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