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.
  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 #include <linux/lockdep.h>
  36
  37 /*
  38  * The per-CPU workqueue (if single thread, we always use the first
  39  * possible cpu).
  40  */
  41 struct cpu_workqueue_struct {
  42
  43         spinlock_t lock;
  44
  45         struct list_head worklist;
  46         wait_queue_head_t more_work;
  47         struct work_struct *current_work;
  48
  49         struct workqueue_struct *wq;
  50         struct task_struct *thread;
  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 #ifdef CONFIG_LOCKDEP
  66         struct lockdep_map lockdep_map;
  67 #endif
  68 };
  69
  70 /* Serializes the accesses to the list of workqueues. */
  71 static DEFINE_SPINLOCK(workqueue_lock);
  72 static LIST_HEAD(workqueues);
  73
  74 static int singlethread_cpu __read_mostly;
  75 static cpumask_t cpu_singlethread_map __read_mostly;
  76 /*
  77  * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
  78  * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
  79  * which comes in between can't use for_each_online_cpu(). We could
  80  * use cpu_possible_map, the cpumask below is more a documentation
  81  * than optimization.
  82  */
  83 static cpumask_t cpu_populated_map __read_mostly;
  84
  85 /* If it's single threaded, it isn't in the list of workqueues. */
  86 static inline int is_single_threaded(struct workqueue_struct *wq)
  87 {
  88         return wq->singlethread;
  89 }
  90
  91 static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
  92 {
  93         return is_single_threaded(wq)
  94                 ? &cpu_singlethread_map : &cpu_populated_map;
  95 }
  96
  97 static
  98 struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
  99 {
 100         if (unlikely(is_single_threaded(wq)))
 101                 cpu = singlethread_cpu;
 102         return per_cpu_ptr(wq->cpu_wq, cpu);
 103 }
 104
 105 /*
 106  * Set the workqueue on which a work item is to be run
 107  * - Must *only* be called if the pending flag is set
 108  */
 109 static inline void set_wq_data(struct work_struct *work,
 110                                 struct cpu_workqueue_struct *cwq)
 111 {
 112         unsigned long new;
 113
 114         BUG_ON(!work_pending(work));
 115
 116         new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
 117         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
 118         atomic_long_set(&work->data, new);
 119 }
 120
 121 static inline
 122 struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
 123 {
 124         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
 125 }
 126
 127 static void insert_work(struct cpu_workqueue_struct *cwq,
 128                                 struct work_struct *work, int tail)
 129 {
 130         set_wq_data(work, cwq);
 131         /*
 132          * Ensure that we get the right work->data if we see the
 133          * result of list_add() below, see try_to_grab_pending().
 134          */
 135         smp_wmb();
 136         if (tail)
 137                 list_add_tail(&work->entry, &cwq->worklist);
 138         else
 139                 list_add(&work->entry, &cwq->worklist);
 140         wake_up(&cwq->more_work);
 141 }
 142
 143 static void __queue_work(struct cpu_workqueue_struct *cwq,
 144                          struct work_struct *work)
 145 {
 146         unsigned long flags;
 147
 148         spin_lock_irqsave(&cwq->lock, flags);
 149         insert_work(cwq, work, 1);
 150         spin_unlock_irqrestore(&cwq->lock, flags);
 151 }
 152
 153 /**
 154  * queue_work - queue work on a workqueue
 155  * @wq: workqueue to use
 156  * @work: work to queue
 157  *
 158  * Returns 0 if @work was already on a queue, non-zero otherwise.
 159  *
 160  * We queue the work to the CPU on which it was submitted, but if the CPU dies
 161  * it can be processed by another CPU.
 162  */
 163 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
 164 {
 165         int ret = 0;
 166
 167         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 168                 BUG_ON(!list_empty(&work->entry));
 169                 __queue_work(wq_per_cpu(wq, get_cpu()), work);
 170                 put_cpu();
 171                 ret = 1;
 172         }
 173         return ret;
 174 }
 175 EXPORT_SYMBOL_GPL(queue_work);
 176
 177 /**
 178  * queue_work_on - queue work on specific cpu
 179  * @cpu: CPU number to execute work on
 180  * @wq: workqueue to use
 181  * @work: work to queue
 182  *
 183  * Returns 0 if @work was already on a queue, non-zero otherwise.
 184  *
 185  * We queue the work to a specific CPU, the caller must ensure it
 186  * can't go away.
 187  */
 188 int
 189 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
 190 {
 191         int ret = 0;
 192
 193         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 194                 BUG_ON(!list_empty(&work->entry));
 195                 __queue_work(wq_per_cpu(wq, cpu), work);
 196                 ret = 1;
 197         }
 198         return ret;
 199 }
 200 EXPORT_SYMBOL_GPL(queue_work_on);
 201
 202 static void delayed_work_timer_fn(unsigned long __data)
 203 {
 204         struct delayed_work *dwork = (struct delayed_work *)__data;
 205         struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
 206         struct workqueue_struct *wq = cwq->wq;
 207
 208         __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
 209 }
 210
 211 /**
 212  * queue_delayed_work - queue work on a workqueue after delay
 213  * @wq: workqueue to use
 214  * @dwork: delayable work to queue
 215  * @delay: number of jiffies to wait before queueing
 216  *
 217  * Returns 0 if @work was already on a queue, non-zero otherwise.
 218  */
 219 int queue_delayed_work(struct workqueue_struct *wq,
 220                         struct delayed_work *dwork, unsigned long delay)
 221 {
 222         if (delay == 0)
 223                 return queue_work(wq, &dwork->work);
 224
 225         return queue_delayed_work_on(-1, wq, dwork, delay);
 226 }
 227 EXPORT_SYMBOL_GPL(queue_delayed_work);
 228
 229 /**
 230  * queue_delayed_work_on - queue work on specific CPU after delay
 231  * @cpu: CPU number to execute work on
 232  * @wq: workqueue to use
 233  * @dwork: work to queue
 234  * @delay: number of jiffies to wait before queueing
 235  *
 236  * Returns 0 if @work was already on a queue, non-zero otherwise.
 237  */
 238 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 239                         struct delayed_work *dwork, unsigned long delay)
 240 {
 241         int ret = 0;
 242         struct timer_list *timer = &dwork->timer;
 243         struct work_struct *work = &dwork->work;
 244
 245         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 246                 BUG_ON(timer_pending(timer));
 247                 BUG_ON(!list_empty(&work->entry));
 248
 249                 timer_stats_timer_set_start_info(&dwork->timer);
 250
 251                 /* This stores cwq for the moment, for the timer_fn */
 252                 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
 253                 timer->expires = jiffies + delay;
 254                 timer->data = (unsigned long)dwork;
 255                 timer->function = delayed_work_timer_fn;
 256
 257                 if (unlikely(cpu >= 0))
 258                         add_timer_on(timer, cpu);
 259                 else
 260                         add_timer(timer);
 261                 ret = 1;
 262         }
 263         return ret;
 264 }
 265 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 266
 267 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 268 {
 269         spin_lock_irq(&cwq->lock);
 270         cwq->run_depth++;
 271         if (cwq->run_depth > 3) {
 272                 /* morton gets to eat his hat */
 273                 printk("%s: recursion depth exceeded: %d\n",
 274                         __func__, cwq->run_depth);
 275                 dump_stack();
 276         }
 277         while (!list_empty(&cwq->worklist)) {
 278                 struct work_struct *work = list_entry(cwq->worklist.next,
 279                                                 struct work_struct, entry);
 280                 work_func_t f = work->func;
 281 #ifdef CONFIG_LOCKDEP
 282                 /*
 283                  * It is permissible to free the struct work_struct
 284                  * from inside the function that is called from it,
 285                  * this we need to take into account for lockdep too.
 286                  * To avoid bogus "held lock freed" warnings as well
 287                  * as problems when looking into work->lockdep_map,
 288                  * make a copy and use that here.
 289                  */
 290                 struct lockdep_map lockdep_map = work->lockdep_map;
 291 #endif
 292
 293                 cwq->current_work = work;
 294                 list_del_init(cwq->worklist.next);
 295                 spin_unlock_irq(&cwq->lock);
 296
 297                 BUG_ON(get_wq_data(work) != cwq);
 298                 work_clear_pending(work);
 299                 lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
 300                 lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_);
 301                 f(work);
 302                 lock_release(&lockdep_map, 1, _THIS_IP_);
 303                 lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
 304
 305                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 306                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 307                                         "%s/0x%08x/%d\n",
 308                                         current->comm, preempt_count(),
 309                                         task_pid_nr(current));
 310                         printk(KERN_ERR "    last function: ");
 311                         print_symbol("%s\n", (unsigned long)f);
 312                         debug_show_held_locks(current);
 313                         dump_stack();
 314                 }
 315
 316                 spin_lock_irq(&cwq->lock);
 317                 cwq->current_work = NULL;
 318         }
 319         cwq->run_depth--;
 320         spin_unlock_irq(&cwq->lock);
 321 }
 322
 323 static int worker_thread(void *__cwq)
 324 {
 325         struct cpu_workqueue_struct *cwq = __cwq;
 326         DEFINE_WAIT(wait);
 327
 328         if (cwq->wq->freezeable)
 329                 set_freezable();
 330
 331         set_user_nice(current, -5);
 332
 333         for (;;) {
 334                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
 335                 if (!freezing(current) &&
 336                     !kthread_should_stop() &&
 337                     list_empty(&cwq->worklist))
 338                         schedule();
 339                 finish_wait(&cwq->more_work, &wait);
 340
 341                 try_to_freeze();
 342
 343                 if (kthread_should_stop())
 344                         break;
 345
 346                 run_workqueue(cwq);
 347         }
 348
 349         return 0;
 350 }
 351
 352 struct wq_barrier {
 353         struct work_struct      work;
 354         struct completion       done;
 355 };
 356
 357 static void wq_barrier_func(struct work_struct *work)
 358 {
 359         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
 360         complete(&barr->done);
 361 }
 362
 363 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
 364                                         struct wq_barrier *barr, int tail)
 365 {
 366         INIT_WORK(&barr->work, wq_barrier_func);
 367         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
 368
 369         init_completion(&barr->done);
 370
 371         insert_work(cwq, &barr->work, tail);
 372 }
 373
 374 static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 375 {
 376         int active;
 377
 378         if (cwq->thread == current) {
 379                 /*
 380                  * Probably keventd trying to flush its own queue. So simply run
 381                  * it by hand rather than deadlocking.
 382                  */
 383                 run_workqueue(cwq);
 384                 active = 1;
 385         } else {
 386                 struct wq_barrier barr;
 387
 388                 active = 0;
 389                 spin_lock_irq(&cwq->lock);
 390                 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
 391                         insert_wq_barrier(cwq, &barr, 1);
 392                         active = 1;
 393                 }
 394                 spin_unlock_irq(&cwq->lock);
 395
 396                 if (active)
 397                         wait_for_completion(&barr.done);
 398         }
 399
 400         return active;
 401 }
 402
 403 /**
 404  * flush_workqueue - ensure that any scheduled work has run to completion.
 405  * @wq: workqueue to flush
 406  *
 407  * Forces execution of the workqueue and blocks until its completion.
 408  * This is typically used in driver shutdown handlers.
 409  *
 410  * We sleep until all works which were queued on entry have been handled,
 411  * but we are not livelocked by new incoming ones.
 412  *
 413  * This function used to run the workqueues itself.  Now we just wait for the
 414  * helper threads to do it.
 415  */
 416 void flush_workqueue(struct workqueue_struct *wq)
 417 {
 418         const cpumask_t *cpu_map = wq_cpu_map(wq);
 419         int cpu;
 420
 421         might_sleep();
 422         lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
 423         lock_release(&wq->lockdep_map, 1, _THIS_IP_);
 424         for_each_cpu_mask_nr(cpu, *cpu_map)
 425                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 426 }
 427 EXPORT_SYMBOL_GPL(flush_workqueue);
 428
 429 /*
 430  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
 431  * so this work can't be re-armed in any way.
 432  */
 433 static int try_to_grab_pending(struct work_struct *work)
 434 {
 435         struct cpu_workqueue_struct *cwq;
 436         int ret = -1;
 437
 438         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
 439                 return 0;
 440
 441         /*
 442          * The queueing is in progress, or it is already queued. Try to
 443          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
 444          */
 445
 446         cwq = get_wq_data(work);
 447         if (!cwq)
 448                 return ret;
 449
 450         spin_lock_irq(&cwq->lock);
 451         if (!list_empty(&work->entry)) {
 452                 /*
 453                  * This work is queued, but perhaps we locked the wrong cwq.
 454                  * In that case we must see the new value after rmb(), see
 455                  * insert_work()->wmb().
 456                  */
 457                 smp_rmb();
 458                 if (cwq == get_wq_data(work)) {
 459                         list_del_init(&work->entry);
 460                         ret = 1;
 461                 }
 462         }
 463         spin_unlock_irq(&cwq->lock);
 464
 465         return ret;
 466 }
 467
 468 static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
 469                                 struct work_struct *work)
 470 {
 471         struct wq_barrier barr;
 472         int running = 0;
 473
 474         spin_lock_irq(&cwq->lock);
 475         if (unlikely(cwq->current_work == work)) {
 476                 insert_wq_barrier(cwq, &barr, 0);
 477                 running = 1;
 478         }
 479         spin_unlock_irq(&cwq->lock);
 480
 481         if (unlikely(running))
 482                 wait_for_completion(&barr.done);
 483 }
 484
 485 static void wait_on_work(struct work_struct *work)
 486 {
 487         struct cpu_workqueue_struct *cwq;
 488         struct workqueue_struct *wq;
 489         const cpumask_t *cpu_map;
 490         int cpu;
 491
 492         might_sleep();
 493
 494         lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
 495         lock_release(&work->lockdep_map, 1, _THIS_IP_);
 496
 497         cwq = get_wq_data(work);
 498         if (!cwq)
 499                 return;
 500
 501         wq = cwq->wq;
 502         cpu_map = wq_cpu_map(wq);
 503
 504         for_each_cpu_mask_nr(cpu, *cpu_map)
 505                 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 506 }
 507
 508 static int __cancel_work_timer(struct work_struct *work,
 509                                 struct timer_list* timer)
 510 {
 511         int ret;
 512
 513         do {
 514                 ret = (timer && likely(del_timer(timer)));
 515                 if (!ret)
 516                         ret = try_to_grab_pending(work);
 517                 wait_on_work(work);
 518         } while (unlikely(ret < 0));
 519
 520         work_clear_pending(work);
 521         return ret;
 522 }
 523
 524 /**
 525  * cancel_work_sync - block until a work_struct's callback has terminated
 526  * @work: the work which is to be flushed
 527  *
 528  * Returns true if @work was pending.
 529  *
 530  * cancel_work_sync() will cancel the work if it is queued. If the work's
 531  * callback appears to be running, cancel_work_sync() will block until it
 532  * has completed.
 533  *
 534  * It is possible to use this function if the work re-queues itself. It can
 535  * cancel the work even if it migrates to another workqueue, however in that
 536  * case it only guarantees that work->func() has completed on the last queued
 537  * workqueue.
 538  *
 539  * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
 540  * pending, otherwise it goes into a busy-wait loop until the timer expires.
 541  *
 542  * The caller must ensure that workqueue_struct on which this work was last
 543  * queued can't be destroyed before this function returns.
 544  */
 545 int cancel_work_sync(struct work_struct *work)
 546 {
 547         return __cancel_work_timer(work, NULL);
 548 }
 549 EXPORT_SYMBOL_GPL(cancel_work_sync);
 550
 551 /**
 552  * cancel_delayed_work_sync - reliably kill off a delayed work.
 553  * @dwork: the delayed work struct
 554  *
 555  * Returns true if @dwork was pending.
 556  *
 557  * It is possible to use this function if @dwork rearms itself via queue_work()
 558  * or queue_delayed_work(). See also the comment for cancel_work_sync().
 559  */
 560 int cancel_delayed_work_sync(struct delayed_work *dwork)
 561 {
 562         return __cancel_work_timer(&dwork->work, &dwork->timer);
 563 }
 564 EXPORT_SYMBOL(cancel_delayed_work_sync);
 565
 566 static struct workqueue_struct *keventd_wq __read_mostly;
 567
 568 /**
 569  * schedule_work - put work task in global workqueue
 570  * @work: job to be done
 571  *
 572  * This puts a job in the kernel-global workqueue.
 573  */
 574 int schedule_work(struct work_struct *work)
 575 {
 576         return queue_work(keventd_wq, work);
 577 }
 578 EXPORT_SYMBOL(schedule_work);
 579
 580 /*
 581  * schedule_work_on - put work task on a specific cpu
 582  * @cpu: cpu to put the work task on
 583  * @work: job to be done
 584  *
 585  * This puts a job on a specific cpu
 586  */
 587 int schedule_work_on(int cpu, struct work_struct *work)
 588 {
 589         return queue_work_on(cpu, keventd_wq, work);
 590 }
 591 EXPORT_SYMBOL(schedule_work_on);
 592
 593 /**
 594  * schedule_delayed_work - put work task in global workqueue after delay
 595  * @dwork: job to be done
 596  * @delay: number of jiffies to wait or 0 for immediate execution
 597  *
 598  * After waiting for a given time this puts a job in the kernel-global
 599  * workqueue.
 600  */
 601 int schedule_delayed_work(struct delayed_work *dwork,
 602                                         unsigned long delay)
 603 {
 604         return queue_delayed_work(keventd_wq, dwork, delay);
 605 }
 606 EXPORT_SYMBOL(schedule_delayed_work);
 607
 608 /**
 609  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 610  * @cpu: cpu to use
 611  * @dwork: job to be done
 612  * @delay: number of jiffies to wait
 613  *
 614  * After waiting for a given time this puts a job in the kernel-global
 615  * workqueue on the specified CPU.
 616  */
 617 int schedule_delayed_work_on(int cpu,
 618                         struct delayed_work *dwork, unsigned long delay)
 619 {
 620         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 621 }
 622 EXPORT_SYMBOL(schedule_delayed_work_on);
 623
 624 /**
 625  * schedule_on_each_cpu - call a function on each online CPU from keventd
 626  * @func: the function to call
 627  *
 628  * Returns zero on success.
 629  * Returns -ve errno on failure.
 630  *
 631  * schedule_on_each_cpu() is very slow.
 632  */
 633 int schedule_on_each_cpu(work_func_t func)
 634 {
 635         int cpu;
 636         struct work_struct *works;
 637
 638         works = alloc_percpu(struct work_struct);
 639         if (!works)
 640                 return -ENOMEM;
 641
 642         get_online_cpus();
 643         for_each_online_cpu(cpu) {
 644                 struct work_struct *work = per_cpu_ptr(works, cpu);
 645
 646                 INIT_WORK(work, func);
 647                 set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
 648                 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
 649         }
 650         flush_workqueue(keventd_wq);
 651         put_online_cpus();
 652         free_percpu(works);
 653         return 0;
 654 }
 655
 656 void flush_scheduled_work(void)
 657 {
 658         flush_workqueue(keventd_wq);
 659 }
 660 EXPORT_SYMBOL(flush_scheduled_work);
 661
 662 /**
 663  * execute_in_process_context - reliably execute the routine with user context
 664  * @fn:         the function to execute
 665  * @ew:         guaranteed storage for the execute work structure (must
 666  *              be available when the work executes)
 667  *
 668  * Executes the function immediately if process context is available,
 669  * otherwise schedules the function for delayed execution.
 670  *
 671  * Returns:     0 - function was executed
 672  *              1 - function was scheduled for execution
 673  */
 674 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 675 {
 676         if (!in_interrupt()) {
 677                 fn(&ew->work);
 678                 return 0;
 679         }
 680
 681         INIT_WORK(&ew->work, fn);
 682         schedule_work(&ew->work);
 683
 684         return 1;
 685 }
 686 EXPORT_SYMBOL_GPL(execute_in_process_context);
 687
 688 int keventd_up(void)
 689 {
 690         return keventd_wq != NULL;
 691 }
 692
 693 int current_is_keventd(void)
 694 {
 695         struct cpu_workqueue_struct *cwq;
 696         int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
 697         int ret = 0;
 698
 699         BUG_ON(!keventd_wq);
 700
 701         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 702         if (current == cwq->thread)
 703                 ret = 1;
 704
 705         return ret;
 706
 707 }
 708
 709 static struct cpu_workqueue_struct *
 710 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 711 {
 712         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 713
 714         cwq->wq = wq;
 715         spin_lock_init(&cwq->lock);
 716         INIT_LIST_HEAD(&cwq->worklist);
 717         init_waitqueue_head(&cwq->more_work);
 718
 719         return cwq;
 720 }
 721
 722 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 723 {
 724         struct workqueue_struct *wq = cwq->wq;
 725         const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 726         struct task_struct *p;
 727
 728         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
 729         /*
 730          * Nobody can add the work_struct to this cwq,
 731          *      if (caller is __create_workqueue)
 732          *              nobody should see this wq
 733          *      else // caller is CPU_UP_PREPARE
 734          *              cpu is not on cpu_online_map
 735          * so we can abort safely.
 736          */
 737         if (IS_ERR(p))
 738                 return PTR_ERR(p);
 739
 740         cwq->thread = p;
 741
 742         return 0;
 743 }
 744
 745 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 746 {
 747         struct task_struct *p = cwq->thread;
 748
 749         if (p != NULL) {
 750                 if (cpu >= 0)
 751                         kthread_bind(p, cpu);
 752                 wake_up_process(p);
 753         }
 754 }
 755
 756 struct workqueue_struct *__create_workqueue_key(const char *name,
 757                                                 int singlethread,
 758                                                 int freezeable,
 759                                                 struct lock_class_key *key,
 760                                                 const char *lock_name)
 761 {
 762         struct workqueue_struct *wq;
 763         struct cpu_workqueue_struct *cwq;
 764         int err = 0, cpu;
 765
 766         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 767         if (!wq)
 768                 return NULL;
 769
 770         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 771         if (!wq->cpu_wq) {
 772                 kfree(wq);
 773                 return NULL;
 774         }
 775
 776         wq->name = name;
 777         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 778         wq->singlethread = singlethread;
 779         wq->freezeable = freezeable;
 780         INIT_LIST_HEAD(&wq->list);
 781
 782         if (singlethread) {
 783                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
 784                 err = create_workqueue_thread(cwq, singlethread_cpu);
 785                 start_workqueue_thread(cwq, -1);
 786         } else {
 787                 get_online_cpus();
 788                 spin_lock(&workqueue_lock);
 789                 list_add(&wq->list, &workqueues);
 790                 spin_unlock(&workqueue_lock);
 791
 792                 for_each_possible_cpu(cpu) {
 793                         cwq = init_cpu_workqueue(wq, cpu);
 794                         if (err || !cpu_online(cpu))
 795                                 continue;
 796                         err = create_workqueue_thread(cwq, cpu);
 797                         start_workqueue_thread(cwq, cpu);
 798                 }
 799                 put_online_cpus();
 800         }
 801
 802         if (err) {
 803                 destroy_workqueue(wq);
 804                 wq = NULL;
 805         }
 806         return wq;
 807 }
 808 EXPORT_SYMBOL_GPL(__create_workqueue_key);
 809
 810 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
 811 {
 812         /*
 813          * Our caller is either destroy_workqueue() or CPU_DEAD,
 814          * get_online_cpus() protects cwq->thread.
 815          */
 816         if (cwq->thread == NULL)
 817                 return;
 818
 819         lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
 820         lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
 821
 822         flush_cpu_workqueue(cwq);
 823         /*
 824          * If the caller is CPU_DEAD and cwq->worklist was not empty,
 825          * a concurrent flush_workqueue() can insert a barrier after us.
 826          * However, in that case run_workqueue() won't return and check
 827          * kthread_should_stop() until it flushes all work_struct's.
 828          * When ->worklist becomes empty it is safe to exit because no
 829          * more work_structs can be queued on this cwq: flush_workqueue
 830          * checks list_empty(), and a "normal" queue_work() can't use
 831          * a dead CPU.
 832          */
 833         kthread_stop(cwq->thread);
 834         cwq->thread = NULL;
 835 }
 836
 837 /**
 838  * destroy_workqueue - safely terminate a workqueue
 839  * @wq: target workqueue
 840  *
 841  * Safely destroy a workqueue. All work currently pending will be done first.
 842  */
 843 void destroy_workqueue(struct workqueue_struct *wq)
 844 {
 845         const cpumask_t *cpu_map = wq_cpu_map(wq);
 846         int cpu;
 847
 848         get_online_cpus();
 849         spin_lock(&workqueue_lock);
 850         list_del(&wq->list);
 851         spin_unlock(&workqueue_lock);
 852
 853         for_each_cpu_mask_nr(cpu, *cpu_map)
 854                 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
 855         put_online_cpus();
 856
 857         free_percpu(wq->cpu_wq);
 858         kfree(wq);
 859 }
 860 EXPORT_SYMBOL_GPL(destroy_workqueue);
 861
 862 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 863                                                 unsigned long action,
 864                                                 void *hcpu)
 865 {
 866         unsigned int cpu = (unsigned long)hcpu;
 867         struct cpu_workqueue_struct *cwq;
 868         struct workqueue_struct *wq;
 869
 870         action &= ~CPU_TASKS_FROZEN;
 871
 872         switch (action) {
 873         case CPU_UP_PREPARE:
 874                 cpu_set(cpu, cpu_populated_map);
 875         }
 876
 877         list_for_each_entry(wq, &workqueues, list) {
 878                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 879
 880                 switch (action) {
 881                 case CPU_UP_PREPARE:
 882                         if (!create_workqueue_thread(cwq, cpu))
 883                                 break;
 884                         printk(KERN_ERR "workqueue [%s] for %i failed\n",
 885                                 wq->name, cpu);
 886                         return NOTIFY_BAD;
 887
 888                 case CPU_ONLINE:
 889                         start_workqueue_thread(cwq, cpu);
 890                         break;
 891
 892                 case CPU_UP_CANCELED:
 893                         start_workqueue_thread(cwq, -1);
 894                 case CPU_DEAD:
 895                         cleanup_workqueue_thread(cwq);
 896                         break;
 897                 }
 898         }
 899
 900         switch (action) {
 901         case CPU_UP_CANCELED:
 902         case CPU_DEAD:
 903                 cpu_clear(cpu, cpu_populated_map);
 904         }
 905
 906         return NOTIFY_OK;
 907 }
 908
 909 void __init init_workqueues(void)
 910 {
 911         cpu_populated_map = cpu_online_map;
 912         singlethread_cpu = first_cpu(cpu_possible_map);
 913         cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
 914         hotcpu_notifier(workqueue_cpu_callback, 0);
 915         keventd_wq = create_workqueue("events");
 916         BUG_ON(!keventd_wq);
 917 }