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   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 #include <linux/freezer.h>
  33
  34 /*
  35  * The per-CPU workqueue (if single thread, we always use the first
  36  * possible cpu).
  37  *
  38  * The sequence counters are for flush_scheduled_work().  It wants to wait
  39  * until all currently-scheduled works are completed, but it doesn't
  40  * want to be livelocked by new, incoming ones.  So it waits until
  41  * remove_sequence is >= the insert_sequence which pertained when
  42  * flush_scheduled_work() was called.
  43  */
  44 struct cpu_workqueue_struct {
  45
  46         spinlock_t lock;
  47
  48         long remove_sequence;   /* Least-recently added (next to run) */
  49         long insert_sequence;   /* Next to add */
  50
  51         struct list_head worklist;
  52         wait_queue_head_t more_work;
  53         wait_queue_head_t work_done;
  54
  55         struct workqueue_struct *wq;
  56         struct task_struct *thread;
  57
  58         int run_depth;          /* Detect run_workqueue() recursion depth */
  59
  60         int freezeable;         /* Freeze the thread during suspend */
  61 } ____cacheline_aligned;
  62
  63 /*
  64  * The externally visible workqueue abstraction is an array of
  65  * per-CPU workqueues:
  66  */
  67 struct workqueue_struct {
  68         struct cpu_workqueue_struct *cpu_wq;
  69         const char *name;
  70         struct list_head list;  /* Empty if single thread */
  71 };
  72
  73 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  74    threads to each one as cpus come/go. */
  75 static DEFINE_MUTEX(workqueue_mutex);
  76 static LIST_HEAD(workqueues);
  77
  78 static int singlethread_cpu;
  79
  80 /* If it's single threaded, it isn't in the list of workqueues. */
  81 static inline int is_single_threaded(struct workqueue_struct *wq)
  82 {
  83         return list_empty(&wq->list);
  84 }
  85
  86 static inline void set_wq_data(struct work_struct *work, void *wq)
  87 {
  88         unsigned long new, old, res;
  89
  90         /* assume the pending flag is already set and that the task has already
  91          * been queued on this workqueue */
  92         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
  93         res = work->management;
  94         if (res != new) {
  95                 do {
  96                         old = res;
  97                         new = (unsigned long) wq;
  98                         new |= (old & WORK_STRUCT_FLAG_MASK);
  99                         res = cmpxchg(&work->management, old, new);
 100                 } while (res != old);
 101         }
 102 }
 103
 104 static inline void *get_wq_data(struct work_struct *work)
 105 {
 106         return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
 107 }
 108
 109 /* Preempt must be disabled. */
 110 static void __queue_work(struct cpu_workqueue_struct *cwq,
 111                          struct work_struct *work)
 112 {
 113         unsigned long flags;
 114
 115         spin_lock_irqsave(&cwq->lock, flags);
 116         set_wq_data(work, cwq);
 117         list_add_tail(&work->entry, &cwq->worklist);
 118         cwq->insert_sequence++;
 119         wake_up(&cwq->more_work);
 120         spin_unlock_irqrestore(&cwq->lock, flags);
 121 }
 122
 123 /**
 124  * queue_work - queue work on a workqueue
 125  * @wq: workqueue to use
 126  * @work: work to queue
 127  *
 128  * Returns 0 if @work was already on a queue, non-zero otherwise.
 129  *
 130  * We queue the work to the CPU it was submitted, but there is no
 131  * guarantee that it will be processed by that CPU.
 132  */
 133 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 134 {
 135         int ret = 0, cpu = get_cpu();
 136
 137         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 138                 if (unlikely(is_single_threaded(wq)))
 139                         cpu = singlethread_cpu;
 140                 BUG_ON(!list_empty(&work->entry));
 141                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 142                 ret = 1;
 143         }
 144         put_cpu();
 145         return ret;
 146 }
 147 EXPORT_SYMBOL_GPL(queue_work);
 148
 149 static void delayed_work_timer_fn(unsigned long __data)
 150 {
 151         struct delayed_work *dwork = (struct delayed_work *)__data;
 152         struct workqueue_struct *wq = get_wq_data(&dwork->work);
 153         int cpu = smp_processor_id();
 154
 155         if (unlikely(is_single_threaded(wq)))
 156                 cpu = singlethread_cpu;
 157
 158         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
 159 }
 160
 161 /**
 162  * queue_delayed_work - queue work on a workqueue after delay
 163  * @wq: workqueue to use
 164  * @work: delayable work to queue
 165  * @delay: number of jiffies to wait before queueing
 166  *
 167  * Returns 0 if @work was already on a queue, non-zero otherwise.
 168  */
 169 int fastcall queue_delayed_work(struct workqueue_struct *wq,
 170                         struct delayed_work *dwork, unsigned long delay)
 171 {
 172         int ret = 0;
 173         struct timer_list *timer = &dwork->timer;
 174         struct work_struct *work = &dwork->work;
 175
 176         if (delay == 0)
 177                 return queue_work(wq, work);
 178
 179         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 180                 BUG_ON(timer_pending(timer));
 181                 BUG_ON(!list_empty(&work->entry));
 182
 183                 /* This stores wq for the moment, for the timer_fn */
 184                 set_wq_data(work, wq);
 185                 timer->expires = jiffies + delay;
 186                 timer->data = (unsigned long)dwork;
 187                 timer->function = delayed_work_timer_fn;
 188                 add_timer(timer);
 189                 ret = 1;
 190         }
 191         return ret;
 192 }
 193 EXPORT_SYMBOL_GPL(queue_delayed_work);
 194
 195 /**
 196  * queue_delayed_work_on - queue work on specific CPU after delay
 197  * @cpu: CPU number to execute work on
 198  * @wq: workqueue to use
 199  * @work: work to queue
 200  * @delay: number of jiffies to wait before queueing
 201  *
 202  * Returns 0 if @work was already on a queue, non-zero otherwise.
 203  */
 204 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 205                         struct delayed_work *dwork, unsigned long delay)
 206 {
 207         int ret = 0;
 208         struct timer_list *timer = &dwork->timer;
 209         struct work_struct *work = &dwork->work;
 210
 211         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 212                 BUG_ON(timer_pending(timer));
 213                 BUG_ON(!list_empty(&work->entry));
 214
 215                 /* This stores wq for the moment, for the timer_fn */
 216                 set_wq_data(work, wq);
 217                 timer->expires = jiffies + delay;
 218                 timer->data = (unsigned long)dwork;
 219                 timer->function = delayed_work_timer_fn;
 220                 add_timer_on(timer, cpu);
 221                 ret = 1;
 222         }
 223         return ret;
 224 }
 225 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 226
 227 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 228 {
 229         unsigned long flags;
 230
 231         /*
 232          * Keep taking off work from the queue until
 233          * done.
 234          */
 235         spin_lock_irqsave(&cwq->lock, flags);
 236         cwq->run_depth++;
 237         if (cwq->run_depth > 3) {
 238                 /* morton gets to eat his hat */
 239                 printk("%s: recursion depth exceeded: %d\n",
 240                         __FUNCTION__, cwq->run_depth);
 241                 dump_stack();
 242         }
 243         while (!list_empty(&cwq->worklist)) {
 244                 struct work_struct *work = list_entry(cwq->worklist.next,
 245                                                 struct work_struct, entry);
 246                 work_func_t f = work->func;
 247
 248                 list_del_init(cwq->worklist.next);
 249                 spin_unlock_irqrestore(&cwq->lock, flags);
 250
 251                 BUG_ON(get_wq_data(work) != cwq);
 252                 if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
 253                         work_release(work);
 254                 f(work);
 255
 256                 spin_lock_irqsave(&cwq->lock, flags);
 257                 cwq->remove_sequence++;
 258                 wake_up(&cwq->work_done);
 259         }
 260         cwq->run_depth--;
 261         spin_unlock_irqrestore(&cwq->lock, flags);
 262 }
 263
 264 static int worker_thread(void *__cwq)
 265 {
 266         struct cpu_workqueue_struct *cwq = __cwq;
 267         DECLARE_WAITQUEUE(wait, current);
 268         struct k_sigaction sa;
 269         sigset_t blocked;
 270
 271         if (!cwq->freezeable)
 272                 current->flags |= PF_NOFREEZE;
 273
 274         set_user_nice(current, -5);
 275
 276         /* Block and flush all signals */
 277         sigfillset(&blocked);
 278         sigprocmask(SIG_BLOCK, &blocked, NULL);
 279         flush_signals(current);
 280
 281         /*
 282          * We inherited MPOL_INTERLEAVE from the booting kernel.
 283          * Set MPOL_DEFAULT to insure node local allocations.
 284          */
 285         numa_default_policy();
 286
 287         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 288         sa.sa.sa_handler = SIG_IGN;
 289         sa.sa.sa_flags = 0;
 290         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 291         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 292
 293         set_current_state(TASK_INTERRUPTIBLE);
 294         while (!kthread_should_stop()) {
 295                 if (cwq->freezeable)
 296                         try_to_freeze();
 297
 298                 add_wait_queue(&cwq->more_work, &wait);
 299                 if (list_empty(&cwq->worklist))
 300                         schedule();
 301                 else
 302                         __set_current_state(TASK_RUNNING);
 303                 remove_wait_queue(&cwq->more_work, &wait);
 304
 305                 if (!list_empty(&cwq->worklist))
 306                         run_workqueue(cwq);
 307                 set_current_state(TASK_INTERRUPTIBLE);
 308         }
 309         __set_current_state(TASK_RUNNING);
 310         return 0;
 311 }
 312
 313 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 314 {
 315         if (cwq->thread == current) {
 316                 /*
 317                  * Probably keventd trying to flush its own queue. So simply run
 318                  * it by hand rather than deadlocking.
 319                  */
 320                 run_workqueue(cwq);
 321         } else {
 322                 DEFINE_WAIT(wait);
 323                 long sequence_needed;
 324
 325                 spin_lock_irq(&cwq->lock);
 326                 sequence_needed = cwq->insert_sequence;
 327
 328                 while (sequence_needed - cwq->remove_sequence > 0) {
 329                         prepare_to_wait(&cwq->work_done, &wait,
 330                                         TASK_UNINTERRUPTIBLE);
 331                         spin_unlock_irq(&cwq->lock);
 332                         schedule();
 333                         spin_lock_irq(&cwq->lock);
 334                 }
 335                 finish_wait(&cwq->work_done, &wait);
 336                 spin_unlock_irq(&cwq->lock);
 337         }
 338 }
 339
 340 /**
 341  * flush_workqueue - ensure that any scheduled work has run to completion.
 342  * @wq: workqueue to flush
 343  *
 344  * Forces execution of the workqueue and blocks until its completion.
 345  * This is typically used in driver shutdown handlers.
 346  *
 347  * This function will sample each workqueue's current insert_sequence number and
 348  * will sleep until the head sequence is greater than or equal to that.  This
 349  * means that we sleep until all works which were queued on entry have been
 350  * handled, but we are not livelocked by new incoming ones.
 351  *
 352  * This function used to run the workqueues itself.  Now we just wait for the
 353  * helper threads to do it.
 354  */
 355 void fastcall flush_workqueue(struct workqueue_struct *wq)
 356 {
 357         might_sleep();
 358
 359         if (is_single_threaded(wq)) {
 360                 /* Always use first cpu's area. */
 361                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
 362         } else {
 363                 int cpu;
 364
 365                 mutex_lock(&workqueue_mutex);
 366                 for_each_online_cpu(cpu)
 367                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 368                 mutex_unlock(&workqueue_mutex);
 369         }
 370 }
 371 EXPORT_SYMBOL_GPL(flush_workqueue);
 372
 373 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
 374                                                    int cpu, int freezeable)
 375 {
 376         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 377         struct task_struct *p;
 378
 379         spin_lock_init(&cwq->lock);
 380         cwq->wq = wq;
 381         cwq->thread = NULL;
 382         cwq->insert_sequence = 0;
 383         cwq->remove_sequence = 0;
 384         cwq->freezeable = freezeable;
 385         INIT_LIST_HEAD(&cwq->worklist);
 386         init_waitqueue_head(&cwq->more_work);
 387         init_waitqueue_head(&cwq->work_done);
 388
 389         if (is_single_threaded(wq))
 390                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
 391         else
 392                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
 393         if (IS_ERR(p))
 394                 return NULL;
 395         cwq->thread = p;
 396         return p;
 397 }
 398
 399 struct workqueue_struct *__create_workqueue(const char *name,
 400                                             int singlethread, int freezeable)
 401 {
 402         int cpu, destroy = 0;
 403         struct workqueue_struct *wq;
 404         struct task_struct *p;
 405
 406         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 407         if (!wq)
 408                 return NULL;
 409
 410         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 411         if (!wq->cpu_wq) {
 412                 kfree(wq);
 413                 return NULL;
 414         }
 415
 416         wq->name = name;
 417         mutex_lock(&workqueue_mutex);
 418         if (singlethread) {
 419                 INIT_LIST_HEAD(&wq->list);
 420                 p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
 421                 if (!p)
 422                         destroy = 1;
 423                 else
 424                         wake_up_process(p);
 425         } else {
 426                 list_add(&wq->list, &workqueues);
 427                 for_each_online_cpu(cpu) {
 428                         p = create_workqueue_thread(wq, cpu, freezeable);
 429                         if (p) {
 430                                 kthread_bind(p, cpu);
 431                                 wake_up_process(p);
 432                         } else
 433                                 destroy = 1;
 434                 }
 435         }
 436         mutex_unlock(&workqueue_mutex);
 437
 438         /*
 439          * Was there any error during startup? If yes then clean up:
 440          */
 441         if (destroy) {
 442                 destroy_workqueue(wq);
 443                 wq = NULL;
 444         }
 445         return wq;
 446 }
 447 EXPORT_SYMBOL_GPL(__create_workqueue);
 448
 449 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
 450 {
 451         struct cpu_workqueue_struct *cwq;
 452         unsigned long flags;
 453         struct task_struct *p;
 454
 455         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 456         spin_lock_irqsave(&cwq->lock, flags);
 457         p = cwq->thread;
 458         cwq->thread = NULL;
 459         spin_unlock_irqrestore(&cwq->lock, flags);
 460         if (p)
 461                 kthread_stop(p);
 462 }
 463
 464 /**
 465  * destroy_workqueue - safely terminate a workqueue
 466  * @wq: target workqueue
 467  *
 468  * Safely destroy a workqueue. All work currently pending will be done first.
 469  */
 470 void destroy_workqueue(struct workqueue_struct *wq)
 471 {
 472         int cpu;
 473
 474         flush_workqueue(wq);
 475
 476         /* We don't need the distraction of CPUs appearing and vanishing. */
 477         mutex_lock(&workqueue_mutex);
 478         if (is_single_threaded(wq))
 479                 cleanup_workqueue_thread(wq, singlethread_cpu);
 480         else {
 481                 for_each_online_cpu(cpu)
 482                         cleanup_workqueue_thread(wq, cpu);
 483                 list_del(&wq->list);
 484         }
 485         mutex_unlock(&workqueue_mutex);
 486         free_percpu(wq->cpu_wq);
 487         kfree(wq);
 488 }
 489 EXPORT_SYMBOL_GPL(destroy_workqueue);
 490
 491 static struct workqueue_struct *keventd_wq;
 492
 493 /**
 494  * schedule_work - put work task in global workqueue
 495  * @work: job to be done
 496  *
 497  * This puts a job in the kernel-global workqueue.
 498  */
 499 int fastcall schedule_work(struct work_struct *work)
 500 {
 501         return queue_work(keventd_wq, work);
 502 }
 503 EXPORT_SYMBOL(schedule_work);
 504
 505 /**
 506  * schedule_delayed_work - put work task in global workqueue after delay
 507  * @dwork: job to be done
 508  * @delay: number of jiffies to wait or 0 for immediate execution
 509  *
 510  * After waiting for a given time this puts a job in the kernel-global
 511  * workqueue.
 512  */
 513 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
 514 {
 515         return queue_delayed_work(keventd_wq, dwork, delay);
 516 }
 517 EXPORT_SYMBOL(schedule_delayed_work);
 518
 519 /**
 520  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 521  * @cpu: cpu to use
 522  * @dwork: job to be done
 523  * @delay: number of jiffies to wait
 524  *
 525  * After waiting for a given time this puts a job in the kernel-global
 526  * workqueue on the specified CPU.
 527  */
 528 int schedule_delayed_work_on(int cpu,
 529                         struct delayed_work *dwork, unsigned long delay)
 530 {
 531         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 532 }
 533 EXPORT_SYMBOL(schedule_delayed_work_on);
 534
 535 /**
 536  * schedule_on_each_cpu - call a function on each online CPU from keventd
 537  * @func: the function to call
 538  *
 539  * Returns zero on success.
 540  * Returns -ve errno on failure.
 541  *
 542  * Appears to be racy against CPU hotplug.
 543  *
 544  * schedule_on_each_cpu() is very slow.
 545  */
 546 int schedule_on_each_cpu(work_func_t func)
 547 {
 548         int cpu;
 549         struct work_struct *works;
 550
 551         works = alloc_percpu(struct work_struct);
 552         if (!works)
 553                 return -ENOMEM;
 554
 555         mutex_lock(&workqueue_mutex);
 556         for_each_online_cpu(cpu) {
 557                 INIT_WORK(per_cpu_ptr(works, cpu), func);
 558                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
 559                                 per_cpu_ptr(works, cpu));
 560         }
 561         mutex_unlock(&workqueue_mutex);
 562         flush_workqueue(keventd_wq);
 563         free_percpu(works);
 564         return 0;
 565 }
 566
 567 void flush_scheduled_work(void)
 568 {
 569         flush_workqueue(keventd_wq);
 570 }
 571 EXPORT_SYMBOL(flush_scheduled_work);
 572
 573 /**
 574  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
 575  *                      work whose handler rearms the delayed work.
 576  * @wq:   the controlling workqueue structure
 577  * @dwork: the delayed work struct
 578  */
 579 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 580                                        struct delayed_work *dwork)
 581 {
 582         while (!cancel_delayed_work(dwork))
 583                 flush_workqueue(wq);
 584 }
 585 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 586
 587 /**
 588  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
 589  *                      work whose handler rearms the delayed work.
 590  * @dwork: the delayed work struct
 591  */
 592 void cancel_rearming_delayed_work(struct delayed_work *dwork)
 593 {
 594         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
 595 }
 596 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 597
 598 /**
 599  * execute_in_process_context - reliably execute the routine with user context
 600  * @fn:         the function to execute
 601  * @ew:         guaranteed storage for the execute work structure (must
 602  *              be available when the work executes)
 603  *
 604  * Executes the function immediately if process context is available,
 605  * otherwise schedules the function for delayed execution.
 606  *
 607  * Returns:     0 - function was executed
 608  *              1 - function was scheduled for execution
 609  */
 610 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 611 {
 612         if (!in_interrupt()) {
 613                 fn(&ew->work);
 614                 return 0;
 615         }
 616
 617         INIT_WORK(&ew->work, fn);
 618         schedule_work(&ew->work);
 619
 620         return 1;
 621 }
 622 EXPORT_SYMBOL_GPL(execute_in_process_context);
 623
 624 int keventd_up(void)
 625 {
 626         return keventd_wq != NULL;
 627 }
 628
 629 int current_is_keventd(void)
 630 {
 631         struct cpu_workqueue_struct *cwq;
 632         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 633         int ret = 0;
 634
 635         BUG_ON(!keventd_wq);
 636
 637         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 638         if (current == cwq->thread)
 639                 ret = 1;
 640
 641         return ret;
 642
 643 }
 644
 645 #ifdef CONFIG_HOTPLUG_CPU
 646 /* Take the work from this (downed) CPU. */
 647 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
 648 {
 649         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 650         struct list_head list;
 651         struct work_struct *work;
 652
 653         spin_lock_irq(&cwq->lock);
 654         list_replace_init(&cwq->worklist, &list);
 655
 656         while (!list_empty(&list)) {
 657                 printk("Taking work for %s\n", wq->name);
 658                 work = list_entry(list.next,struct work_struct,entry);
 659                 list_del(&work->entry);
 660                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
 661         }
 662         spin_unlock_irq(&cwq->lock);
 663 }
 664
 665 /* We're holding the cpucontrol mutex here */
 666 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 667                                   unsigned long action,
 668                                   void *hcpu)
 669 {
 670         unsigned int hotcpu = (unsigned long)hcpu;
 671         struct workqueue_struct *wq;
 672
 673         switch (action) {
 674         case CPU_UP_PREPARE:
 675                 mutex_lock(&workqueue_mutex);
 676                 /* Create a new workqueue thread for it. */
 677                 list_for_each_entry(wq, &workqueues, list) {
 678                         if (!create_workqueue_thread(wq, hotcpu, 0)) {
 679                                 printk("workqueue for %i failed\n", hotcpu);
 680                                 return NOTIFY_BAD;
 681                         }
 682                 }
 683                 break;
 684
 685         case CPU_ONLINE:
 686                 /* Kick off worker threads. */
 687                 list_for_each_entry(wq, &workqueues, list) {
 688                         struct cpu_workqueue_struct *cwq;
 689
 690                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
 691                         kthread_bind(cwq->thread, hotcpu);
 692                         wake_up_process(cwq->thread);
 693                 }
 694                 mutex_unlock(&workqueue_mutex);
 695                 break;
 696
 697         case CPU_UP_CANCELED:
 698                 list_for_each_entry(wq, &workqueues, list) {
 699                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
 700                                 continue;
 701                         /* Unbind so it can run. */
 702                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
 703                                      any_online_cpu(cpu_online_map));
 704                         cleanup_workqueue_thread(wq, hotcpu);
 705                 }
 706                 mutex_unlock(&workqueue_mutex);
 707                 break;
 708
 709         case CPU_DOWN_PREPARE:
 710                 mutex_lock(&workqueue_mutex);
 711                 break;
 712
 713         case CPU_DOWN_FAILED:
 714                 mutex_unlock(&workqueue_mutex);
 715                 break;
 716
 717         case CPU_DEAD:
 718                 list_for_each_entry(wq, &workqueues, list)
 719                         cleanup_workqueue_thread(wq, hotcpu);
 720                 list_for_each_entry(wq, &workqueues, list)
 721                         take_over_work(wq, hotcpu);
 722                 mutex_unlock(&workqueue_mutex);
 723                 break;
 724         }
 725
 726         return NOTIFY_OK;
 727 }
 728 #endif
 729
 730 void init_workqueues(void)
 731 {
 732         singlethread_cpu = first_cpu(cpu_possible_map);
 733         hotcpu_notifier(workqueue_cpu_callback, 0);
 734         keventd_wq = create_workqueue("events");
 735         BUG_ON(!keventd_wq);
 736 }
 737