git.oblomov.eu Git - linux-2.6/blob - 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 #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 struct cpu_workqueue_struct {
  41
  42         spinlock_t lock;
  43
  44         struct list_head worklist;
  45         wait_queue_head_t more_work;
  46         struct work_struct *current_work;
  47
  48         struct workqueue_struct *wq;
  49         struct task_struct *thread;
  50         int should_stop;
  51
  52         int run_depth;          /* Detect run_workqueue() recursion depth */
  53 } ____cacheline_aligned;
  54
  55 /*
  56  * The externally visible workqueue abstraction is an array of
  57  * per-CPU workqueues:
  58  */
  59 struct workqueue_struct {
  60         struct cpu_workqueue_struct *cpu_wq;
  61         struct list_head list;
  62         const char *name;
  63         int singlethread;
  64         int freezeable;         /* Freeze threads during suspend */
  65 };
  66
  67 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  68    threads to each one as cpus come/go. */
  69 static DEFINE_MUTEX(workqueue_mutex);
  70 static LIST_HEAD(workqueues);
  71
  72 static int singlethread_cpu __read_mostly;
  73 static cpumask_t cpu_singlethread_map __read_mostly;
  74 /* optimization, we could use cpu_possible_map */
  75 static cpumask_t cpu_populated_map __read_mostly;
  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 wq->singlethread;
  81 }
  82
  83 static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
  84 {
  85         return is_single_threaded(wq)
  86                 ? &cpu_singlethread_map : &cpu_populated_map;
  87 }
  88
  89 /*
  90  * Set the workqueue on which a work item is to be run
  91  * - Must *only* be called if the pending flag is set
  92  */
  93 static inline void set_wq_data(struct work_struct *work,
  94                                 struct cpu_workqueue_struct *cwq)
  95 {
  96         unsigned long new;
  97
  98         BUG_ON(!work_pending(work));
  99
 100         new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
 101         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
 102         atomic_long_set(&work->data, new);
 103 }
 104
 105 static inline
 106 struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
 107 {
 108         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
 109 }
 110
 111 static void insert_work(struct cpu_workqueue_struct *cwq,
 112                                 struct work_struct *work, int tail)
 113 {
 114         set_wq_data(work, cwq);
 115         if (tail)
 116                 list_add_tail(&work->entry, &cwq->worklist);
 117         else
 118                 list_add(&work->entry, &cwq->worklist);
 119         wake_up(&cwq->more_work);
 120 }
 121
 122 /* Preempt must be disabled. */
 123 static void __queue_work(struct cpu_workqueue_struct *cwq,
 124                          struct work_struct *work)
 125 {
 126         unsigned long flags;
 127
 128         spin_lock_irqsave(&cwq->lock, flags);
 129         insert_work(cwq, work, 1);
 130         spin_unlock_irqrestore(&cwq->lock, flags);
 131 }
 132
 133 /**
 134  * queue_work - queue work on a workqueue
 135  * @wq: workqueue to use
 136  * @work: work to queue
 137  *
 138  * Returns 0 if @work was already on a queue, non-zero otherwise.
 139  *
 140  * We queue the work to the CPU it was submitted, but there is no
 141  * guarantee that it will be processed by that CPU.
 142  */
 143 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 144 {
 145         int ret = 0, cpu = get_cpu();
 146
 147         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 148                 if (unlikely(is_single_threaded(wq)))
 149                         cpu = singlethread_cpu;
 150                 BUG_ON(!list_empty(&work->entry));
 151                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 152                 ret = 1;
 153         }
 154         put_cpu();
 155         return ret;
 156 }
 157 EXPORT_SYMBOL_GPL(queue_work);
 158
 159 void delayed_work_timer_fn(unsigned long __data)
 160 {
 161         struct delayed_work *dwork = (struct delayed_work *)__data;
 162         struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
 163         struct workqueue_struct *wq = cwq->wq;
 164         int cpu = smp_processor_id();
 165
 166         if (unlikely(is_single_threaded(wq)))
 167                 cpu = singlethread_cpu;
 168
 169         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), &dwork->work);
 170 }
 171
 172 /**
 173  * queue_delayed_work - queue work on a workqueue after delay
 174  * @wq: workqueue to use
 175  * @dwork: delayable work to queue
 176  * @delay: number of jiffies to wait before queueing
 177  *
 178  * Returns 0 if @work was already on a queue, non-zero otherwise.
 179  */
 180 int fastcall queue_delayed_work(struct workqueue_struct *wq,
 181                         struct delayed_work *dwork, unsigned long delay)
 182 {
 183         int ret = 0;
 184         struct timer_list *timer = &dwork->timer;
 185         struct work_struct *work = &dwork->work;
 186
 187         timer_stats_timer_set_start_info(timer);
 188         if (delay == 0)
 189                 return queue_work(wq, work);
 190
 191         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 192                 BUG_ON(timer_pending(timer));
 193                 BUG_ON(!list_empty(&work->entry));
 194
 195                 /* This stores cwq for the moment, for the timer_fn */
 196                 set_wq_data(work,
 197                         per_cpu_ptr(wq->cpu_wq, raw_smp_processor_id()));
 198                 timer->expires = jiffies + delay;
 199                 timer->data = (unsigned long)dwork;
 200                 timer->function = delayed_work_timer_fn;
 201                 add_timer(timer);
 202                 ret = 1;
 203         }
 204         return ret;
 205 }
 206 EXPORT_SYMBOL_GPL(queue_delayed_work);
 207
 208 /**
 209  * queue_delayed_work_on - queue work on specific CPU after delay
 210  * @cpu: CPU number to execute work on
 211  * @wq: workqueue to use
 212  * @dwork: work to queue
 213  * @delay: number of jiffies to wait before queueing
 214  *
 215  * Returns 0 if @work was already on a queue, non-zero otherwise.
 216  */
 217 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 218                         struct delayed_work *dwork, unsigned long delay)
 219 {
 220         int ret = 0;
 221         struct timer_list *timer = &dwork->timer;
 222         struct work_struct *work = &dwork->work;
 223
 224         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 225                 BUG_ON(timer_pending(timer));
 226                 BUG_ON(!list_empty(&work->entry));
 227
 228                 /* This stores cwq for the moment, for the timer_fn */
 229                 set_wq_data(work,
 230                         per_cpu_ptr(wq->cpu_wq, raw_smp_processor_id()));
 231                 timer->expires = jiffies + delay;
 232                 timer->data = (unsigned long)dwork;
 233                 timer->function = delayed_work_timer_fn;
 234                 add_timer_on(timer, cpu);
 235                 ret = 1;
 236         }
 237         return ret;
 238 }
 239 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 240
 241 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 242 {
 243         spin_lock_irq(&cwq->lock);
 244         cwq->run_depth++;
 245         if (cwq->run_depth > 3) {
 246                 /* morton gets to eat his hat */
 247                 printk("%s: recursion depth exceeded: %d\n",
 248                         __FUNCTION__, cwq->run_depth);
 249                 dump_stack();
 250         }
 251         while (!list_empty(&cwq->worklist)) {
 252                 struct work_struct *work = list_entry(cwq->worklist.next,
 253                                                 struct work_struct, entry);
 254                 work_func_t f = work->func;
 255
 256                 cwq->current_work = work;
 257                 list_del_init(cwq->worklist.next);
 258                 spin_unlock_irq(&cwq->lock);
 259
 260                 BUG_ON(get_wq_data(work) != cwq);
 261                 if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
 262                         work_release(work);
 263                 f(work);
 264
 265                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 266                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 267                                         "%s/0x%08x/%d\n",
 268                                         current->comm, preempt_count(),
 269                                         current->pid);
 270                         printk(KERN_ERR "    last function: ");
 271                         print_symbol("%s\n", (unsigned long)f);
 272                         debug_show_held_locks(current);
 273                         dump_stack();
 274                 }
 275
 276                 spin_lock_irq(&cwq->lock);
 277                 cwq->current_work = NULL;
 278         }
 279         cwq->run_depth--;
 280         spin_unlock_irq(&cwq->lock);
 281 }
 282
 283 /*
 284  * NOTE: the caller must not touch *cwq if this func returns true
 285  */
 286 static int cwq_should_stop(struct cpu_workqueue_struct *cwq)
 287 {
 288         int should_stop = cwq->should_stop;
 289
 290         if (unlikely(should_stop)) {
 291                 spin_lock_irq(&cwq->lock);
 292                 should_stop = cwq->should_stop && list_empty(&cwq->worklist);
 293                 if (should_stop)
 294                         cwq->thread = NULL;
 295                 spin_unlock_irq(&cwq->lock);
 296         }
 297
 298         return should_stop;
 299 }
 300
 301 static int worker_thread(void *__cwq)
 302 {
 303         struct cpu_workqueue_struct *cwq = __cwq;
 304         DEFINE_WAIT(wait);
 305         struct k_sigaction sa;
 306         sigset_t blocked;
 307
 308         if (!cwq->wq->freezeable)
 309                 current->flags |= PF_NOFREEZE;
 310
 311         set_user_nice(current, -5);
 312
 313         /* Block and flush all signals */
 314         sigfillset(&blocked);
 315         sigprocmask(SIG_BLOCK, &blocked, NULL);
 316         flush_signals(current);
 317
 318         /*
 319          * We inherited MPOL_INTERLEAVE from the booting kernel.
 320          * Set MPOL_DEFAULT to insure node local allocations.
 321          */
 322         numa_default_policy();
 323
 324         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 325         sa.sa.sa_handler = SIG_IGN;
 326         sa.sa.sa_flags = 0;
 327         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 328         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 329
 330         for (;;) {
 331                 if (cwq->wq->freezeable)
 332                         try_to_freeze();
 333
 334                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
 335                 if (!cwq->should_stop && list_empty(&cwq->worklist))
 336                         schedule();
 337                 finish_wait(&cwq->more_work, &wait);
 338
 339                 if (cwq_should_stop(cwq))
 340                         break;
 341
 342                 run_workqueue(cwq);
 343         }
 344
 345         return 0;
 346 }
 347
 348 struct wq_barrier {
 349         struct work_struct      work;
 350         struct completion       done;
 351 };
 352
 353 static void wq_barrier_func(struct work_struct *work)
 354 {
 355         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
 356         complete(&barr->done);
 357 }
 358
 359 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
 360                                         struct wq_barrier *barr, int tail)
 361 {
 362         INIT_WORK(&barr->work, wq_barrier_func);
 363         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
 364
 365         init_completion(&barr->done);
 366
 367         insert_work(cwq, &barr->work, tail);
 368 }
 369
 370 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 371 {
 372         if (cwq->thread == current) {
 373                 /*
 374                  * Probably keventd trying to flush its own queue. So simply run
 375                  * it by hand rather than deadlocking.
 376                  */
 377                 run_workqueue(cwq);
 378         } else {
 379                 struct wq_barrier barr;
 380                 int active = 0;
 381
 382                 spin_lock_irq(&cwq->lock);
 383                 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
 384                         insert_wq_barrier(cwq, &barr, 1);
 385                         active = 1;
 386                 }
 387                 spin_unlock_irq(&cwq->lock);
 388
 389                 if (active)
 390                         wait_for_completion(&barr.done);
 391         }
 392 }
 393
 394 /**
 395  * flush_workqueue - ensure that any scheduled work has run to completion.
 396  * @wq: workqueue to flush
 397  *
 398  * Forces execution of the workqueue and blocks until its completion.
 399  * This is typically used in driver shutdown handlers.
 400  *
 401  * We sleep until all works which were queued on entry have been handled,
 402  * but we are not livelocked by new incoming ones.
 403  *
 404  * This function used to run the workqueues itself.  Now we just wait for the
 405  * helper threads to do it.
 406  */
 407 void fastcall flush_workqueue(struct workqueue_struct *wq)
 408 {
 409         const cpumask_t *cpu_map = wq_cpu_map(wq);
 410         int cpu;
 411
 412         might_sleep();
 413         for_each_cpu_mask(cpu, *cpu_map)
 414                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 415 }
 416 EXPORT_SYMBOL_GPL(flush_workqueue);
 417
 418 static void wait_on_work(struct cpu_workqueue_struct *cwq,
 419                                 struct work_struct *work)
 420 {
 421         struct wq_barrier barr;
 422         int running = 0;
 423
 424         spin_lock_irq(&cwq->lock);
 425         if (unlikely(cwq->current_work == work)) {
 426                 insert_wq_barrier(cwq, &barr, 0);
 427                 running = 1;
 428         }
 429         spin_unlock_irq(&cwq->lock);
 430
 431         if (unlikely(running))
 432                 wait_for_completion(&barr.done);
 433 }
 434
 435 /**
 436  * flush_work - block until a work_struct's callback has terminated
 437  * @wq: the workqueue on which the work is queued
 438  * @work: the work which is to be flushed
 439  *
 440  * flush_work() will attempt to cancel the work if it is queued.  If the work's
 441  * callback appears to be running, flush_work() will block until it has
 442  * completed.
 443  *
 444  * flush_work() is designed to be used when the caller is tearing down data
 445  * structures which the callback function operates upon.  It is expected that,
 446  * prior to calling flush_work(), the caller has arranged for the work to not
 447  * be requeued.
 448  */
 449 void flush_work(struct workqueue_struct *wq, struct work_struct *work)
 450 {
 451         const cpumask_t *cpu_map = wq_cpu_map(wq);
 452         struct cpu_workqueue_struct *cwq;
 453         int cpu;
 454
 455         might_sleep();
 456
 457         cwq = get_wq_data(work);
 458         /* Was it ever queued ? */
 459         if (!cwq)
 460                 return;
 461
 462         /*
 463          * This work can't be re-queued, no need to re-check that
 464          * get_wq_data() is still the same when we take cwq->lock.
 465          */
 466         spin_lock_irq(&cwq->lock);
 467         list_del_init(&work->entry);
 468         work_release(work);
 469         spin_unlock_irq(&cwq->lock);
 470
 471         for_each_cpu_mask(cpu, *cpu_map)
 472                 wait_on_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 473 }
 474 EXPORT_SYMBOL_GPL(flush_work);
 475
 476
 477 static struct workqueue_struct *keventd_wq;
 478
 479 /**
 480  * schedule_work - put work task in global workqueue
 481  * @work: job to be done
 482  *
 483  * This puts a job in the kernel-global workqueue.
 484  */
 485 int fastcall schedule_work(struct work_struct *work)
 486 {
 487         return queue_work(keventd_wq, work);
 488 }
 489 EXPORT_SYMBOL(schedule_work);
 490
 491 /**
 492  * schedule_delayed_work - put work task in global workqueue after delay
 493  * @dwork: job to be done
 494  * @delay: number of jiffies to wait or 0 for immediate execution
 495  *
 496  * After waiting for a given time this puts a job in the kernel-global
 497  * workqueue.
 498  */
 499 int fastcall schedule_delayed_work(struct delayed_work *dwork,
 500                                         unsigned long delay)
 501 {
 502         timer_stats_timer_set_start_info(&dwork->timer);
 503         return queue_delayed_work(keventd_wq, dwork, delay);
 504 }
 505 EXPORT_SYMBOL(schedule_delayed_work);
 506
 507 /**
 508  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 509  * @cpu: cpu to use
 510  * @dwork: job to be done
 511  * @delay: number of jiffies to wait
 512  *
 513  * After waiting for a given time this puts a job in the kernel-global
 514  * workqueue on the specified CPU.
 515  */
 516 int schedule_delayed_work_on(int cpu,
 517                         struct delayed_work *dwork, unsigned long delay)
 518 {
 519         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 520 }
 521 EXPORT_SYMBOL(schedule_delayed_work_on);
 522
 523 /**
 524  * schedule_on_each_cpu - call a function on each online CPU from keventd
 525  * @func: the function to call
 526  *
 527  * Returns zero on success.
 528  * Returns -ve errno on failure.
 529  *
 530  * Appears to be racy against CPU hotplug.
 531  *
 532  * schedule_on_each_cpu() is very slow.
 533  */
 534 int schedule_on_each_cpu(work_func_t func)
 535 {
 536         int cpu;
 537         struct work_struct *works;
 538
 539         works = alloc_percpu(struct work_struct);
 540         if (!works)
 541                 return -ENOMEM;
 542
 543         preempt_disable();              /* CPU hotplug */
 544         for_each_online_cpu(cpu) {
 545                 struct work_struct *work = per_cpu_ptr(works, cpu);
 546
 547                 INIT_WORK(work, func);
 548                 set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
 549                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
 550         }
 551         preempt_enable();
 552         flush_workqueue(keventd_wq);
 553         free_percpu(works);
 554         return 0;
 555 }
 556
 557 void flush_scheduled_work(void)
 558 {
 559         flush_workqueue(keventd_wq);
 560 }
 561 EXPORT_SYMBOL(flush_scheduled_work);
 562
 563 void flush_work_keventd(struct work_struct *work)
 564 {
 565         flush_work(keventd_wq, work);
 566 }
 567 EXPORT_SYMBOL(flush_work_keventd);
 568
 569 /**
 570  * cancel_rearming_delayed_workqueue - kill off a delayed work whose handler rearms the delayed work.
 571  * @wq:   the controlling workqueue structure
 572  * @dwork: the delayed work struct
 573  *
 574  * Note that the work callback function may still be running on return from
 575  * cancel_delayed_work(). Run flush_workqueue() or flush_work() to wait on it.
 576  */
 577 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 578                                        struct delayed_work *dwork)
 579 {
 580         /* Was it ever queued ? */
 581         if (!get_wq_data(&dwork->work))
 582                 return;
 583
 584         while (!cancel_delayed_work(dwork))
 585                 flush_workqueue(wq);
 586 }
 587 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 588
 589 /**
 590  * cancel_rearming_delayed_work - kill off a delayed keventd work whose handler rearms the delayed work.
 591  * @dwork: the delayed work struct
 592  */
 593 void cancel_rearming_delayed_work(struct delayed_work *dwork)
 594 {
 595         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
 596 }
 597 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 598
 599 /**
 600  * execute_in_process_context - reliably execute the routine with user context
 601  * @fn:         the function to execute
 602  * @ew:         guaranteed storage for the execute work structure (must
 603  *              be available when the work executes)
 604  *
 605  * Executes the function immediately if process context is available,
 606  * otherwise schedules the function for delayed execution.
 607  *
 608  * Returns:     0 - function was executed
 609  *              1 - function was scheduled for execution
 610  */
 611 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 612 {
 613         if (!in_interrupt()) {
 614                 fn(&ew->work);
 615                 return 0;
 616         }
 617
 618         INIT_WORK(&ew->work, fn);
 619         schedule_work(&ew->work);
 620
 621         return 1;
 622 }
 623 EXPORT_SYMBOL_GPL(execute_in_process_context);
 624
 625 int keventd_up(void)
 626 {
 627         return keventd_wq != NULL;
 628 }
 629
 630 int current_is_keventd(void)
 631 {
 632         struct cpu_workqueue_struct *cwq;
 633         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 634         int ret = 0;
 635
 636         BUG_ON(!keventd_wq);
 637
 638         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 639         if (current == cwq->thread)
 640                 ret = 1;
 641
 642         return ret;
 643
 644 }
 645
 646 static struct cpu_workqueue_struct *
 647 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 648 {
 649         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 650
 651         cwq->wq = wq;
 652         spin_lock_init(&cwq->lock);
 653         INIT_LIST_HEAD(&cwq->worklist);
 654         init_waitqueue_head(&cwq->more_work);
 655
 656         return cwq;
 657 }
 658
 659 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 660 {
 661         struct workqueue_struct *wq = cwq->wq;
 662         const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 663         struct task_struct *p;
 664
 665         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
 666         /*
 667          * Nobody can add the work_struct to this cwq,
 668          *      if (caller is __create_workqueue)
 669          *              nobody should see this wq
 670          *      else // caller is CPU_UP_PREPARE
 671          *              cpu is not on cpu_online_map
 672          * so we can abort safely.
 673          */
 674         if (IS_ERR(p))
 675                 return PTR_ERR(p);
 676
 677         cwq->thread = p;
 678         cwq->should_stop = 0;
 679
 680         return 0;
 681 }
 682
 683 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 684 {
 685         struct task_struct *p = cwq->thread;
 686
 687         if (p != NULL) {
 688                 if (cpu >= 0)
 689                         kthread_bind(p, cpu);
 690                 wake_up_process(p);
 691         }
 692 }
 693
 694 struct workqueue_struct *__create_workqueue(const char *name,
 695                                             int singlethread, int freezeable)
 696 {
 697         struct workqueue_struct *wq;
 698         struct cpu_workqueue_struct *cwq;
 699         int err = 0, cpu;
 700
 701         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 702         if (!wq)
 703                 return NULL;
 704
 705         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 706         if (!wq->cpu_wq) {
 707                 kfree(wq);
 708                 return NULL;
 709         }
 710
 711         wq->name = name;
 712         wq->singlethread = singlethread;
 713         wq->freezeable = freezeable;
 714         INIT_LIST_HEAD(&wq->list);
 715
 716         if (singlethread) {
 717                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
 718                 err = create_workqueue_thread(cwq, singlethread_cpu);
 719                 start_workqueue_thread(cwq, -1);
 720         } else {
 721                 mutex_lock(&workqueue_mutex);
 722                 list_add(&wq->list, &workqueues);
 723
 724                 for_each_possible_cpu(cpu) {
 725                         cwq = init_cpu_workqueue(wq, cpu);
 726                         if (err || !cpu_online(cpu))
 727                                 continue;
 728                         err = create_workqueue_thread(cwq, cpu);
 729                         start_workqueue_thread(cwq, cpu);
 730                 }
 731                 mutex_unlock(&workqueue_mutex);
 732         }
 733
 734         if (err) {
 735                 destroy_workqueue(wq);
 736                 wq = NULL;
 737         }
 738         return wq;
 739 }
 740 EXPORT_SYMBOL_GPL(__create_workqueue);
 741
 742 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 743 {
 744         struct wq_barrier barr;
 745         int alive = 0;
 746
 747         spin_lock_irq(&cwq->lock);
 748         if (cwq->thread != NULL) {
 749                 insert_wq_barrier(cwq, &barr, 1);
 750                 cwq->should_stop = 1;
 751                 alive = 1;
 752         }
 753         spin_unlock_irq(&cwq->lock);
 754
 755         if (alive) {
 756                 wait_for_completion(&barr.done);
 757
 758                 while (unlikely(cwq->thread != NULL))
 759                         cpu_relax();
 760                 /*
 761                  * Wait until cwq->thread unlocks cwq->lock,
 762                  * it won't touch *cwq after that.
 763                  */
 764                 smp_rmb();
 765                 spin_unlock_wait(&cwq->lock);
 766         }
 767 }
 768
 769 /**
 770  * destroy_workqueue - safely terminate a workqueue
 771  * @wq: target workqueue
 772  *
 773  * Safely destroy a workqueue. All work currently pending will be done first.
 774  */
 775 void destroy_workqueue(struct workqueue_struct *wq)
 776 {
 777         const cpumask_t *cpu_map = wq_cpu_map(wq);
 778         struct cpu_workqueue_struct *cwq;
 779         int cpu;
 780
 781         mutex_lock(&workqueue_mutex);
 782         list_del(&wq->list);
 783         mutex_unlock(&workqueue_mutex);
 784
 785         for_each_cpu_mask(cpu, *cpu_map) {
 786                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 787                 cleanup_workqueue_thread(cwq, cpu);
 788         }
 789
 790         free_percpu(wq->cpu_wq);
 791         kfree(wq);
 792 }
 793 EXPORT_SYMBOL_GPL(destroy_workqueue);
 794
 795 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 796                                                 unsigned long action,
 797                                                 void *hcpu)
 798 {
 799         unsigned int cpu = (unsigned long)hcpu;
 800         struct cpu_workqueue_struct *cwq;
 801         struct workqueue_struct *wq;
 802
 803         switch (action) {
 804         case CPU_LOCK_ACQUIRE:
 805                 mutex_lock(&workqueue_mutex);
 806                 return NOTIFY_OK;
 807
 808         case CPU_LOCK_RELEASE:
 809                 mutex_unlock(&workqueue_mutex);
 810                 return NOTIFY_OK;
 811
 812         case CPU_UP_PREPARE:
 813                 cpu_set(cpu, cpu_populated_map);
 814         }
 815
 816         list_for_each_entry(wq, &workqueues, list) {
 817                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 818
 819                 switch (action) {
 820                 case CPU_UP_PREPARE:
 821                         if (!create_workqueue_thread(cwq, cpu))
 822                                 break;
 823                         printk(KERN_ERR "workqueue for %i failed\n", cpu);
 824                         return NOTIFY_BAD;
 825
 826                 case CPU_ONLINE:
 827                         start_workqueue_thread(cwq, cpu);
 828                         break;
 829
 830                 case CPU_UP_CANCELED:
 831                         start_workqueue_thread(cwq, -1);
 832                 case CPU_DEAD:
 833                         cleanup_workqueue_thread(cwq, cpu);
 834                         break;
 835                 }
 836         }
 837
 838         return NOTIFY_OK;
 839 }
 840
 841 void __init init_workqueues(void)
 842 {
 843         cpu_populated_map = cpu_online_map;
 844         singlethread_cpu = first_cpu(cpu_possible_map);
 845         cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
 846         hotcpu_notifier(workqueue_cpu_callback, 0);
 847         keventd_wq = create_workqueue("events");
 848         BUG_ON(!keventd_wq);
 849 }