linux/kernel/smp.c
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   1/*
   2 * Generic helpers for smp ipi calls
   3 *
   4 * (C) Jens Axboe <jens.axboe@oracle.com> 2008
   5 */
   6#include <linux/rcupdate.h>
   7#include <linux/rculist.h>
   8#include <linux/kernel.h>
   9#include <linux/export.h>
  10#include <linux/percpu.h>
  11#include <linux/init.h>
  12#include <linux/gfp.h>
  13#include <linux/smp.h>
  14#include <linux/cpu.h>
  15
  16#include "smpboot.h"
  17
  18#ifdef CONFIG_USE_GENERIC_SMP_HELPERS
  19static struct {
  20        struct list_head        queue;
  21        raw_spinlock_t          lock;
  22} call_function __cacheline_aligned_in_smp =
  23        {
  24                .queue          = LIST_HEAD_INIT(call_function.queue),
  25                .lock           = __RAW_SPIN_LOCK_UNLOCKED(call_function.lock),
  26        };
  27
  28enum {
  29        CSD_FLAG_LOCK           = 0x01,
  30};
  31
  32struct call_function_data {
  33        struct call_single_data csd;
  34        atomic_t                refs;
  35        cpumask_var_t           cpumask;
  36};
  37
  38static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
  39
  40struct call_single_queue {
  41        struct list_head        list;
  42        raw_spinlock_t          lock;
  43};
  44
  45static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_queue, call_single_queue);
  46
  47static int
  48hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
  49{
  50        long cpu = (long)hcpu;
  51        struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
  52
  53        switch (action) {
  54        case CPU_UP_PREPARE:
  55        case CPU_UP_PREPARE_FROZEN:
  56                if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
  57                                cpu_to_node(cpu)))
  58                        return notifier_from_errno(-ENOMEM);
  59                break;
  60
  61#ifdef CONFIG_HOTPLUG_CPU
  62        case CPU_UP_CANCELED:
  63        case CPU_UP_CANCELED_FROZEN:
  64
  65        case CPU_DEAD:
  66        case CPU_DEAD_FROZEN:
  67                free_cpumask_var(cfd->cpumask);
  68                break;
  69#endif
  70        };
  71
  72        return NOTIFY_OK;
  73}
  74
  75static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
  76        .notifier_call          = hotplug_cfd,
  77};
  78
  79void __init call_function_init(void)
  80{
  81        void *cpu = (void *)(long)smp_processor_id();
  82        int i;
  83
  84        for_each_possible_cpu(i) {
  85                struct call_single_queue *q = &per_cpu(call_single_queue, i);
  86
  87                raw_spin_lock_init(&q->lock);
  88                INIT_LIST_HEAD(&q->list);
  89        }
  90
  91        hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
  92        register_cpu_notifier(&hotplug_cfd_notifier);
  93}
  94
  95/*
  96 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
  97 *
  98 * For non-synchronous ipi calls the csd can still be in use by the
  99 * previous function call. For multi-cpu calls its even more interesting
 100 * as we'll have to ensure no other cpu is observing our csd.
 101 */
 102static void csd_lock_wait(struct call_single_data *data)
 103{
 104        while (data->flags & CSD_FLAG_LOCK)
 105                cpu_relax();
 106}
 107
 108static void csd_lock(struct call_single_data *data)
 109{
 110        csd_lock_wait(data);
 111        data->flags = CSD_FLAG_LOCK;
 112
 113        /*
 114         * prevent CPU from reordering the above assignment
 115         * to ->flags with any subsequent assignments to other
 116         * fields of the specified call_single_data structure:
 117         */
 118        smp_mb();
 119}
 120
 121static void csd_unlock(struct call_single_data *data)
 122{
 123        WARN_ON(!(data->flags & CSD_FLAG_LOCK));
 124
 125        /*
 126         * ensure we're all done before releasing data:
 127         */
 128        smp_mb();
 129
 130        data->flags &= ~CSD_FLAG_LOCK;
 131}
 132
 133/*
 134 * Insert a previously allocated call_single_data element
 135 * for execution on the given CPU. data must already have
 136 * ->func, ->info, and ->flags set.
 137 */
 138static
 139void generic_exec_single(int cpu, struct call_single_data *data, int wait)
 140{
 141        struct call_single_queue *dst = &per_cpu(call_single_queue, cpu);
 142        unsigned long flags;
 143        int ipi;
 144
 145        raw_spin_lock_irqsave(&dst->lock, flags);
 146        ipi = list_empty(&dst->list);
 147        list_add_tail(&data->list, &dst->list);
 148        raw_spin_unlock_irqrestore(&dst->lock, flags);
 149
 150        /*
 151         * The list addition should be visible before sending the IPI
 152         * handler locks the list to pull the entry off it because of
 153         * normal cache coherency rules implied by spinlocks.
 154         *
 155         * If IPIs can go out of order to the cache coherency protocol
 156         * in an architecture, sufficient synchronisation should be added
 157         * to arch code to make it appear to obey cache coherency WRT
 158         * locking and barrier primitives. Generic code isn't really
 159         * equipped to do the right thing...
 160         */
 161        if (ipi)
 162                arch_send_call_function_single_ipi(cpu);
 163
 164        if (wait)
 165                csd_lock_wait(data);
 166}
 167
 168/*
 169 * Invoked by arch to handle an IPI for call function. Must be called with
 170 * interrupts disabled.
 171 */
 172void generic_smp_call_function_interrupt(void)
 173{
 174        struct call_function_data *data;
 175        int cpu = smp_processor_id();
 176
 177        /*
 178         * Shouldn't receive this interrupt on a cpu that is not yet online.
 179         */
 180        WARN_ON_ONCE(!cpu_online(cpu));
 181
 182        /*
 183         * Ensure entry is visible on call_function_queue after we have
 184         * entered the IPI. See comment in smp_call_function_many.
 185         * If we don't have this, then we may miss an entry on the list
 186         * and never get another IPI to process it.
 187         */
 188        smp_mb();
 189
 190        /*
 191         * It's ok to use list_for_each_rcu() here even though we may
 192         * delete 'pos', since list_del_rcu() doesn't clear ->next
 193         */
 194        list_for_each_entry_rcu(data, &call_function.queue, csd.list) {
 195                int refs;
 196                smp_call_func_t func;
 197
 198                /*
 199                 * Since we walk the list without any locks, we might
 200                 * see an entry that was completed, removed from the
 201                 * list and is in the process of being reused.
 202                 *
 203                 * We must check that the cpu is in the cpumask before
 204                 * checking the refs, and both must be set before
 205                 * executing the callback on this cpu.
 206                 */
 207
 208                if (!cpumask_test_cpu(cpu, data->cpumask))
 209                        continue;
 210
 211                smp_rmb();
 212
 213                if (atomic_read(&data->refs) == 0)
 214                        continue;
 215
 216                func = data->csd.func;          /* save for later warn */
 217                func(data->csd.info);
 218
 219                /*
 220                 * If the cpu mask is not still set then func enabled
 221                 * interrupts (BUG), and this cpu took another smp call
 222                 * function interrupt and executed func(info) twice
 223                 * on this cpu.  That nested execution decremented refs.
 224                 */
 225                if (!cpumask_test_and_clear_cpu(cpu, data->cpumask)) {
 226                        WARN(1, "%pf enabled interrupts and double executed\n", func);
 227                        continue;
 228                }
 229
 230                refs = atomic_dec_return(&data->refs);
 231                WARN_ON(refs < 0);
 232
 233                if (refs)
 234                        continue;
 235
 236                WARN_ON(!cpumask_empty(data->cpumask));
 237
 238                raw_spin_lock(&call_function.lock);
 239                list_del_rcu(&data->csd.list);
 240                raw_spin_unlock(&call_function.lock);
 241
 242                csd_unlock(&data->csd);
 243        }
 244
 245}
 246
 247/*
 248 * Invoked by arch to handle an IPI for call function single. Must be
 249 * called from the arch with interrupts disabled.
 250 */
 251void generic_smp_call_function_single_interrupt(void)
 252{
 253        struct call_single_queue *q = &__get_cpu_var(call_single_queue);
 254        unsigned int data_flags;
 255        LIST_HEAD(list);
 256
 257        /*
 258         * Shouldn't receive this interrupt on a cpu that is not yet online.
 259         */
 260        WARN_ON_ONCE(!cpu_online(smp_processor_id()));
 261
 262        raw_spin_lock(&q->lock);
 263        list_replace_init(&q->list, &list);
 264        raw_spin_unlock(&q->lock);
 265
 266        while (!list_empty(&list)) {
 267                struct call_single_data *data;
 268
 269                data = list_entry(list.next, struct call_single_data, list);
 270                list_del(&data->list);
 271
 272                /*
 273                 * 'data' can be invalid after this call if flags == 0
 274                 * (when called through generic_exec_single()),
 275                 * so save them away before making the call:
 276                 */
 277                data_flags = data->flags;
 278
 279                data->func(data->info);
 280
 281                /*
 282                 * Unlocked CSDs are valid through generic_exec_single():
 283                 */
 284                if (data_flags & CSD_FLAG_LOCK)
 285                        csd_unlock(data);
 286        }
 287}
 288
 289static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_single_data, csd_data);
 290
 291/*
 292 * smp_call_function_single - Run a function on a specific CPU
 293 * @func: The function to run. This must be fast and non-blocking.
 294 * @info: An arbitrary pointer to pass to the function.
 295 * @wait: If true, wait until function has completed on other CPUs.
 296 *
 297 * Returns 0 on success, else a negative status code.
 298 */
 299int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
 300                             int wait)
 301{
 302        struct call_single_data d = {
 303                .flags = 0,
 304        };
 305        unsigned long flags;
 306        int this_cpu;
 307        int err = 0;
 308
 309        /*
 310         * prevent preemption and reschedule on another processor,
 311         * as well as CPU removal
 312         */
 313        this_cpu = get_cpu();
 314
 315        /*
 316         * Can deadlock when called with interrupts disabled.
 317         * We allow cpu's that are not yet online though, as no one else can
 318         * send smp call function interrupt to this cpu and as such deadlocks
 319         * can't happen.
 320         */
 321        WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
 322                     && !oops_in_progress);
 323
 324        if (cpu == this_cpu) {
 325                local_irq_save(flags);
 326                func(info);
 327                local_irq_restore(flags);
 328        } else {
 329                if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
 330                        struct call_single_data *data = &d;
 331
 332                        if (!wait)
 333                                data = &__get_cpu_var(csd_data);
 334
 335                        csd_lock(data);
 336
 337                        data->func = func;
 338                        data->info = info;
 339                        generic_exec_single(cpu, data, wait);
 340                } else {
 341                        err = -ENXIO;   /* CPU not online */
 342                }
 343        }
 344
 345        put_cpu();
 346
 347        return err;
 348}
 349EXPORT_SYMBOL(smp_call_function_single);
 350
 351/*
 352 * smp_call_function_any - Run a function on any of the given cpus
 353 * @mask: The mask of cpus it can run on.
 354 * @func: The function to run. This must be fast and non-blocking.
 355 * @info: An arbitrary pointer to pass to the function.
 356 * @wait: If true, wait until function has completed.
 357 *
 358 * Returns 0 on success, else a negative status code (if no cpus were online).
 359 * Note that @wait will be implicitly turned on in case of allocation failures,
 360 * since we fall back to on-stack allocation.
 361 *
 362 * Selection preference:
 363 *      1) current cpu if in @mask
 364 *      2) any cpu of current node if in @mask
 365 *      3) any other online cpu in @mask
 366 */
 367int smp_call_function_any(const struct cpumask *mask,
 368                          smp_call_func_t func, void *info, int wait)
 369{
 370        unsigned int cpu;
 371        const struct cpumask *nodemask;
 372        int ret;
 373
 374        /* Try for same CPU (cheapest) */
 375        cpu = get_cpu();
 376        if (cpumask_test_cpu(cpu, mask))
 377                goto call;
 378
 379        /* Try for same node. */
 380        nodemask = cpumask_of_node(cpu_to_node(cpu));
 381        for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
 382             cpu = cpumask_next_and(cpu, nodemask, mask)) {
 383                if (cpu_online(cpu))
 384                        goto call;
 385        }
 386
 387        /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
 388        cpu = cpumask_any_and(mask, cpu_online_mask);
 389call:
 390        ret = smp_call_function_single(cpu, func, info, wait);
 391        put_cpu();
 392        return ret;
 393}
 394EXPORT_SYMBOL_GPL(smp_call_function_any);
 395
 396/**
 397 * __smp_call_function_single(): Run a function on a specific CPU
 398 * @cpu: The CPU to run on.
 399 * @data: Pre-allocated and setup data structure
 400 * @wait: If true, wait until function has completed on specified CPU.
 401 *
 402 * Like smp_call_function_single(), but allow caller to pass in a
 403 * pre-allocated data structure. Useful for embedding @data inside
 404 * other structures, for instance.
 405 */
 406void __smp_call_function_single(int cpu, struct call_single_data *data,
 407                                int wait)
 408{
 409        unsigned int this_cpu;
 410        unsigned long flags;
 411
 412        this_cpu = get_cpu();
 413        /*
 414         * Can deadlock when called with interrupts disabled.
 415         * We allow cpu's that are not yet online though, as no one else can
 416         * send smp call function interrupt to this cpu and as such deadlocks
 417         * can't happen.
 418         */
 419        WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled()
 420                     && !oops_in_progress);
 421
 422        if (cpu == this_cpu) {
 423                local_irq_save(flags);
 424                data->func(data->info);
 425                local_irq_restore(flags);
 426        } else {
 427                csd_lock(data);
 428                generic_exec_single(cpu, data, wait);
 429        }
 430        put_cpu();
 431}
 432
 433/**
 434 * smp_call_function_many(): Run a function on a set of other CPUs.
 435 * @mask: The set of cpus to run on (only runs on online subset).
 436 * @func: The function to run. This must be fast and non-blocking.
 437 * @info: An arbitrary pointer to pass to the function.
 438 * @wait: If true, wait (atomically) until function has completed
 439 *        on other CPUs.
 440 *
 441 * If @wait is true, then returns once @func has returned.
 442 *
 443 * You must not call this function with disabled interrupts or from a
 444 * hardware interrupt handler or from a bottom half handler. Preemption
 445 * must be disabled when calling this function.
 446 */
 447void smp_call_function_many(const struct cpumask *mask,
 448                            smp_call_func_t func, void *info, bool wait)
 449{
 450        struct call_function_data *data;
 451        unsigned long flags;
 452        int refs, cpu, next_cpu, this_cpu = smp_processor_id();
 453
 454        /*
 455         * Can deadlock when called with interrupts disabled.
 456         * We allow cpu's that are not yet online though, as no one else can
 457         * send smp call function interrupt to this cpu and as such deadlocks
 458         * can't happen.
 459         */
 460        WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
 461                     && !oops_in_progress && !early_boot_irqs_disabled);
 462
 463        /* Try to fastpath.  So, what's a CPU they want? Ignoring this one. */
 464        cpu = cpumask_first_and(mask, cpu_online_mask);
 465        if (cpu == this_cpu)
 466                cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
 467
 468        /* No online cpus?  We're done. */
 469        if (cpu >= nr_cpu_ids)
 470                return;
 471
 472        /* Do we have another CPU which isn't us? */
 473        next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
 474        if (next_cpu == this_cpu)
 475                next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask);
 476
 477        /* Fastpath: do that cpu by itself. */
 478        if (next_cpu >= nr_cpu_ids) {
 479                smp_call_function_single(cpu, func, info, wait);
 480                return;
 481        }
 482
 483        data = &__get_cpu_var(cfd_data);
 484        csd_lock(&data->csd);
 485
 486        /* This BUG_ON verifies our reuse assertions and can be removed */
 487        BUG_ON(atomic_read(&data->refs) || !cpumask_empty(data->cpumask));
 488
 489        /*
 490         * The global call function queue list add and delete are protected
 491         * by a lock, but the list is traversed without any lock, relying
 492         * on the rcu list add and delete to allow safe concurrent traversal.
 493         * We reuse the call function data without waiting for any grace
 494         * period after some other cpu removes it from the global queue.
 495         * This means a cpu might find our data block as it is being
 496         * filled out.
 497         *
 498         * We hold off the interrupt handler on the other cpu by
 499         * ordering our writes to the cpu mask vs our setting of the
 500         * refs counter.  We assert only the cpu owning the data block
 501         * will set a bit in cpumask, and each bit will only be cleared
 502         * by the subject cpu.  Each cpu must first find its bit is
 503         * set and then check that refs is set indicating the element is
 504         * ready to be processed, otherwise it must skip the entry.
 505         *
 506         * On the previous iteration refs was set to 0 by another cpu.
 507         * To avoid the use of transitivity, set the counter to 0 here
 508         * so the wmb will pair with the rmb in the interrupt handler.
 509         */
 510        atomic_set(&data->refs, 0);     /* convert 3rd to 1st party write */
 511
 512        data->csd.func = func;
 513        data->csd.info = info;
 514
 515        /* Ensure 0 refs is visible before mask.  Also orders func and info */
 516        smp_wmb();
 517
 518        /* We rely on the "and" being processed before the store */
 519        cpumask_and(data->cpumask, mask, cpu_online_mask);
 520        cpumask_clear_cpu(this_cpu, data->cpumask);
 521        refs = cpumask_weight(data->cpumask);
 522
 523        /* Some callers race with other cpus changing the passed mask */
 524        if (unlikely(!refs)) {
 525                csd_unlock(&data->csd);
 526                return;
 527        }
 528
 529        raw_spin_lock_irqsave(&call_function.lock, flags);
 530        /*
 531         * Place entry at the _HEAD_ of the list, so that any cpu still
 532         * observing the entry in generic_smp_call_function_interrupt()
 533         * will not miss any other list entries:
 534         */
 535        list_add_rcu(&data->csd.list, &call_function.queue);
 536        /*
 537         * We rely on the wmb() in list_add_rcu to complete our writes
 538         * to the cpumask before this write to refs, which indicates
 539         * data is on the list and is ready to be processed.
 540         */
 541        atomic_set(&data->refs, refs);
 542        raw_spin_unlock_irqrestore(&call_function.lock, flags);
 543
 544        /*
 545         * Make the list addition visible before sending the ipi.
 546         * (IPIs must obey or appear to obey normal Linux cache
 547         * coherency rules -- see comment in generic_exec_single).
 548         */
 549        smp_mb();
 550
 551        /* Send a message to all CPUs in the map */
 552        arch_send_call_function_ipi_mask(data->cpumask);
 553
 554        /* Optionally wait for the CPUs to complete */
 555        if (wait)
 556                csd_lock_wait(&data->csd);
 557}
 558EXPORT_SYMBOL(smp_call_function_many);
 559
 560/**
 561 * smp_call_function(): Run a function on all other CPUs.
 562 * @func: The function to run. This must be fast and non-blocking.
 563 * @info: An arbitrary pointer to pass to the function.
 564 * @wait: If true, wait (atomically) until function has completed
 565 *        on other CPUs.
 566 *
 567 * Returns 0.
 568 *
 569 * If @wait is true, then returns once @func has returned; otherwise
 570 * it returns just before the target cpu calls @func.
 571 *
 572 * You must not call this function with disabled interrupts or from a
 573 * hardware interrupt handler or from a bottom half handler.
 574 */
 575int smp_call_function(smp_call_func_t func, void *info, int wait)
 576{
 577        preempt_disable();
 578        smp_call_function_many(cpu_online_mask, func, info, wait);
 579        preempt_enable();
 580
 581        return 0;
 582}
 583EXPORT_SYMBOL(smp_call_function);
 584#endif /* USE_GENERIC_SMP_HELPERS */
 585
 586/* Setup configured maximum number of CPUs to activate */
 587unsigned int setup_max_cpus = NR_CPUS;
 588EXPORT_SYMBOL(setup_max_cpus);
 589
 590
 591/*
 592 * Setup routine for controlling SMP activation
 593 *
 594 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP
 595 * activation entirely (the MPS table probe still happens, though).
 596 *
 597 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer
 598 * greater than 0, limits the maximum number of CPUs activated in
 599 * SMP mode to <NUM>.
 600 */
 601
 602void __weak arch_disable_smp_support(void) { }
 603
 604static int __init nosmp(char *str)
 605{
 606        setup_max_cpus = 0;
 607        arch_disable_smp_support();
 608
 609        return 0;
 610}
 611
 612early_param("nosmp", nosmp);
 613
 614/* this is hard limit */
 615static int __init nrcpus(char *str)
 616{
 617        int nr_cpus;
 618
 619        get_option(&str, &nr_cpus);
 620        if (nr_cpus > 0 && nr_cpus < nr_cpu_ids)
 621                nr_cpu_ids = nr_cpus;
 622
 623        return 0;
 624}
 625
 626early_param("nr_cpus", nrcpus);
 627
 628static int __init maxcpus(char *str)
 629{
 630        get_option(&str, &setup_max_cpus);
 631        if (setup_max_cpus == 0)
 632                arch_disable_smp_support();
 633
 634        return 0;
 635}
 636
 637early_param("maxcpus", maxcpus);
 638
 639/* Setup number of possible processor ids */
 640int nr_cpu_ids __read_mostly = NR_CPUS;
 641EXPORT_SYMBOL(nr_cpu_ids);
 642
 643/* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */
 644void __init setup_nr_cpu_ids(void)
 645{
 646        nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
 647}
 648
 649/* Called by boot processor to activate the rest. */
 650void __init smp_init(void)
 651{
 652        unsigned int cpu;
 653
 654        idle_threads_init();
 655
 656        /* FIXME: This should be done in userspace --RR */
 657        for_each_present_cpu(cpu) {
 658                if (num_online_cpus() >= setup_max_cpus)
 659                        break;
 660                if (!cpu_online(cpu))
 661                        cpu_up(cpu);
 662        }
 663
 664        /* Any cleanup work */
 665        printk(KERN_INFO "Brought up %ld CPUs\n", (long)num_online_cpus());
 666        smp_cpus_done(setup_max_cpus);
 667}
 668
 669/*
 670 * Call a function on all processors.  May be used during early boot while
 671 * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
 672 * of local_irq_disable/enable().
 673 */
 674int on_each_cpu(void (*func) (void *info), void *info, int wait)
 675{
 676        unsigned long flags;
 677        int ret = 0;
 678
 679        preempt_disable();
 680        ret = smp_call_function(func, info, wait);
 681        local_irq_save(flags);
 682        func(info);
 683        local_irq_restore(flags);
 684        preempt_enable();
 685        return ret;
 686}
 687EXPORT_SYMBOL(on_each_cpu);
 688
 689/**
 690 * on_each_cpu_mask(): Run a function on processors specified by
 691 * cpumask, which may include the local processor.
 692 * @mask: The set of cpus to run on (only runs on online subset).
 693 * @func: The function to run. This must be fast and non-blocking.
 694 * @info: An arbitrary pointer to pass to the function.
 695 * @wait: If true, wait (atomically) until function has completed
 696 *        on other CPUs.
 697 *
 698 * If @wait is true, then returns once @func has returned.
 699 *
 700 * You must not call this function with disabled interrupts or
 701 * from a hardware interrupt handler or from a bottom half handler.
 702 */
 703void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
 704                        void *info, bool wait)
 705{
 706        int cpu = get_cpu();
 707
 708        smp_call_function_many(mask, func, info, wait);
 709        if (cpumask_test_cpu(cpu, mask)) {
 710                local_irq_disable();
 711                func(info);
 712                local_irq_enable();
 713        }
 714        put_cpu();
 715}
 716EXPORT_SYMBOL(on_each_cpu_mask);
 717
 718/*
 719 * on_each_cpu_cond(): Call a function on each processor for which
 720 * the supplied function cond_func returns true, optionally waiting
 721 * for all the required CPUs to finish. This may include the local
 722 * processor.
 723 * @cond_func:  A callback function that is passed a cpu id and
 724 *              the the info parameter. The function is called
 725 *              with preemption disabled. The function should
 726 *              return a blooean value indicating whether to IPI
 727 *              the specified CPU.
 728 * @func:       The function to run on all applicable CPUs.
 729 *              This must be fast and non-blocking.
 730 * @info:       An arbitrary pointer to pass to both functions.
 731 * @wait:       If true, wait (atomically) until function has
 732 *              completed on other CPUs.
 733 * @gfp_flags:  GFP flags to use when allocating the cpumask
 734 *              used internally by the function.
 735 *
 736 * The function might sleep if the GFP flags indicates a non
 737 * atomic allocation is allowed.
 738 *
 739 * Preemption is disabled to protect against CPUs going offline but not online.
 740 * CPUs going online during the call will not be seen or sent an IPI.
 741 *
 742 * You must not call this function with disabled interrupts or
 743 * from a hardware interrupt handler or from a bottom half handler.
 744 */
 745void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
 746                        smp_call_func_t func, void *info, bool wait,
 747                        gfp_t gfp_flags)
 748{
 749        cpumask_var_t cpus;
 750        int cpu, ret;
 751
 752        might_sleep_if(gfp_flags & __GFP_WAIT);
 753
 754        if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
 755                preempt_disable();
 756                for_each_online_cpu(cpu)
 757                        if (cond_func(cpu, info))
 758                                cpumask_set_cpu(cpu, cpus);
 759                on_each_cpu_mask(cpus, func, info, wait);
 760                preempt_enable();
 761                free_cpumask_var(cpus);
 762        } else {
 763                /*
 764                 * No free cpumask, bother. No matter, we'll
 765                 * just have to IPI them one by one.
 766                 */
 767                preempt_disable();
 768                for_each_online_cpu(cpu)
 769                        if (cond_func(cpu, info)) {
 770                                ret = smp_call_function_single(cpu, func,
 771                                                                info, wait);
 772                                WARN_ON_ONCE(!ret);
 773                        }
 774                preempt_enable();
 775        }
 776}
 777EXPORT_SYMBOL(on_each_cpu_cond);
 778
 779static void do_nothing(void *unused)
 780{
 781}
 782
 783/**
 784 * kick_all_cpus_sync - Force all cpus out of idle
 785 *
 786 * Used to synchronize the update of pm_idle function pointer. It's
 787 * called after the pointer is updated and returns after the dummy
 788 * callback function has been executed on all cpus. The execution of
 789 * the function can only happen on the remote cpus after they have
 790 * left the idle function which had been called via pm_idle function
 791 * pointer. So it's guaranteed that nothing uses the previous pointer
 792 * anymore.
 793 */
 794void kick_all_cpus_sync(void)
 795{
 796        /* Make sure the change is visible before we kick the cpus */
 797        smp_mb();
 798        smp_call_function(do_nothing, NULL, 1);
 799}
 800EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
 801
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