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_SMP
   7
   8 static inline int rt_overloaded(struct rq *rq)
   9 {
  10         return atomic_read(&rq->rd->rto_count);
  11 }
  12
  13 static inline void rt_set_overload(struct rq *rq)
  14 {
  15         if (!rq->online)
  16                 return;
  17
  18         cpu_set(rq->cpu, rq->rd->rto_mask);
  19         /*
  20          * Make sure the mask is visible before we set
  21          * the overload count. That is checked to determine
  22          * if we should look at the mask. It would be a shame
  23          * if we looked at the mask, but the mask was not
  24          * updated yet.
  25          */
  26         wmb();
  27         atomic_inc(&rq->rd->rto_count);
  28 }
  29
  30 static inline void rt_clear_overload(struct rq *rq)
  31 {
  32         if (!rq->online)
  33                 return;
  34
  35         /* the order here really doesn't matter */
  36         atomic_dec(&rq->rd->rto_count);
  37         cpu_clear(rq->cpu, rq->rd->rto_mask);
  38 }
  39
  40 static void update_rt_migration(struct rq *rq)
  41 {
  42         if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
  43                 if (!rq->rt.overloaded) {
  44                         rt_set_overload(rq);
  45                         rq->rt.overloaded = 1;
  46                 }
  47         } else if (rq->rt.overloaded) {
  48                 rt_clear_overload(rq);
  49                 rq->rt.overloaded = 0;
  50         }
  51 }
  52 #endif /* CONFIG_SMP */
  53
  54 static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
  55 {
  56         return container_of(rt_se, struct task_struct, rt);
  57 }
  58
  59 static inline int on_rt_rq(struct sched_rt_entity *rt_se)
  60 {
  61         return !list_empty(&rt_se->run_list);
  62 }
  63
  64 #ifdef CONFIG_RT_GROUP_SCHED
  65
  66 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
  67 {
  68         if (!rt_rq->tg)
  69                 return RUNTIME_INF;
  70
  71         return rt_rq->rt_runtime;
  72 }
  73
  74 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
  75 {
  76         return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
  77 }
  78
  79 #define for_each_leaf_rt_rq(rt_rq, rq) \
  80         list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
  81
  82 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
  83 {
  84         return rt_rq->rq;
  85 }
  86
  87 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
  88 {
  89         return rt_se->rt_rq;
  90 }
  91
  92 #define for_each_sched_rt_entity(rt_se) \
  93         for (; rt_se; rt_se = rt_se->parent)
  94
  95 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
  96 {
  97         return rt_se->my_q;
  98 }
  99
 100 static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
 101 static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
 102
 103 static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 104 {
 105         struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
 106         struct sched_rt_entity *rt_se = rt_rq->rt_se;
 107
 108         if (rt_rq->rt_nr_running) {
 109                 if (rt_se && !on_rt_rq(rt_se))
 110                         enqueue_rt_entity(rt_se);
 111                 if (rt_rq->highest_prio < curr->prio)
 112                         resched_task(curr);
 113         }
 114 }
 115
 116 static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 117 {
 118         struct sched_rt_entity *rt_se = rt_rq->rt_se;
 119
 120         if (rt_se && on_rt_rq(rt_se))
 121                 dequeue_rt_entity(rt_se);
 122 }
 123
 124 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 125 {
 126         return rt_rq->rt_throttled && !rt_rq->rt_nr_boosted;
 127 }
 128
 129 static int rt_se_boosted(struct sched_rt_entity *rt_se)
 130 {
 131         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 132         struct task_struct *p;
 133
 134         if (rt_rq)
 135                 return !!rt_rq->rt_nr_boosted;
 136
 137         p = rt_task_of(rt_se);
 138         return p->prio != p->normal_prio;
 139 }
 140
 141 #ifdef CONFIG_SMP
 142 static inline cpumask_t sched_rt_period_mask(void)
 143 {
 144         return cpu_rq(smp_processor_id())->rd->span;
 145 }
 146 #else
 147 static inline cpumask_t sched_rt_period_mask(void)
 148 {
 149         return cpu_online_map;
 150 }
 151 #endif
 152
 153 static inline
 154 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 155 {
 156         return container_of(rt_b, struct task_group, rt_bandwidth)->rt_rq[cpu];
 157 }
 158
 159 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 160 {
 161         return &rt_rq->tg->rt_bandwidth;
 162 }
 163
 164 #else /* !CONFIG_RT_GROUP_SCHED */
 165
 166 static inline u64 sched_rt_runtime(struct rt_rq *rt_rq)
 167 {
 168         return rt_rq->rt_runtime;
 169 }
 170
 171 static inline u64 sched_rt_period(struct rt_rq *rt_rq)
 172 {
 173         return ktime_to_ns(def_rt_bandwidth.rt_period);
 174 }
 175
 176 #define for_each_leaf_rt_rq(rt_rq, rq) \
 177         for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
 178
 179 static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
 180 {
 181         return container_of(rt_rq, struct rq, rt);
 182 }
 183
 184 static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
 185 {
 186         struct task_struct *p = rt_task_of(rt_se);
 187         struct rq *rq = task_rq(p);
 188
 189         return &rq->rt;
 190 }
 191
 192 #define for_each_sched_rt_entity(rt_se) \
 193         for (; rt_se; rt_se = NULL)
 194
 195 static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
 196 {
 197         return NULL;
 198 }
 199
 200 static inline void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
 201 {
 202         if (rt_rq->rt_nr_running)
 203                 resched_task(rq_of_rt_rq(rt_rq)->curr);
 204 }
 205
 206 static inline void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
 207 {
 208 }
 209
 210 static inline int rt_rq_throttled(struct rt_rq *rt_rq)
 211 {
 212         return rt_rq->rt_throttled;
 213 }
 214
 215 static inline cpumask_t sched_rt_period_mask(void)
 216 {
 217         return cpu_online_map;
 218 }
 219
 220 static inline
 221 struct rt_rq *sched_rt_period_rt_rq(struct rt_bandwidth *rt_b, int cpu)
 222 {
 223         return &cpu_rq(cpu)->rt;
 224 }
 225
 226 static inline struct rt_bandwidth *sched_rt_bandwidth(struct rt_rq *rt_rq)
 227 {
 228         return &def_rt_bandwidth;
 229 }
 230
 231 #endif /* CONFIG_RT_GROUP_SCHED */
 232
 233 #ifdef CONFIG_SMP
 234 /*
 235  * We ran out of runtime, see if we can borrow some from our neighbours.
 236  */
 237 static int do_balance_runtime(struct rt_rq *rt_rq)
 238 {
 239         struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 240         struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
 241         int i, weight, more = 0;
 242         u64 rt_period;
 243
 244         weight = cpus_weight(rd->span);
 245
 246         spin_lock(&rt_b->rt_runtime_lock);
 247         rt_period = ktime_to_ns(rt_b->rt_period);
 248         for_each_cpu_mask_nr(i, rd->span) {
 249                 struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 250                 s64 diff;
 251
 252                 if (iter == rt_rq)
 253                         continue;
 254
 255                 spin_lock(&iter->rt_runtime_lock);
 256                 /*
 257                  * Either all rqs have inf runtime and there's nothing to steal
 258                  * or __disable_runtime() below sets a specific rq to inf to
 259                  * indicate its been disabled and disalow stealing.
 260                  */
 261                 if (iter->rt_runtime == RUNTIME_INF)
 262                         goto next;
 263
 264                 /*
 265                  * From runqueues with spare time, take 1/n part of their
 266                  * spare time, but no more than our period.
 267                  */
 268                 diff = iter->rt_runtime - iter->rt_time;
 269                 if (diff > 0) {
 270                         diff = div_u64((u64)diff, weight);
 271                         if (rt_rq->rt_runtime + diff > rt_period)
 272                                 diff = rt_period - rt_rq->rt_runtime;
 273                         iter->rt_runtime -= diff;
 274                         rt_rq->rt_runtime += diff;
 275                         more = 1;
 276                         if (rt_rq->rt_runtime == rt_period) {
 277                                 spin_unlock(&iter->rt_runtime_lock);
 278                                 break;
 279                         }
 280                 }
 281 next:
 282                 spin_unlock(&iter->rt_runtime_lock);
 283         }
 284         spin_unlock(&rt_b->rt_runtime_lock);
 285
 286         return more;
 287 }
 288
 289 /*
 290  * Ensure this RQ takes back all the runtime it lend to its neighbours.
 291  */
 292 static void __disable_runtime(struct rq *rq)
 293 {
 294         struct root_domain *rd = rq->rd;
 295         struct rt_rq *rt_rq;
 296
 297         if (unlikely(!scheduler_running))
 298                 return;
 299
 300         for_each_leaf_rt_rq(rt_rq, rq) {
 301                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 302                 s64 want;
 303                 int i;
 304
 305                 spin_lock(&rt_b->rt_runtime_lock);
 306                 spin_lock(&rt_rq->rt_runtime_lock);
 307                 /*
 308                  * Either we're all inf and nobody needs to borrow, or we're
 309                  * already disabled and thus have nothing to do, or we have
 310                  * exactly the right amount of runtime to take out.
 311                  */
 312                 if (rt_rq->rt_runtime == RUNTIME_INF ||
 313                                 rt_rq->rt_runtime == rt_b->rt_runtime)
 314                         goto balanced;
 315                 spin_unlock(&rt_rq->rt_runtime_lock);
 316
 317                 /*
 318                  * Calculate the difference between what we started out with
 319                  * and what we current have, that's the amount of runtime
 320                  * we lend and now have to reclaim.
 321                  */
 322                 want = rt_b->rt_runtime - rt_rq->rt_runtime;
 323
 324                 /*
 325                  * Greedy reclaim, take back as much as we can.
 326                  */
 327                 for_each_cpu_mask(i, rd->span) {
 328                         struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
 329                         s64 diff;
 330
 331                         /*
 332                          * Can't reclaim from ourselves or disabled runqueues.
 333                          */
 334                         if (iter == rt_rq || iter->rt_runtime == RUNTIME_INF)
 335                                 continue;
 336
 337                         spin_lock(&iter->rt_runtime_lock);
 338                         if (want > 0) {
 339                                 diff = min_t(s64, iter->rt_runtime, want);
 340                                 iter->rt_runtime -= diff;
 341                                 want -= diff;
 342                         } else {
 343                                 iter->rt_runtime -= want;
 344                                 want -= want;
 345                         }
 346                         spin_unlock(&iter->rt_runtime_lock);
 347
 348                         if (!want)
 349                                 break;
 350                 }
 351
 352                 spin_lock(&rt_rq->rt_runtime_lock);
 353                 /*
 354                  * We cannot be left wanting - that would mean some runtime
 355                  * leaked out of the system.
 356                  */
 357                 BUG_ON(want);
 358 balanced:
 359                 /*
 360                  * Disable all the borrow logic by pretending we have inf
 361                  * runtime - in which case borrowing doesn't make sense.
 362                  */
 363                 rt_rq->rt_runtime = RUNTIME_INF;
 364                 spin_unlock(&rt_rq->rt_runtime_lock);
 365                 spin_unlock(&rt_b->rt_runtime_lock);
 366         }
 367 }
 368
 369 static void disable_runtime(struct rq *rq)
 370 {
 371         unsigned long flags;
 372
 373         spin_lock_irqsave(&rq->lock, flags);
 374         __disable_runtime(rq);
 375         spin_unlock_irqrestore(&rq->lock, flags);
 376 }
 377
 378 static void __enable_runtime(struct rq *rq)
 379 {
 380         struct rt_rq *rt_rq;
 381
 382         if (unlikely(!scheduler_running))
 383                 return;
 384
 385         /*
 386          * Reset each runqueue's bandwidth settings
 387          */
 388         for_each_leaf_rt_rq(rt_rq, rq) {
 389                 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
 390
 391                 spin_lock(&rt_b->rt_runtime_lock);
 392                 spin_lock(&rt_rq->rt_runtime_lock);
 393                 rt_rq->rt_runtime = rt_b->rt_runtime;
 394                 rt_rq->rt_time = 0;
 395                 rt_rq->rt_throttled = 0;
 396                 spin_unlock(&rt_rq->rt_runtime_lock);
 397                 spin_unlock(&rt_b->rt_runtime_lock);
 398         }
 399 }
 400
 401 static void enable_runtime(struct rq *rq)
 402 {
 403         unsigned long flags;
 404
 405         spin_lock_irqsave(&rq->lock, flags);
 406         __enable_runtime(rq);
 407         spin_unlock_irqrestore(&rq->lock, flags);
 408 }
 409
 410 static int balance_runtime(struct rt_rq *rt_rq)
 411 {
 412         int more = 0;
 413
 414         if (rt_rq->rt_time > rt_rq->rt_runtime) {
 415                 spin_unlock(&rt_rq->rt_runtime_lock);
 416                 more = do_balance_runtime(rt_rq);
 417                 spin_lock(&rt_rq->rt_runtime_lock);
 418         }
 419
 420         return more;
 421 }
 422 #else /* !CONFIG_SMP */
 423 static inline int balance_runtime(struct rt_rq *rt_rq)
 424 {
 425         return 0;
 426 }
 427 #endif /* CONFIG_SMP */
 428
 429 static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
 430 {
 431         int i, idle = 1;
 432         cpumask_t span;
 433
 434         if (!rt_bandwidth_enabled() || rt_b->rt_runtime == RUNTIME_INF)
 435                 return 1;
 436
 437         span = sched_rt_period_mask();
 438         for_each_cpu_mask(i, span) {
 439                 int enqueue = 0;
 440                 struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);
 441                 struct rq *rq = rq_of_rt_rq(rt_rq);
 442
 443                 spin_lock(&rq->lock);
 444                 if (rt_rq->rt_time) {
 445                         u64 runtime;
 446
 447                         spin_lock(&rt_rq->rt_runtime_lock);
 448                         if (rt_rq->rt_throttled)
 449                                 balance_runtime(rt_rq);
 450                         runtime = rt_rq->rt_runtime;
 451                         rt_rq->rt_time -= min(rt_rq->rt_time, overrun*runtime);
 452                         if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) {
 453                                 rt_rq->rt_throttled = 0;
 454                                 enqueue = 1;
 455                         }
 456                         if (rt_rq->rt_time || rt_rq->rt_nr_running)
 457                                 idle = 0;
 458                         spin_unlock(&rt_rq->rt_runtime_lock);
 459                 } else if (rt_rq->rt_nr_running)
 460                         idle = 0;
 461
 462                 if (enqueue)
 463                         sched_rt_rq_enqueue(rt_rq);
 464                 spin_unlock(&rq->lock);
 465         }
 466
 467         return idle;
 468 }
 469
 470 static inline int rt_se_prio(struct sched_rt_entity *rt_se)
 471 {
 472 #ifdef CONFIG_RT_GROUP_SCHED
 473         struct rt_rq *rt_rq = group_rt_rq(rt_se);
 474
 475         if (rt_rq)
 476                 return rt_rq->highest_prio;
 477 #endif
 478
 479         return rt_task_of(rt_se)->prio;
 480 }
 481
 482 static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
 483 {
 484         u64 runtime = sched_rt_runtime(rt_rq);
 485
 486         if (rt_rq->rt_throttled)
 487                 return rt_rq_throttled(rt_rq);
 488
 489         if (sched_rt_runtime(rt_rq) >= sched_rt_period(rt_rq))
 490                 return 0;
 491
 492         balance_runtime(rt_rq);
 493         runtime = sched_rt_runtime(rt_rq);
 494         if (runtime == RUNTIME_INF)
 495                 return 0;
 496
 497         if (rt_rq->rt_time > runtime) {
 498                 rt_rq->rt_throttled = 1;
 499                 if (rt_rq_throttled(rt_rq)) {
 500                         sched_rt_rq_dequeue(rt_rq);
 501                         return 1;
 502                 }
 503         }
 504
 505         return 0;
 506 }
 507
 508 /*
 509  * Update the current task's runtime statistics. Skip current tasks that
 510  * are not in our scheduling class.
 511  */
 512 static void update_curr_rt(struct rq *rq)
 513 {
 514         struct task_struct *curr = rq->curr;
 515         struct sched_rt_entity *rt_se = &curr->rt;
 516         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 517         u64 delta_exec;
 518
 519         if (!task_has_rt_policy(curr))
 520                 return;
 521
 522         delta_exec = rq->clock - curr->se.exec_start;
 523         if (unlikely((s64)delta_exec < 0))
 524                 delta_exec = 0;
 525
 526         schedstat_set(curr->se.exec_max, max(curr->se.exec_max, delta_exec));
 527
 528         curr->se.sum_exec_runtime += delta_exec;
 529         curr->se.exec_start = rq->clock;
 530         cpuacct_charge(curr, delta_exec);
 531
 532         if (!rt_bandwidth_enabled())
 533                 return;
 534
 535         for_each_sched_rt_entity(rt_se) {
 536                 rt_rq = rt_rq_of_se(rt_se);
 537
 538                 spin_lock(&rt_rq->rt_runtime_lock);
 539                 if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
 540                         rt_rq->rt_time += delta_exec;
 541                         if (sched_rt_runtime_exceeded(rt_rq))
 542                                 resched_task(curr);
 543                 }
 544                 spin_unlock(&rt_rq->rt_runtime_lock);
 545         }
 546 }
 547
 548 static inline
 549 void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 550 {
 551         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 552         rt_rq->rt_nr_running++;
 553 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 554         if (rt_se_prio(rt_se) < rt_rq->highest_prio) {
 555 #ifdef CONFIG_SMP
 556                 struct rq *rq = rq_of_rt_rq(rt_rq);
 557 #endif
 558
 559                 rt_rq->highest_prio = rt_se_prio(rt_se);
 560 #ifdef CONFIG_SMP
 561                 if (rq->online)
 562                         cpupri_set(&rq->rd->cpupri, rq->cpu,
 563                                    rt_se_prio(rt_se));
 564 #endif
 565         }
 566 #endif
 567 #ifdef CONFIG_SMP
 568         if (rt_se->nr_cpus_allowed > 1) {
 569                 struct rq *rq = rq_of_rt_rq(rt_rq);
 570
 571                 rq->rt.rt_nr_migratory++;
 572         }
 573
 574         update_rt_migration(rq_of_rt_rq(rt_rq));
 575 #endif
 576 #ifdef CONFIG_RT_GROUP_SCHED
 577         if (rt_se_boosted(rt_se))
 578                 rt_rq->rt_nr_boosted++;
 579
 580         if (rt_rq->tg)
 581                 start_rt_bandwidth(&rt_rq->tg->rt_bandwidth);
 582 #else
 583         start_rt_bandwidth(&def_rt_bandwidth);
 584 #endif
 585 }
 586
 587 static inline
 588 void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
 589 {
 590 #ifdef CONFIG_SMP
 591         int highest_prio = rt_rq->highest_prio;
 592 #endif
 593
 594         WARN_ON(!rt_prio(rt_se_prio(rt_se)));
 595         WARN_ON(!rt_rq->rt_nr_running);
 596         rt_rq->rt_nr_running--;
 597 #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED
 598         if (rt_rq->rt_nr_running) {
 599                 struct rt_prio_array *array;
 600
 601                 WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
 602                 if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
 603                         /* recalculate */
 604                         array = &rt_rq->active;
 605                         rt_rq->highest_prio =
 606                                 sched_find_first_bit(array->bitmap);
 607                 } /* otherwise leave rq->highest prio alone */
 608         } else
 609                 rt_rq->highest_prio = MAX_RT_PRIO;
 610 #endif
 611 #ifdef CONFIG_SMP
 612         if (rt_se->nr_cpus_allowed > 1) {
 613                 struct rq *rq = rq_of_rt_rq(rt_rq);
 614                 rq->rt.rt_nr_migratory--;
 615         }
 616
 617         if (rt_rq->highest_prio != highest_prio) {
 618                 struct rq *rq = rq_of_rt_rq(rt_rq);
 619
 620                 if (rq->online)
 621                         cpupri_set(&rq->rd->cpupri, rq->cpu,
 622                                    rt_rq->highest_prio);
 623         }
 624
 625         update_rt_migration(rq_of_rt_rq(rt_rq));
 626 #endif /* CONFIG_SMP */
 627 #ifdef CONFIG_RT_GROUP_SCHED
 628         if (rt_se_boosted(rt_se))
 629                 rt_rq->rt_nr_boosted--;
 630
 631         WARN_ON(!rt_rq->rt_nr_running && rt_rq->rt_nr_boosted);
 632 #endif
 633 }
 634
 635 static void __enqueue_rt_entity(struct sched_rt_entity *rt_se)
 636 {
 637         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 638         struct rt_prio_array *array = &rt_rq->active;
 639         struct rt_rq *group_rq = group_rt_rq(rt_se);
 640         struct list_head *queue = array->queue + rt_se_prio(rt_se);
 641
 642         /*
 643          * Don't enqueue the group if its throttled, or when empty.
 644          * The latter is a consequence of the former when a child group
 645          * get throttled and the current group doesn't have any other
 646          * active members.
 647          */
 648         if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
 649                 return;
 650
 651         list_add_tail(&rt_se->run_list, queue);
 652         __set_bit(rt_se_prio(rt_se), array->bitmap);
 653
 654         inc_rt_tasks(rt_se, rt_rq);
 655 }
 656
 657 static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
 658 {
 659         struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
 660         struct rt_prio_array *array = &rt_rq->active;
 661
 662         list_del_init(&rt_se->run_list);
 663         if (list_empty(array->queue + rt_se_prio(rt_se)))
 664                 __clear_bit(rt_se_prio(rt_se), array->bitmap);
 665
 666         dec_rt_tasks(rt_se, rt_rq);
 667 }
 668
 669 /*
 670  * Because the prio of an upper entry depends on the lower
 671  * entries, we must remove entries top - down.
 672  */
 673 static void dequeue_rt_stack(struct sched_rt_entity *rt_se)
 674 {
 675         struct sched_rt_entity *back = NULL;
 676
 677         for_each_sched_rt_entity(rt_se) {
 678                 rt_se->back = back;
 679                 back = rt_se;
 680         }
 681
 682         for (rt_se = back; rt_se; rt_se = rt_se->back) {
 683                 if (on_rt_rq(rt_se))
 684                         __dequeue_rt_entity(rt_se);
 685         }
 686 }
 687
 688 static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
 689 {
 690         dequeue_rt_stack(rt_se);
 691         for_each_sched_rt_entity(rt_se)
 692                 __enqueue_rt_entity(rt_se);
 693 }
 694
 695 static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 696 {
 697         dequeue_rt_stack(rt_se);
 698
 699         for_each_sched_rt_entity(rt_se) {
 700                 struct rt_rq *rt_rq = group_rt_rq(rt_se);
 701
 702                 if (rt_rq && rt_rq->rt_nr_running)
 703                         __enqueue_rt_entity(rt_se);
 704         }
 705 }
 706
 707 /*
 708  * Adding/removing a task to/from a priority array:
 709  */
 710 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
 711 {
 712         struct sched_rt_entity *rt_se = &p->rt;
 713
 714         if (wakeup)
 715                 rt_se->timeout = 0;
 716
 717         enqueue_rt_entity(rt_se);
 718
 719         inc_cpu_load(rq, p->se.load.weight);
 720 }
 721
 722 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
 723 {
 724         struct sched_rt_entity *rt_se = &p->rt;
 725
 726         update_curr_rt(rq);
 727         dequeue_rt_entity(rt_se);
 728
 729         dec_cpu_load(rq, p->se.load.weight);
 730 }
 731
 732 /*
 733  * Put task to the end of the run list without the overhead of dequeue
 734  * followed by enqueue.
 735  */
 736 static void
 737 requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int head)
 738 {
 739         if (on_rt_rq(rt_se)) {
 740                 struct rt_prio_array *array = &rt_rq->active;
 741                 struct list_head *queue = array->queue + rt_se_prio(rt_se);
 742
 743                 if (head)
 744                         list_move(&rt_se->run_list, queue);
 745                 else
 746                         list_move_tail(&rt_se->run_list, queue);
 747         }
 748 }
 749
 750 static void requeue_task_rt(struct rq *rq, struct task_struct *p, int head)
 751 {
 752         struct sched_rt_entity *rt_se = &p->rt;
 753         struct rt_rq *rt_rq;
 754
 755         for_each_sched_rt_entity(rt_se) {
 756                 rt_rq = rt_rq_of_se(rt_se);
 757                 requeue_rt_entity(rt_rq, rt_se, head);
 758         }
 759 }
 760
 761 static void yield_task_rt(struct rq *rq)
 762 {
 763         requeue_task_rt(rq, rq->curr, 0);
 764 }
 765
 766 #ifdef CONFIG_SMP
 767 static int find_lowest_rq(struct task_struct *task);
 768
 769 static int select_task_rq_rt(struct task_struct *p, int sync)
 770 {
 771         struct rq *rq = task_rq(p);
 772
 773         /*
 774          * If the current task is an RT task, then
 775          * try to see if we can wake this RT task up on another
 776          * runqueue. Otherwise simply start this RT task
 777          * on its current runqueue.
 778          *
 779          * We want to avoid overloading runqueues. Even if
 780          * the RT task is of higher priority than the current RT task.
 781          * RT tasks behave differently than other tasks. If
 782          * one gets preempted, we try to push it off to another queue.
 783          * So trying to keep a preempting RT task on the same
 784          * cache hot CPU will force the running RT task to
 785          * a cold CPU. So we waste all the cache for the lower
 786          * RT task in hopes of saving some of a RT task
 787          * that is just being woken and probably will have
 788          * cold cache anyway.
 789          */
 790         if (unlikely(rt_task(rq->curr)) &&
 791             (p->rt.nr_cpus_allowed > 1)) {
 792                 int cpu = find_lowest_rq(p);
 793
 794                 return (cpu == -1) ? task_cpu(p) : cpu;
 795         }
 796
 797         /*
 798          * Otherwise, just let it ride on the affined RQ and the
 799          * post-schedule router will push the preempted task away
 800          */
 801         return task_cpu(p);
 802 }
 803
 804 static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)
 805 {
 806         cpumask_t mask;
 807
 808         if (rq->curr->rt.nr_cpus_allowed == 1)
 809                 return;
 810
 811         if (p->rt.nr_cpus_allowed != 1
 812             && cpupri_find(&rq->rd->cpupri, p, &mask))
 813                 return;
 814
 815         if (!cpupri_find(&rq->rd->cpupri, rq->curr, &mask))
 816                 return;
 817
 818         /*
 819          * There appears to be other cpus that can accept
 820          * current and none to run 'p', so lets reschedule
 821          * to try and push current away:
 822          */
 823         requeue_task_rt(rq, p, 1);
 824         resched_task(rq->curr);
 825 }
 826
 827 #endif /* CONFIG_SMP */
 828
 829 /*
 830  * Preempt the current task with a newly woken task if needed:
 831  */
 832 static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int sync)
 833 {
 834         if (p->prio < rq->curr->prio) {
 835                 resched_task(rq->curr);
 836                 return;
 837         }
 838
 839 #ifdef CONFIG_SMP
 840         /*
 841          * If:
 842          *
 843          * - the newly woken task is of equal priority to the current task
 844          * - the newly woken task is non-migratable while current is migratable
 845          * - current will be preempted on the next reschedule
 846          *
 847          * we should check to see if current can readily move to a different
 848          * cpu.  If so, we will reschedule to allow the push logic to try
 849          * to move current somewhere else, making room for our non-migratable
 850          * task.
 851          */
 852         if (p->prio == rq->curr->prio && !need_resched())
 853                 check_preempt_equal_prio(rq, p);
 854 #endif
 855 }
 856
 857 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
 858                                                    struct rt_rq *rt_rq)
 859 {
 860         struct rt_prio_array *array = &rt_rq->active;
 861         struct sched_rt_entity *next = NULL;
 862         struct list_head *queue;
 863         int idx;
 864
 865         idx = sched_find_first_bit(array->bitmap);
 866         BUG_ON(idx >= MAX_RT_PRIO);
 867
 868         queue = array->queue + idx;
 869         next = list_entry(queue->next, struct sched_rt_entity, run_list);
 870
 871         return next;
 872 }
 873
 874 static struct task_struct *pick_next_task_rt(struct rq *rq)
 875 {
 876         struct sched_rt_entity *rt_se;
 877         struct task_struct *p;
 878         struct rt_rq *rt_rq;
 879
 880         rt_rq = &rq->rt;
 881
 882         if (unlikely(!rt_rq->rt_nr_running))
 883                 return NULL;
 884
 885         if (rt_rq_throttled(rt_rq))
 886                 return NULL;
 887
 888         do {
 889                 rt_se = pick_next_rt_entity(rq, rt_rq);
 890                 BUG_ON(!rt_se);
 891                 rt_rq = group_rt_rq(rt_se);
 892         } while (rt_rq);
 893
 894         p = rt_task_of(rt_se);
 895         p->se.exec_start = rq->clock;
 896         return p;
 897 }
 898
 899 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 900 {
 901         update_curr_rt(rq);
 902         p->se.exec_start = 0;
 903 }
 904
 905 #ifdef CONFIG_SMP
 906
 907 /* Only try algorithms three times */
 908 #define RT_MAX_TRIES 3
 909
 910 static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
 911 static void double_unlock_balance(struct rq *this_rq, struct rq *busiest);
 912
 913 static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
 914
 915 static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
 916 {
 917         if (!task_running(rq, p) &&
 918             (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
 919             (p->rt.nr_cpus_allowed > 1))
 920                 return 1;
 921         return 0;
 922 }
 923
 924 /* Return the second highest RT task, NULL otherwise */
 925 static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
 926 {
 927         struct task_struct *next = NULL;
 928         struct sched_rt_entity *rt_se;
 929         struct rt_prio_array *array;
 930         struct rt_rq *rt_rq;
 931         int idx;
 932
 933         for_each_leaf_rt_rq(rt_rq, rq) {
 934                 array = &rt_rq->active;
 935                 idx = sched_find_first_bit(array->bitmap);
 936  next_idx:
 937                 if (idx >= MAX_RT_PRIO)
 938                         continue;
 939                 if (next && next->prio < idx)
 940                         continue;
 941                 list_for_each_entry(rt_se, array->queue + idx, run_list) {
 942                         struct task_struct *p = rt_task_of(rt_se);
 943                         if (pick_rt_task(rq, p, cpu)) {
 944                                 next = p;
 945                                 break;
 946                         }
 947                 }
 948                 if (!next) {
 949                         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
 950                         goto next_idx;
 951                 }
 952         }
 953
 954         return next;
 955 }
 956
 957 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
 958
 959 static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
 960 {
 961         int first;
 962
 963         /* "this_cpu" is cheaper to preempt than a remote processor */
 964         if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
 965                 return this_cpu;
 966
 967         first = first_cpu(*mask);
 968         if (first != NR_CPUS)
 969                 return first;
 970
 971         return -1;
 972 }
 973
 974 static int find_lowest_rq(struct task_struct *task)
 975 {
 976         struct sched_domain *sd;
 977         cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
 978         int this_cpu = smp_processor_id();
 979         int cpu      = task_cpu(task);
 980
 981         if (task->rt.nr_cpus_allowed == 1)
 982                 return -1; /* No other targets possible */
 983
 984         if (!cpupri_find(&task_rq(task)->rd->cpupri, task, lowest_mask))
 985                 return -1; /* No targets found */
 986
 987         /*
 988          * Only consider CPUs that are usable for migration.
 989          * I guess we might want to change cpupri_find() to ignore those
 990          * in the first place.
 991          */
 992         cpus_and(*lowest_mask, *lowest_mask, cpu_active_map);
 993
 994         /*
 995          * At this point we have built a mask of cpus representing the
 996          * lowest priority tasks in the system.  Now we want to elect
 997          * the best one based on our affinity and topology.
 998          *
 999          * We prioritize the last cpu that the task executed on since
1000          * it is most likely cache-hot in that location.
1001          */
1002         if (cpu_isset(cpu, *lowest_mask))
1003                 return cpu;
1004
1005         /*
1006          * Otherwise, we consult the sched_domains span maps to figure
1007          * out which cpu is logically closest to our hot cache data.
1008          */
1009         if (this_cpu == cpu)
1010                 this_cpu = -1; /* Skip this_cpu opt if the same */
1011
1012         for_each_domain(cpu, sd) {
1013                 if (sd->flags & SD_WAKE_AFFINE) {
1014                         cpumask_t domain_mask;
1015                         int       best_cpu;
1016
1017                         cpus_and(domain_mask, sd->span, *lowest_mask);
1018
1019                         best_cpu = pick_optimal_cpu(this_cpu,
1020                                                     &domain_mask);
1021                         if (best_cpu != -1)
1022                                 return best_cpu;
1023                 }
1024         }
1025
1026         /*
1027          * And finally, if there were no matches within the domains
1028          * just give the caller *something* to work with from the compatible
1029          * locations.
1030          */
1031         return pick_optimal_cpu(this_cpu, lowest_mask);
1032 }
1033
1034 /* Will lock the rq it finds */
1035 static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
1036 {
1037         struct rq *lowest_rq = NULL;
1038         int tries;
1039         int cpu;
1040
1041         for (tries = 0; tries < RT_MAX_TRIES; tries++) {
1042                 cpu = find_lowest_rq(task);
1043
1044                 if ((cpu == -1) || (cpu == rq->cpu))
1045                         break;
1046
1047                 lowest_rq = cpu_rq(cpu);
1048
1049                 /* if the prio of this runqueue changed, try again */
1050                 if (double_lock_balance(rq, lowest_rq)) {
1051                         /*
1052                          * We had to unlock the run queue. In
1053                          * the mean time, task could have
1054                          * migrated already or had its affinity changed.
1055                          * Also make sure that it wasn't scheduled on its rq.
1056                          */
1057                         if (unlikely(task_rq(task) != rq ||
1058                                      !cpu_isset(lowest_rq->cpu,
1059                                                 task->cpus_allowed) ||
1060                                      task_running(rq, task) ||
1061                                      !task->se.on_rq)) {
1062
1063                                 spin_unlock(&lowest_rq->lock);
1064                                 lowest_rq = NULL;
1065                                 break;
1066                         }
1067                 }
1068
1069                 /* If this rq is still suitable use it. */
1070                 if (lowest_rq->rt.highest_prio > task->prio)
1071                         break;
1072
1073                 /* try again */
1074                 double_unlock_balance(rq, lowest_rq);
1075                 lowest_rq = NULL;
1076         }
1077
1078         return lowest_rq;
1079 }
1080
1081 /*
1082  * If the current CPU has more than one RT task, see if the non
1083  * running task can migrate over to a CPU that is running a task
1084  * of lesser priority.
1085  */
1086 static int push_rt_task(struct rq *rq)
1087 {
1088         struct task_struct *next_task;
1089         struct rq *lowest_rq;
1090         int ret = 0;
1091         int paranoid = RT_MAX_TRIES;
1092
1093         if (!rq->rt.overloaded)
1094                 return 0;
1095
1096         next_task = pick_next_highest_task_rt(rq, -1);
1097         if (!next_task)
1098                 return 0;
1099
1100  retry:
1101         if (unlikely(next_task == rq->curr)) {
1102                 WARN_ON(1);
1103                 return 0;
1104         }
1105
1106         /*
1107          * It's possible that the next_task slipped in of
1108          * higher priority than current. If that's the case
1109          * just reschedule current.
1110          */
1111         if (unlikely(next_task->prio < rq->curr->prio)) {
1112                 resched_task(rq->curr);
1113                 return 0;
1114         }
1115
1116         /* We might release rq lock */
1117         get_task_struct(next_task);
1118
1119         /* find_lock_lowest_rq locks the rq if found */
1120         lowest_rq = find_lock_lowest_rq(next_task, rq);
1121         if (!lowest_rq) {
1122                 struct task_struct *task;
1123                 /*
1124                  * find lock_lowest_rq releases rq->lock
1125                  * so it is possible that next_task has changed.
1126                  * If it has, then try again.
1127                  */
1128                 task = pick_next_highest_task_rt(rq, -1);
1129                 if (unlikely(task != next_task) && task && paranoid--) {
1130                         put_task_struct(next_task);
1131                         next_task = task;
1132                         goto retry;
1133                 }
1134                 goto out;
1135         }
1136
1137         deactivate_task(rq, next_task, 0);
1138         set_task_cpu(next_task, lowest_rq->cpu);
1139         activate_task(lowest_rq, next_task, 0);
1140
1141         resched_task(lowest_rq->curr);
1142
1143         double_unlock_balance(rq, lowest_rq);
1144
1145         ret = 1;
1146 out:
1147         put_task_struct(next_task);
1148
1149         return ret;
1150 }
1151
1152 /*
1153  * TODO: Currently we just use the second highest prio task on
1154  *       the queue, and stop when it can't migrate (or there's
1155  *       no more RT tasks).  There may be a case where a lower
1156  *       priority RT task has a different affinity than the
1157  *       higher RT task. In this case the lower RT task could
1158  *       possibly be able to migrate where as the higher priority
1159  *       RT task could not.  We currently ignore this issue.
1160  *       Enhancements are welcome!
1161  */
1162 static void push_rt_tasks(struct rq *rq)
1163 {
1164         /* push_rt_task will return true if it moved an RT */
1165         while (push_rt_task(rq))
1166                 ;
1167 }
1168
1169 static int pull_rt_task(struct rq *this_rq)
1170 {
1171         int this_cpu = this_rq->cpu, ret = 0, cpu;
1172         struct task_struct *p, *next;
1173         struct rq *src_rq;
1174
1175         if (likely(!rt_overloaded(this_rq)))
1176                 return 0;
1177
1178         next = pick_next_task_rt(this_rq);
1179
1180         for_each_cpu_mask_nr(cpu, this_rq->rd->rto_mask) {
1181                 if (this_cpu == cpu)
1182                         continue;
1183
1184                 src_rq = cpu_rq(cpu);
1185                 /*
1186                  * We can potentially drop this_rq's lock in
1187                  * double_lock_balance, and another CPU could
1188                  * steal our next task - hence we must cause
1189                  * the caller to recalculate the next task
1190                  * in that case:
1191                  */
1192                 if (double_lock_balance(this_rq, src_rq)) {
1193                         struct task_struct *old_next = next;
1194
1195                         next = pick_next_task_rt(this_rq);
1196                         if (next != old_next)
1197                                 ret = 1;
1198                 }
1199
1200                 /*
1201                  * Are there still pullable RT tasks?
1202                  */
1203                 if (src_rq->rt.rt_nr_running <= 1)
1204                         goto skip;
1205
1206                 p = pick_next_highest_task_rt(src_rq, this_cpu);
1207
1208                 /*
1209                  * Do we have an RT task that preempts
1210                  * the to-be-scheduled task?
1211                  */
1212                 if (p && (!next || (p->prio < next->prio))) {
1213                         WARN_ON(p == src_rq->curr);
1214                         WARN_ON(!p->se.on_rq);
1215
1216                         /*
1217                          * There's a chance that p is higher in priority
1218                          * than what's currently running on its cpu.
1219                          * This is just that p is wakeing up and hasn't
1220                          * had a chance to schedule. We only pull
1221                          * p if it is lower in priority than the
1222                          * current task on the run queue or
1223                          * this_rq next task is lower in prio than
1224                          * the current task on that rq.
1225                          */
1226                         if (p->prio < src_rq->curr->prio ||
1227                             (next && next->prio < src_rq->curr->prio))
1228                                 goto skip;
1229
1230                         ret = 1;
1231
1232                         deactivate_task(src_rq, p, 0);
1233                         set_task_cpu(p, this_cpu);
1234                         activate_task(this_rq, p, 0);
1235                         /*
1236                          * We continue with the search, just in
1237                          * case there's an even higher prio task
1238                          * in another runqueue. (low likelyhood
1239                          * but possible)
1240                          *
1241                          * Update next so that we won't pick a task
1242                          * on another cpu with a priority lower (or equal)
1243                          * than the one we just picked.
1244                          */
1245                         next = p;
1246
1247                 }
1248  skip:
1249                 double_unlock_balance(this_rq, src_rq);
1250         }
1251
1252         return ret;
1253 }
1254
1255 static void pre_schedule_rt(struct rq *rq, struct task_struct *prev)
1256 {
1257         /* Try to pull RT tasks here if we lower this rq's prio */
1258         if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
1259                 pull_rt_task(rq);
1260 }
1261
1262 static void post_schedule_rt(struct rq *rq)
1263 {
1264         /*
1265          * If we have more than one rt_task queued, then
1266          * see if we can push the other rt_tasks off to other CPUS.
1267          * Note we may release the rq lock, and since
1268          * the lock was owned by prev, we need to release it
1269          * first via finish_lock_switch and then reaquire it here.
1270          */
1271         if (unlikely(rq->rt.overloaded)) {
1272                 spin_lock_irq(&rq->lock);
1273                 push_rt_tasks(rq);
1274                 spin_unlock_irq(&rq->lock);
1275         }
1276 }
1277
1278 /*
1279  * If we are not running and we are not going to reschedule soon, we should
1280  * try to push tasks away now
1281  */
1282 static void task_wake_up_rt(struct rq *rq, struct task_struct *p)
1283 {
1284         if (!task_running(rq, p) &&
1285             !test_tsk_need_resched(rq->curr) &&
1286             rq->rt.overloaded)
1287                 push_rt_tasks(rq);
1288 }
1289
1290 static unsigned long
1291 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1292                 unsigned long max_load_move,
1293                 struct sched_domain *sd, enum cpu_idle_type idle,
1294                 int *all_pinned, int *this_best_prio)
1295 {
1296         /* don't touch RT tasks */
1297         return 0;
1298 }
1299
1300 static int
1301 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
1302                  struct sched_domain *sd, enum cpu_idle_type idle)
1303 {
1304         /* don't touch RT tasks */
1305         return 0;
1306 }
1307
1308 static void set_cpus_allowed_rt(struct task_struct *p,
1309                                 const cpumask_t *new_mask)
1310 {
1311         int weight = cpus_weight(*new_mask);
1312
1313         BUG_ON(!rt_task(p));
1314
1315         /*
1316          * Update the migration status of the RQ if we have an RT task
1317          * which is running AND changing its weight value.
1318          */
1319         if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
1320                 struct rq *rq = task_rq(p);
1321
1322                 if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
1323                         rq->rt.rt_nr_migratory++;
1324                 } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
1325                         BUG_ON(!rq->rt.rt_nr_migratory);
1326                         rq->rt.rt_nr_migratory--;
1327                 }
1328
1329                 update_rt_migration(rq);
1330         }
1331
1332         p->cpus_allowed    = *new_mask;
1333         p->rt.nr_cpus_allowed = weight;
1334 }
1335
1336 /* Assumes rq->lock is held */
1337 static void rq_online_rt(struct rq *rq)
1338 {
1339         if (rq->rt.overloaded)
1340                 rt_set_overload(rq);
1341
1342         __enable_runtime(rq);
1343
1344         cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);
1345 }
1346
1347 /* Assumes rq->lock is held */
1348 static void rq_offline_rt(struct rq *rq)
1349 {
1350         if (rq->rt.overloaded)
1351                 rt_clear_overload(rq);
1352
1353         __disable_runtime(rq);
1354
1355         cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);
1356 }
1357
1358 /*
1359  * When switch from the rt queue, we bring ourselves to a position
1360  * that we might want to pull RT tasks from other runqueues.
1361  */
1362 static void switched_from_rt(struct rq *rq, struct task_struct *p,
1363                            int running)
1364 {
1365         /*
1366          * If there are other RT tasks then we will reschedule
1367          * and the scheduling of the other RT tasks will handle
1368          * the balancing. But if we are the last RT task
1369          * we may need to handle the pulling of RT tasks
1370          * now.
1371          */
1372         if (!rq->rt.rt_nr_running)
1373                 pull_rt_task(rq);
1374 }
1375 #endif /* CONFIG_SMP */
1376
1377 /*
1378  * When switching a task to RT, we may overload the runqueue
1379  * with RT tasks. In this case we try to push them off to
1380  * other runqueues.
1381  */
1382 static void switched_to_rt(struct rq *rq, struct task_struct *p,
1383                            int running)
1384 {
1385         int check_resched = 1;
1386
1387         /*
1388          * If we are already running, then there's nothing
1389          * that needs to be done. But if we are not running
1390          * we may need to preempt the current running task.
1391          * If that current running task is also an RT task
1392          * then see if we can move to another run queue.
1393          */
1394         if (!running) {
1395 #ifdef CONFIG_SMP
1396                 if (rq->rt.overloaded && push_rt_task(rq) &&
1397                     /* Don't resched if we changed runqueues */
1398                     rq != task_rq(p))
1399                         check_resched = 0;
1400 #endif /* CONFIG_SMP */
1401                 if (check_resched && p->prio < rq->curr->prio)
1402                         resched_task(rq->curr);
1403         }
1404 }
1405
1406 /*
1407  * Priority of the task has changed. This may cause
1408  * us to initiate a push or pull.
1409  */
1410 static void prio_changed_rt(struct rq *rq, struct task_struct *p,
1411                             int oldprio, int running)
1412 {
1413         if (running) {
1414 #ifdef CONFIG_SMP
1415                 /*
1416                  * If our priority decreases while running, we
1417                  * may need to pull tasks to this runqueue.
1418                  */
1419                 if (oldprio < p->prio)
1420                         pull_rt_task(rq);
1421                 /*
1422                  * If there's a higher priority task waiting to run
1423                  * then reschedule. Note, the above pull_rt_task
1424                  * can release the rq lock and p could migrate.
1425                  * Only reschedule if p is still on the same runqueue.
1426                  */
1427                 if (p->prio > rq->rt.highest_prio && rq->curr == p)
1428                         resched_task(p);
1429 #else
1430                 /* For UP simply resched on drop of prio */
1431                 if (oldprio < p->prio)
1432                         resched_task(p);
1433 #endif /* CONFIG_SMP */
1434         } else {
1435                 /*
1436                  * This task is not running, but if it is
1437                  * greater than the current running task
1438                  * then reschedule.
1439                  */
1440                 if (p->prio < rq->curr->prio)
1441                         resched_task(rq->curr);
1442         }
1443 }
1444
1445 static void watchdog(struct rq *rq, struct task_struct *p)
1446 {
1447         unsigned long soft, hard;
1448
1449         if (!p->signal)
1450                 return;
1451
1452         soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
1453         hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
1454
1455         if (soft != RLIM_INFINITY) {
1456                 unsigned long next;
1457
1458                 p->rt.timeout++;
1459                 next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
1460                 if (p->rt.timeout > next)
1461                         p->it_sched_expires = p->se.sum_exec_runtime;
1462         }
1463 }
1464
1465 static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
1466 {
1467         update_curr_rt(rq);
1468
1469         watchdog(rq, p);
1470
1471         /*
1472          * RR tasks need a special form of timeslice management.
1473          * FIFO tasks have no timeslices.
1474          */
1475         if (p->policy != SCHED_RR)
1476                 return;
1477
1478         if (--p->rt.time_slice)
1479                 return;
1480
1481         p->rt.time_slice = DEF_TIMESLICE;
1482
1483         /*
1484          * Requeue to the end of queue if we are not the only element
1485          * on the queue:
1486          */
1487         if (p->rt.run_list.prev != p->rt.run_list.next) {
1488                 requeue_task_rt(rq, p, 0);
1489                 set_tsk_need_resched(p);
1490         }
1491 }
1492
1493 static void set_curr_task_rt(struct rq *rq)
1494 {
1495         struct task_struct *p = rq->curr;
1496
1497         p->se.exec_start = rq->clock;
1498 }
1499
1500 static const struct sched_class rt_sched_class = {
1501         .next                   = &fair_sched_class,
1502         .enqueue_task           = enqueue_task_rt,
1503         .dequeue_task           = dequeue_task_rt,
1504         .yield_task             = yield_task_rt,
1505 #ifdef CONFIG_SMP
1506         .select_task_rq         = select_task_rq_rt,
1507 #endif /* CONFIG_SMP */
1508
1509         .check_preempt_curr     = check_preempt_curr_rt,
1510
1511         .pick_next_task         = pick_next_task_rt,
1512         .put_prev_task          = put_prev_task_rt,
1513
1514 #ifdef CONFIG_SMP
1515         .load_balance           = load_balance_rt,
1516         .move_one_task          = move_one_task_rt,
1517         .set_cpus_allowed       = set_cpus_allowed_rt,
1518         .rq_online              = rq_online_rt,
1519         .rq_offline             = rq_offline_rt,
1520         .pre_schedule           = pre_schedule_rt,
1521         .post_schedule          = post_schedule_rt,
1522         .task_wake_up           = task_wake_up_rt,
1523         .switched_from          = switched_from_rt,
1524 #endif
1525
1526         .set_curr_task          = set_curr_task_rt,
1527         .task_tick              = task_tick_rt,
1528
1529         .prio_changed           = prio_changed_rt,
1530         .switched_to            = switched_to_rt,
1531 };
1532
1533 #ifdef CONFIG_SCHED_DEBUG
1534 extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1535
1536 static void print_rt_stats(struct seq_file *m, int cpu)
1537 {
1538         struct rt_rq *rt_rq;
1539
1540         rcu_read_lock();
1541         for_each_leaf_rt_rq(rt_rq, cpu_rq(cpu))
1542                 print_rt_rq(m, cpu, rt_rq);
1543         rcu_read_unlock();
1544 }
1545 #endif /* CONFIG_SCHED_DEBUG */