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
  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 #include <trace/workqueue.h>
  37
  38 /*
  39  * The per-CPU workqueue (if single thread, we always use the first
  40  * possible cpu).
  41  */
  42 struct cpu_workqueue_struct {
  43
  44         spinlock_t lock;
  45
  46         struct list_head worklist;
  47         wait_queue_head_t more_work;
  48         struct work_struct *current_work;
  49
  50         struct workqueue_struct *wq;
  51         struct task_struct *thread;
  52 } ____cacheline_aligned;
  53
  54 /*
  55  * The externally visible workqueue abstraction is an array of
  56  * per-CPU workqueues:
  57  */
  58 struct workqueue_struct {
  59         struct cpu_workqueue_struct *cpu_wq;
  60         struct list_head list;
  61         const char *name;
  62         int singlethread;
  63         int freezeable;         /* Freeze threads during suspend */
  64         int rt;
  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 const struct cpumask *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_var_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_wq_single_threaded(struct workqueue_struct *wq)
  87 {
  88         return wq->singlethread;
  89 }
  90
  91 static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
  92 {
  93         return is_wq_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_wq_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 DEFINE_TRACE(workqueue_insertion);
 128
 129 static void insert_work(struct cpu_workqueue_struct *cwq,
 130                         struct work_struct *work, struct list_head *head)
 131 {
 132         trace_workqueue_insertion(cwq->thread, work);
 133
 134         set_wq_data(work, cwq);
 135         /*
 136          * Ensure that we get the right work->data if we see the
 137          * result of list_add() below, see try_to_grab_pending().
 138          */
 139         smp_wmb();
 140         list_add_tail(&work->entry, head);
 141         wake_up(&cwq->more_work);
 142 }
 143
 144 static void __queue_work(struct cpu_workqueue_struct *cwq,
 145                          struct work_struct *work)
 146 {
 147         unsigned long flags;
 148
 149         spin_lock_irqsave(&cwq->lock, flags);
 150         insert_work(cwq, work, &cwq->worklist);
 151         spin_unlock_irqrestore(&cwq->lock, flags);
 152 }
 153
 154 /**
 155  * queue_work - queue work on a workqueue
 156  * @wq: workqueue to use
 157  * @work: work to queue
 158  *
 159  * Returns 0 if @work was already on a queue, non-zero otherwise.
 160  *
 161  * We queue the work to the CPU on which it was submitted, but if the CPU dies
 162  * it can be processed by another CPU.
 163  */
 164 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
 165 {
 166         int ret;
 167
 168         ret = queue_work_on(get_cpu(), wq, work);
 169         put_cpu();
 170
 171         return ret;
 172 }
 173 EXPORT_SYMBOL_GPL(queue_work);
 174
 175 /**
 176  * queue_work_on - queue work on specific cpu
 177  * @cpu: CPU number to execute work on
 178  * @wq: workqueue to use
 179  * @work: work to queue
 180  *
 181  * Returns 0 if @work was already on a queue, non-zero otherwise.
 182  *
 183  * We queue the work to a specific CPU, the caller must ensure it
 184  * can't go away.
 185  */
 186 int
 187 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
 188 {
 189         int ret = 0;
 190
 191         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 192                 BUG_ON(!list_empty(&work->entry));
 193                 __queue_work(wq_per_cpu(wq, cpu), work);
 194                 ret = 1;
 195         }
 196         return ret;
 197 }
 198 EXPORT_SYMBOL_GPL(queue_work_on);
 199
 200 static void delayed_work_timer_fn(unsigned long __data)
 201 {
 202         struct delayed_work *dwork = (struct delayed_work *)__data;
 203         struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
 204         struct workqueue_struct *wq = cwq->wq;
 205
 206         __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
 207 }
 208
 209 /**
 210  * queue_delayed_work - queue work on a workqueue after delay
 211  * @wq: workqueue to use
 212  * @dwork: delayable work to queue
 213  * @delay: number of jiffies to wait before queueing
 214  *
 215  * Returns 0 if @work was already on a queue, non-zero otherwise.
 216  */
 217 int queue_delayed_work(struct workqueue_struct *wq,
 218                         struct delayed_work *dwork, unsigned long delay)
 219 {
 220         if (delay == 0)
 221                 return queue_work(wq, &dwork->work);
 222
 223         return queue_delayed_work_on(-1, wq, dwork, delay);
 224 }
 225 EXPORT_SYMBOL_GPL(queue_delayed_work);
 226
 227 /**
 228  * queue_delayed_work_on - queue work on specific CPU after delay
 229  * @cpu: CPU number to execute work on
 230  * @wq: workqueue to use
 231  * @dwork: work to queue
 232  * @delay: number of jiffies to wait before queueing
 233  *
 234  * Returns 0 if @work was already on a queue, non-zero otherwise.
 235  */
 236 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 237                         struct delayed_work *dwork, unsigned long delay)
 238 {
 239         int ret = 0;
 240         struct timer_list *timer = &dwork->timer;
 241         struct work_struct *work = &dwork->work;
 242
 243         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 244                 BUG_ON(timer_pending(timer));
 245                 BUG_ON(!list_empty(&work->entry));
 246
 247                 timer_stats_timer_set_start_info(&dwork->timer);
 248
 249                 /* This stores cwq for the moment, for the timer_fn */
 250                 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
 251                 timer->expires = jiffies + delay;
 252                 timer->data = (unsigned long)dwork;
 253                 timer->function = delayed_work_timer_fn;
 254
 255                 if (unlikely(cpu >= 0))
 256                         add_timer_on(timer, cpu);
 257                 else
 258                         add_timer(timer);
 259                 ret = 1;
 260         }
 261         return ret;
 262 }
 263 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 264
 265 DEFINE_TRACE(workqueue_execution);
 266
 267 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 268 {
 269         spin_lock_irq(&cwq->lock);
 270         while (!list_empty(&cwq->worklist)) {
 271                 struct work_struct *work = list_entry(cwq->worklist.next,
 272                                                 struct work_struct, entry);
 273                 work_func_t f = work->func;
 274 #ifdef CONFIG_LOCKDEP
 275                 /*
 276                  * It is permissible to free the struct work_struct
 277                  * from inside the function that is called from it,
 278                  * this we need to take into account for lockdep too.
 279                  * To avoid bogus "held lock freed" warnings as well
 280                  * as problems when looking into work->lockdep_map,
 281                  * make a copy and use that here.
 282                  */
 283                 struct lockdep_map lockdep_map = work->lockdep_map;
 284 #endif
 285                 trace_workqueue_execution(cwq->thread, work);
 286                 cwq->current_work = work;
 287                 list_del_init(cwq->worklist.next);
 288                 spin_unlock_irq(&cwq->lock);
 289
 290                 BUG_ON(get_wq_data(work) != cwq);
 291                 work_clear_pending(work);
 292                 lock_map_acquire(&cwq->wq->lockdep_map);
 293                 lock_map_acquire(&lockdep_map);
 294                 f(work);
 295                 lock_map_release(&lockdep_map);
 296                 lock_map_release(&cwq->wq->lockdep_map);
 297
 298                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 299                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 300                                         "%s/0x%08x/%d\n",
 301                                         current->comm, preempt_count(),
 302                                         task_pid_nr(current));
 303                         printk(KERN_ERR "    last function: ");
 304                         print_symbol("%s\n", (unsigned long)f);
 305                         debug_show_held_locks(current);
 306                         dump_stack();
 307                 }
 308
 309                 spin_lock_irq(&cwq->lock);
 310                 cwq->current_work = NULL;
 311         }
 312         spin_unlock_irq(&cwq->lock);
 313 }
 314
 315 static int worker_thread(void *__cwq)
 316 {
 317         struct cpu_workqueue_struct *cwq = __cwq;
 318         DEFINE_WAIT(wait);
 319
 320         if (cwq->wq->freezeable)
 321                 set_freezable();
 322
 323         set_user_nice(current, -5);
 324
 325         for (;;) {
 326                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
 327                 if (!freezing(current) &&
 328                     !kthread_should_stop() &&
 329                     list_empty(&cwq->worklist))
 330                         schedule();
 331                 finish_wait(&cwq->more_work, &wait);
 332
 333                 try_to_freeze();
 334
 335                 if (kthread_should_stop())
 336                         break;
 337
 338                 run_workqueue(cwq);
 339         }
 340
 341         return 0;
 342 }
 343
 344 struct wq_barrier {
 345         struct work_struct      work;
 346         struct completion       done;
 347 };
 348
 349 static void wq_barrier_func(struct work_struct *work)
 350 {
 351         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
 352         complete(&barr->done);
 353 }
 354
 355 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
 356                         struct wq_barrier *barr, struct list_head *head)
 357 {
 358         INIT_WORK(&barr->work, wq_barrier_func);
 359         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
 360
 361         init_completion(&barr->done);
 362
 363         insert_work(cwq, &barr->work, head);
 364 }
 365
 366 static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 367 {
 368         int active = 0;
 369         struct wq_barrier barr;
 370
 371         WARN_ON(cwq->thread == current);
 372
 373         spin_lock_irq(&cwq->lock);
 374         if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
 375                 insert_wq_barrier(cwq, &barr, &cwq->worklist);
 376                 active = 1;
 377         }
 378         spin_unlock_irq(&cwq->lock);
 379
 380         if (active)
 381                 wait_for_completion(&barr.done);
 382
 383         return active;
 384 }
 385
 386 /**
 387  * flush_workqueue - ensure that any scheduled work has run to completion.
 388  * @wq: workqueue to flush
 389  *
 390  * Forces execution of the workqueue and blocks until its completion.
 391  * This is typically used in driver shutdown handlers.
 392  *
 393  * We sleep until all works which were queued on entry have been handled,
 394  * but we are not livelocked by new incoming ones.
 395  *
 396  * This function used to run the workqueues itself.  Now we just wait for the
 397  * helper threads to do it.
 398  */
 399 void flush_workqueue(struct workqueue_struct *wq)
 400 {
 401         const struct cpumask *cpu_map = wq_cpu_map(wq);
 402         int cpu;
 403
 404         might_sleep();
 405         lock_map_acquire(&wq->lockdep_map);
 406         lock_map_release(&wq->lockdep_map);
 407         for_each_cpu(cpu, cpu_map)
 408                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 409 }
 410 EXPORT_SYMBOL_GPL(flush_workqueue);
 411
 412 /**
 413  * flush_work - block until a work_struct's callback has terminated
 414  * @work: the work which is to be flushed
 415  *
 416  * Returns false if @work has already terminated.
 417  *
 418  * It is expected that, prior to calling flush_work(), the caller has
 419  * arranged for the work to not be requeued, otherwise it doesn't make
 420  * sense to use this function.
 421  */
 422 int flush_work(struct work_struct *work)
 423 {
 424         struct cpu_workqueue_struct *cwq;
 425         struct list_head *prev;
 426         struct wq_barrier barr;
 427
 428         might_sleep();
 429         cwq = get_wq_data(work);
 430         if (!cwq)
 431                 return 0;
 432
 433         lock_map_acquire(&cwq->wq->lockdep_map);
 434         lock_map_release(&cwq->wq->lockdep_map);
 435
 436         prev = NULL;
 437         spin_lock_irq(&cwq->lock);
 438         if (!list_empty(&work->entry)) {
 439                 /*
 440                  * See the comment near try_to_grab_pending()->smp_rmb().
 441                  * If it was re-queued under us we are not going to wait.
 442                  */
 443                 smp_rmb();
 444                 if (unlikely(cwq != get_wq_data(work)))
 445                         goto out;
 446                 prev = &work->entry;
 447         } else {
 448                 if (cwq->current_work != work)
 449                         goto out;
 450                 prev = &cwq->worklist;
 451         }
 452         insert_wq_barrier(cwq, &barr, prev->next);
 453 out:
 454         spin_unlock_irq(&cwq->lock);
 455         if (!prev)
 456                 return 0;
 457
 458         wait_for_completion(&barr.done);
 459         return 1;
 460 }
 461 EXPORT_SYMBOL_GPL(flush_work);
 462
 463 /*
 464  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
 465  * so this work can't be re-armed in any way.
 466  */
 467 static int try_to_grab_pending(struct work_struct *work)
 468 {
 469         struct cpu_workqueue_struct *cwq;
 470         int ret = -1;
 471
 472         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
 473                 return 0;
 474
 475         /*
 476          * The queueing is in progress, or it is already queued. Try to
 477          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
 478          */
 479
 480         cwq = get_wq_data(work);
 481         if (!cwq)
 482                 return ret;
 483
 484         spin_lock_irq(&cwq->lock);
 485         if (!list_empty(&work->entry)) {
 486                 /*
 487                  * This work is queued, but perhaps we locked the wrong cwq.
 488                  * In that case we must see the new value after rmb(), see
 489                  * insert_work()->wmb().
 490                  */
 491                 smp_rmb();
 492                 if (cwq == get_wq_data(work)) {
 493                         list_del_init(&work->entry);
 494                         ret = 1;
 495                 }
 496         }
 497         spin_unlock_irq(&cwq->lock);
 498
 499         return ret;
 500 }
 501
 502 static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
 503                                 struct work_struct *work)
 504 {
 505         struct wq_barrier barr;
 506         int running = 0;
 507
 508         spin_lock_irq(&cwq->lock);
 509         if (unlikely(cwq->current_work == work)) {
 510                 insert_wq_barrier(cwq, &barr, cwq->worklist.next);
 511                 running = 1;
 512         }
 513         spin_unlock_irq(&cwq->lock);
 514
 515         if (unlikely(running))
 516                 wait_for_completion(&barr.done);
 517 }
 518
 519 static void wait_on_work(struct work_struct *work)
 520 {
 521         struct cpu_workqueue_struct *cwq;
 522         struct workqueue_struct *wq;
 523         const struct cpumask *cpu_map;
 524         int cpu;
 525
 526         might_sleep();
 527
 528         lock_map_acquire(&work->lockdep_map);
 529         lock_map_release(&work->lockdep_map);
 530
 531         cwq = get_wq_data(work);
 532         if (!cwq)
 533                 return;
 534
 535         wq = cwq->wq;
 536         cpu_map = wq_cpu_map(wq);
 537
 538         for_each_cpu(cpu, cpu_map)
 539                 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 540 }
 541
 542 static int __cancel_work_timer(struct work_struct *work,
 543                                 struct timer_list* timer)
 544 {
 545         int ret;
 546
 547         do {
 548                 ret = (timer && likely(del_timer(timer)));
 549                 if (!ret)
 550                         ret = try_to_grab_pending(work);
 551                 wait_on_work(work);
 552         } while (unlikely(ret < 0));
 553
 554         work_clear_pending(work);
 555         return ret;
 556 }
 557
 558 /**
 559  * cancel_work_sync - block until a work_struct's callback has terminated
 560  * @work: the work which is to be flushed
 561  *
 562  * Returns true if @work was pending.
 563  *
 564  * cancel_work_sync() will cancel the work if it is queued. If the work's
 565  * callback appears to be running, cancel_work_sync() will block until it
 566  * has completed.
 567  *
 568  * It is possible to use this function if the work re-queues itself. It can
 569  * cancel the work even if it migrates to another workqueue, however in that
 570  * case it only guarantees that work->func() has completed on the last queued
 571  * workqueue.
 572  *
 573  * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
 574  * pending, otherwise it goes into a busy-wait loop until the timer expires.
 575  *
 576  * The caller must ensure that workqueue_struct on which this work was last
 577  * queued can't be destroyed before this function returns.
 578  */
 579 int cancel_work_sync(struct work_struct *work)
 580 {
 581         return __cancel_work_timer(work, NULL);
 582 }
 583 EXPORT_SYMBOL_GPL(cancel_work_sync);
 584
 585 /**
 586  * cancel_delayed_work_sync - reliably kill off a delayed work.
 587  * @dwork: the delayed work struct
 588  *
 589  * Returns true if @dwork was pending.
 590  *
 591  * It is possible to use this function if @dwork rearms itself via queue_work()
 592  * or queue_delayed_work(). See also the comment for cancel_work_sync().
 593  */
 594 int cancel_delayed_work_sync(struct delayed_work *dwork)
 595 {
 596         return __cancel_work_timer(&dwork->work, &dwork->timer);
 597 }
 598 EXPORT_SYMBOL(cancel_delayed_work_sync);
 599
 600 static struct workqueue_struct *keventd_wq __read_mostly;
 601
 602 /**
 603  * schedule_work - put work task in global workqueue
 604  * @work: job to be done
 605  *
 606  * This puts a job in the kernel-global workqueue.
 607  */
 608 int schedule_work(struct work_struct *work)
 609 {
 610         return queue_work(keventd_wq, work);
 611 }
 612 EXPORT_SYMBOL(schedule_work);
 613
 614 /*
 615  * schedule_work_on - put work task on a specific cpu
 616  * @cpu: cpu to put the work task on
 617  * @work: job to be done
 618  *
 619  * This puts a job on a specific cpu
 620  */
 621 int schedule_work_on(int cpu, struct work_struct *work)
 622 {
 623         return queue_work_on(cpu, keventd_wq, work);
 624 }
 625 EXPORT_SYMBOL(schedule_work_on);
 626
 627 /**
 628  * schedule_delayed_work - put work task in global workqueue after delay
 629  * @dwork: job to be done
 630  * @delay: number of jiffies to wait or 0 for immediate execution
 631  *
 632  * After waiting for a given time this puts a job in the kernel-global
 633  * workqueue.
 634  */
 635 int schedule_delayed_work(struct delayed_work *dwork,
 636                                         unsigned long delay)
 637 {
 638         return queue_delayed_work(keventd_wq, dwork, delay);
 639 }
 640 EXPORT_SYMBOL(schedule_delayed_work);
 641
 642 /**
 643  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 644  * @cpu: cpu to use
 645  * @dwork: job to be done
 646  * @delay: number of jiffies to wait
 647  *
 648  * After waiting for a given time this puts a job in the kernel-global
 649  * workqueue on the specified CPU.
 650  */
 651 int schedule_delayed_work_on(int cpu,
 652                         struct delayed_work *dwork, unsigned long delay)
 653 {
 654         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 655 }
 656 EXPORT_SYMBOL(schedule_delayed_work_on);
 657
 658 /**
 659  * schedule_on_each_cpu - call a function on each online CPU from keventd
 660  * @func: the function to call
 661  *
 662  * Returns zero on success.
 663  * Returns -ve errno on failure.
 664  *
 665  * schedule_on_each_cpu() is very slow.
 666  */
 667 int schedule_on_each_cpu(work_func_t func)
 668 {
 669         int cpu;
 670         struct work_struct *works;
 671
 672         works = alloc_percpu(struct work_struct);
 673         if (!works)
 674                 return -ENOMEM;
 675
 676         get_online_cpus();
 677         for_each_online_cpu(cpu) {
 678                 struct work_struct *work = per_cpu_ptr(works, cpu);
 679
 680                 INIT_WORK(work, func);
 681                 schedule_work_on(cpu, work);
 682         }
 683         for_each_online_cpu(cpu)
 684                 flush_work(per_cpu_ptr(works, cpu));
 685         put_online_cpus();
 686         free_percpu(works);
 687         return 0;
 688 }
 689
 690 void flush_scheduled_work(void)
 691 {
 692         flush_workqueue(keventd_wq);
 693 }
 694 EXPORT_SYMBOL(flush_scheduled_work);
 695
 696 /**
 697  * execute_in_process_context - reliably execute the routine with user context
 698  * @fn:         the function to execute
 699  * @ew:         guaranteed storage for the execute work structure (must
 700  *              be available when the work executes)
 701  *
 702  * Executes the function immediately if process context is available,
 703  * otherwise schedules the function for delayed execution.
 704  *
 705  * Returns:     0 - function was executed
 706  *              1 - function was scheduled for execution
 707  */
 708 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 709 {
 710         if (!in_interrupt()) {
 711                 fn(&ew->work);
 712                 return 0;
 713         }
 714
 715         INIT_WORK(&ew->work, fn);
 716         schedule_work(&ew->work);
 717
 718         return 1;
 719 }
 720 EXPORT_SYMBOL_GPL(execute_in_process_context);
 721
 722 int keventd_up(void)
 723 {
 724         return keventd_wq != NULL;
 725 }
 726
 727 int current_is_keventd(void)
 728 {
 729         struct cpu_workqueue_struct *cwq;
 730         int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
 731         int ret = 0;
 732
 733         BUG_ON(!keventd_wq);
 734
 735         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 736         if (current == cwq->thread)
 737                 ret = 1;
 738
 739         return ret;
 740
 741 }
 742
 743 static struct cpu_workqueue_struct *
 744 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 745 {
 746         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 747
 748         cwq->wq = wq;
 749         spin_lock_init(&cwq->lock);
 750         INIT_LIST_HEAD(&cwq->worklist);
 751         init_waitqueue_head(&cwq->more_work);
 752
 753         return cwq;
 754 }
 755
 756 DEFINE_TRACE(workqueue_creation);
 757
 758 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 759 {
 760         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 761         struct workqueue_struct *wq = cwq->wq;
 762         const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
 763         struct task_struct *p;
 764
 765         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
 766         /*
 767          * Nobody can add the work_struct to this cwq,
 768          *      if (caller is __create_workqueue)
 769          *              nobody should see this wq
 770          *      else // caller is CPU_UP_PREPARE
 771          *              cpu is not on cpu_online_map
 772          * so we can abort safely.
 773          */
 774         if (IS_ERR(p))
 775                 return PTR_ERR(p);
 776         if (cwq->wq->rt)
 777                 sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
 778         cwq->thread = p;
 779
 780         trace_workqueue_creation(cwq->thread, cpu);
 781
 782         return 0;
 783 }
 784
 785 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 786 {
 787         struct task_struct *p = cwq->thread;
 788
 789         if (p != NULL) {
 790                 if (cpu >= 0)
 791                         kthread_bind(p, cpu);
 792                 wake_up_process(p);
 793         }
 794 }
 795
 796 struct workqueue_struct *__create_workqueue_key(const char *name,
 797                                                 int singlethread,
 798                                                 int freezeable,
 799                                                 int rt,
 800                                                 struct lock_class_key *key,
 801                                                 const char *lock_name)
 802 {
 803         struct workqueue_struct *wq;
 804         struct cpu_workqueue_struct *cwq;
 805         int err = 0, cpu;
 806
 807         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 808         if (!wq)
 809                 return NULL;
 810
 811         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 812         if (!wq->cpu_wq) {
 813                 kfree(wq);
 814                 return NULL;
 815         }
 816
 817         wq->name = name;
 818         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 819         wq->singlethread = singlethread;
 820         wq->freezeable = freezeable;
 821         wq->rt = rt;
 822         INIT_LIST_HEAD(&wq->list);
 823
 824         if (singlethread) {
 825                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
 826                 err = create_workqueue_thread(cwq, singlethread_cpu);
 827                 start_workqueue_thread(cwq, -1);
 828         } else {
 829                 cpu_maps_update_begin();
 830                 /*
 831                  * We must place this wq on list even if the code below fails.
 832                  * cpu_down(cpu) can remove cpu from cpu_populated_map before
 833                  * destroy_workqueue() takes the lock, in that case we leak
 834                  * cwq[cpu]->thread.
 835                  */
 836                 spin_lock(&workqueue_lock);
 837                 list_add(&wq->list, &workqueues);
 838                 spin_unlock(&workqueue_lock);
 839                 /*
 840                  * We must initialize cwqs for each possible cpu even if we
 841                  * are going to call destroy_workqueue() finally. Otherwise
 842                  * cpu_up() can hit the uninitialized cwq once we drop the
 843                  * lock.
 844                  */
 845                 for_each_possible_cpu(cpu) {
 846                         cwq = init_cpu_workqueue(wq, cpu);
 847                         if (err || !cpu_online(cpu))
 848                                 continue;
 849                         err = create_workqueue_thread(cwq, cpu);
 850                         start_workqueue_thread(cwq, cpu);
 851                 }
 852                 cpu_maps_update_done();
 853         }
 854
 855         if (err) {
 856                 destroy_workqueue(wq);
 857                 wq = NULL;
 858         }
 859         return wq;
 860 }
 861 EXPORT_SYMBOL_GPL(__create_workqueue_key);
 862
 863 DEFINE_TRACE(workqueue_destruction);
 864
 865 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
 866 {
 867         /*
 868          * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
 869          * cpu_add_remove_lock protects cwq->thread.
 870          */
 871         if (cwq->thread == NULL)
 872                 return;
 873
 874         lock_map_acquire(&cwq->wq->lockdep_map);
 875         lock_map_release(&cwq->wq->lockdep_map);
 876
 877         flush_cpu_workqueue(cwq);
 878         /*
 879          * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
 880          * a concurrent flush_workqueue() can insert a barrier after us.
 881          * However, in that case run_workqueue() won't return and check
 882          * kthread_should_stop() until it flushes all work_struct's.
 883          * When ->worklist becomes empty it is safe to exit because no
 884          * more work_structs can be queued on this cwq: flush_workqueue
 885          * checks list_empty(), and a "normal" queue_work() can't use
 886          * a dead CPU.
 887          */
 888         trace_workqueue_destruction(cwq->thread);
 889         kthread_stop(cwq->thread);
 890         cwq->thread = NULL;
 891 }
 892
 893 /**
 894  * destroy_workqueue - safely terminate a workqueue
 895  * @wq: target workqueue
 896  *
 897  * Safely destroy a workqueue. All work currently pending will be done first.
 898  */
 899 void destroy_workqueue(struct workqueue_struct *wq)
 900 {
 901         const struct cpumask *cpu_map = wq_cpu_map(wq);
 902         int cpu;
 903
 904         cpu_maps_update_begin();
 905         spin_lock(&workqueue_lock);
 906         list_del(&wq->list);
 907         spin_unlock(&workqueue_lock);
 908
 909         for_each_cpu(cpu, cpu_map)
 910                 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
 911         cpu_maps_update_done();
 912
 913         free_percpu(wq->cpu_wq);
 914         kfree(wq);
 915 }
 916 EXPORT_SYMBOL_GPL(destroy_workqueue);
 917
 918 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 919                                                 unsigned long action,
 920                                                 void *hcpu)
 921 {
 922         unsigned int cpu = (unsigned long)hcpu;
 923         struct cpu_workqueue_struct *cwq;
 924         struct workqueue_struct *wq;
 925         int ret = NOTIFY_OK;
 926
 927         action &= ~CPU_TASKS_FROZEN;
 928
 929         switch (action) {
 930         case CPU_UP_PREPARE:
 931                 cpumask_set_cpu(cpu, cpu_populated_map);
 932         }
 933 undo:
 934         list_for_each_entry(wq, &workqueues, list) {
 935                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 936
 937                 switch (action) {
 938                 case CPU_UP_PREPARE:
 939                         if (!create_workqueue_thread(cwq, cpu))
 940                                 break;
 941                         printk(KERN_ERR "workqueue [%s] for %i failed\n",
 942                                 wq->name, cpu);
 943                         action = CPU_UP_CANCELED;
 944                         ret = NOTIFY_BAD;
 945                         goto undo;
 946
 947                 case CPU_ONLINE:
 948                         start_workqueue_thread(cwq, cpu);
 949                         break;
 950
 951                 case CPU_UP_CANCELED:
 952                         start_workqueue_thread(cwq, -1);
 953                 case CPU_POST_DEAD:
 954                         cleanup_workqueue_thread(cwq);
 955                         break;
 956                 }
 957         }
 958
 959         switch (action) {
 960         case CPU_UP_CANCELED:
 961         case CPU_POST_DEAD:
 962                 cpumask_clear_cpu(cpu, cpu_populated_map);
 963         }
 964
 965         return ret;
 966 }
 967
 968 #ifdef CONFIG_SMP
 969 static struct workqueue_struct *work_on_cpu_wq __read_mostly;
 970
 971 struct work_for_cpu {
 972         struct work_struct work;
 973         long (*fn)(void *);
 974         void *arg;
 975         long ret;
 976 };
 977
 978 static void do_work_for_cpu(struct work_struct *w)
 979 {
 980         struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
 981
 982         wfc->ret = wfc->fn(wfc->arg);
 983 }
 984
 985 /**
 986  * work_on_cpu - run a function in user context on a particular cpu
 987  * @cpu: the cpu to run on
 988  * @fn: the function to run
 989  * @arg: the function arg
 990  *
 991  * This will return the value @fn returns.
 992  * It is up to the caller to ensure that the cpu doesn't go offline.
 993  */
 994 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
 995 {
 996         struct work_for_cpu wfc;
 997
 998         INIT_WORK(&wfc.work, do_work_for_cpu);
 999         wfc.fn = fn;
1000         wfc.arg = arg;
1001         queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
1002         flush_work(&wfc.work);
1003
1004         return wfc.ret;
1005 }
1006 EXPORT_SYMBOL_GPL(work_on_cpu);
1007 #endif /* CONFIG_SMP */
1008
1009 void __init init_workqueues(void)
1010 {
1011         alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
1012
1013         cpumask_copy(cpu_populated_map, cpu_online_mask);
1014         singlethread_cpu = cpumask_first(cpu_possible_mask);
1015         cpu_singlethread_map = cpumask_of(singlethread_cpu);
1016         hotcpu_notifier(workqueue_cpu_callback, 0);
1017         keventd_wq = create_workqueue("events");
1018         BUG_ON(!keventd_wq);
1019 #ifdef CONFIG_SMP
1020         work_on_cpu_wq = create_workqueue("work_on_cpu");
1021         BUG_ON(!work_on_cpu_wq);
1022 #endif
1023 }