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