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