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