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
  32 /*
  33  * The per-CPU workqueue (if single thread, we always use the first
  34  * possible cpu).
  35  *
  36  * The sequence counters are for flush_scheduled_work().  It wants to wait
  37  * until until all currently-scheduled works are completed, but it doesn't
  38  * want to be livelocked by new, incoming ones.  So it waits until
  39  * remove_sequence is >= the insert_sequence which pertained when
  40  * flush_scheduled_work() was called.
  41  */
  42 struct cpu_workqueue_struct {
  43
  44         spinlock_t lock;
  45
  46         long remove_sequence;   /* Least-recently added (next to run) */
  47         long insert_sequence;   /* Next to add */
  48
  49         struct list_head worklist;
  50         wait_queue_head_t more_work;
  51         wait_queue_head_t work_done;
  52
  53         struct workqueue_struct *wq;
  54         struct task_struct *thread;
  55
  56         int run_depth;          /* Detect run_workqueue() recursion depth */
  57 } ____cacheline_aligned;
  58
  59 /*
  60  * The externally visible workqueue abstraction is an array of
  61  * per-CPU workqueues:
  62  */
  63 struct workqueue_struct {
  64         struct cpu_workqueue_struct *cpu_wq;
  65         const char *name;
  66         struct list_head list;  /* Empty if single thread */
  67 };
  68
  69 /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
  70    threads to each one as cpus come/go. */
  71 static DEFINE_SPINLOCK(workqueue_lock);
  72 static LIST_HEAD(workqueues);
  73
  74 static int singlethread_cpu;
  75
  76 /* If it's single threaded, it isn't in the list of workqueues. */
  77 static inline int is_single_threaded(struct workqueue_struct *wq)
  78 {
  79         return list_empty(&wq->list);
  80 }
  81
  82 /* Preempt must be disabled. */
  83 static void __queue_work(struct cpu_workqueue_struct *cwq,
  84                          struct work_struct *work)
  85 {
  86         unsigned long flags;
  87
  88         spin_lock_irqsave(&cwq->lock, flags);
  89         work->wq_data = cwq;
  90         list_add_tail(&work->entry, &cwq->worklist);
  91         cwq->insert_sequence++;
  92         wake_up(&cwq->more_work);
  93         spin_unlock_irqrestore(&cwq->lock, flags);
  94 }
  95
  96 /*
  97  * Queue work on a workqueue. Return non-zero if it was successfully
  98  * added.
  99  *
 100  * We queue the work to the CPU it was submitted, but there is no
 101  * guarantee that it will be processed by that CPU.
 102  */
 103 int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
 104 {
 105         int ret = 0, cpu = get_cpu();
 106
 107         if (!test_and_set_bit(0, &work->pending)) {
 108                 if (unlikely(is_single_threaded(wq)))
 109                         cpu = singlethread_cpu;
 110                 BUG_ON(!list_empty(&work->entry));
 111                 __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 112                 ret = 1;
 113         }
 114         put_cpu();
 115         return ret;
 116 }
 117 EXPORT_SYMBOL_GPL(queue_work);
 118
 119 static void delayed_work_timer_fn(unsigned long __data)
 120 {
 121         struct work_struct *work = (struct work_struct *)__data;
 122         struct workqueue_struct *wq = work->wq_data;
 123         int cpu = smp_processor_id();
 124
 125         if (unlikely(is_single_threaded(wq)))
 126                 cpu = singlethread_cpu;
 127
 128         __queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 129 }
 130
 131 int fastcall queue_delayed_work(struct workqueue_struct *wq,
 132                         struct work_struct *work, unsigned long delay)
 133 {
 134         int ret = 0;
 135         struct timer_list *timer = &work->timer;
 136
 137         if (!test_and_set_bit(0, &work->pending)) {
 138                 BUG_ON(timer_pending(timer));
 139                 BUG_ON(!list_empty(&work->entry));
 140
 141                 /* This stores wq for the moment, for the timer_fn */
 142                 work->wq_data = wq;
 143                 timer->expires = jiffies + delay;
 144                 timer->data = (unsigned long)work;
 145                 timer->function = delayed_work_timer_fn;
 146                 add_timer(timer);
 147                 ret = 1;
 148         }
 149         return ret;
 150 }
 151 EXPORT_SYMBOL_GPL(queue_delayed_work);
 152
 153 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 154                         struct work_struct *work, unsigned long delay)
 155 {
 156         int ret = 0;
 157         struct timer_list *timer = &work->timer;
 158
 159         if (!test_and_set_bit(0, &work->pending)) {
 160                 BUG_ON(timer_pending(timer));
 161                 BUG_ON(!list_empty(&work->entry));
 162
 163                 /* This stores wq for the moment, for the timer_fn */
 164                 work->wq_data = wq;
 165                 timer->expires = jiffies + delay;
 166                 timer->data = (unsigned long)work;
 167                 timer->function = delayed_work_timer_fn;
 168                 add_timer_on(timer, cpu);
 169                 ret = 1;
 170         }
 171         return ret;
 172 }
 173 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 174
 175 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 176 {
 177         unsigned long flags;
 178
 179         /*
 180          * Keep taking off work from the queue until
 181          * done.
 182          */
 183         spin_lock_irqsave(&cwq->lock, flags);
 184         cwq->run_depth++;
 185         if (cwq->run_depth > 3) {
 186                 /* morton gets to eat his hat */
 187                 printk("%s: recursion depth exceeded: %d\n",
 188                         __FUNCTION__, cwq->run_depth);
 189                 dump_stack();
 190         }
 191         while (!list_empty(&cwq->worklist)) {
 192                 struct work_struct *work = list_entry(cwq->worklist.next,
 193                                                 struct work_struct, entry);
 194                 void (*f) (void *) = work->func;
 195                 void *data = work->data;
 196
 197                 list_del_init(cwq->worklist.next);
 198                 spin_unlock_irqrestore(&cwq->lock, flags);
 199
 200                 BUG_ON(work->wq_data != cwq);
 201                 clear_bit(0, &work->pending);
 202                 f(data);
 203
 204                 spin_lock_irqsave(&cwq->lock, flags);
 205                 cwq->remove_sequence++;
 206                 wake_up(&cwq->work_done);
 207         }
 208         cwq->run_depth--;
 209         spin_unlock_irqrestore(&cwq->lock, flags);
 210 }
 211
 212 static int worker_thread(void *__cwq)
 213 {
 214         struct cpu_workqueue_struct *cwq = __cwq;
 215         DECLARE_WAITQUEUE(wait, current);
 216         struct k_sigaction sa;
 217         sigset_t blocked;
 218
 219         current->flags |= PF_NOFREEZE;
 220
 221         set_user_nice(current, -5);
 222
 223         /* Block and flush all signals */
 224         sigfillset(&blocked);
 225         sigprocmask(SIG_BLOCK, &blocked, NULL);
 226         flush_signals(current);
 227
 228         /* SIG_IGN makes children autoreap: see do_notify_parent(). */
 229         sa.sa.sa_handler = SIG_IGN;
 230         sa.sa.sa_flags = 0;
 231         siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
 232         do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
 233
 234         set_current_state(TASK_INTERRUPTIBLE);
 235         while (!kthread_should_stop()) {
 236                 add_wait_queue(&cwq->more_work, &wait);
 237                 if (list_empty(&cwq->worklist))
 238                         schedule();
 239                 else
 240                         __set_current_state(TASK_RUNNING);
 241                 remove_wait_queue(&cwq->more_work, &wait);
 242
 243                 if (!list_empty(&cwq->worklist))
 244                         run_workqueue(cwq);
 245                 set_current_state(TASK_INTERRUPTIBLE);
 246         }
 247         __set_current_state(TASK_RUNNING);
 248         return 0;
 249 }
 250
 251 static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 252 {
 253         if (cwq->thread == current) {
 254                 /*
 255                  * Probably keventd trying to flush its own queue. So simply run
 256                  * it by hand rather than deadlocking.
 257                  */
 258                 run_workqueue(cwq);
 259         } else {
 260                 DEFINE_WAIT(wait);
 261                 long sequence_needed;
 262
 263                 spin_lock_irq(&cwq->lock);
 264                 sequence_needed = cwq->insert_sequence;
 265
 266                 while (sequence_needed - cwq->remove_sequence > 0) {
 267                         prepare_to_wait(&cwq->work_done, &wait,
 268                                         TASK_UNINTERRUPTIBLE);
 269                         spin_unlock_irq(&cwq->lock);
 270                         schedule();
 271                         spin_lock_irq(&cwq->lock);
 272                 }
 273                 finish_wait(&cwq->work_done, &wait);
 274                 spin_unlock_irq(&cwq->lock);
 275         }
 276 }
 277
 278 /*
 279  * flush_workqueue - ensure that any scheduled work has run to completion.
 280  *
 281  * Forces execution of the workqueue and blocks until its completion.
 282  * This is typically used in driver shutdown handlers.
 283  *
 284  * This function will sample each workqueue's current insert_sequence number and
 285  * will sleep until the head sequence is greater than or equal to that.  This
 286  * means that we sleep until all works which were queued on entry have been
 287  * handled, but we are not livelocked by new incoming ones.
 288  *
 289  * This function used to run the workqueues itself.  Now we just wait for the
 290  * helper threads to do it.
 291  */
 292 void fastcall flush_workqueue(struct workqueue_struct *wq)
 293 {
 294         might_sleep();
 295
 296         if (is_single_threaded(wq)) {
 297                 /* Always use first cpu's area. */
 298                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
 299         } else {
 300                 int cpu;
 301
 302                 lock_cpu_hotplug();
 303                 for_each_online_cpu(cpu)
 304                         flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 305                 unlock_cpu_hotplug();
 306         }
 307 }
 308 EXPORT_SYMBOL_GPL(flush_workqueue);
 309
 310 static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
 311                                                    int cpu)
 312 {
 313         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 314         struct task_struct *p;
 315
 316         spin_lock_init(&cwq->lock);
 317         cwq->wq = wq;
 318         cwq->thread = NULL;
 319         cwq->insert_sequence = 0;
 320         cwq->remove_sequence = 0;
 321         INIT_LIST_HEAD(&cwq->worklist);
 322         init_waitqueue_head(&cwq->more_work);
 323         init_waitqueue_head(&cwq->work_done);
 324
 325         if (is_single_threaded(wq))
 326                 p = kthread_create(worker_thread, cwq, "%s", wq->name);
 327         else
 328                 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
 329         if (IS_ERR(p))
 330                 return NULL;
 331         cwq->thread = p;
 332         return p;
 333 }
 334
 335 struct workqueue_struct *__create_workqueue(const char *name,
 336                                             int singlethread)
 337 {
 338         int cpu, destroy = 0;
 339         struct workqueue_struct *wq;
 340         struct task_struct *p;
 341
 342         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 343         if (!wq)
 344                 return NULL;
 345
 346         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 347         if (!wq->cpu_wq) {
 348                 kfree(wq);
 349                 return NULL;
 350         }
 351
 352         wq->name = name;
 353         /* We don't need the distraction of CPUs appearing and vanishing. */
 354         lock_cpu_hotplug();
 355         if (singlethread) {
 356                 INIT_LIST_HEAD(&wq->list);
 357                 p = create_workqueue_thread(wq, singlethread_cpu);
 358                 if (!p)
 359                         destroy = 1;
 360                 else
 361                         wake_up_process(p);
 362         } else {
 363                 spin_lock(&workqueue_lock);
 364                 list_add(&wq->list, &workqueues);
 365                 spin_unlock(&workqueue_lock);
 366                 for_each_online_cpu(cpu) {
 367                         p = create_workqueue_thread(wq, cpu);
 368                         if (p) {
 369                                 kthread_bind(p, cpu);
 370                                 wake_up_process(p);
 371                         } else
 372                                 destroy = 1;
 373                 }
 374         }
 375         unlock_cpu_hotplug();
 376
 377         /*
 378          * Was there any error during startup? If yes then clean up:
 379          */
 380         if (destroy) {
 381                 destroy_workqueue(wq);
 382                 wq = NULL;
 383         }
 384         return wq;
 385 }
 386 EXPORT_SYMBOL_GPL(__create_workqueue);
 387
 388 static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
 389 {
 390         struct cpu_workqueue_struct *cwq;
 391         unsigned long flags;
 392         struct task_struct *p;
 393
 394         cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 395         spin_lock_irqsave(&cwq->lock, flags);
 396         p = cwq->thread;
 397         cwq->thread = NULL;
 398         spin_unlock_irqrestore(&cwq->lock, flags);
 399         if (p)
 400                 kthread_stop(p);
 401 }
 402
 403 void destroy_workqueue(struct workqueue_struct *wq)
 404 {
 405         int cpu;
 406
 407         flush_workqueue(wq);
 408
 409         /* We don't need the distraction of CPUs appearing and vanishing. */
 410         lock_cpu_hotplug();
 411         if (is_single_threaded(wq))
 412                 cleanup_workqueue_thread(wq, singlethread_cpu);
 413         else {
 414                 for_each_online_cpu(cpu)
 415                         cleanup_workqueue_thread(wq, cpu);
 416                 spin_lock(&workqueue_lock);
 417                 list_del(&wq->list);
 418                 spin_unlock(&workqueue_lock);
 419         }
 420         unlock_cpu_hotplug();
 421         free_percpu(wq->cpu_wq);
 422         kfree(wq);
 423 }
 424 EXPORT_SYMBOL_GPL(destroy_workqueue);
 425
 426 static struct workqueue_struct *keventd_wq;
 427
 428 int fastcall schedule_work(struct work_struct *work)
 429 {
 430         return queue_work(keventd_wq, work);
 431 }
 432 EXPORT_SYMBOL(schedule_work);
 433
 434 int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
 435 {
 436         return queue_delayed_work(keventd_wq, work, delay);
 437 }
 438 EXPORT_SYMBOL(schedule_delayed_work);
 439
 440 int schedule_delayed_work_on(int cpu,
 441                         struct work_struct *work, unsigned long delay)
 442 {
 443         return queue_delayed_work_on(cpu, keventd_wq, work, delay);
 444 }
 445 EXPORT_SYMBOL(schedule_delayed_work_on);
 446
 447 /**
 448  * schedule_on_each_cpu - call a function on each online CPU from keventd
 449  * @func: the function to call
 450  * @info: a pointer to pass to func()
 451  *
 452  * Returns zero on success.
 453  * Returns -ve errno on failure.
 454  *
 455  * Appears to be racy against CPU hotplug.
 456  *
 457  * schedule_on_each_cpu() is very slow.
 458  */
 459 int schedule_on_each_cpu(void (*func)(void *info), void *info)
 460 {
 461         int cpu;
 462         struct work_struct *works;
 463
 464         works = alloc_percpu(struct work_struct);
 465         if (!works)
 466                 return -ENOMEM;
 467
 468         for_each_online_cpu(cpu) {
 469                 INIT_WORK(per_cpu_ptr(works, cpu), func, info);
 470                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
 471                                 per_cpu_ptr(works, cpu));
 472         }
 473         flush_workqueue(keventd_wq);
 474         free_percpu(works);
 475         return 0;
 476 }
 477
 478 void flush_scheduled_work(void)
 479 {
 480         flush_workqueue(keventd_wq);
 481 }
 482 EXPORT_SYMBOL(flush_scheduled_work);
 483
 484 /**
 485  * cancel_rearming_delayed_workqueue - reliably kill off a delayed
 486  *                      work whose handler rearms the delayed work.
 487  * @wq:   the controlling workqueue structure
 488  * @work: the delayed work struct
 489  */
 490 void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
 491                                        struct work_struct *work)
 492 {
 493         while (!cancel_delayed_work(work))
 494                 flush_workqueue(wq);
 495 }
 496 EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);
 497
 498 /**
 499  * cancel_rearming_delayed_work - reliably kill off a delayed keventd
 500  *                      work whose handler rearms the delayed work.
 501  * @work: the delayed work struct
 502  */
 503 void cancel_rearming_delayed_work(struct work_struct *work)
 504 {
 505         cancel_rearming_delayed_workqueue(keventd_wq, work);
 506 }
 507 EXPORT_SYMBOL(cancel_rearming_delayed_work);
 508
 509 /**
 510  * execute_in_process_context - reliably execute the routine with user context
 511  * @fn:         the function to execute
 512  * @data:       data to pass to the function
 513  * @ew:         guaranteed storage for the execute work structure (must
 514  *              be available when the work executes)
 515  *
 516  * Executes the function immediately if process context is available,
 517  * otherwise schedules the function for delayed execution.
 518  *
 519  * Returns:     0 - function was executed
 520  *              1 - function was scheduled for execution
 521  */
 522 int execute_in_process_context(void (*fn)(void *data), void *data,
 523                                struct execute_work *ew)
 524 {
 525         if (!in_interrupt()) {
 526                 fn(data);
 527                 return 0;
 528         }
 529
 530         INIT_WORK(&ew->work, fn, data);
 531         schedule_work(&ew->work);
 532
 533         return 1;
 534 }
 535 EXPORT_SYMBOL_GPL(execute_in_process_context);
 536
 537 int keventd_up(void)
 538 {
 539         return keventd_wq != NULL;
 540 }
 541
 542 int current_is_keventd(void)
 543 {
 544         struct cpu_workqueue_struct *cwq;
 545         int cpu = smp_processor_id();   /* preempt-safe: keventd is per-cpu */
 546         int ret = 0;
 547
 548         BUG_ON(!keventd_wq);
 549
 550         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 551         if (current == cwq->thread)
 552                 ret = 1;
 553
 554         return ret;
 555
 556 }
 557
 558 #ifdef CONFIG_HOTPLUG_CPU
 559 /* Take the work from this (downed) CPU. */
 560 static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
 561 {
 562         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 563         struct list_head list;
 564         struct work_struct *work;
 565
 566         spin_lock_irq(&cwq->lock);
 567         list_replace_init(&cwq->worklist, &list);
 568
 569         while (!list_empty(&list)) {
 570                 printk("Taking work for %s\n", wq->name);
 571                 work = list_entry(list.next,struct work_struct,entry);
 572                 list_del(&work->entry);
 573                 __queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);
 574         }
 575         spin_unlock_irq(&cwq->lock);
 576 }
 577
 578 /* We're holding the cpucontrol mutex here */
 579 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 580                                   unsigned long action,
 581                                   void *hcpu)
 582 {
 583         unsigned int hotcpu = (unsigned long)hcpu;
 584         struct workqueue_struct *wq;
 585
 586         switch (action) {
 587         case CPU_UP_PREPARE:
 588                 /* Create a new workqueue thread for it. */
 589                 list_for_each_entry(wq, &workqueues, list) {
 590                         if (!create_workqueue_thread(wq, hotcpu)) {
 591                                 printk("workqueue for %i failed\n", hotcpu);
 592                                 return NOTIFY_BAD;
 593                         }
 594                 }
 595                 break;
 596
 597         case CPU_ONLINE:
 598                 /* Kick off worker threads. */
 599                 list_for_each_entry(wq, &workqueues, list) {
 600                         struct cpu_workqueue_struct *cwq;
 601
 602                         cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
 603                         kthread_bind(cwq->thread, hotcpu);
 604                         wake_up_process(cwq->thread);
 605                 }
 606                 break;
 607
 608         case CPU_UP_CANCELED:
 609                 list_for_each_entry(wq, &workqueues, list) {
 610                         if (!per_cpu_ptr(wq->cpu_wq, hotcpu)->thread)
 611                                 continue;
 612                         /* Unbind so it can run. */
 613                         kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,
 614                                      any_online_cpu(cpu_online_map));
 615                         cleanup_workqueue_thread(wq, hotcpu);
 616                 }
 617                 break;
 618
 619         case CPU_DEAD:
 620                 list_for_each_entry(wq, &workqueues, list)
 621                         cleanup_workqueue_thread(wq, hotcpu);
 622                 list_for_each_entry(wq, &workqueues, list)
 623                         take_over_work(wq, hotcpu);
 624                 break;
 625         }
 626
 627         return NOTIFY_OK;
 628 }
 629 #endif
 630
 631 void init_workqueues(void)
 632 {
 633         singlethread_cpu = first_cpu(cpu_possible_map);
 634         hotcpu_notifier(workqueue_cpu_callback, 0);
 635         keventd_wq = create_workqueue("events");
 636         BUG_ON(!keventd_wq);
 637 }
 638