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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 #include <linux/kallsyms.h>
  34 #include <linux/debug_locks.h>
  35
  36 /*
  37  * The per-CPU workqueue (if single thread, we always use the first
  38  * possible cpu).
  39  *
  40  * The sequence counters are for flush_scheduled_work().  It wants to wait
  41  * until all currently-scheduled works are completed, but it doesn't
  42  * want to be livelocked by new, incoming ones.  So it waits until
  43  * remove_sequence is >= the insert_sequence which pertained when
  44  * flush_scheduled_work() was called.
  45  */
  46 struct cpu_workqueue_struct {
  47
  48         spinlock_t lock;
  49
  50         long remove_sequence;   /* Least-recently added (next to run) */
  51         long insert_sequence;   /* Next to add */
  52
  53         struct list_head worklist;
  54         wait_queue_head_t more_work;
  55         wait_queue_head_t work_done;
  56
  57         struct workqueue_struct *wq;
  58         struct task_struct *thread;
  59
  60         int run_depth;          /* Detect run_workqueue() recursion depth */
  61
  62         int freezeable;         /* Freeze the thread during suspend */
  63 } ____cacheline_aligned;
  64
  65 /*
  66  * The externally visible workqueue abstraction is an array of
  67  * per-CPU workqueues:
  68  */
  69 struct workqueue_struct {
  70         struct cpu_workqueue_struct *cpu_wq;
  71         const char *name;
  72         struct list_head list;  /* Empty if single thread */
  73 };
  74
  75 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  76    threads to each one as cpus come/go. */
  77 static DEFINE_MUTEX(workqueue_mutex);
  78 static LIST_HEAD(workqueues);
  79
  80 static int singlethread_cpu;
  81
  82 /* If it's single threaded, it isn't in the list of workqueues. */
  83 static inline int is_single_threaded(struct workqueue_struct *wq)
  84 {
  85         return list_empty(&wq->list);
  86 }
  87
  88 static inline void set_wq_data(struct work_struct *work, void *wq)
  89 {
  90         unsigned long new, old, res;
  91
  92         /* assume the pending flag is already set and that the task has already
  93          * been queued on this workqueue */
  94         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
  95         res = work->management;
  96         if (res != new) {
  97                 do {
  98                         old = res;
  99                         new = (unsigned long) wq;
 100                         new |= (old & WORK_STRUCT_FLAG_MASK);
 101                         res = cmpxchg(&work->management, old, new);
 102                 } while (res != old);
 103         }
 104 }
 105
 106 static inline void *get_wq_data(struct work_struct *work)
 107 {
 108         return (void *) (work->management & WORK_STRUCT_WQ_DATA_MASK);
 109 }
 110
 111 static int __run_work(struct cpu_workqueue_struct *cwq, struct work_struct *work)
 112 {
 113         int ret = 0;
 114         unsigned long flags;
 115
 116         spin_lock_irqsave(&cwq->lock, flags);
 117         /*
 118          * We need to re-validate the work info after we've gotten
 119          * the cpu_workqueue lock. We can run the work now iff:
 120          *
 121          *  - the wq_data still matches the cpu_workqueue_struct
 122          *  - AND the work is still marked pending
 123          *  - AND the work is still on a list (which will be this
 124          *    workqueue_struct list)
 125          *
 126          * All these conditions are important, because we
 127          * need to protect against the work being run right
 128          * now on another CPU (all but the last one might be
 129          * true if it's currently running and has not been
 130          * released yet, for example).
 131          */
 132         if (get_wq_data(work) == cwq
 133             && work_pending(work)
 134             && !list_empty(&work->entry)) {
 135                 work_func_t f = work->func;
 136                 list_del_init(&work->entry);
 137                 spin_unlock_irqrestore(&cwq->lock, flags);
 138
 139                 if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
 140                         work_release(work);
 141                 f(work);
 142
 143                 spin_lock_irqsave(&cwq->lock, flags);
 144                 cwq->remove_sequence++;
 145                 wake_up(&cwq->work_done);
 146                 ret = 1;
 147         }
 148         spin_unlock_irqrestore(&cwq->lock, flags);
 149         return ret;
 150 }
 151
 152 /**
 153  * run_scheduled_work - run scheduled work synchronously
 154  * @work: work to run
 155  *
 156  * This checks if the work was pending, and runs it
 157  * synchronously if so. It returns a boolean to indicate
 158  * whether it had any scheduled work to run or not.
 159  *
 160  * NOTE! This _only_ works for normal work_structs. You
 161  * CANNOT use this for delayed work, because the wq data
 162  * for delayed work will not point properly to the per-
 163  * CPU workqueue struct, but will change!
 164  */
 165 int fastcall run_scheduled_work(struct work_struct *work)
 166 {
 167         for (;;) {
 168                 struct cpu_workqueue_struct *cwq;
 169
 170                 if (!work_pending(work))
 171                         return 0;
 172                 if (list_empty(&work->entry))
 173                         return 0;
 174                 /* NOTE! This depends intimately on __queue_work! */
 175                 cwq = get_wq_data(work);
 176                 if (!cwq)
 177                         return 0;
 178                 if (__run_work(cwq, work))
 179                         return 1;
 180         }
 181 }
 182 EXPORT_SYMBOL(run_scheduled_work);
 183
 184 /* Preempt must be disabled. */
 185 static void __queue_work(struct cpu_workqueue_struct *cwq,
 186                          struct work_struct *work)
 187 {
 188         unsigned long flags;
 189
 190         spin_lock_irqsave(&cwq->lock, flags);
 191         set_wq_data(work, cwq);
 192         list_add_tail(&work->entry, &cwq->worklist);
 193         cwq->insert_sequence++;
 194         wake_up(&cwq->more_work);
 195         spin_unlock_irqrestore(&cwq->lock, flags);
 196 }
 197
 198 /**
 199  * queue_work - queue work on a workqueue
 200  * @wq: workqueue to use
 201  * @work: work to queue
 202  *
 203  * Returns 0 if @work was already on a queue, non-zero otherwise.
 204  *
 205  * We queue the work to the CPU it was submitted, but there is no
 206  * guarantee that it will be processed by that CPU.
 207  */
 208 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 209 {
 210         int ret = 0, cpu = get_cpu();
 211
 212         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 213                 if (unlikely(is_single_threaded(wq)))
 214                         cpu = singlethread_cpu;
 215                 BUG_ON(!list_empty(&work->entry));
 216                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 217                 ret = 1;
 218         }
 219         put_cpu();
 220         return ret;
 221 }
 222 EXPORT_SYMBOL_GPL(queue_work);
 223
 224 static void delayed_work_timer_fn(unsigned long __data)
 225 {
 226         struct delayed_work *dwork = (struct delayed_work *)__data;
 227         struct workqueue_struct *wq = get_wq_data(&dwork->work);
 228         int cpu = smp_processor_id();
 229
 230         if (unlikely(is_single_threaded(wq)))
 231                 cpu = singlethread_cpu;
 232
 233         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
 234 }
 235
 236 /**
 237  * queue_delayed_work - queue work on a workqueue after delay
 238  * @wq: workqueue to use
 239  * @work: delayable work to queue
 240  * @delay: number of jiffies to wait before queueing
 241  *
 242  * Returns 0 if @work was already on a queue, non-zero otherwise.
 243  */
 244 int fastcall queue_delayed_work(struct workqueue_struct *wq,
 245                         struct delayed_work *dwork, unsigned long delay)
 246 {
 247         int ret = 0;
 248         struct timer_list *timer = &dwork->timer;
 249         struct work_struct *work = &dwork->work;
 250
 251         if (delay == 0)
 252                 return queue_work(wq, work);
 253
 254         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 255                 BUG_ON(timer_pending(timer));
 256                 BUG_ON(!list_empty(&work->entry));
 257
 258                 /* This stores wq for the moment, for the timer_fn */
 259                 set_wq_data(work, wq);
 260                 timer->expires = jiffies + delay;
 261                 timer->data = (unsigned long)dwork;
 262                 timer->function = delayed_work_timer_fn;
 263                 add_timer(timer);
 264                 ret = 1;
 265         }
 266         return ret;
 267 }
 268 EXPORT_SYMBOL_GPL(queue_delayed_work);
 269
 270 /**
 271  * queue_delayed_work_on - queue work on specific CPU after delay
 272  * @cpu: CPU number to execute work on
 273  * @wq: workqueue to use
 274  * @work: work to queue
 275  * @delay: number of jiffies to wait before queueing
 276  *
 277  * Returns 0 if @work was already on a queue, non-zero otherwise.
 278  */
 279 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 280                         struct delayed_work *dwork, unsigned long delay)
 281 {
 282         int ret = 0;
 283         struct timer_list *timer = &dwork->timer;
 284         struct work_struct *work = &dwork->work;
 285
 286         if (!test_and_set_bit(WORK_STRUCT_PENDING, &work->management)) {
 287                 BUG_ON(timer_pending(timer));
 288                 BUG_ON(!list_empty(&work->entry));
 289
 290                 /* This stores wq for the moment, for the timer_fn */
 291                 set_wq_data(work, wq);
 292                 timer->expires = jiffies + delay;
 293                 timer->data = (unsigned long)dwork;
 294                 timer->function = delayed_work_timer_fn;
 295                 add_timer_on(timer, cpu);
 296                 ret = 1;
 297         }
 298         return ret;
 299 }
 300 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 301
 302 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 303 {
 304         unsigned long flags;
 305
 306         /*
 307          * Keep taking off work from the queue until
 308          * done.
 309          */
 310         spin_lock_irqsave(&cwq->lock, flags);
 311         cwq->run_depth++;
 312         if (cwq->run_depth > 3) {
 313                 /* morton gets to eat his hat */
 314                 printk("%s: recursion depth exceeded: %d\n",
 315                         __FUNCTION__, cwq->run_depth);
 316                 dump_stack();
 317         }
 318         while (!list_empty(&cwq->worklist)) {
 319                 struct work_struct *work = list_entry(cwq->worklist.next,
 320                                                 struct work_struct, entry);
 321                 work_func_t f = work->func;
 322
 323                 list_del_init(cwq->worklist.next);
 324                 spin_unlock_irqrestore(&cwq->lock, flags);
 325
 326                 BUG_ON(get_wq_data(work) != cwq);
 327                 if (!test_bit(WORK_STRUCT_NOAUTOREL, &work->management))
 328                         work_release(work);
 329                 f(work);
 330
 331                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 332                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 333                                         "%s/0x%08x/%d\n",
 334                                         current->comm, preempt_count(),
 335                                         current->pid);
 336                         printk(KERN_ERR "    last function: ");
 337                         print_symbol("%s\n", (unsigned long)f);
 338                         debug_show_held_locks(current);
 339                         dump_stack();
 340                 }
 341
 342                 spin_lock_irqsave(&cwq->lock, flags);
 343                 cwq->remove_sequence++;
 344                 wake_up(&cwq->work_done);
 345         }
 346         cwq->run_depth--;
 347         spin_unlock_irqrestore(&cwq->lock, flags);
 348 }
 349
 350 static int worker_thread(void *__cwq)
 351 {
 352         struct cpu_workqueue_struct *cwq = __cwq;
 353         DECLARE_WAITQUEUE(wait, current);
 354         struct k_sigaction sa;
 355         sigset_t blocked;
 356
 357         if (!cwq->freezeable)
 358                 current->flags |= PF_NOFREEZE;
 359
 360         set_user_nice(current, -5);
 361
 362         /* Block and flush all signals */
 363         sigfillset(&blocked);
 364         sigprocmask(SIG_BLOCK, &blocked, NULL);
 365         flush_signals(current);
 366
 367         /*
 368          * We inherited MPOL_INTERLEAVE from the booting kernel.
 369          * Set MPOL_DEFAULT to insure node local allocations.
 370          */
 371         numa_default_policy();
 372
 373         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 374         sa.sa.sa_handler = SIG_IGN;
 375         sa.sa.sa_flags = 0;
 376         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 377         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 378
 379         set_current_state(TASK_INTERRUPTIBLE);
 380         while (!kthread_should_stop()) {
 381                 if (cwq->freezeable)
 382                         try_to_freeze();
 383
 384                 add_wait_queue(&cwq->more_work, &wait);
 385                 if (list_empty(&cwq->worklist))
 386                         schedule();
 387                 else
 388                         __set_current_state(TASK_RUNNING);
 389                 remove_wait_queue(&cwq->more_work, &wait);
 390
 391                 if (!list_empty(&cwq->worklist))
 392                         run_workqueue(cwq);
 393                 set_current_state(TASK_INTERRUPTIBLE);
 394         }
 395         __set_current_state(TASK_RUNNING);
 396         return 0;
 397 }
 398
 399 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 400 {
 401         if (cwq->thread == current) {
 402                 /*
 403                  * Probably keventd trying to flush its own queue. So simply run
 404                  * it by hand rather than deadlocking.
 405                  */
 406                 run_workqueue(cwq);
 407         } else {
 408                 DEFINE_WAIT(wait);
 409                 long sequence_needed;
 410
 411                 spin_lock_irq(&cwq->lock);
 412                 sequence_needed = cwq->insert_sequence;
 413
 414                 while (sequence_needed - cwq->remove_sequence > 0) {
 415                         prepare_to_wait(&cwq->work_done, &wait,
 416                                         TASK_UNINTERRUPTIBLE);
 417                         spin_unlock_irq(&cwq->lock);
 418                         schedule();
 419                         spin_lock_irq(&cwq->lock);
 420                 }
 421                 finish_wait(&cwq->work_done, &wait);
 422                 spin_unlock_irq(&cwq->lock);
 423         }
 424 }
 425
 426 /**
 427  * flush_workqueue - ensure that any scheduled work has run to completion.
 428  * @wq: workqueue to flush
 429  *
 430  * Forces execution of the workqueue and blocks until its completion.
 431  * This is typically used in driver shutdown handlers.
 432  *
 433  * This function will sample each workqueue's current insert_sequence number and
 434  * will sleep until the head sequence is greater than or equal to that.  This
 435  * means that we sleep until all works which were queued on entry have been
 436  * handled, but we are not livelocked by new incoming ones.
 437  *
 438  * This function used to run the workqueues itself.  Now we just wait for the
 439  * helper threads to do it.
 440  */
 441 void fastcall flush_workqueue(struct workqueue_struct *wq)
 442 {
 443         might_sleep();
 444
 445         if (is_single_threaded(wq)) {
 446                 /* Always use first cpu's area. */
 447                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
 448         } else {
 449                 int cpu;
 450
 451                 mutex_lock(&workqueue_mutex);
 452                 for_each_online_cpu(cpu)
 453                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 454                 mutex_unlock(&workqueue_mutex);
 455         }
 456 }
 457 EXPORT_SYMBOL_GPL(flush_workqueue);
 458
 459 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
 460                                                    int cpu, int freezeable)
 461 {
 462         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 463         struct task_struct *p;
 464
 465         spin_lock_init(&cwq->lock);
 466         cwq->wq = wq;
 467         cwq->thread = NULL;
 468         cwq->insert_sequence = 0;
 469         cwq->remove_sequence = 0;
 470         cwq->freezeable = freezeable;
 471         INIT_LIST_HEAD(&cwq->worklist);
 472         init_waitqueue_head(&cwq->more_work);
 473         init_waitqueue_head(&cwq->work_done);
 474
 475         if (is_single_threaded(wq))
 476                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
 477         else
 478                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
 479         if (IS_ERR(p))
 480                 return NULL;
 481         cwq->thread = p;
 482         return p;
 483 }
 484
 485 struct workqueue_struct *__create_workqueue(const char *name,
 486                                             int singlethread, int freezeable)
 487 {
 488         int cpu, destroy = 0;
 489         struct workqueue_struct *wq;
 490         struct task_struct *p;
 491
 492         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 493         if (!wq)
 494                 return NULL;
 495
 496         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 497         if (!wq->cpu_wq) {
 498                 kfree(wq);
 499                 return NULL;
 500         }
 501
 502         wq->name = name;
 503         mutex_lock(&workqueue_mutex);
 504         if (singlethread) {
 505                 INIT_LIST_HEAD(&wq->list);
 506                 p = create_workqueue_thread(wq, singlethread_cpu, freezeable);
 507                 if (!p)
 508                         destroy = 1;
 509                 else
 510                         wake_up_process(p);
 511         } else {
 512                 list_add(&wq->list, &workqueues);
 513                 for_each_online_cpu(cpu) {
 514                         p = create_workqueue_thread(wq, cpu, freezeable);
 515                         if (p) {
 516                                 kthread_bind(p, cpu);
 517                                 wake_up_process(p);
 518                         } else
 519                                 destroy = 1;
 520                 }
 521         }
 522         mutex_unlock(&workqueue_mutex);
 523
 524         /*
 525          * Was there any error during startup? If yes then clean up:
 526          */
 527         if (destroy) {
 528                 destroy_workqueue(wq);
 529                 wq = NULL;
 530         }
 531         return wq;
 532 }
 533 EXPORT_SYMBOL_GPL(__create_workqueue);
 534
 535 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
 536 {
 537         struct cpu_workqueue_struct *cwq;
 538         unsigned long flags;
 539         struct task_struct *p;
 540
 541         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 542         spin_lock_irqsave(&cwq->lock, flags);
 543         p = cwq->thread;
 544         cwq->thread = NULL;
 545         spin_unlock_irqrestore(&cwq->lock, flags);
 546         if (p)
 547                 kthread_stop(p);
 548 }
 549
 550 /**
 551  * destroy_workqueue - safely terminate a workqueue
 552  * @wq: target workqueue
 553  *
 554  * Safely destroy a workqueue. All work currently pending will be done first.
 555  */
 556 void destroy_workqueue(struct workqueue_struct *wq)
 557 {
 558         int cpu;
 559
 560         flush_workqueue(wq);
 561
 562         /* We don't need the distraction of CPUs appearing and vanishing. */
 563         mutex_lock(&workqueue_mutex);
 564         if (is_single_threaded(wq))
 565                 cleanup_workqueue_thread(wq, singlethread_cpu);
 566         else {
 567                 for_each_online_cpu(cpu)
 568                         cleanup_workqueue_thread(wq, cpu);
 569                 list_del(&wq->list);
 570         }
 571         mutex_unlock(&workqueue_mutex);
 572         free_percpu(wq->cpu_wq);
 573         kfree(wq);
 574 }
 575 EXPORT_SYMBOL_GPL(destroy_workqueue);
 576
 577 static struct workqueue_struct *keventd_wq;
 578
 579 /**
 580  * schedule_work - put work task in global workqueue
 581  * @work: job to be done
 582  *
 583  * This puts a job in the kernel-global workqueue.
 584  */
 585 int fastcall schedule_work(struct work_struct *work)
 586 {
 587         return queue_work(keventd_wq, work);
 588 }
 589 EXPORT_SYMBOL(schedule_work);
 590
 591 /**
 592  * schedule_delayed_work - put work task in global workqueue after delay
 593  * @dwork: job to be done
 594  * @delay: number of jiffies to wait or 0 for immediate execution
 595  *
 596  * After waiting for a given time this puts a job in the kernel-global
 597  * workqueue.
 598  */
 599 int fastcall schedule_delayed_work(struct delayed_work *dwork, unsigned long delay)
 600 {
 601         return queue_delayed_work(keventd_wq, dwork, delay);
 602 }
 603 EXPORT_SYMBOL(schedule_delayed_work);
 604
 605 /**
 606  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 607  * @cpu: cpu to use
 608  * @dwork: job to be done
 609  * @delay: number of jiffies to wait
 610  *
 611  * After waiting for a given time this puts a job in the kernel-global
 612  * workqueue on the specified CPU.
 613  */
 614 int schedule_delayed_work_on(int cpu,
 615                         struct delayed_work *dwork, unsigned long delay)
 616 {
 617         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 618 }
 619 EXPORT_SYMBOL(schedule_delayed_work_on);
 620
 621 /**
 622  * schedule_on_each_cpu - call a function on each online CPU from keventd
 623  * @func: the function to call
 624  *
 625  * Returns zero on success.
 626  * Returns -ve errno on failure.
 627  *
 628  * Appears to be racy against CPU hotplug.
 629  *
 630  * schedule_on_each_cpu() is very slow.
 631  */
 632 int schedule_on_each_cpu(work_func_t func)
 633 {
 634         int cpu;
 635         struct work_struct *works;
 636
 637         works = alloc_percpu(struct work_struct);
 638         if (!works)
 639                 return -ENOMEM;
 640
 641         mutex_lock(&workqueue_mutex);
 642         for_each_online_cpu(cpu) {
 643                 INIT_WORK(per_cpu_ptr(works, cpu), func);
 644                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
 645                                 per_cpu_ptr(works, cpu));
 646         }
 647         mutex_unlock(&workqueue_mutex);
 648         flush_workqueue(keventd_wq);
 649         free_percpu(works);
 650         return 0;
 651 }
 652
 653 void flush_scheduled_work(void)
 654 {
 655         flush_workqueue(keventd_wq);
 656 }
 657 EXPORT_SYMBOL(flush_scheduled_work);
 658
 659 /**
 660  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
 661  *                      work whose handler rearms the delayed work.
 662  * @wq:   the controlling workqueue structure
 663  * @dwork: the delayed work struct
 664  */
 665 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 666                                        struct delayed_work *dwork)
 667 {
 668         while (!cancel_delayed_work(dwork))
 669                 flush_workqueue(wq);
 670 }
 671 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 672
 673 /**
 674  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
 675  *                      work whose handler rearms the delayed work.
 676  * @dwork: the delayed work struct
 677  */
 678 void cancel_rearming_delayed_work(struct delayed_work *dwork)
 679 {
 680         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
 681 }
 682 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 683
 684 /**
 685  * execute_in_process_context - reliably execute the routine with user context
 686  * @fn:         the function to execute
 687  * @ew:         guaranteed storage for the execute work structure (must
 688  *              be available when the work executes)
 689  *
 690  * Executes the function immediately if process context is available,
 691  * otherwise schedules the function for delayed execution.
 692  *
 693  * Returns:     0 - function was executed
 694  *              1 - function was scheduled for execution
 695  */
 696 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 697 {
 698         if (!in_interrupt()) {
 699                 fn(&ew->work);
 700                 return 0;
 701         }
 702
 703         INIT_WORK(&ew->work, fn);
 704         schedule_work(&ew->work);
 705
 706         return 1;
 707 }
 708 EXPORT_SYMBOL_GPL(execute_in_process_context);
 709
 710 int keventd_up(void)
 711 {
 712         return keventd_wq != NULL;
 713 }
 714
 715 int current_is_keventd(void)
 716 {
 717         struct cpu_workqueue_struct *cwq;
 718         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 719         int ret = 0;
 720
 721         BUG_ON(!keventd_wq);
 722
 723         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 724         if (current == cwq->thread)
 725                 ret = 1;
 726
 727         return ret;
 728
 729 }
 730
 731 /* Take the work from this (downed) CPU. */
 732 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
 733 {
 734         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 735         struct list_head list;
 736         struct work_struct *work;
 737
 738         spin_lock_irq(&cwq->lock);
 739         list_replace_init(&cwq->worklist, &list);
 740
 741         while (!list_empty(&list)) {
 742                 printk("Taking work for %s\n", wq->name);
 743                 work = list_entry(list.next,struct work_struct,entry);
 744                 list_del(&work->entry);
 745                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
 746         }
 747         spin_unlock_irq(&cwq->lock);
 748 }
 749
 750 /* We're holding the cpucontrol mutex here */
 751 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 752                                   unsigned long action,
 753                                   void *hcpu)
 754 {
 755         unsigned int hotcpu = (unsigned long)hcpu;
 756         struct workqueue_struct *wq;
 757
 758         switch (action) {
 759         case CPU_UP_PREPARE:
 760                 mutex_lock(&workqueue_mutex);
 761                 /* Create a new workqueue thread for it. */
 762                 list_for_each_entry(wq, &workqueues, list) {
 763                         if (!create_workqueue_thread(wq, hotcpu, 0)) {
 764                                 printk("workqueue for %i failed\n", hotcpu);
 765                                 return NOTIFY_BAD;
 766                         }
 767                 }
 768                 break;
 769
 770         case CPU_ONLINE:
 771                 /* Kick off worker threads. */
 772                 list_for_each_entry(wq, &workqueues, list) {
 773                         struct cpu_workqueue_struct *cwq;
 774
 775                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
 776                         kthread_bind(cwq->thread, hotcpu);
 777                         wake_up_process(cwq->thread);
 778                 }
 779                 mutex_unlock(&workqueue_mutex);
 780                 break;
 781
 782         case CPU_UP_CANCELED:
 783                 list_for_each_entry(wq, &workqueues, list) {
 784                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
 785                                 continue;
 786                         /* Unbind so it can run. */
 787                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
 788                                      any_online_cpu(cpu_online_map));
 789                         cleanup_workqueue_thread(wq, hotcpu);
 790                 }
 791                 mutex_unlock(&workqueue_mutex);
 792                 break;
 793
 794         case CPU_DOWN_PREPARE:
 795                 mutex_lock(&workqueue_mutex);
 796                 break;
 797
 798         case CPU_DOWN_FAILED:
 799                 mutex_unlock(&workqueue_mutex);
 800                 break;
 801
 802         case CPU_DEAD:
 803                 list_for_each_entry(wq, &workqueues, list)
 804                         cleanup_workqueue_thread(wq, hotcpu);
 805                 list_for_each_entry(wq, &workqueues, list)
 806                         take_over_work(wq, hotcpu);
 807                 mutex_unlock(&workqueue_mutex);
 808                 break;
 809         }
 810
 811         return NOTIFY_OK;
 812 }
 813
 814 void init_workqueues(void)
 815 {
 816         singlethread_cpu = first_cpu(cpu_possible_map);
 817         hotcpu_notifier(workqueue_cpu_callback, 0);
 818         keventd_wq = create_workqueue("events");
 819         BUG_ON(!keventd_wq);
 820 }
 821