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
  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         int rt;
  66 #ifdef CONFIG_LOCKDEP
  67         struct lockdep_map lockdep_map;
  68 #endif
  69 };
  70
  71 /* Serializes the accesses to the list of workqueues. */
  72 static DEFINE_SPINLOCK(workqueue_lock);
  73 static LIST_HEAD(workqueues);
  74
  75 static int singlethread_cpu __read_mostly;
  76 static cpumask_t cpu_singlethread_map __read_mostly;
  77 /*
  78  * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
  79  * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
  80  * which comes in between can't use for_each_online_cpu(). We could
  81  * use cpu_possible_map, the cpumask below is more a documentation
  82  * than optimization.
  83  */
  84 static cpumask_t cpu_populated_map __read_mostly;
  85
  86 /* If it's single threaded, it isn't in the list of workqueues. */
  87 static inline int is_single_threaded(struct workqueue_struct *wq)
  88 {
  89         return wq->singlethread;
  90 }
  91
  92 static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
  93 {
  94         return is_single_threaded(wq)
  95                 ? &cpu_singlethread_map : &cpu_populated_map;
  96 }
  97
  98 static
  99 struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
 100 {
 101         if (unlikely(is_single_threaded(wq)))
 102                 cpu = singlethread_cpu;
 103         return per_cpu_ptr(wq->cpu_wq, cpu);
 104 }
 105
 106 /*
 107  * Set the workqueue on which a work item is to be run
 108  * - Must *only* be called if the pending flag is set
 109  */
 110 static inline void set_wq_data(struct work_struct *work,
 111                                 struct cpu_workqueue_struct *cwq)
 112 {
 113         unsigned long new;
 114
 115         BUG_ON(!work_pending(work));
 116
 117         new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
 118         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
 119         atomic_long_set(&work->data, new);
 120 }
 121
 122 static inline
 123 struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
 124 {
 125         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
 126 }
 127
 128 static void insert_work(struct cpu_workqueue_struct *cwq,
 129                         struct work_struct *work, struct list_head *head)
 130 {
 131         set_wq_data(work, cwq);
 132         /*
 133          * Ensure that we get the right work->data if we see the
 134          * result of list_add() below, see try_to_grab_pending().
 135          */
 136         smp_wmb();
 137         list_add_tail(&work->entry, head);
 138         wake_up(&cwq->more_work);
 139 }
 140
 141 static void __queue_work(struct cpu_workqueue_struct *cwq,
 142                          struct work_struct *work)
 143 {
 144         unsigned long flags;
 145
 146         spin_lock_irqsave(&cwq->lock, flags);
 147         insert_work(cwq, work, &cwq->worklist);
 148         spin_unlock_irqrestore(&cwq->lock, flags);
 149 }
 150
 151 /**
 152  * queue_work - queue work on a workqueue
 153  * @wq: workqueue to use
 154  * @work: work to queue
 155  *
 156  * Returns 0 if @work was already on a queue, non-zero otherwise.
 157  *
 158  * We queue the work to the CPU on which it was submitted, but if the CPU dies
 159  * it can be processed by another CPU.
 160  */
 161 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
 162 {
 163         int ret;
 164
 165         ret = queue_work_on(get_cpu(), wq, work);
 166         put_cpu();
 167
 168         return ret;
 169 }
 170 EXPORT_SYMBOL_GPL(queue_work);
 171
 172 /**
 173  * queue_work_on - queue work on specific cpu
 174  * @cpu: CPU number to execute work on
 175  * @wq: workqueue to use
 176  * @work: work to queue
 177  *
 178  * Returns 0 if @work was already on a queue, non-zero otherwise.
 179  *
 180  * We queue the work to a specific CPU, the caller must ensure it
 181  * can't go away.
 182  */
 183 int
 184 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
 185 {
 186         int ret = 0;
 187
 188         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 189                 BUG_ON(!list_empty(&work->entry));
 190                 __queue_work(wq_per_cpu(wq, cpu), work);
 191                 ret = 1;
 192         }
 193         return ret;
 194 }
 195 EXPORT_SYMBOL_GPL(queue_work_on);
 196
 197 static void delayed_work_timer_fn(unsigned long __data)
 198 {
 199         struct delayed_work *dwork = (struct delayed_work *)__data;
 200         struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
 201         struct workqueue_struct *wq = cwq->wq;
 202
 203         __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
 204 }
 205
 206 /**
 207  * queue_delayed_work - queue work on a workqueue after delay
 208  * @wq: workqueue to use
 209  * @dwork: delayable work to queue
 210  * @delay: number of jiffies to wait before queueing
 211  *
 212  * Returns 0 if @work was already on a queue, non-zero otherwise.
 213  */
 214 int queue_delayed_work(struct workqueue_struct *wq,
 215                         struct delayed_work *dwork, unsigned long delay)
 216 {
 217         if (delay == 0)
 218                 return queue_work(wq, &dwork->work);
 219
 220         return queue_delayed_work_on(-1, wq, dwork, delay);
 221 }
 222 EXPORT_SYMBOL_GPL(queue_delayed_work);
 223
 224 /**
 225  * queue_delayed_work_on - queue work on specific CPU after delay
 226  * @cpu: CPU number to execute work on
 227  * @wq: workqueue to use
 228  * @dwork: work to queue
 229  * @delay: number of jiffies to wait before queueing
 230  *
 231  * Returns 0 if @work was already on a queue, non-zero otherwise.
 232  */
 233 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
 234                         struct delayed_work *dwork, unsigned long delay)
 235 {
 236         int ret = 0;
 237         struct timer_list *timer = &dwork->timer;
 238         struct work_struct *work = &dwork->work;
 239
 240         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
 241                 BUG_ON(timer_pending(timer));
 242                 BUG_ON(!list_empty(&work->entry));
 243
 244                 timer_stats_timer_set_start_info(&dwork->timer);
 245
 246                 /* This stores cwq for the moment, for the timer_fn */
 247                 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
 248                 timer->expires = jiffies + delay;
 249                 timer->data = (unsigned long)dwork;
 250                 timer->function = delayed_work_timer_fn;
 251
 252                 if (unlikely(cpu >= 0))
 253                         add_timer_on(timer, cpu);
 254                 else
 255                         add_timer(timer);
 256                 ret = 1;
 257         }
 258         return ret;
 259 }
 260 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
 261
 262 static void run_workqueue(struct cpu_workqueue_struct *cwq)
 263 {
 264         spin_lock_irq(&cwq->lock);
 265         cwq->run_depth++;
 266         if (cwq->run_depth > 3) {
 267                 /* morton gets to eat his hat */
 268                 printk("%s: recursion depth exceeded: %d\n",
 269                         __func__, cwq->run_depth);
 270                 dump_stack();
 271         }
 272         while (!list_empty(&cwq->worklist)) {
 273                 struct work_struct *work = list_entry(cwq->worklist.next,
 274                                                 struct work_struct, entry);
 275                 work_func_t f = work->func;
 276 #ifdef CONFIG_LOCKDEP
 277                 /*
 278                  * It is permissible to free the struct work_struct
 279                  * from inside the function that is called from it,
 280                  * this we need to take into account for lockdep too.
 281                  * To avoid bogus "held lock freed" warnings as well
 282                  * as problems when looking into work->lockdep_map,
 283                  * make a copy and use that here.
 284                  */
 285                 struct lockdep_map lockdep_map = work->lockdep_map;
 286 #endif
 287
 288                 cwq->current_work = work;
 289                 list_del_init(cwq->worklist.next);
 290                 spin_unlock_irq(&cwq->lock);
 291
 292                 BUG_ON(get_wq_data(work) != cwq);
 293                 work_clear_pending(work);
 294                 lock_map_acquire(&cwq->wq->lockdep_map);
 295                 lock_map_acquire(&lockdep_map);
 296                 f(work);
 297                 lock_map_release(&lockdep_map);
 298                 lock_map_release(&cwq->wq->lockdep_map);
 299
 300                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
 301                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
 302                                         "%s/0x%08x/%d\n",
 303                                         current->comm, preempt_count(),
 304                                         task_pid_nr(current));
 305                         printk(KERN_ERR "    last function: ");
 306                         print_symbol("%s\n", (unsigned long)f);
 307                         debug_show_held_locks(current);
 308                         dump_stack();
 309                 }
 310
 311                 spin_lock_irq(&cwq->lock);
 312                 cwq->current_work = NULL;
 313         }
 314         cwq->run_depth--;
 315         spin_unlock_irq(&cwq->lock);
 316 }
 317
 318 static int worker_thread(void *__cwq)
 319 {
 320         struct cpu_workqueue_struct *cwq = __cwq;
 321         DEFINE_WAIT(wait);
 322
 323         if (cwq->wq->freezeable)
 324                 set_freezable();
 325
 326         set_user_nice(current, -5);
 327
 328         for (;;) {
 329                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
 330                 if (!freezing(current) &&
 331                     !kthread_should_stop() &&
 332                     list_empty(&cwq->worklist))
 333                         schedule();
 334                 finish_wait(&cwq->more_work, &wait);
 335
 336                 try_to_freeze();
 337
 338                 if (kthread_should_stop())
 339                         break;
 340
 341                 run_workqueue(cwq);
 342         }
 343
 344         return 0;
 345 }
 346
 347 struct wq_barrier {
 348         struct work_struct      work;
 349         struct completion       done;
 350 };
 351
 352 static void wq_barrier_func(struct work_struct *work)
 353 {
 354         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
 355         complete(&barr->done);
 356 }
 357
 358 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
 359                         struct wq_barrier *barr, struct list_head *head)
 360 {
 361         INIT_WORK(&barr->work, wq_barrier_func);
 362         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
 363
 364         init_completion(&barr->done);
 365
 366         insert_work(cwq, &barr->work, head);
 367 }
 368
 369 static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
 370 {
 371         int active;
 372
 373         if (cwq->thread == current) {
 374                 /*
 375                  * Probably keventd trying to flush its own queue. So simply run
 376                  * it by hand rather than deadlocking.
 377                  */
 378                 run_workqueue(cwq);
 379                 active = 1;
 380         } else {
 381                 struct wq_barrier barr;
 382
 383                 active = 0;
 384                 spin_lock_irq(&cwq->lock);
 385                 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
 386                         insert_wq_barrier(cwq, &barr, &cwq->worklist);
 387                         active = 1;
 388                 }
 389                 spin_unlock_irq(&cwq->lock);
 390
 391                 if (active)
 392                         wait_for_completion(&barr.done);
 393         }
 394
 395         return active;
 396 }
 397
 398 /**
 399  * flush_workqueue - ensure that any scheduled work has run to completion.
 400  * @wq: workqueue to flush
 401  *
 402  * Forces execution of the workqueue and blocks until its completion.
 403  * This is typically used in driver shutdown handlers.
 404  *
 405  * We sleep until all works which were queued on entry have been handled,
 406  * but we are not livelocked by new incoming ones.
 407  *
 408  * This function used to run the workqueues itself.  Now we just wait for the
 409  * helper threads to do it.
 410  */
 411 void flush_workqueue(struct workqueue_struct *wq)
 412 {
 413         const cpumask_t *cpu_map = wq_cpu_map(wq);
 414         int cpu;
 415
 416         might_sleep();
 417         lock_map_acquire(&wq->lockdep_map);
 418         lock_map_release(&wq->lockdep_map);
 419         for_each_cpu_mask_nr(cpu, *cpu_map)
 420                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 421 }
 422 EXPORT_SYMBOL_GPL(flush_workqueue);
 423
 424 /**
 425  * flush_work - block until a work_struct's callback has terminated
 426  * @work: the work which is to be flushed
 427  *
 428  * Returns false if @work has already terminated.
 429  *
 430  * It is expected that, prior to calling flush_work(), the caller has
 431  * arranged for the work to not be requeued, otherwise it doesn't make
 432  * sense to use this function.
 433  */
 434 int flush_work(struct work_struct *work)
 435 {
 436         struct cpu_workqueue_struct *cwq;
 437         struct list_head *prev;
 438         struct wq_barrier barr;
 439
 440         might_sleep();
 441         cwq = get_wq_data(work);
 442         if (!cwq)
 443                 return 0;
 444
 445         lock_map_acquire(&cwq->wq->lockdep_map);
 446         lock_map_release(&cwq->wq->lockdep_map);
 447
 448         prev = NULL;
 449         spin_lock_irq(&cwq->lock);
 450         if (!list_empty(&work->entry)) {
 451                 /*
 452                  * See the comment near try_to_grab_pending()->smp_rmb().
 453                  * If it was re-queued under us we are not going to wait.
 454                  */
 455                 smp_rmb();
 456                 if (unlikely(cwq != get_wq_data(work)))
 457                         goto out;
 458                 prev = &work->entry;
 459         } else {
 460                 if (cwq->current_work != work)
 461                         goto out;
 462                 prev = &cwq->worklist;
 463         }
 464         insert_wq_barrier(cwq, &barr, prev->next);
 465 out:
 466         spin_unlock_irq(&cwq->lock);
 467         if (!prev)
 468                 return 0;
 469
 470         wait_for_completion(&barr.done);
 471         return 1;
 472 }
 473 EXPORT_SYMBOL_GPL(flush_work);
 474
 475 /*
 476  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
 477  * so this work can't be re-armed in any way.
 478  */
 479 static int try_to_grab_pending(struct work_struct *work)
 480 {
 481         struct cpu_workqueue_struct *cwq;
 482         int ret = -1;
 483
 484         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
 485                 return 0;
 486
 487         /*
 488          * The queueing is in progress, or it is already queued. Try to
 489          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
 490          */
 491
 492         cwq = get_wq_data(work);
 493         if (!cwq)
 494                 return ret;
 495
 496         spin_lock_irq(&cwq->lock);
 497         if (!list_empty(&work->entry)) {
 498                 /*
 499                  * This work is queued, but perhaps we locked the wrong cwq.
 500                  * In that case we must see the new value after rmb(), see
 501                  * insert_work()->wmb().
 502                  */
 503                 smp_rmb();
 504                 if (cwq == get_wq_data(work)) {
 505                         list_del_init(&work->entry);
 506                         ret = 1;
 507                 }
 508         }
 509         spin_unlock_irq(&cwq->lock);
 510
 511         return ret;
 512 }
 513
 514 static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
 515                                 struct work_struct *work)
 516 {
 517         struct wq_barrier barr;
 518         int running = 0;
 519
 520         spin_lock_irq(&cwq->lock);
 521         if (unlikely(cwq->current_work == work)) {
 522                 insert_wq_barrier(cwq, &barr, cwq->worklist.next);
 523                 running = 1;
 524         }
 525         spin_unlock_irq(&cwq->lock);
 526
 527         if (unlikely(running))
 528                 wait_for_completion(&barr.done);
 529 }
 530
 531 static void wait_on_work(struct work_struct *work)
 532 {
 533         struct cpu_workqueue_struct *cwq;
 534         struct workqueue_struct *wq;
 535         const cpumask_t *cpu_map;
 536         int cpu;
 537
 538         might_sleep();
 539
 540         lock_map_acquire(&work->lockdep_map);
 541         lock_map_release(&work->lockdep_map);
 542
 543         cwq = get_wq_data(work);
 544         if (!cwq)
 545                 return;
 546
 547         wq = cwq->wq;
 548         cpu_map = wq_cpu_map(wq);
 549
 550         for_each_cpu_mask_nr(cpu, *cpu_map)
 551                 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 552 }
 553
 554 static int __cancel_work_timer(struct work_struct *work,
 555                                 struct timer_list* timer)
 556 {
 557         int ret;
 558
 559         do {
 560                 ret = (timer && likely(del_timer(timer)));
 561                 if (!ret)
 562                         ret = try_to_grab_pending(work);
 563                 wait_on_work(work);
 564         } while (unlikely(ret < 0));
 565
 566         work_clear_pending(work);
 567         return ret;
 568 }
 569
 570 /**
 571  * cancel_work_sync - block until a work_struct's callback has terminated
 572  * @work: the work which is to be flushed
 573  *
 574  * Returns true if @work was pending.
 575  *
 576  * cancel_work_sync() will cancel the work if it is queued. If the work's
 577  * callback appears to be running, cancel_work_sync() will block until it
 578  * has completed.
 579  *
 580  * It is possible to use this function if the work re-queues itself. It can
 581  * cancel the work even if it migrates to another workqueue, however in that
 582  * case it only guarantees that work->func() has completed on the last queued
 583  * workqueue.
 584  *
 585  * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
 586  * pending, otherwise it goes into a busy-wait loop until the timer expires.
 587  *
 588  * The caller must ensure that workqueue_struct on which this work was last
 589  * queued can't be destroyed before this function returns.
 590  */
 591 int cancel_work_sync(struct work_struct *work)
 592 {
 593         return __cancel_work_timer(work, NULL);
 594 }
 595 EXPORT_SYMBOL_GPL(cancel_work_sync);
 596
 597 /**
 598  * cancel_delayed_work_sync - reliably kill off a delayed work.
 599  * @dwork: the delayed work struct
 600  *
 601  * Returns true if @dwork was pending.
 602  *
 603  * It is possible to use this function if @dwork rearms itself via queue_work()
 604  * or queue_delayed_work(). See also the comment for cancel_work_sync().
 605  */
 606 int cancel_delayed_work_sync(struct delayed_work *dwork)
 607 {
 608         return __cancel_work_timer(&dwork->work, &dwork->timer);
 609 }
 610 EXPORT_SYMBOL(cancel_delayed_work_sync);
 611
 612 static struct workqueue_struct *keventd_wq __read_mostly;
 613
 614 /**
 615  * schedule_work - put work task in global workqueue
 616  * @work: job to be done
 617  *
 618  * This puts a job in the kernel-global workqueue.
 619  */
 620 int schedule_work(struct work_struct *work)
 621 {
 622         return queue_work(keventd_wq, work);
 623 }
 624 EXPORT_SYMBOL(schedule_work);
 625
 626 /*
 627  * schedule_work_on - put work task on a specific cpu
 628  * @cpu: cpu to put the work task on
 629  * @work: job to be done
 630  *
 631  * This puts a job on a specific cpu
 632  */
 633 int schedule_work_on(int cpu, struct work_struct *work)
 634 {
 635         return queue_work_on(cpu, keventd_wq, work);
 636 }
 637 EXPORT_SYMBOL(schedule_work_on);
 638
 639 /**
 640  * schedule_delayed_work - put work task in global workqueue after delay
 641  * @dwork: job to be done
 642  * @delay: number of jiffies to wait or 0 for immediate execution
 643  *
 644  * After waiting for a given time this puts a job in the kernel-global
 645  * workqueue.
 646  */
 647 int schedule_delayed_work(struct delayed_work *dwork,
 648                                         unsigned long delay)
 649 {
 650         return queue_delayed_work(keventd_wq, dwork, delay);
 651 }
 652 EXPORT_SYMBOL(schedule_delayed_work);
 653
 654 /**
 655  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 656  * @cpu: cpu to use
 657  * @dwork: job to be done
 658  * @delay: number of jiffies to wait
 659  *
 660  * After waiting for a given time this puts a job in the kernel-global
 661  * workqueue on the specified CPU.
 662  */
 663 int schedule_delayed_work_on(int cpu,
 664                         struct delayed_work *dwork, unsigned long delay)
 665 {
 666         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
 667 }
 668 EXPORT_SYMBOL(schedule_delayed_work_on);
 669
 670 /**
 671  * schedule_on_each_cpu - call a function on each online CPU from keventd
 672  * @func: the function to call
 673  *
 674  * Returns zero on success.
 675  * Returns -ve errno on failure.
 676  *
 677  * schedule_on_each_cpu() is very slow.
 678  */
 679 int schedule_on_each_cpu(work_func_t func)
 680 {
 681         int cpu;
 682         struct work_struct *works;
 683
 684         works = alloc_percpu(struct work_struct);
 685         if (!works)
 686                 return -ENOMEM;
 687
 688         get_online_cpus();
 689         for_each_online_cpu(cpu) {
 690                 struct work_struct *work = per_cpu_ptr(works, cpu);
 691
 692                 INIT_WORK(work, func);
 693                 schedule_work_on(cpu, work);
 694         }
 695         for_each_online_cpu(cpu)
 696                 flush_work(per_cpu_ptr(works, cpu));
 697         put_online_cpus();
 698         free_percpu(works);
 699         return 0;
 700 }
 701
 702 void flush_scheduled_work(void)
 703 {
 704         flush_workqueue(keventd_wq);
 705 }
 706 EXPORT_SYMBOL(flush_scheduled_work);
 707
 708 /**
 709  * execute_in_process_context - reliably execute the routine with user context
 710  * @fn:         the function to execute
 711  * @ew:         guaranteed storage for the execute work structure (must
 712  *              be available when the work executes)
 713  *
 714  * Executes the function immediately if process context is available,
 715  * otherwise schedules the function for delayed execution.
 716  *
 717  * Returns:     0 - function was executed
 718  *              1 - function was scheduled for execution
 719  */
 720 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
 721 {
 722         if (!in_interrupt()) {
 723                 fn(&ew->work);
 724                 return 0;
 725         }
 726
 727         INIT_WORK(&ew->work, fn);
 728         schedule_work(&ew->work);
 729
 730         return 1;
 731 }
 732 EXPORT_SYMBOL_GPL(execute_in_process_context);
 733
 734 int keventd_up(void)
 735 {
 736         return keventd_wq != NULL;
 737 }
 738
 739 int current_is_keventd(void)
 740 {
 741         struct cpu_workqueue_struct *cwq;
 742         int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
 743         int ret = 0;
 744
 745         BUG_ON(!keventd_wq);
 746
 747         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
 748         if (current == cwq->thread)
 749                 ret = 1;
 750
 751         return ret;
 752
 753 }
 754
 755 static struct cpu_workqueue_struct *
 756 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
 757 {
 758         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 759
 760         cwq->wq = wq;
 761         spin_lock_init(&cwq->lock);
 762         INIT_LIST_HEAD(&cwq->worklist);
 763         init_waitqueue_head(&cwq->more_work);
 764
 765         return cwq;
 766 }
 767
 768 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 769 {
 770         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
 771         struct workqueue_struct *wq = cwq->wq;
 772         const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
 773         struct task_struct *p;
 774
 775         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
 776         /*
 777          * Nobody can add the work_struct to this cwq,
 778          *      if (caller is __create_workqueue)
 779          *              nobody should see this wq
 780          *      else // caller is CPU_UP_PREPARE
 781          *              cpu is not on cpu_online_map
 782          * so we can abort safely.
 783          */
 784         if (IS_ERR(p))
 785                 return PTR_ERR(p);
 786         if (cwq->wq->rt)
 787                 sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
 788         cwq->thread = p;
 789
 790         return 0;
 791 }
 792
 793 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
 794 {
 795         struct task_struct *p = cwq->thread;
 796
 797         if (p != NULL) {
 798                 if (cpu >= 0)
 799                         kthread_bind(p, cpu);
 800                 wake_up_process(p);
 801         }
 802 }
 803
 804 struct workqueue_struct *__create_workqueue_key(const char *name,
 805                                                 int singlethread,
 806                                                 int freezeable,
 807                                                 int rt,
 808                                                 struct lock_class_key *key,
 809                                                 const char *lock_name)
 810 {
 811         struct workqueue_struct *wq;
 812         struct cpu_workqueue_struct *cwq;
 813         int err = 0, cpu;
 814
 815         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
 816         if (!wq)
 817                 return NULL;
 818
 819         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
 820         if (!wq->cpu_wq) {
 821                 kfree(wq);
 822                 return NULL;
 823         }
 824
 825         wq->name = name;
 826         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 827         wq->singlethread = singlethread;
 828         wq->freezeable = freezeable;
 829         wq->rt = rt;
 830         INIT_LIST_HEAD(&wq->list);
 831
 832         if (singlethread) {
 833                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
 834                 err = create_workqueue_thread(cwq, singlethread_cpu);
 835                 start_workqueue_thread(cwq, -1);
 836         } else {
 837                 cpu_maps_update_begin();
 838                 /*
 839                  * We must place this wq on list even if the code below fails.
 840                  * cpu_down(cpu) can remove cpu from cpu_populated_map before
 841                  * destroy_workqueue() takes the lock, in that case we leak
 842                  * cwq[cpu]->thread.
 843                  */
 844                 spin_lock(&workqueue_lock);
 845                 list_add(&wq->list, &workqueues);
 846                 spin_unlock(&workqueue_lock);
 847                 /*
 848                  * We must initialize cwqs for each possible cpu even if we
 849                  * are going to call destroy_workqueue() finally. Otherwise
 850                  * cpu_up() can hit the uninitialized cwq once we drop the
 851                  * lock.
 852                  */
 853                 for_each_possible_cpu(cpu) {
 854                         cwq = init_cpu_workqueue(wq, cpu);
 855                         if (err || !cpu_online(cpu))
 856                                 continue;
 857                         err = create_workqueue_thread(cwq, cpu);
 858                         start_workqueue_thread(cwq, cpu);
 859                 }
 860                 cpu_maps_update_done();
 861         }
 862
 863         if (err) {
 864                 destroy_workqueue(wq);
 865                 wq = NULL;
 866         }
 867         return wq;
 868 }
 869 EXPORT_SYMBOL_GPL(__create_workqueue_key);
 870
 871 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
 872 {
 873         /*
 874          * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
 875          * cpu_add_remove_lock protects cwq->thread.
 876          */
 877         if (cwq->thread == NULL)
 878                 return;
 879
 880         lock_map_acquire(&cwq->wq->lockdep_map);
 881         lock_map_release(&cwq->wq->lockdep_map);
 882
 883         flush_cpu_workqueue(cwq);
 884         /*
 885          * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
 886          * a concurrent flush_workqueue() can insert a barrier after us.
 887          * However, in that case run_workqueue() won't return and check
 888          * kthread_should_stop() until it flushes all work_struct's.
 889          * When ->worklist becomes empty it is safe to exit because no
 890          * more work_structs can be queued on this cwq: flush_workqueue
 891          * checks list_empty(), and a "normal" queue_work() can't use
 892          * a dead CPU.
 893          */
 894         kthread_stop(cwq->thread);
 895         cwq->thread = NULL;
 896 }
 897
 898 /**
 899  * destroy_workqueue - safely terminate a workqueue
 900  * @wq: target workqueue
 901  *
 902  * Safely destroy a workqueue. All work currently pending will be done first.
 903  */
 904 void destroy_workqueue(struct workqueue_struct *wq)
 905 {
 906         const cpumask_t *cpu_map = wq_cpu_map(wq);
 907         int cpu;
 908
 909         cpu_maps_update_begin();
 910         spin_lock(&workqueue_lock);
 911         list_del(&wq->list);
 912         spin_unlock(&workqueue_lock);
 913
 914         for_each_cpu_mask_nr(cpu, *cpu_map)
 915                 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
 916         cpu_maps_update_done();
 917
 918         free_percpu(wq->cpu_wq);
 919         kfree(wq);
 920 }
 921 EXPORT_SYMBOL_GPL(destroy_workqueue);
 922
 923 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 924                                                 unsigned long action,
 925                                                 void *hcpu)
 926 {
 927         unsigned int cpu = (unsigned long)hcpu;
 928         struct cpu_workqueue_struct *cwq;
 929         struct workqueue_struct *wq;
 930         int ret = NOTIFY_OK;
 931
 932         action &= ~CPU_TASKS_FROZEN;
 933
 934         switch (action) {
 935         case CPU_UP_PREPARE:
 936                 cpu_set(cpu, cpu_populated_map);
 937         }
 938 undo:
 939         list_for_each_entry(wq, &workqueues, list) {
 940                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
 941
 942                 switch (action) {
 943                 case CPU_UP_PREPARE:
 944                         if (!create_workqueue_thread(cwq, cpu))
 945                                 break;
 946                         printk(KERN_ERR "workqueue [%s] for %i failed\n",
 947                                 wq->name, cpu);
 948                         action = CPU_UP_CANCELED;
 949                         ret = NOTIFY_BAD;
 950                         goto undo;
 951
 952                 case CPU_ONLINE:
 953                         start_workqueue_thread(cwq, cpu);
 954                         break;
 955
 956                 case CPU_UP_CANCELED:
 957                         start_workqueue_thread(cwq, -1);
 958                 case CPU_POST_DEAD:
 959                         cleanup_workqueue_thread(cwq);
 960                         break;
 961                 }
 962         }
 963
 964         switch (action) {
 965         case CPU_UP_CANCELED:
 966         case CPU_POST_DEAD:
 967                 cpu_clear(cpu, cpu_populated_map);
 968         }
 969
 970         return ret;
 971 }
 972
 973 #ifdef CONFIG_SMP
 974 struct work_for_cpu {
 975         struct work_struct work;
 976         long (*fn)(void *);
 977         void *arg;
 978         long ret;
 979 };
 980
 981 static void do_work_for_cpu(struct work_struct *w)
 982 {
 983         struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
 984
 985         wfc->ret = wfc->fn(wfc->arg);
 986 }
 987
 988 /**
 989  * work_on_cpu - run a function in user context on a particular cpu
 990  * @cpu: the cpu to run on
 991  * @fn: the function to run
 992  * @arg: the function arg
 993  *
 994  * This will return -EINVAL in the cpu is not online, or the return value
 995  * of @fn otherwise.
 996  */
 997 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
 998 {
 999         struct work_for_cpu wfc;
1000
1001         INIT_WORK(&wfc.work, do_work_for_cpu);
1002         wfc.fn = fn;
1003         wfc.arg = arg;
1004         get_online_cpus();
1005         if (unlikely(!cpu_online(cpu)))
1006                 wfc.ret = -EINVAL;
1007         else {
1008                 schedule_work_on(cpu, &wfc.work);
1009                 flush_work(&wfc.work);
1010         }
1011         put_online_cpus();
1012
1013         return wfc.ret;
1014 }
1015 EXPORT_SYMBOL_GPL(work_on_cpu);
1016 #endif /* CONFIG_SMP */
1017
1018 void __init init_workqueues(void)
1019 {
1020         cpu_populated_map = cpu_online_map;
1021         singlethread_cpu = first_cpu(cpu_possible_map);
1022         cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
1023         hotcpu_notifier(workqueue_cpu_callback, 0);
1024         keventd_wq = create_workqueue("events");
1025         BUG_ON(!keventd_wq);
1026 }