group_rq = group_rt_rq(rt_se);
 874         struct list_head *queue = array->queue + rt_se_prio(rt_se);
 875
 876         /*
 877          * Don't enqueue the group if its throttled, or when empty.
 878          * The latter is a consequence of the former when a child group
 879          * get throttled and the current group doesn't have any other
 880          * active members.
 881          */
 882         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 883                 return;
 884
 885         if (!rt_rq->rt_nr_running)
 886                 list_add_leaf_rt_rq(rt_rq);
 887
 888         if (head)
 889                 list_add(&rt_se->run_list, queue);
 890         else
 891                 list_add_tail(&rt_se->run_list, queue);
 892         __set_bit(rt_se_prio(rt_se), array->bitmap);
 893
 894         inc_rt_tasks(rt_se, rt_rq);
 895 }
 896
 897 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
 898 {
 899         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 900         struct rt_prio_array *array = &rt_rq->active;
 901
 902         list_del_init(&rt_se->run_list);
 903         if (list_empty(array->queue + rt_se_prio(rt_se)))
 904                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
 905
 906         dec_rt_tasks(rt_se, rt_rq);
 907         if (!rt_rq->rt_nr_running)
 908                 list_del_leaf_rt_rq(rt_rq);
 909 }
 910
 911 /*
 912  * Because the prio of an upper entry depends on the lower
 913  * entries, we must remove entries top - down.
 914  */
 915 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 916 {
 917         struct sched_rt_entity *back = NULL;
 918
 919         for_each_sched_rt_entity(rt_se) {
 920                 rt_se->back = back;
 921                 back = rt_se;
 922         }
 923
 924         for (rt_se = back; rt_se; rt_se = rt_se->back) {
 925                 if (on_rt_rq(rt_se))
 926                         __dequeue_rt_entity(rt_se);
 927         }
 928 }
 929
 930 static void enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
 931 {
 932         dequeue_rt_stack(rt_se);
 933         for_each_sched_rt_entity(rt_se)
 934                 __enqueue_rt_entity(rt_se, head);
 935 }
 936
 937 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 938 {
 939         dequeue_rt_stack(rt_se);
 940
 941         for_each_sched_rt_entity(rt_se) {
 942                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
 943
 944                 if (rt_rq && rt_rq->rt_nr_running)
 945                         __enqueue_rt_entity(rt_se, false);
 946         }
 947 }
 948
 949 /*
 950  * Adding/removing a task to/from a priority array:
 951  */
 952 static void
 953 enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 954 {
 955         struct sched_rt_entity *rt_se = &p->rt;
 956
 957         if (flags & ENQUEUE_WAKEUP)
 958                 rt_se->timeout = 0;
 959
 960         enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD);
 961
 962         if (!task_current(rq, p) && p->rt.nr_cpus_allowed > 1)
 963                 enqueue_pushable_task(rq, p);
 964 }
 965
 966 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags)
 967 {
 968         struct sched_rt_entity *rt_se = &p->rt;
 969
 970         update_curr_rt(rq);
 971         dequeue_rt_entity(rt_se);
 972
 973         dequeue_pushable_task(rq, p);
 974 }
 975
 976 /*
 977  * Put task to the end of the run list without the overhead of dequeue
 978  * followed by enqueue.
 979  */
 980 static void
 981 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
 982 {
 983         if (on_rt_rq(rt_se)) {
 984                 struct rt_prio_array *array = &rt_rq->active;
 985                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
 986
 987                 if (head)
 988                         list_move(&rt_se->run_list, queue);
 989                 else
 990                         list_move_tail(&rt_se->run_list, queue);
 991         }
 992 }
 993
 994 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
 995 {
 996         struct sched_rt_entity *rt_se = &p->rt;
 997         struct rt_rq *rt_rq;
 998
 999         for_each_sched_rt_entity(rt_se) {
1000                 rt_rq = rt_rq_of_se(rt_se);
1001                 requeue_rt_entity(rt_rq, rt_se, head);
1002         }
1003 }
1004
1005 static void yield_task_rt(struct rq *rq)
1006 {
1007         requeue_task_rt(rq, rq->curr, 0);
1008 }
1009
1010 #ifdef CONFIG_SMP
1011 static int find_lowest_rq(struct task_struct *task);
1012
1013 static int
1014 select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
1015 {
1016         struct task_struct *curr;
1017         struct rq *rq;
1018         int cpu;
1019
1020         if (sd_flag != SD_BALANCE_WAKE)
1021                 return smp_processor_id();
1022
1023         cpu = task_cpu(p);
1024         rq = cpu_rq(cpu);
1025
1026         rcu_read_lock();
1027         curr = ACCESS_ONCE(rq->curr); /* unlocked access */
1028
1029         /*
1030          * If the current task on @p's runqueue is an RT task, then
1031          * try to see if we can wake this RT task up on another
1032          * runqueue. Otherwise simply start this RT task
1033          * on its current runqueue.
1034          *
1035          * We want to avoid overloading runqueues. If the woken
1036          * task is a higher priority, then it will stay on this CPU
1037          * and the lower prio task should be moved to another CPU.
1038          * Even though this will probably make the lower prio task
1039          * lose its cache, we do not want to bounce a higher task
1040          * around just because it gave up its CPU, perhaps for a
1041          * lock?
1042          *
1043          * For equal prio tasks, we just let the scheduler sort it out.
1044          *
1045          * Otherwise, just let it ride on the affined RQ and the
1046          * post-schedule router will push the preempted task away
1047          *
1048          * This test is optimistic, if we get it wrong the load-balancer
1049          * will have to sort it out.
1050          */
1051         if (curr && unlikely(rt_task(curr)) &&
1052             (curr->rt.nr_cpus_allowed < 2 ||
1053              curr->prio < p->prio) &&
1054             (p->rt.nr_cpus_allowed > 1)) {
1055                 int target = find_lowest_rq(p);
1056
1057                 if (target != -1)
1058                         cpu = target;
1059         }
1060         rcu_read_unlock();
1061
1062         return cpu;
1063 }
1064
1065 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
1066 {
1067         if (rq->curr->rt.nr_cpus_allowed == 1)
1068                 return;
1069
1070         if (p->rt.nr_cpus_allowed != 1
1071             && cpupri_find(&rq->rd->cpupri, p, NULL))
1072                 return;
1073
1074         if (!cpupri_find(&rq->rd->cpupri, rq->curr, NULL))
1075                 return;
1076
1077         /*
1078          * There appears to be other cpus that can accept
1079          * current and none to run 'p', so lets reschedule
1080          * to try and push current away:
1081          */
1082         requeue_task_rt(rq, p, 1);
1083         resched_task(rq->curr);
1084 }
1085
1086 #endif /* CONFIG_SMP */
1087
1088 /*
1089  * Preempt the current task with a newly woken task if needed:
1090  */
1091 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flags)
1092 {
1093         if (p->prio < rq->curr->prio) {
1094                 resched_task(rq->curr);
1095                 return;
1096         }
1097
1098 #ifdef CONFIG_SMP
1099         /*
1100          * If:
1101          *
1102          * - the newly woken task is of equal priority to the current task
1103          * - the newly woken task is non-migratable while current is migratable
1104          * - current will be preempted on the next reschedule
1105          *
1106          * we should check to see if current can readily move to a different
1107          * cpu.  If so, we will reschedule to allow the push logic to try
1108          * to move current somewhere else, making room for our non-migratable
1109          * task.
1110          */
1111         if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr))
1112                 check_preempt_equal_prio(rq, p);
1113 #endif
1114 }
1115
1116 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
1117                                                    struct rt_rq *rt_rq)
1118 {
1119         struct rt_prio_array *array = &rt_rq->active;
1120         struct sched_rt_entity *next = NULL;
1121         struct list_head *queue;
1122         int idx;
1123
1124         idx = sched_find_first_bit(array->bitmap);
1125         BUG_ON(idx >= MAX_RT_PRIO);
1126
1127         queue = array->queue + idx;
1128         next = list_entry(queue->next, struct sched_rt_entity, run_list);
1129
1130         return next;
1131 }
1132
1133 static struct task_struct *_pick_next_task_rt(struct rq *rq)
1134 {
1135         struct sched_rt_entity *rt_se;
1136         struct task_struct *p;
1137         struct rt_rq *rt_rq;
1138
1139         rt_rq = &rq->rt;
1140
1141         if (!rt_rq->rt_nr_running)
1142                 return NULL;
1143
1144         if (rt_rq_throttled(rt_rq))
1145                 return NULL;
1146
1147         do {
1148                 rt_se = pick_next_rt_entity(rq, rt_rq);
1149                 BUG_ON(!rt_se);
1150                 rt_rq = group_rt_rq(rt_se);
1151         } while (rt_rq);
1152
1153         p = rt_task_of(rt_se);
1154         p->se.exec_start = rq->clock_task;
1155
1156         return p;
1157 }
1158
1159 static struct task_struct *pick_next_task_rt(struct rq *rq)
1160 {
1161         struct task_struct *p = _pick_next_task_rt(rq);
1162
1163         /* The running task is never eligible for pushing */
1164         if (p)
1165                 dequeue_pushable_task(rq, p);
1166
1167 #ifdef CONFIG_SMP
1168         /*
1169          * We detect this state here so that we can avoid taking the RQ
1170          * lock again later if there is no need to push
1171          */
1172         rq->post_schedule = has_pushable_tasks(rq);
1173 #endif
1174
1175         return p;
1176 }
1177
1178 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
1179 {
1180         update_curr_rt(rq);
1181         p->se.exec_start = 0;
1182
1183         /*
1184          * The previous task needs to be made eligible for pushing
1185          * if it is still active
1186          */
1187         if (on_rt_rq(&p->rt) && p->rt.nr_cpus_allowed > 1)
1188                 enqueue_pushable_task(rq, p);
1189 }
1190
1191 #ifdef CONFIG_SMP
1192
1193 /* Only try algorithms three times */
1194 #define RT_MAX_TRIES 3
1195
1196 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
1197
1198 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
1199 {
1200         if (!task_running(rq, p) &&
1201             (cpu < 0 || cpumask_test_cpu(cpu, &p->cpus_allowed)) &&
1202             (p->rt.nr_cpus_allowed > 1))
1203                 return 1;
1204         return 0;
1205 }
1206
1207 /* Return the second highest RT task, NULL otherwise */
1208 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
1209 {
1210         struct task_struct *next = NULL;
1211         struct sched_rt_entity *rt_se;
1212         struct rt_prio_array *array;
1213         struct rt_rq *rt_rq;
1214         int idx;
1215
1216         for_each_leaf_rt_rq(rt_rq, rq) {
1217                 array = &rt_rq->active;
1218                 idx = sched_find_first_bit(array->bitmap);
1219 next_idx:
1220                 if (idx >= MAX_RT_PRIO)
1221                         continue;
1222                 if (next && next->prio < idx)
1223                         continue;
1224                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
1225                         struct task_struct *p;
1226
1227                         if (!rt_entity_is_task(rt_se))
1228                                 continue;
1229
1230                         p = rt_task_of(rt_se);
1231                         if (pick_rt_task(rq, p, cpu)) {
1232                                 next = p;
1233                                 break;
1234                         }
1235                 }
1236                 if (!next) {
1237                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
1238                         goto next_idx;
1239                 }
1240         }
1241
1242         return next;
1243 }
1244
1245 static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
1246
1247 static int find_lowest_rq(struct task_struct *task)
1248 {
1249         struct sched_domain *sd;
1250         struct cpumask *lowest_mask = __get_cpu_var(local_cpu_mask);
1251         int this_cpu = smp_processor_id();
1252         int cpu      = task_cpu(task);
1253
1254         /* Make sure the mask is initialized first */
1255         if (unlikely(!lowest_mask))
1256                 return -1;
1257
1258         if (task->rt.nr_cpus_allowed == 1)
1259                 return -1; /* No other targets possible */
1260
1261         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
1262                 return -1; /* No targets found */
1263
1264         /*
1265          * At this point we have built a mask of cpus representing the
1266          * lowest priority tasks in the system.  Now we want to elect
1267          * the best one based on our affinity and topology.
1268          *
1269          * We prioritize the last cpu that the task executed on since
1270          * it is most likely cache-hot in that location.
1271          */
1272         if (cpumask_test_cpu(cpu, lowest_mask))
1273                 return cpu;
1274
1275         /*
1276          * Otherwise, we consult the sched_domains span maps to figure
1277          * out which cpu is logically closest to our hot cache data.
1278          */
1279         if (!cpumask_test_cpu(this_cpu, lowest_mask))
1280                 this_cpu = -1; /* Skip this_cpu opt if not among lowest */
1281
1282         rcu_read_lock();
1283         for_each_domain(cpu, sd) {
1284                 if (sd->flags & SD_WAKE_AFFINE) {
1285                         int best_cpu;
1286
1287                         /*
1288                          * "this_cpu" is cheaper to preempt than a
1289                          * remote processor.
1290                          */
1291                         if (this_cpu != -1 &&
1292                             cpumask_test_cpu(this_cpu, sched_domain_span(sd))) {
1293                                 rcu_read_unlock();
1294                                 return this_cpu;
1295                         }
1296
1297                         best_cpu = cpumask_first_and(lowest_mask,
1298                                                      sched_domain_span(sd));
1299                         if (best_cpu < nr_cpu_ids) {
1300                                 rcu_read_unlock();
1301                                 return best_cpu;
1302                         }
1303                 }
1304         }
1305         rcu_read_unlock();
1306
1307         /*
1308          * And finally, if there were no matches within the domains
1309          * just give the caller *something* to work with from the compatible
1310          * locations.
1311          */
1312         if (this_cpu != -1)
1313                 return this_cpu;
1314
1315         cpu = cpumask_any(lowest_mask);
1316         if (cpu < nr_cpu_ids)
1317                 return cpu;
1318         return -1;
1319 }
1320
1321 /* Will lock the rq it finds */
1322 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1323 {
1324         struct rq *lowest_rq = NULL;
1325         int tries;
1326         int cpu;
1327
1328         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1329                 cpu = find_lowest_rq(task);
1330
1331                 if ((cpu == -1) || (cpu == rq->cpu))
1332                         break;
1333
1334                 lowest_rq = cpu_rq(cpu);
1335
1336                 /* if the prio of this runqueue changed, try again */
1337                 if (double_lock_balance(rq, lowest_rq)) {
1338                         /*
1339                          * We had to unlock the run queue. In
1340                          * the mean time, task could have
1341                          * migrated already or had its affinity changed.
1342                          * Also make sure that it wasn't scheduled on its rq.
1343                          */
1344                         if (unlikely(task_rq(task) != rq ||
1345                                      !cpumask_test_cpu(lowest_rq->cpu,
1346                                                        &task->cpus_allowed) ||
1347                                      task_running(rq, task) ||
1348                                      !task->on_rq)) {
1349
1350                                 raw_spin_unlock(&lowest_rq->lock);
1351                                 lowest_rq = NULL;
1352                                 break;
1353                         }
1354                 }
1355
1356                 /* If this rq is still suitable use it. */
1357                 if (lowest_rq->rt.highest_prio.curr > task->prio)
1358                         break;
1359
1360                 /* try again */
1361                 double_unlock_balance(rq, lowest_rq);
1362                 lowest_rq = NULL;
1363         }
1364
1365         return lowest_rq;
1366 }
1367
1368 static struct task_struct *pick_next_pushable_task(struct rq *rq)
1369 {
1370         struct task_struct *p;
1371
1372         if (!has_pushable_tasks(rq))
1373                 return NULL;
1374
1375         p = plist_first_entry(&rq->rt.pushable_tasks,
1376                               struct task_struct, pushable_tasks);
1377
1378         BUG_ON(rq->cpu != task_cpu(p));
1379         BUG_ON(task_current(rq, p));
1380         BUG_ON(p->rt.nr_cpus_allowed <= 1);
1381
1382         BUG_ON(!p->on_rq);
1383         BUG_ON(!rt_task(p));
1384
1385         return p;
1386 }
1387
1388 /*
1389  * If the current CPU has more than one RT task, see if the non
1390  * running task can migrate over to a CPU that is running a task
1391  * of lesser priority.
1392  */
1393 static int push_rt_task(struct rq *rq)
1394 {
1395         struct task_struct *next_task;
1396         struct rq *lowest_rq;
1397
1398         if (!rq->rt.overloaded)
1399                 return 0;
1400
1401         next_task = pick_next_pushable_task(rq);
1402         if (!next_task)
1403                 return 0;
1404
1405 retry:
1406         if (unlikely(next_task == rq->curr)) {
1407                 WARN_ON(1);
1408                 return 0;
1409         }
1410
1411         /*
1412          * It's possible that the next_task slipped in of
1413          * higher priority than current. If that's the case
1414          * just reschedule current.
1415          */
1416         if (unlikely(next_task->prio < rq->curr->prio)) {
1417                 resched_task(rq->curr);
1418                 return 0;
1419         }
1420
1421         /* We might release rq lock */
1422         get_task_struct(next_task);
1423
1424         /* find_lock_lowest_rq locks the rq if found */
1425         lowest_rq = find_lock_lowest_rq(next_task, rq);
1426         if (!lowest_rq) {
1427                 struct task_struct *task;
1428                 /*
1429                  * find lock_lowest_rq releases rq->lock
1430                  * so it is possible that next_task has migrated.
1431                  *
1432                  * We need to make sure that the task is still on the same
1433                  * run-queue and is also still the next task eligible for
1434                  * pushing.
1435                  */
1436                 task = pick_next_pushable_task(rq);
1437                 if (task_cpu(next_task) == rq->cpu && task == next_task) {
1438                         /*
1439                          * If we get here, the task hasn't moved at all, but
1440                          * it has failed to push.  We will not try again,
1441                          * since the other cpus will pull from us when they
1442                          * are ready.
1443                          */
1444                         dequeue_pushable_task(rq, next_task);
1445                         goto out;
1446                 }
1447
1448                 if (!task)
1449                         /* No more tasks, just exit */
1450                         goto out;
1451
1452                 /*
1453                  * Something has shifted, try again.
1454                  */
1455                 put_task_struct(next_task);
1456                 next_task = task;
1457                 goto retry;
1458         }
1459
1460         deactivate_task(rq, next_task, 0);
1461         set_task_cpu(next_task, lowest_rq->cpu);
1462         activate_task(lowest_rq, next_task, 0);
1463
1464         resched_task(lowest_rq->curr);
1465
1466         double_unlock_balance(rq, lowest_rq);
1467
1468 out:
1469         put_task_struct(next_task);
1470
1471         return 1;
1472 }
1473
1474 static void push_rt_tasks(struct rq *rq)
1475 {
1476         /* push_rt_task will return true if it moved an RT */
1477         while (push_rt_task(rq))
1478                 ;
1479 }
1480
1481 static int pull_rt_task(struct rq *this_rq)
1482 {
1483         int this_cpu = this_rq->cpu, ret = 0, cpu;
1484         struct task_struct *p;
1485         struct rq *src_rq;
1486
1487         if (likely(!rt_overloaded(this_rq)))
1488                 return 0;
1489
1490         for_each_cpu(cpu, this_rq->rd->rto_mask) {
1491                 if (this_cpu == cpu)
1492                         continue;
1493
1494                 src_rq = cpu_rq(cpu);
1495
1496                 /*
1497                  * Don't bother taking the src_rq->lock if the next highest
1498                  * task is known to be lower-priority than our current task.
1499                  * This may look racy, but if this value is about to go
1500                  * logically higher, the src_rq will push this task away.
1501                  * And if its going logically lower, we do not care
1502                  */
1503                 if (src_rq->rt.highest_prio.next >=
1504                     this_rq->rt.highest_prio.curr)
1505                         continue;
1506
1507                 /*
1508                  * We can potentially drop this_rq's lock in
1509                  * double_lock_balance, and another CPU could
1510                  * alter this_rq
1511                  */
1512                 double_lock_balance(this_rq, src_rq);
1513
1514                 /*
1515                  * Are there still pullable RT tasks?
1516                  */
1517                 if (src_rq->rt.rt_nr_running <= 1)
1518                         goto skip;
1519
1520                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1521
1522                 /*
1523                  * Do we have an RT task that preempts
1524                  * the to-be-scheduled task?
1525                  */
1526                 if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
1527                         WARN_ON(p == src_rq->curr);
1528                         WARN_ON(!p->on_rq);
1529
1530                         /*
1531                          * There's a chance that p is higher in priority
1532                          * than what's currently running on its cpu.
1533                          * This is just that p is wakeing up and hasn't
1534                          * had a chance to schedule. We only pull
1535                          * p if it is lower in priority than the
1536                          * current task on the run queue
1537                          */
1538                         if (p->prio < src_rq->curr->prio)
1539                                 goto skip;
1540
1541                         ret = 1;
1542
1543                         deactivate_task(src_rq, p, 0);
1544                         set_task_cpu(p, this_cpu);
1545                         activate_task(this_rq, p, 0);
1546                         /*
1547                          * We continue with the search, just in
1548                          * case there's an even higher prio task
1549                          * in another runqueue. (low likelihood
1550                          * but possible)
1551                          */
1552                 }
1553 skip:
1554                 double_unlock_balance(this_rq, src_rq);
1555         }
1556
1557         return ret;
1558 }
1559
1560 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1561 {
1562         /* Try to pull RT tasks here if we lower this rq's prio */
1563         if (rq->rt.highest_prio.curr > prev->prio)
1564                 pull_rt_task(rq);
1565 }
1566
1567 static void post_schedule_rt(struct rq *rq)
1568 {
1569         push_rt_tasks(rq);
1570 }
1571
1572 /*
1573  * If we are not running and we are not going to reschedule soon, we should
1574  * try to push tasks away now
1575  */
1576 static void task_woken_rt(struct rq *rq, struct task_struct *p)
1577 {
1578         if (!task_running(rq, p) &&
1579             !test_tsk_need_resched(rq->curr) &&
1580             has_pushable_tasks(rq) &&
1581             p->rt.nr_cpus_allowed > 1 &&
1582             rt_task(rq->curr) &&
1583             (rq->curr->rt.nr_cpus_allowed < 2 ||
1584              rq->curr->prio < p->prio))
1585                 push_rt_tasks(rq);
1586 }
1587
1588 static void set_cpus_allowed_rt(struct task_struct *p,
1589                                 const struct cpumask *new_mask)
1590 {
1591         int weight = cpumask_weight(new_mask);
1592
1593         BUG_ON(!rt_task(p));
1594
1595         /*
1596          * Update the migration status of the RQ if we have an RT task
1597          * which is running AND changing its weight value.
1598          */
1599         if (p->on_rq && (weight != p->rt.nr_cpus_allowed)) {
1600                 struct rq *rq = task_rq(p);
1601
1602                 if (!task_current(rq, p)) {
1603                         /*
1604                          * Make sure we dequeue this task from the pushable list
1605                          * before going further.  It will either remain off of
1606                          * the list because we are no longer pushable, or it
1607                          * will be requeued.
1608                          */
1609                         if (p->rt.nr_cpus_allowed > 1)
1610                                 dequeue_pushable_task(rq, p);
1611
1612                         /*
1613                          * Requeue if our weight is changing and still > 1
1614                          */
1615                         if (weight > 1)
1616                                 enqueue_pushable_task(rq, p);
1617
1618                 }
1619
1620                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1621                         rq->rt.rt_nr_migratory++;
1622                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1623                         BUG_ON(!rq->rt.rt_nr_migratory);
1624                         rq->rt.rt_nr_migratory--;
1625                 }
1626
1627                 update_rt_migration(&rq->rt);
1628         }
1629
1630         cpumask_copy(&p->cpus_allowed, new_mask);
1631         p->rt.nr_cpus_allowed = weight;
1632 }
1633
1634 /* Assumes rq->lock is held */
1635 static void rq_online_rt(struct rq *rq)
1636 {
1637         if (rq->rt.overloaded)
1638                 rt_set_overload(rq);
1639
1640         __enable_runtime(rq);
1641
1642         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
1643 }
1644
1645 /* Assumes rq->lock is held */
1646 static void rq_offline_rt(struct rq *rq)
1647 {
1648         if (rq->rt.overloaded)
1649                 rt_clear_overload(rq);
1650
1651         __disable_runtime(rq);
1652
1653         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1654 }
1655
1656 /*
1657  * When switch from the rt queue, we bring ourselves to a position
1658  * that we might want to pull RT tasks from other runqueues.
1659  */
1660 static void switched_from_rt(struct rq *rq, struct task_struct *p)
1661 {
1662         /*
1663          * If there are other RT tasks then we will reschedule
1664          * and the scheduling of the other RT tasks will handle
1665          * the balancing. But if we are the last RT task
1666          * we may need to handle the pulling of RT tasks
1667          * now.
1668          */
1669         if (p->on_rq && !rq->rt.rt_nr_running)
1670                 pull_rt_task(rq);
1671 }
1672
1673 static inline void init_sched_rt_class(void)
1674 {
1675         unsigned int i;
1676
1677         for_each_possible_cpu(i)
1678                 zalloc_cpumask_var_node(&per_cpu(local_cpu_mask, i),
1679                                         GFP_KERNEL, cpu_to_node(i));
1680 }
1681 #endif /* CONFIG_SMP */
1682
1683 /*
1684  * When switching a task to RT, we may overload the runqueue
1685  * with RT tasks. In this case we try to push them off to
1686  * other runqueues.
1687  */
1688 static void switched_to_rt(struct rq *rq, struct task_struct *p)
1689 {
1690         int check_resched = 1;
1691
1692         /*
1693          * If we are already running, then there's nothing
1694          * that needs to be done. But if we are not running
1695          * we may need to preempt the current running task.
1696          * If that current running task is also an RT task
1697          * then see if we can move to another run queue.
1698          */
1699         if (p->on_rq && rq->curr != p) {
1700 #ifdef CONFIG_SMP
1701                 if (rq->rt.overloaded && push_rt_task(rq) &&
1702                     /* Don't resched if we changed runqueues */
1703                     rq != task_rq(p))
1704                         check_resched = 0;
1705 #endif /* CONFIG_SMP */
1706                 if (check_resched && p->prio < rq->curr->prio)
1707                         resched_task(rq->curr);
1708         }
1709 }
1710
1711 /*
1712  * Priority of the task has changed. This may cause
1713  * us to initiate a push or pull.
1714  */
1715 static void
1716 prio_changed_rt(struct rq *rq, struct task_struct *p, int oldprio)
1717 {
1718         if (!p->on_rq)
1719                 return;
1720
1721         if (rq->curr == p) {
1722 #ifdef CONFIG_SMP
1723                 /*
1724                  * If our priority decreases while running, we
1725                  * may need to pull tasks to this runqueue.
1726                  */
1727                 if (oldprio < p->prio)
1728                         pull_rt_task(rq);
1729                 /*
1730                  * If there's a higher priority task waiting to run
1731                  * then reschedule. Note, the above pull_rt_task
1732                  * can release the rq lock and p could migrate.
1733                  * Only reschedule if p is still on the same runqueue.
1734                  */
1735                 if (p->prio > rq->rt.highest_prio.curr && rq->curr == p)
1736                         resched_task(p);
1737 #else
1738                 /* For UP simply resched on drop of prio */
1739                 if (oldprio < p->prio)
1740                         resched_task(p);
1741 #endif /* CONFIG_SMP */
1742         } else {
1743                 /*
1744                  * This task is not running, but if it is
1745                  * greater than the current running task
1746                  * then reschedule.
1747                  */
1748                 if (p->prio < rq->curr->prio)
1749                         resched_task(rq->curr);
1750         }
1751 }
1752
1753 static void watchdog(struct rq *rq, struct task_struct *p)
1754 {
1755         unsigned long soft, hard;
1756
1757         /* max may change after cur was read, this will be fixed next tick */
1758         soft = task_rlimit(p, RLIMIT_RTTIME);
1759         hard = task_rlimit_max(p, RLIMIT_RTTIME);
1760
1761         if (soft != RLIM_INFINITY) {
1762                 unsigned long next;
1763
1764                 p->rt.timeout++;
1765                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1766                 if (p->rt.timeout > next)
1767                         p->cputime_expires.sched_exp = p->se.sum_exec_runtime;
1768         }
1769 }
1770
1771 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1772 {
1773         update_curr_rt(rq);
1774
1775         watchdog(rq, p);
1776
1777         /*
1778          * RR tasks need a special form of timeslice management.
1779          * FIFO tasks have no timeslices.
1780          */
1781         if (p->policy != SCHED_RR)
1782                 return;
1783
1784         if (--p->rt.time_slice)
1785                 return;
1786
1787         p->rt.time_slice = DEF_TIMESLICE;
1788
1789         /*
1790          * Requeue to the end of queue if we are not the only element
1791          * on the queue:
1792          */
1793         if (p->rt.run_list.prev != p->rt.run_list.next) {
1794                 requeue_task_rt(rq, p, 0);
1795                 set_tsk_need_resched(p);
1796         }
1797 }
1798
1799 static void set_curr_task_rt(struct rq *rq)
1800 {
1801         struct task_struct *p = rq->curr;
1802
1803         p->se.exec_start = rq->clock_task;
1804
1805         /* The running task is never eligible for pushing */
1806         dequeue_pushable_task(rq, p);
1807 }
1808
1809 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
1810 {
1811         /*
1812          * Time slice is 0 for SCHED_FIFO tasks
1813          */
1814         if (task->policy == SCHED_RR)
1815                 return DEF_TIMESLICE;
1816         else
1817                 return 0;
1818 }
1819
1820 static const struct sched_class rt_sched_class = {
1821         .next                   = &fair_sched_class,
1822         .enqueue_task           = enqueue_task_rt,
1823         .dequeue_task           = dequeue_task_rt,
1824         .yield_task             = yield_task_rt,
1825
1826         .check_preempt_curr     = check_preempt_curr_rt,
1827
1828         .pick_next_task         = pick_next_task_rt,
1829         .put_prev_task          = put_prev_task_rt,
1830
1831 #ifdef CONFIG_SMP
1832         .select_task_rq         = select_task_rq_rt,
1833
1834         .set_cpus_allowed       = set_cpus_allowed_rt,
1835         .rq_online              = rq_online_rt,
1836         .rq_offline             = rq_offline_rt,
1837         .pre_schedule           = pre_schedule_rt,
1838         .post_schedule          = post_schedule_rt,
1839         .task_woken             = task_woken_rt,
1840         .switched_from          = switched_from_rt,
1841 #endif
1842
1843         .set_curr_task          = set_curr_task_rt,
1844         .task_tick              = task_tick_rt,
1845
1846         .get_rr_interval        = get_rr_interval_rt,
1847
1848         .prio_changed           = prio_changed_rt,
1849         .switched_to            = switched_to_rt,
1850 };
1851
1852 #ifdef CONFIG_SCHED_DEBUG
1853 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1854
1855 static void print_rt_stats(struct seq_file *m, int cpu)
1856 {
1857         rt_rq_iter_t iter;
1858         struct rt_rq *rt_rq;
1859
1860         rcu_read_lock();
1861         for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1862                 print_rt_rq(m, cpu, rt_rq);
1863         rcu_read_unlock();
1864 }
1865 #endif /* CONFIG_SCHED_DEBUG */
1866