kernel/workqueue.c

   1 /*
   2  * linux/kernel/workqueue.c
   3  *
   4  * Generic mechanism for defining kernel helper threads for running
   5  * arbitrary tasks in process context.
   6  *
   7  * Started by Ingo Molnar, Copyright (C) 2002
   8  *
   9  * Derived from the taskqueue/keventd code by:
  10  *
  11  *   David Woodhouse <dwmw2@infradead.org>
  12  *   Andrew Morton <andrewm@uow.edu.au>
  13  *   Kai Petzke <wpp@marie.physik.tu-berlin.de>
  14  *   Theodore Ts'o <tytso@mit.edu>
  15  *
  16  * Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/kernel.h>
  21 #include <linux/sched.h>
  22 #include <linux/init.h>
  23 #include <linux/signal.h>
  24 #include <linux/completion.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/slab.h>
  27 #include <linux/cpu.h>
  28 #include <linux/notifier.h>
  29 #include <linux/kthread.h>
  30 #include <linux/hardirq.h>
  31 #include <linux/mempolicy.h>
  32
  33 /*
  34  * The per-CPU workqueue (if single thread, we always use the first
  35  * possible cpu).
  36  *
  37  * The sequence counters are for flush_scheduled_work().  It wants to wait
  38  * until all currently-scheduled works are completed, but it doesn't
  39  * want to be livelocked by new, incoming ones.  So it waits until
  40  * remove_sequence is >= the insert_sequence which pertained when
  41  * flush_scheduled_work() was called.
  42  */
  43 struct cpu_workqueue_struct {
  44
  45         spinlock_t lock;
  46
  47         long remove_sequence;   /* Least-recently added (next to run) */
  48         long insert_sequence;   /* Next to add */
  49
  50         struct list_head worklist;
  51         wait_queue_head_t more_work;
  52         wait_queue_head_t work_done;
  53
  54         struct workqueue_struct *wq;
  55         struct task_struct *thread;
  56
  57         int run_depth;          /* Detect run_workqueue() recursion depth */
  58 } ____cacheline_aligned;
  59
  60 /*
  61  * The externally visible workqueue abstraction is an array of
  62  * per-CPU workqueues:
  63  */
  64 struct workqueue_struct {
  65         struct cpu_workqueue_struct *cpu_wq;
  66         const char *name;
  67         struct list_head list;  /* Empty if single thread */
  68 };
  69
  70 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  71    threads to each one as cpus come/go. */
  72 static DEFINE_MUTEX(workqueue_mutex);
  73 static LIST_HEAD(workqueues);
  74
  75 static int singlethread_cpu;
  76
  77 /* If it's single threaded, it isn't in the list of workqueues. */
  78 static inline int is_single_threaded(struct workqueue_struct *wq)
  79 {
  80         return list_empty(&wq->list);
  81 }
  82
  83 /* Preempt must be disabled. */
  84 static void __queue_work(struct cpu_workqueue_struct *cwq,
  85                          struct work_struct *work)
  86 {
  87         unsigned long flags;
  88
  89         spin_lock_irqsave(&cwq->lock, flags);
  90         work->wq_data = cwq;
  91         list_add_tail(&work->entry, &cwq->worklist);
  92         cwq->insert_sequence++;
  93         wake_up(&cwq->more_work);
  94         spin_unlock_irqrestore(&cwq->lock, flags);
  95 }
  96
  97 /**
  98  * queue_work - queue work on a workqueue
  99  * @wq: workqueue to use
 100  * @work: work to queue
 101  *
 102  * Returns 0 if @work was already on a queue, non-zero otherwise.
 103  *
 104  * We queue the work to the CPU it was submitted, but there is no
 105  * guarantee that it will be processed by that CPU.
 106  */
 107 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 108 {
 109         int ret = 0, cpu = get_cpu();
 110
 111         if (!test_and_set_bit(0, &work->pending)) {
 112                 if (unlikely(is_single_threaded(wq)))
 113                         cpu = singlethread_cpu;
 114                 BUG_ON(!list_empty(&work->entry));
 115                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 116                 ret = 1;
 117         }
 118         put_cpu();
 119         return ret;
 120 }
 121 EXPORT_SYMBOL_GPL(queue_work);
 122
 123 static void delayed_work_timer_fn(unsigned long __data)
 124 {
 125         struct delayed_work *dwork = (struct delayed_work *)__data;
 126         struct workqueue_struct *wq = dwork->work.wq_data;
 127         int cpu = smp_processor_id();
 128
 129         if (unlikely(is_single_threaded(wq)))
 130                 cpu = singlethread_cpu;
 131
 132         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
 133 }
 134
 135 /**
 136  * queue_delayed_work - queue work on a workqueue after delay
 137  * @wq: workqueue to use
 138  * @work: delayable work to queue
 139  * @delay: number of jiffies to wait before queueing
 140  *
 141  * Returns 0 if @work was already on a queue, non-zero otherwise.
 142  */
 143 int fastcall queue_delayed_work(struct workqueue_struct *wq,
 144                         struct delayed_work *dwork, unsigned long delay)
 145 {
 146         int ret = 0;
 147         struct timer_list *timer = &dwork->timer;
 148         struct work_struct *work = &dwork->work;
 149
 150         if (delay == 0)
 151                 return queue_work(wq, work);
 152
 153         if (!test_and_set_bit(0, &work->pending)) {
 154                 BUG_ON(timer_pending(timer));
 155                 BUG_ON(!list_empty(&work->entry));
 156
 157                 /* This stores wq for the moment, for the timer_fn */
 158                 work->wq_data = wq;
 159                 timer->expires = jiffies + delay;
 160                 timer->data = (unsigned long)dwork;
 161                 timer->function = delayed_work_timer_fn;
 162                 add_timer(timer);
 163                 ret = 1;
 164         }
 165         return ret;
 166 }
 167 EXPORT_SYMBOL_GPL(queue_delayed_work);
 168
 169 /**
 170  * queue_delayed_work_on - queue work on specific CPU after delay
 171  * @cpu: CPU number to execute work on
 172  * @wq: workqueue to use
 173  * @work: work to queue
 174  * @delay: number of jiffies to wait before queueing
 175  *
 176  * Returns 0 if @work was already on a queue, non-zero otherwise.
 177  */
 178 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 179                         struct delayed_work *dwork, unsigned long delay)
 180 {
 181         int ret = 0;
 182         struct timer_list *timer = &dwork->timer;
 183         struct work_struct *work = &dwork->work;
 184
 185         if (!test_and_set_bit(0, &work->pending)) {
 186                 BUG_ON(timer_pending(timer));
 187                 BUG_ON(!list_empty(&work->entry));
 188
 189                 /* This stores wq for the moment, for the timer_fn */
 190                 work->wq_data = wq;
 191                 timer->expires = jiffies + delay;
 192                 timer->data = (unsigned long)dwork;
 193                 timer->function = delayed_work_timer_fn;
 194                 add_timer_on(timer, cpu);
 195                 ret = 1;
 196         }
 197         return ret;
 198 }
 199 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 200
 201 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 202 {
 203         unsigned long flags;
 204
 205         /*
 206          * Keep taking off work from the queue until
 207          * done.
 208          */
 209         spin_lock_irqsave(&cwq->lock, flags);
 210         cwq->run_depth++;
 211         if (cwq->run_depth > 3) {
 212                 /* morton gets to eat his hat */
 213                 printk("%s: recursion depth exceeded: %d\n",
 214                         __FUNCTION__, cwq->run_depth);
 215                 dump_stack();
 216         }
 217         while (!list_empty(&cwq->worklist)) {
 218                 struct work_struct *work = list_entry(cwq->worklist.next,
 219                                                 struct work_struct, entry);
 220                 work_func_t f = work->func;
 221                 void *data = work->data;
 222
 223                 list_del_init(cwq->worklist.next);
 224                 spin_unlock_irqrestore(&cwq->lock, flags);
 225
 226                 BUG_ON(work->wq_data != cwq);
 227                 clear_bit(0, &work->pending);
 228                 f(data);
 229
 230                 spin_lock_irqsave(&cwq->lock, flags);
 231                 cwq->remove_sequence++;
 232                 wake_up(&cwq->work_done);
 233         }
 234         cwq->run_depth--;
 235         spin_unlock_irqrestore(&cwq->lock, flags);
 236 }
 237
 238 static int worker_thread(void *__cwq)
 239 {
 240         struct cpu_workqueue_struct *cwq = __cwq;
 241         DECLARE_WAITQUEUE(wait, current);
 242         struct k_sigaction sa;
 243         sigset_t blocked;
 244
 245         current->flags |= PF_NOFREEZE;
 246
 247         set_user_nice(current, -5);
 248
 249         /* Block and flush all signals */
 250         sigfillset(&blocked);
 251         sigprocmask(SIG_BLOCK, &blocked, NULL);
 252         flush_signals(current);
 253
 254         /*
 255          * We inherited MPOL_INTERLEAVE from the booting kernel.
 256          * Set MPOL_DEFAULT to insure node local allocations.
 257          */
 258         numa_default_policy();
 259
 260         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 261         sa.sa.sa_handler = SIG_IGN;
 262         sa.sa.sa_flags = 0;
 263         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 264         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 265
 266         set_current_state(TASK_INTERRUPTIBLE);
 267         while (!kthread_should_stop()) {
 268                 add_wait_queue(&cwq->more_work, &wait);
 269                 if (list_empty(&cwq->worklist))
 270                         schedule();
 271                 else
 272                         __set_current_state(TASK_RUNNING);
 273                 remove_wait_queue(&cwq->more_work, &wait);
 274
 275                 if (!list_empty(&cwq->worklist))
 276                         run_workqueue(cwq);
 277                 set_current_state(TASK_INTERRUPTIBLE);
 278         }
 279         __set_current_state(TASK_RUNNING);
 280         return 0;
 281 }
 282
 283 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 284 {
 285         if (cwq->thread == current) {
 286                 /*
 287                  * Probably keventd trying to flush its own queue. So simply run
 288                  * it by hand rather than deadlocking.
 289                  */
 290                 run_workqueue(cwq);
 291         } else {
 292                 DEFINE_WAIT(wait);
 293                 long sequence_needed;
 294
 295                 spin_lock_irq(&cwq->lock);
 296                 sequence_needed = cwq->insert_sequence;
 297
 298                 while (sequence_needed - cwq->remove_sequence > 0) {
 299                         prepare_to_wait(&cwq->work_done, &wait,
 300                                         TASK_UNINTERRUPTIBLE);
 301                         spin_unlock_irq(&cwq->lock);
 302                         schedule();
 303                         spin_lock_irq(&cwq->lock);
 304                 }
 305                 finish_wait(&cwq->work_done, &wait);
 306                 spin_unlock_irq(&cwq->lock);
 307         }
 308 }
 309
 310 /**
 311  * flush_workqueue - ensure that any scheduled work has run to completion.
 312  * @wq: workqueue to flush
 313  *
 314  * Forces execution of the workqueue and blocks until its completion.
 315  * This is typically used in driver shutdown handlers.
 316  *
 317  * This function will sample each workqueue's current insert_sequence number and
 318  * will sleep until the head sequence is greater than or equal to that.  This
 319  * means that we sleep until all works which were queued on entry have been
 320  * handled, but we are not livelocked by new incoming ones.
 321  *
 322  * This function used to run the workqueues itself.  Now we just wait for the
 323  * helper threads to do it.
 324  */
 325 void fastcall flush_workqueue(struct workqueue_struct *wq)
 326 {
 327         might_sleep();
 328
 329         if (is_single_threaded(wq)) {
 330                 /* Always use first cpu's area. */
 331                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
 332         } else {
 333                 int cpu;
 334
 335                 mutex_lock(&workqueue_mutex);
 336                 for_each_online_cpu(cpu)
 337                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 338                 mutex_unlock(&workqueue_mutex);
 339         }
 340 }
 341 EXPORT_SYMBOL_GPL(flush_workqueue);
 342
 343 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
 344                                                    int cpu)
 345 {
 346         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 347         struct task_struct *p;
 348
 349         spin_lock_init(&cwq->lock);
 350         cwq->wq = wq;
 351         cwq->thread = NULL;
 352         cwq->insert_sequence = 0;
 353         cwq->remove_sequence = 0;
 354         INIT_LIST_HEAD(&cwq->worklist);
 355         init_waitqueue_head(&cwq->more_work);
 356         init_waitqueue_head(&cwq->work_done);
 357
 358         if (is_single_threaded(wq))
 359                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
 360         else
 361                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
 362         if (IS_ERR(p))
 363                 return NULL;
 364         cwq->thread = p;
 365         return p;
 366 }
 367
 368 struct workqueue_struct *__create_workqueue(const char *name,
 369                                             int singlethread)
 370 {
 371         int cpu, destroy = 0;
 372         struct workqueue_struct *wq;
 373         struct task_struct *p;
 374
 375         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 376         if (!wq)
 377                 return NULL;
 378
 379         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 380         if (!wq->cpu_wq) {
 381                 kfree(wq);
 382                 return NULL;
 383         }
 384
 385         wq->name = name;
 386         mutex_lock(&workqueue_mutex);
 387         if (singlethread) {
 388                 INIT_LIST_HEAD(&wq->list);
 389                 p = create_workqueue_thread(wq, singlethread_cpu);
 390                 if (!p)
 391                         destroy = 1;
 392                 else
 393                         wake_up_process(p);
 394         } else {
 395                 list_add(&wq->list, &workqueues);
 396                 for_each_online_cpu(cpu) {
 397                         p = create_workqueue_thread(wq, cpu);
 398                         if (p) {
 399                                 kthread_bind(p, cpu);
 400                                 wake_up_process(p);
 401                         } else
 402                                 destroy = 1;
 403                 }
 404         }
 405         mutex_unlock(&workqueue_mutex);
 406
 407         /*
 408          * Was there any error during startup? If yes then clean up:
 409          */
 410         if (destroy) {
 411                 destroy_workqueue(wq);
 412                 wq = NULL;
 413         }
 414         return wq;
 415 }
 416 EXPORT_SYMBOL_GPL(__create_workqueue);
 417
 418 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
 419 {
 420         struct cpu_workqueue_struct *cwq;
 421         unsigned long flags;
 422         struct task_struct *p;
 423
 424         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 425         spin_lock_irqsave(&cwq->lock, flags);
 426         p = cwq->thread;
 427         cwq->thread = NULL;
 428         spin_unlock_irqrestore(&cwq->lock, flags);
 429         if (p)
 430                 kthread_stop(p);
 431 }
 432
 433 /**
 434  * destroy_workqueue - safely terminate a workqueue
 435  * @wq: target workqueue
 436  *
 437  * Safely destroy a workqueue. All work currently pending will be done first.
 438  */
 439 void destroy_workqueue(struct workqueue_struct *wq)
 440 {
 441         int cpu;
 442
 443         flush_workqueue(wq);
 444
 445         /* We don't need the distraction of CPUs appearing and vanishing. */
 446         mutex_lock(&workqueue_mutex);
 447         if (is_single_threaded(wq))
 448                 cleanup_workqueue_thread(wq, singlethread_cpu);
 449         else {
 450                 for_each_online_cpu(cpu)
 451                         cleanup_workqueue_thread(wq, cpu);
 452                 list_del(&wq->list);
 453         }
 454         mutex_unlock(&workqueue_mutex);
 455         free_percpu(wq->cpu_wq);
 456         kfree(wq);
 457 }
 458 EXPORT_SYMBOL_GPL(destroy_workqueue);
 459
 460 static struct workqueue_struct *keventd_wq;
 461
 462 /**
 463  * schedule_work - put work task in global workqueue
 464  * @work: job to be done
 465  *
 466  * This puts a job in the kernel-global workqueue.
 467  */
 468 int fastcall schedule_work(struct work_struct *work)
 469 {
 470         return queue_work(keventd_wq, work);
 471 }
 472 EXPORT_SYMBOL(schedule_work);
 473
 474 /**
 475  * schedule_delayed_work - put work task in global workqueue after delay
 476  * @dwork: job to be done
 477  * @delay: number of jiffies to wait or 0 for immediate execution
 478  *
 479  * After waiting for a given time this puts a job in the kernel-global
 480  * workqueue.
 481  */
 482 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
 483 {
 484         return queue_delayed_work(keventd_wq, dwork, delay);
 485 }
 486 EXPORT_SYMBOL(schedule_delayed_work);
 487
 488 /**
 489  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 490  * @cpu: cpu to use
 491  * @dwork: job to be done
 492  * @delay: number of jiffies to wait
 493  *
 494  * After waiting for a given time this puts a job in the kernel-global
 495  * workqueue on the specified CPU.
 496  */
 497 int schedule_delayed_work_on(int cpu,
 498                         struct delayed_work *dwork, unsigned long delay)
 499 {
 500         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 501 }
 502 EXPORT_SYMBOL(schedule_delayed_work_on);
 503
 504 /**
 505  * schedule_on_each_cpu - call a function on each online CPU from keventd
 506  * @func: the function to call
 507  * @info: a pointer to pass to func()
 508  *
 509  * Returns zero on success.
 510  * Returns -ve errno on failure.
 511  *
 512  * Appears to be racy against CPU hotplug.
 513  *
 514  * schedule_on_each_cpu() is very slow.
 515  */
 516 int schedule_on_each_cpu(work_func_t func, void *info)
 517 {
 518         int cpu;
 519         struct work_struct *works;
 520
 521         works = alloc_percpu(struct work_struct);
 522         if (!works)
 523                 return -ENOMEM;
 524
 525         mutex_lock(&workqueue_mutex);
 526         for_each_online_cpu(cpu) {
 527                 INIT_WORK(per_cpu_ptr(works, cpu), func, info);
 528                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
 529                                 per_cpu_ptr(works, cpu));
 530         }
 531         mutex_unlock(&workqueue_mutex);
 532         flush_workqueue(keventd_wq);
 533         free_percpu(works);
 534         return 0;
 535 }
 536
 537 void flush_scheduled_work(void)
 538 {
 539         flush_workqueue(keventd_wq);
 540 }
 541 EXPORT_SYMBOL(flush_scheduled_work);
 542
 543 /**
 544  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
 545  *                      work whose handler rearms the delayed work.
 546  * @wq:   the controlling workqueue structure
 547  * @dwork: the delayed work struct
 548  */
 549 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 550                                        struct delayed_work *dwork)
 551 {
 552         while (!cancel_delayed_work(dwork))
 553                 flush_workqueue(wq);
 554 }
 555 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 556
 557 /**
 558  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
 559  *                      work whose handler rearms the delayed work.
 560  * @dwork: the delayed work struct
 561  */
 562 void cancel_rearming_delayed_work(struct delayed_work *dwork)
 563 {
 564         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
 565 }
 566 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 567
 568 /**
 569  * execute_in_process_context - reliably execute the routine with user context
 570  * @fn:         the function to execute
 571  * @data:       data to pass to the function
 572  * @ew:         guaranteed storage for the execute work structure (must
 573  *              be available when the work executes)
 574  *
 575  * Executes the function immediately if process context is available,
 576  * otherwise schedules the function for delayed execution.
 577  *
 578  * Returns:     0 - function was executed
 579  *              1 - function was scheduled for execution
 580  */
 581 int execute_in_process_context(work_func_t fn, void *data,
 582                                struct execute_work *ew)
 583 {
 584         if (!in_interrupt()) {
 585                 fn(data);
 586                 return 0;
 587         }
 588
 589         INIT_WORK(&ew->work, fn, data);
 590         schedule_work(&ew->work);
 591
 592         return 1;
 593 }
 594 EXPORT_SYMBOL_GPL(execute_in_process_context);
 595
 596 int keventd_up(void)
 597 {
 598         return keventd_wq != NULL;
 599 }
 600
 601 int current_is_keventd(void)
 602 {
 603         struct cpu_workqueue_struct *cwq;
 604         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 605         int ret = 0;
 606
 607         BUG_ON(!keventd_wq);
 608
 609         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 610         if (current == cwq->thread)
 611                 ret = 1;
 612
 613         return ret;
 614
 615 }
 616
 617 #ifdef CONFIG_HOTPLUG_CPU
 618 /* Take the work from this (downed) CPU. */
 619 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
 620 {
 621         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 622         struct list_head list;
 623         struct work_struct *work;
 624
 625         spin_lock_irq(&cwq->lock);
 626         list_replace_init(&cwq->worklist, &list);
 627
 628         while (!list_empty(&list)) {
 629                 printk("Taking work for %s\n", wq->name);
 630                 work = list_entry(list.next,struct work_struct,entry);
 631                 list_del(&work->entry);
 632                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
 633         }
 634         spin_unlock_irq(&cwq->lock);
 635 }
 636
 637 /* We're holding the cpucontrol mutex here */
 638 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 639                                   unsigned long action,
 640                                   void *hcpu)
 641 {
 642         unsigned int hotcpu = (unsigned long)hcpu;
 643         struct workqueue_struct *wq;
 644
 645         switch (action) {
 646         case CPU_UP_PREPARE:
 647                 mutex_lock(&workqueue_mutex);
 648                 /* Create a new workqueue thread for it. */
 649                 list_for_each_entry(wq, &workqueues, list) {
 650                         if (!create_workqueue_thread(wq, hotcpu)) {
 651                                 printk("workqueue for %i failed\n", hotcpu);
 652                                 return NOTIFY_BAD;
 653                         }
 654                 }
 655                 break;
 656
 657         case CPU_ONLINE:
 658                 /* Kick off worker threads. */
 659                 list_for_each_entry(wq, &workqueues, list) {
 660                         struct cpu_workqueue_struct *cwq;
 661
 662                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
 663                         kthread_bind(cwq->thread, hotcpu);
 664                         wake_up_process(cwq->thread);
 665                 }
 666                 mutex_unlock(&workqueue_mutex);
 667                 break;
 668
 669         case CPU_UP_CANCELED:
 670                 list_for_each_entry(wq, &workqueues, list) {
 671                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
 672                                 continue;
 673                         /* Unbind so it can run. */
 674                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
 675                                      any_online_cpu(cpu_online_map));
 676                         cleanup_workqueue_thread(wq, hotcpu);
 677                 }
 678                 mutex_unlock(&workqueue_mutex);
 679                 break;
 680
 681         case CPU_DOWN_PREPARE:
 682                 mutex_lock(&workqueue_mutex);
 683                 break;
 684
 685         case CPU_DOWN_FAILED:
 686                 mutex_unlock(&workqueue_mutex);
 687                 break;
 688
 689         case CPU_DEAD:
 690                 list_for_each_entry(wq, &workqueues, list)
 691                         cleanup_workqueue_thread(wq, hotcpu);
 692                 list_for_each_entry(wq, &workqueues, list)
 693                         take_over_work(wq, hotcpu);
 694                 mutex_unlock(&workqueue_mutex);
 695                 break;
 696         }
 697
 698         return NOTIFY_OK;
 699 }
 700 #endif
 701
 702 void init_workqueues(void)
 703 {
 704         singlethread_cpu = first_cpu(cpu_possible_map);
 705         hotcpu_notifier(workqueue_cpu_callback, 0);
 706         keventd_wq = create_workqueue("events");
 707         BUG_ON(!keventd_wq);
 708 }
 709