kernel/sched_rt.c

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