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