| 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 | } |