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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         const char *name;
  62         struct list_head list;  /* Empty if single thread */
  63         int freezeable;         /* Freeze threads during suspend */
  64 };
  65
  66 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  67    threads to each one as cpus come/go. */
  68 static DEFINE_MUTEX(workqueue_mutex);
  69 static LIST_HEAD(workqueues);
  70
  71 static int singlethread_cpu __read_mostly;
  72 /* optimization, we could use cpu_possible_map */
  73 static cpumask_t cpu_populated_map __read_mostly;
  74
  75 /* If it's single threaded, it isn't in the list of workqueues. */
  76 static inline int is_single_threaded(struct workqueue_struct *wq)
  77 {
  78         return list_empty(&wq->list);
  79 }
  80
  81 /*
  82  * Set the workqueue on which a work item is to be run
  83  * - Must *only* be called if the pending flag is set
  84  */
  85 static inline void set_wq_data(struct work_struct *work, void *wq)
  86 {
  87         unsigned long new;
  88
  89         BUG_ON(!work_pending(work));
  90
  91         new = (unsigned long) wq | (1UL << WORK_STRUCT_PENDING);
  92         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
  93         atomic_long_set(&work->data, new);
  94 }
  95
  96 static inline void *get_wq_data(struct work_struct *work)
  97 {
  98         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
  99 }
 100
 101 static void insert_work(struct cpu_workqueue_struct *cwq,
 102                                 struct work_struct *work, int tail)
 103 {
 104         set_wq_data(work, cwq);
 105         if (tail)
 106                 list_add_tail(&work->entry, &cwq->worklist);
 107         else
 108                 list_add(&work->entry, &cwq->worklist);
 109         wake_up(&cwq->more_work);
 110 }
 111
 112 /* Preempt must be disabled. */
 113 static void __queue_work(struct cpu_workqueue_struct *cwq,
 114                          struct work_struct *work)
 115 {
 116         unsigned long flags;
 117
 118         spin_lock_irqsave(&cwq->lock, flags);
 119         insert_work(cwq, work, 1);
 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_data_bits(work))) {
 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 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  * @dwork: 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         timer_stats_timer_set_start_info(timer);
 177         if (delay == 0)
 178                 return queue_work(wq, work);
 179
 180         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 181                 BUG_ON(timer_pending(timer));
 182                 BUG_ON(!list_empty(&work->entry));
 183
 184                 /* This stores wq for the moment, for the timer_fn */
 185                 set_wq_data(work, wq);
 186                 timer->expires = jiffies + delay;
 187                 timer->data = (unsigned long)dwork;
 188                 timer->function = delayed_work_timer_fn;
 189                 add_timer(timer);
 190                 ret = 1;
 191         }
 192         return ret;
 193 }
 194 EXPORT_SYMBOL_GPL(queue_delayed_work);
 195
 196 /**
 197  * queue_delayed_work_on - queue work on specific CPU after delay
 198  * @cpu: CPU number to execute work on
 199  * @wq: workqueue to use
 200  * @dwork: work to queue
 201  * @delay: number of jiffies to wait before queueing
 202  *
 203  * Returns 0 if @work was already on a queue, non-zero otherwise.
 204  */
 205 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 206                         struct delayed_work *dwork, unsigned long delay)
 207 {
 208         int ret = 0;
 209         struct timer_list *timer = &dwork->timer;
 210         struct work_struct *work = &dwork->work;
 211
 212         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 213                 BUG_ON(timer_pending(timer));
 214                 BUG_ON(!list_empty(&work->entry));
 215
 216                 /* This stores wq for the moment, for the timer_fn */
 217                 set_wq_data(work, wq);
 218                 timer->expires = jiffies + delay;
 219                 timer->data = (unsigned long)dwork;
 220                 timer->function = delayed_work_timer_fn;
 221                 add_timer_on(timer, cpu);
 222                 ret = 1;
 223         }
 224         return ret;
 225 }
 226 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 227
 228 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 229 {
 230         unsigned long flags;
 231
 232         /*
 233          * Keep taking off work from the queue until
 234          * done.
 235          */
 236         spin_lock_irqsave(&cwq->lock, flags);
 237         cwq->run_depth++;
 238         if (cwq->run_depth > 3) {
 239                 /* morton gets to eat his hat */
 240                 printk("%s: recursion depth exceeded: %d\n",
 241                         __FUNCTION__, cwq->run_depth);
 242                 dump_stack();
 243         }
 244         while (!list_empty(&cwq->worklist)) {
 245                 struct work_struct *work = list_entry(cwq->worklist.next,
 246                                                 struct work_struct, entry);
 247                 work_func_t f = work->func;
 248
 249                 cwq->current_work = work;
 250                 list_del_init(cwq->worklist.next);
 251                 spin_unlock_irqrestore(&cwq->lock, flags);
 252
 253                 BUG_ON(get_wq_data(work) != cwq);
 254                 if (!test_bit(WORK_STRUCT_NOAUTOREL, work_data_bits(work)))
 255                         work_release(work);
 256                 f(work);
 257
 258                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 259                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 260                                         "%s/0x%08x/%d\n",
 261                                         current->comm, preempt_count(),
 262                                         current->pid);
 263                         printk(KERN_ERR "    last function: ");
 264                         print_symbol("%s\n", (unsigned long)f);
 265                         debug_show_held_locks(current);
 266                         dump_stack();
 267                 }
 268
 269                 spin_lock_irqsave(&cwq->lock, flags);
 270                 cwq->current_work = NULL;
 271         }
 272         cwq->run_depth--;
 273         spin_unlock_irqrestore(&cwq->lock, flags);
 274 }
 275
 276 /*
 277  * NOTE: the caller must not touch *cwq if this func returns true
 278  */
 279 static int cwq_should_stop(struct cpu_workqueue_struct *cwq)
 280 {
 281         int should_stop = cwq->should_stop;
 282
 283         if (unlikely(should_stop)) {
 284                 spin_lock_irq(&cwq->lock);
 285                 should_stop = cwq->should_stop && list_empty(&cwq->worklist);
 286                 if (should_stop)
 287                         cwq->thread = NULL;
 288                 spin_unlock_irq(&cwq->lock);
 289         }
 290
 291         return should_stop;
 292 }
 293
 294 static int worker_thread(void *__cwq)
 295 {
 296         struct cpu_workqueue_struct *cwq = __cwq;
 297         DEFINE_WAIT(wait);
 298         struct k_sigaction sa;
 299         sigset_t blocked;
 300
 301         if (!cwq->wq->freezeable)
 302                 current->flags |= PF_NOFREEZE;
 303
 304         set_user_nice(current, -5);
 305
 306         /* Block and flush all signals */
 307         sigfillset(&blocked);
 308         sigprocmask(SIG_BLOCK, &blocked, NULL);
 309         flush_signals(current);
 310
 311         /*
 312          * We inherited MPOL_INTERLEAVE from the booting kernel.
 313          * Set MPOL_DEFAULT to insure node local allocations.
 314          */
 315         numa_default_policy();
 316
 317         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 318         sa.sa.sa_handler = SIG_IGN;
 319         sa.sa.sa_flags = 0;
 320         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 321         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 322
 323         for (;;) {
 324                 if (cwq->wq->freezeable)
 325                         try_to_freeze();
 326
 327                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
 328                 if (!cwq->should_stop && list_empty(&cwq->worklist))
 329                         schedule();
 330                 finish_wait(&cwq->more_work, &wait);
 331
 332                 if (cwq_should_stop(cwq))
 333                         break;
 334
 335                 run_workqueue(cwq);
 336         }
 337
 338         return 0;
 339 }
 340
 341 struct wq_barrier {
 342         struct work_struct      work;
 343         struct completion       done;
 344 };
 345
 346 static void wq_barrier_func(struct work_struct *work)
 347 {
 348         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
 349         complete(&barr->done);
 350 }
 351
 352 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
 353                                         struct wq_barrier *barr, int tail)
 354 {
 355         INIT_WORK(&barr->work, wq_barrier_func);
 356         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
 357
 358         init_completion(&barr->done);
 359
 360         insert_work(cwq, &barr->work, tail);
 361 }
 362
 363 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 364 {
 365         if (cwq->thread == current) {
 366                 /*
 367                  * Probably keventd trying to flush its own queue. So simply run
 368                  * it by hand rather than deadlocking.
 369                  */
 370                 run_workqueue(cwq);
 371         } else {
 372                 struct wq_barrier barr;
 373                 int active = 0;
 374
 375                 spin_lock_irq(&cwq->lock);
 376                 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
 377                         insert_wq_barrier(cwq, &barr, 1);
 378                         active = 1;
 379                 }
 380                 spin_unlock_irq(&cwq->lock);
 381
 382                 if (active)
 383                         wait_for_completion(&barr.done);
 384         }
 385 }
 386
 387 /**
 388  * flush_workqueue - ensure that any scheduled work has run to completion.
 389  * @wq: workqueue to flush
 390  *
 391  * Forces execution of the workqueue and blocks until its completion.
 392  * This is typically used in driver shutdown handlers.
 393  *
 394  * We sleep until all works which were queued on entry have been handled,
 395  * but we are not livelocked by new incoming ones.
 396  *
 397  * This function used to run the workqueues itself.  Now we just wait for the
 398  * helper threads to do it.
 399  */
 400 void fastcall flush_workqueue(struct workqueue_struct *wq)
 401 {
 402         if (is_single_threaded(wq))
 403                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
 404         else {
 405                 int cpu;
 406
 407                 for_each_cpu_mask(cpu, cpu_populated_map)
 408                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 409         }
 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         struct cpu_workqueue_struct *cwq;
 447
 448         cwq = get_wq_data(work);
 449         /* Was it ever queued ? */
 450         if (!cwq)
 451                 return;
 452
 453         /*
 454          * This work can't be re-queued, no need to re-check that
 455          * get_wq_data() is still the same when we take cwq->lock.
 456          */
 457         spin_lock_irq(&cwq->lock);
 458         list_del_init(&work->entry);
 459         work_release(work);
 460         spin_unlock_irq(&cwq->lock);
 461
 462         if (is_single_threaded(wq))
 463                 wait_on_work(per_cpu_ptr(wq->cpu_wq, singlethread_cpu), work);
 464         else {
 465                 int cpu;
 466
 467                 for_each_cpu_mask(cpu, cpu_populated_map)
 468                         wait_on_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 469         }
 470 }
 471 EXPORT_SYMBOL_GPL(flush_work);
 472
 473
 474 static struct workqueue_struct *keventd_wq;
 475
 476 /**
 477  * schedule_work - put work task in global workqueue
 478  * @work: job to be done
 479  *
 480  * This puts a job in the kernel-global workqueue.
 481  */
 482 int fastcall schedule_work(struct work_struct *work)
 483 {
 484         return queue_work(keventd_wq, work);
 485 }
 486 EXPORT_SYMBOL(schedule_work);
 487
 488 /**
 489  * schedule_delayed_work - put work task in global workqueue after delay
 490  * @dwork: job to be done
 491  * @delay: number of jiffies to wait or 0 for immediate execution
 492  *
 493  * After waiting for a given time this puts a job in the kernel-global
 494  * workqueue.
 495  */
 496 int fastcall schedule_delayed_work(struct delayed_work *dwork,
 497                                         unsigned long delay)
 498 {
 499         timer_stats_timer_set_start_info(&dwork->timer);
 500         return queue_delayed_work(keventd_wq, dwork, delay);
 501 }
 502 EXPORT_SYMBOL(schedule_delayed_work);
 503
 504 /**
 505  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 506  * @cpu: cpu to use
 507  * @dwork: job to be done
 508  * @delay: number of jiffies to wait
 509  *
 510  * After waiting for a given time this puts a job in the kernel-global
 511  * workqueue on the specified CPU.
 512  */
 513 int schedule_delayed_work_on(int cpu,
 514                         struct delayed_work *dwork, unsigned long delay)
 515 {
 516         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 517 }
 518 EXPORT_SYMBOL(schedule_delayed_work_on);
 519
 520 /**
 521  * schedule_on_each_cpu - call a function on each online CPU from keventd
 522  * @func: the function to call
 523  *
 524  * Returns zero on success.
 525  * Returns -ve errno on failure.
 526  *
 527  * Appears to be racy against CPU hotplug.
 528  *
 529  * schedule_on_each_cpu() is very slow.
 530  */
 531 int schedule_on_each_cpu(work_func_t func)
 532 {
 533         int cpu;
 534         struct work_struct *works;
 535
 536         works = alloc_percpu(struct work_struct);
 537         if (!works)
 538                 return -ENOMEM;
 539
 540         preempt_disable();              /* CPU hotplug */
 541         for_each_online_cpu(cpu) {
 542                 struct work_struct *work = per_cpu_ptr(works, cpu);
 543
 544                 INIT_WORK(work, func);
 545                 set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
 546                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
 547         }
 548         preempt_enable();
 549         flush_workqueue(keventd_wq);
 550         free_percpu(works);
 551         return 0;
 552 }
 553
 554 void flush_scheduled_work(void)
 555 {
 556         flush_workqueue(keventd_wq);
 557 }
 558 EXPORT_SYMBOL(flush_scheduled_work);
 559
 560 void flush_work_keventd(struct work_struct *work)
 561 {
 562         flush_work(keventd_wq, work);
 563 }
 564 EXPORT_SYMBOL(flush_work_keventd);
 565
 566 /**
 567  * cancel_rearming_delayed_workqueue - reliably kill off a delayed work whose handler rearms the delayed work.
 568  * @wq:   the controlling workqueue structure
 569  * @dwork: the delayed work struct
 570  */
 571 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 572                                        struct delayed_work *dwork)
 573 {
 574         while (!cancel_delayed_work(dwork))
 575                 flush_workqueue(wq);
 576 }
 577 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 578
 579 /**
 580  * cancel_rearming_delayed_work - reliably kill off a delayed keventd work whose handler rearms the delayed work.
 581  * @dwork: the delayed work struct
 582  */
 583 void cancel_rearming_delayed_work(struct delayed_work *dwork)
 584 {
 585         cancel_rearming_delayed_workqueue(keventd_wq, dwork);
 586 }
 587 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 588
 589 /**
 590  * execute_in_process_context - reliably execute the routine with user context
 591  * @fn:         the function to execute
 592  * @ew:         guaranteed storage for the execute work structure (must
 593  *              be available when the work executes)
 594  *
 595  * Executes the function immediately if process context is available,
 596  * otherwise schedules the function for delayed execution.
 597  *
 598  * Returns:     0 - function was executed
 599  *              1 - function was scheduled for execution
 600  */
 601 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 602 {
 603         if (!in_interrupt()) {
 604                 fn(&ew->work);
 605                 return 0;
 606         }
 607
 608         INIT_WORK(&ew->work, fn);
 609         schedule_work(&ew->work);
 610
 611         return 1;
 612 }
 613 EXPORT_SYMBOL_GPL(execute_in_process_context);
 614
 615 int keventd_up(void)
 616 {
 617         return keventd_wq != NULL;
 618 }
 619
 620 int current_is_keventd(void)
 621 {
 622         struct cpu_workqueue_struct *cwq;
 623         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 624         int ret = 0;
 625
 626         BUG_ON(!keventd_wq);
 627
 628         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 629         if (current == cwq->thread)
 630                 ret = 1;
 631
 632         return ret;
 633
 634 }
 635
 636 static struct cpu_workqueue_struct *
 637 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 638 {
 639         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 640
 641         cwq->wq = wq;
 642         spin_lock_init(&cwq->lock);
 643         INIT_LIST_HEAD(&cwq->worklist);
 644         init_waitqueue_head(&cwq->more_work);
 645
 646         return cwq;
 647 }
 648
 649 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 650 {
 651         struct workqueue_struct *wq = cwq->wq;
 652         const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 653         struct task_struct *p;
 654
 655         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
 656         /*
 657          * Nobody can add the work_struct to this cwq,
 658          *      if (caller is __create_workqueue)
 659          *              nobody should see this wq
 660          *      else // caller is CPU_UP_PREPARE
 661          *              cpu is not on cpu_online_map
 662          * so we can abort safely.
 663          */
 664         if (IS_ERR(p))
 665                 return PTR_ERR(p);
 666
 667         cwq->thread = p;
 668         cwq->should_stop = 0;
 669         if (!is_single_threaded(wq))
 670                 kthread_bind(p, cpu);
 671
 672         if (is_single_threaded(wq) || cpu_online(cpu))
 673                 wake_up_process(p);
 674
 675         return 0;
 676 }
 677
 678 struct workqueue_struct *__create_workqueue(const char *name,
 679                                             int singlethread, int freezeable)
 680 {
 681         struct workqueue_struct *wq;
 682         struct cpu_workqueue_struct *cwq;
 683         int err = 0, cpu;
 684
 685         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 686         if (!wq)
 687                 return NULL;
 688
 689         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 690         if (!wq->cpu_wq) {
 691                 kfree(wq);
 692                 return NULL;
 693         }
 694
 695         wq->name = name;
 696         wq->freezeable = freezeable;
 697
 698         if (singlethread) {
 699                 INIT_LIST_HEAD(&wq->list);
 700                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
 701                 err = create_workqueue_thread(cwq, singlethread_cpu);
 702         } else {
 703                 mutex_lock(&workqueue_mutex);
 704                 list_add(&wq->list, &workqueues);
 705
 706                 for_each_possible_cpu(cpu) {
 707                         cwq = init_cpu_workqueue(wq, cpu);
 708                         if (err || !cpu_online(cpu))
 709                                 continue;
 710                         err = create_workqueue_thread(cwq, cpu);
 711                 }
 712                 mutex_unlock(&workqueue_mutex);
 713         }
 714
 715         if (err) {
 716                 destroy_workqueue(wq);
 717                 wq = NULL;
 718         }
 719         return wq;
 720 }
 721 EXPORT_SYMBOL_GPL(__create_workqueue);
 722
 723 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 724 {
 725         struct wq_barrier barr;
 726         int alive = 0;
 727
 728         spin_lock_irq(&cwq->lock);
 729         if (cwq->thread != NULL) {
 730                 insert_wq_barrier(cwq, &barr, 1);
 731                 cwq->should_stop = 1;
 732                 alive = 1;
 733         }
 734         spin_unlock_irq(&cwq->lock);
 735
 736         if (alive) {
 737                 wait_for_completion(&barr.done);
 738
 739                 while (unlikely(cwq->thread != NULL))
 740                         cpu_relax();
 741                 /*
 742                  * Wait until cwq->thread unlocks cwq->lock,
 743                  * it won't touch *cwq after that.
 744                  */
 745                 smp_rmb();
 746                 spin_unlock_wait(&cwq->lock);
 747         }
 748 }
 749
 750 /**
 751  * destroy_workqueue - safely terminate a workqueue
 752  * @wq: target workqueue
 753  *
 754  * Safely destroy a workqueue. All work currently pending will be done first.
 755  */
 756 void destroy_workqueue(struct workqueue_struct *wq)
 757 {
 758         struct cpu_workqueue_struct *cwq;
 759
 760         if (is_single_threaded(wq)) {
 761                 cwq = per_cpu_ptr(wq->cpu_wq, singlethread_cpu);
 762                 cleanup_workqueue_thread(cwq, singlethread_cpu);
 763         } else {
 764                 int cpu;
 765
 766                 mutex_lock(&workqueue_mutex);
 767                 list_del(&wq->list);
 768                 mutex_unlock(&workqueue_mutex);
 769
 770                 for_each_cpu_mask(cpu, cpu_populated_map) {
 771                         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 772                         cleanup_workqueue_thread(cwq, cpu);
 773                 }
 774         }
 775
 776         free_percpu(wq->cpu_wq);
 777         kfree(wq);
 778 }
 779 EXPORT_SYMBOL_GPL(destroy_workqueue);
 780
 781 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 782                                                 unsigned long action,
 783                                                 void *hcpu)
 784 {
 785         unsigned int cpu = (unsigned long)hcpu;
 786         struct cpu_workqueue_struct *cwq;
 787         struct workqueue_struct *wq;
 788
 789         switch (action) {
 790         case CPU_LOCK_ACQUIRE:
 791                 mutex_lock(&workqueue_mutex);
 792                 return NOTIFY_OK;
 793
 794         case CPU_LOCK_RELEASE:
 795                 mutex_unlock(&workqueue_mutex);
 796                 return NOTIFY_OK;
 797
 798         case CPU_UP_PREPARE:
 799                 cpu_set(cpu, cpu_populated_map);
 800         }
 801
 802         list_for_each_entry(wq, &workqueues, list) {
 803                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 804
 805                 switch (action) {
 806                 case CPU_UP_PREPARE:
 807                         if (!create_workqueue_thread(cwq, cpu))
 808                                 break;
 809                         printk(KERN_ERR "workqueue for %i failed\n", cpu);
 810                         return NOTIFY_BAD;
 811
 812                 case CPU_ONLINE:
 813                         wake_up_process(cwq->thread);
 814                         break;
 815
 816                 case CPU_UP_CANCELED:
 817                         if (cwq->thread)
 818                                 wake_up_process(cwq->thread);
 819                 case CPU_DEAD:
 820                         cleanup_workqueue_thread(cwq, cpu);
 821                         break;
 822                 }
 823         }
 824
 825         return NOTIFY_OK;
 826 }
 827
 828 void init_workqueues(void)
 829 {
 830         cpu_populated_map = cpu_online_map;
 831         singlethread_cpu = first_cpu(cpu_possible_map);
 832         hotcpu_notifier(workqueue_cpu_callback, 0);
 833         keventd_wq = create_workqueue("events");
 834         BUG_ON(!keventd_wq);
 835 }