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