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