kernel/sched/wait.c

   1 /*
   2  * Generic waiting primitives.
   3  *
   4  * (C) 2004 Nadia Yvette Chambers, Oracle
   5  */
   6 #include <linux/init.h>
   7 #include <linux/export.h>
   8 #include <linux/sched.h>
   9 #include <linux/mm.h>
  10 #include <linux/wait.h>
  11 #include <linux/hash.h>
  12 #include <linux/kthread.h>
  13
  14 void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key)
  15 {
  16         spin_lock_init(&q->lock);
  17         lockdep_set_class_and_name(&q->lock, key, name);
  18         INIT_LIST_HEAD(&q->task_list);
  19 }
  20
  21 EXPORT_SYMBOL(__init_waitqueue_head);
  22
  23 void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
  24 {
  25         unsigned long flags;
  26
  27         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
  28         spin_lock_irqsave(&q->lock, flags);
  29         __add_wait_queue(q, wait);
  30         spin_unlock_irqrestore(&q->lock, flags);
  31 }
  32 EXPORT_SYMBOL(add_wait_queue);
  33
  34 void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
  35 {
  36         unsigned long flags;
  37
  38         wait->flags |= WQ_FLAG_EXCLUSIVE;
  39         spin_lock_irqsave(&q->lock, flags);
  40         __add_wait_queue_tail(q, wait);
  41         spin_unlock_irqrestore(&q->lock, flags);
  42 }
  43 EXPORT_SYMBOL(add_wait_queue_exclusive);
  44
  45 void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
  46 {
  47         unsigned long flags;
  48
  49         spin_lock_irqsave(&q->lock, flags);
  50         __remove_wait_queue(q, wait);
  51         spin_unlock_irqrestore(&q->lock, flags);
  52 }
  53 EXPORT_SYMBOL(remove_wait_queue);
  54
  55
  56 /*
  57  * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
  58  * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
  59  * number) then we wake all the non-exclusive tasks and one exclusive task.
  60  *
  61  * There are circumstances in which we can try to wake a task which has already
  62  * started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
  63  * zero in this (rare) case, and we handle it by continuing to scan the queue.
  64  */
  65 static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
  66                         int nr_exclusive, int wake_flags, void *key)
  67 {
  68         wait_queue_t *curr, *next;
  69
  70         list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
  71                 unsigned flags = curr->flags;
  72
  73                 if (curr->func(curr, mode, wake_flags, key) &&
  74                                 (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
  75                         break;
  76         }
  77 }
  78
  79 /**
  80  * __wake_up - wake up threads blocked on a waitqueue.
  81  * @q: the waitqueue
  82  * @mode: which threads
  83  * @nr_exclusive: how many wake-one or wake-many threads to wake up
  84  * @key: is directly passed to the wakeup function
  85  *
  86  * It may be assumed that this function implies a write memory barrier before
  87  * changing the task state if and only if any tasks are woken up.
  88  */
  89 void __wake_up(wait_queue_head_t *q, unsigned int mode,
  90                         int nr_exclusive, void *key)
  91 {
  92         unsigned long flags;
  93
  94         spin_lock_irqsave(&q->lock, flags);
  95         __wake_up_common(q, mode, nr_exclusive, 0, key);
  96         spin_unlock_irqrestore(&q->lock, flags);
  97 }
  98 EXPORT_SYMBOL(__wake_up);
  99
 100 /*
 101  * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
 102  */
 103 void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr)
 104 {
 105         __wake_up_common(q, mode, nr, 0, NULL);
 106 }
 107 EXPORT_SYMBOL_GPL(__wake_up_locked);
 108
 109 void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, int nr,
 110                           void *key)
 111 {
 112         __wake_up_common(q, mode, nr, 0, key);
 113 }
 114 EXPORT_SYMBOL_GPL(__wake_up_locked_key);
 115
 116 /**
 117  * __wake_up_sync_key - wake up threads blocked on a waitqueue.
 118  * @q: the waitqueue
 119  * @mode: which threads
 120  * @nr_exclusive: how many wake-one or wake-many threads to wake up
 121  * @key: opaque value to be passed to wakeup targets
 122  *
 123  * The sync wakeup differs that the waker knows that it will schedule
 124  * away soon, so while the target thread will be woken up, it will not
 125  * be migrated to another CPU - ie. the two threads are 'synchronized'
 126  * with each other. This can prevent needless bouncing between CPUs.
 127  *
 128  * On UP it can prevent extra preemption.
 129  *
 130  * It may be assumed that this function implies a write memory barrier before
 131  * changing the task state if and only if any tasks are woken up.
 132  */
 133 void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode,
 134                         int nr_exclusive, void *key)
 135 {
 136         unsigned long flags;
 137         int wake_flags = 1; /* XXX WF_SYNC */
 138
 139         if (unlikely(!q))
 140                 return;
 141
 142         if (unlikely(nr_exclusive != 1))
 143                 wake_flags = 0;
 144
 145         spin_lock_irqsave(&q->lock, flags);
 146         __wake_up_common(q, mode, nr_exclusive, wake_flags, key);
 147         spin_unlock_irqrestore(&q->lock, flags);
 148 }
 149 EXPORT_SYMBOL_GPL(__wake_up_sync_key);
 150
 151 /*
 152  * __wake_up_sync - see __wake_up_sync_key()
 153  */
 154 void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
 155 {
 156         __wake_up_sync_key(q, mode, nr_exclusive, NULL);
 157 }
 158 EXPORT_SYMBOL_GPL(__wake_up_sync);      /* For internal use only */
 159
 160 /*
 161  * Note: we use "set_current_state()" _after_ the wait-queue add,
 162  * because we need a memory barrier there on SMP, so that any
 163  * wake-function that tests for the wait-queue being active
 164  * will be guaranteed to see waitqueue addition _or_ subsequent
 165  * tests in this thread will see the wakeup having taken place.
 166  *
 167  * The spin_unlock() itself is semi-permeable and only protects
 168  * one way (it only protects stuff inside the critical region and
 169  * stops them from bleeding out - it would still allow subsequent
 170  * loads to move into the critical region).
 171  */
 172 void
 173 prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
 174 {
 175         unsigned long flags;
 176
 177         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
 178         spin_lock_irqsave(&q->lock, flags);
 179         if (list_empty(&wait->task_list))
 180                 __add_wait_queue(q, wait);
 181         set_current_state(state);
 182         spin_unlock_irqrestore(&q->lock, flags);
 183 }
 184 EXPORT_SYMBOL(prepare_to_wait);
 185
 186 void
 187 prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
 188 {
 189         unsigned long flags;
 190
 191         wait->flags |= WQ_FLAG_EXCLUSIVE;
 192         spin_lock_irqsave(&q->lock, flags);
 193         if (list_empty(&wait->task_list))
 194                 __add_wait_queue_tail(q, wait);
 195         set_current_state(state);
 196         spin_unlock_irqrestore(&q->lock, flags);
 197 }
 198 EXPORT_SYMBOL(prepare_to_wait_exclusive);
 199
 200 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
 201 {
 202         unsigned long flags;
 203
 204         if (signal_pending_state(state, current))
 205                 return -ERESTARTSYS;
 206
 207         wait->private = current;
 208         wait->func = autoremove_wake_function;
 209
 210         spin_lock_irqsave(&q->lock, flags);
 211         if (list_empty(&wait->task_list)) {
 212                 if (wait->flags & WQ_FLAG_EXCLUSIVE)
 213                         __add_wait_queue_tail(q, wait);
 214                 else
 215                         __add_wait_queue(q, wait);
 216         }
 217         set_current_state(state);
 218         spin_unlock_irqrestore(&q->lock, flags);
 219
 220         return 0;
 221 }
 222 EXPORT_SYMBOL(prepare_to_wait_event);
 223
 224 /**
 225  * finish_wait - clean up after waiting in a queue
 226  * @q: waitqueue waited on
 227  * @wait: wait descriptor
 228  *
 229  * Sets current thread back to running state and removes
 230  * the wait descriptor from the given waitqueue if still
 231  * queued.
 232  */
 233 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
 234 {
 235         unsigned long flags;
 236
 237         __set_current_state(TASK_RUNNING);
 238         /*
 239          * We can check for list emptiness outside the lock
 240          * IFF:
 241          *  - we use the "careful" check that verifies both
 242          *    the next and prev pointers, so that there cannot
 243          *    be any half-pending updates in progress on other
 244          *    CPU's that we haven't seen yet (and that might
 245          *    still change the stack area.
 246          * and
 247          *  - all other users take the lock (ie we can only
 248          *    have _one_ other CPU that looks at or modifies
 249          *    the list).
 250          */
 251         if (!list_empty_careful(&wait->task_list)) {
 252                 spin_lock_irqsave(&q->lock, flags);
 253                 list_del_init(&wait->task_list);
 254                 spin_unlock_irqrestore(&q->lock, flags);
 255         }
 256 }
 257 EXPORT_SYMBOL(finish_wait);
 258
 259 /**
 260  * abort_exclusive_wait - abort exclusive waiting in a queue
 261  * @q: waitqueue waited on
 262  * @wait: wait descriptor
 263  * @mode: runstate of the waiter to be woken
 264  * @key: key to identify a wait bit queue or %NULL
 265  *
 266  * Sets current thread back to running state and removes
 267  * the wait descriptor from the given waitqueue if still
 268  * queued.
 269  *
 270  * Wakes up the next waiter if the caller is concurrently
 271  * woken up through the queue.
 272  *
 273  * This prevents waiter starvation where an exclusive waiter
 274  * aborts and is woken up concurrently and no one wakes up
 275  * the next waiter.
 276  */
 277 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
 278                         unsigned int mode, void *key)
 279 {
 280         unsigned long flags;
 281
 282         __set_current_state(TASK_RUNNING);
 283         spin_lock_irqsave(&q->lock, flags);
 284         if (!list_empty(&wait->task_list))
 285                 list_del_init(&wait->task_list);
 286         else if (waitqueue_active(q))
 287                 __wake_up_locked_key(q, mode, 1, key);
 288         spin_unlock_irqrestore(&q->lock, flags);
 289 }
 290 EXPORT_SYMBOL(abort_exclusive_wait);
 291
 292 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 293 {
 294         int ret = default_wake_function(wait, mode, sync, key);
 295
 296         if (ret)
 297                 list_del_init(&wait->task_list);
 298         return ret;
 299 }
 300 EXPORT_SYMBOL(autoremove_wake_function);
 301
 302 static inline bool is_kthread_should_stop(void)
 303 {
 304         return (current->flags & PF_KTHREAD) && kthread_should_stop();
 305 }
 306
 307 /*
 308  * DEFINE_WAIT_FUNC(wait, woken_wake_func);
 309  *
 310  * add_wait_queue(&wq, &wait);
 311  * for (;;) {
 312  *     if (condition)
 313  *         break;
 314  *
 315  *     p->state = mode;                         condition = true;
 316  *     smp_mb(); // A                           smp_wmb(); // C
 317  *     if (!wait->flags & WQ_FLAG_WOKEN)        wait->flags |= WQ_FLAG_WOKEN;
 318  *         schedule()                           try_to_wake_up();
 319  *     p->state = TASK_RUNNING;             ~~~~~~~~~~~~~~~~~~
 320  *     wait->flags &= ~WQ_FLAG_WOKEN;           condition = true;
 321  *     smp_mb() // B                            smp_wmb(); // C
 322  *                                              wait->flags |= WQ_FLAG_WOKEN;
 323  * }
 324  * remove_wait_queue(&wq, &wait);
 325  *
 326  */
 327 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
 328 {
 329         set_current_state(mode); /* A */
 330         /*
 331          * The above implies an smp_mb(), which matches with the smp_wmb() from
 332          * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
 333          * also observe all state before the wakeup.
 334          */
 335         if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
 336                 timeout = schedule_timeout(timeout);
 337         __set_current_state(TASK_RUNNING);
 338
 339         /*
 340          * The below implies an smp_mb(), it too pairs with the smp_wmb() from
 341          * woken_wake_function() such that we must either observe the wait
 342          * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
 343          * an event.
 344          */
 345         smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
 346
 347         return timeout;
 348 }
 349 EXPORT_SYMBOL(wait_woken);
 350
 351 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 352 {
 353         /*
 354          * Although this function is called under waitqueue lock, LOCK
 355          * doesn't imply write barrier and the users expects write
 356          * barrier semantics on wakeup functions.  The following
 357          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 358          * and is paired with smp_store_mb() in wait_woken().
 359          */
 360         smp_wmb(); /* C */
 361         wait->flags |= WQ_FLAG_WOKEN;
 362
 363         return default_wake_function(wait, mode, sync, key);
 364 }
 365 EXPORT_SYMBOL(woken_wake_function);
 366
 367 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 368 {
 369         struct wait_bit_key *key = arg;
 370         struct wait_bit_queue *wait_bit
 371                 = container_of(wait, struct wait_bit_queue, wait);
 372
 373         if (wait_bit->key.flags != key->flags ||
 374                         wait_bit->key.bit_nr != key->bit_nr ||
 375                         test_bit(key->bit_nr, key->flags))
 376                 return 0;
 377         else
 378                 return autoremove_wake_function(wait, mode, sync, key);
 379 }
 380 EXPORT_SYMBOL(wake_bit_function);
 381
 382 /*
 383  * To allow interruptible waiting and asynchronous (i.e. nonblocking)
 384  * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
 385  * permitted return codes. Nonzero return codes halt waiting and return.
 386  */
 387 int __sched
 388 __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
 389               wait_bit_action_f *action, unsigned mode)
 390 {
 391         int ret = 0;
 392
 393         do {
 394                 prepare_to_wait(wq, &q->wait, mode);
 395                 if (test_bit(q->key.bit_nr, q->key.flags))
 396                         ret = (*action)(&q->key);
 397         } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
 398         finish_wait(wq, &q->wait);
 399         return ret;
 400 }
 401 EXPORT_SYMBOL(__wait_on_bit);
 402
 403 int __sched out_of_line_wait_on_bit(void *word, int bit,
 404                                     wait_bit_action_f *action, unsigned mode)
 405 {
 406         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 407         DEFINE_WAIT_BIT(wait, word, bit);
 408
 409         return __wait_on_bit(wq, &wait, action, mode);
 410 }
 411 EXPORT_SYMBOL(out_of_line_wait_on_bit);
 412
 413 int __sched out_of_line_wait_on_bit_timeout(
 414         void *word, int bit, wait_bit_action_f *action,
 415         unsigned mode, unsigned long timeout)
 416 {
 417         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 418         DEFINE_WAIT_BIT(wait, word, bit);
 419
 420         wait.key.timeout = jiffies + timeout;
 421         return __wait_on_bit(wq, &wait, action, mode);
 422 }
 423 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
 424
 425 int __sched
 426 __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
 427                         wait_bit_action_f *action, unsigned mode)
 428 {
 429         do {
 430                 int ret;
 431
 432                 prepare_to_wait_exclusive(wq, &q->wait, mode);
 433                 if (!test_bit(q->key.bit_nr, q->key.flags))
 434                         continue;
 435                 ret = action(&q->key);
 436                 if (!ret)
 437                         continue;
 438                 abort_exclusive_wait(wq, &q->wait, mode, &q->key);
 439                 return ret;
 440         } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
 441         finish_wait(wq, &q->wait);
 442         return 0;
 443 }
 444 EXPORT_SYMBOL(__wait_on_bit_lock);
 445
 446 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
 447                                          wait_bit_action_f *action, unsigned mode)
 448 {
 449         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 450         DEFINE_WAIT_BIT(wait, word, bit);
 451
 452         return __wait_on_bit_lock(wq, &wait, action, mode);
 453 }
 454 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
 455
 456 void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
 457 {
 458         struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
 459         if (waitqueue_active(wq))
 460                 __wake_up(wq, TASK_NORMAL, 1, &key);
 461 }
 462 EXPORT_SYMBOL(__wake_up_bit);
 463
 464 /**
 465  * wake_up_bit - wake up a waiter on a bit
 466  * @word: the word being waited on, a kernel virtual address
 467  * @bit: the bit of the word being waited on
 468  *
 469  * There is a standard hashed waitqueue table for generic use. This
 470  * is the part of the hashtable's accessor API that wakes up waiters
 471  * on a bit. For instance, if one were to have waiters on a bitflag,
 472  * one would call wake_up_bit() after clearing the bit.
 473  *
 474  * In order for this to function properly, as it uses waitqueue_active()
 475  * internally, some kind of memory barrier must be done prior to calling
 476  * this. Typically, this will be smp_mb__after_atomic(), but in some
 477  * cases where bitflags are manipulated non-atomically under a lock, one
 478  * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
 479  * because spin_unlock() does not guarantee a memory barrier.
 480  */
 481 void wake_up_bit(void *word, int bit)
 482 {
 483         __wake_up_bit(bit_waitqueue(word, bit), word, bit);
 484 }
 485 EXPORT_SYMBOL(wake_up_bit);
 486
 487 wait_queue_head_t *bit_waitqueue(void *word, int bit)
 488 {
 489         const int shift = BITS_PER_LONG == 32 ? 5 : 6;
 490         const struct zone *zone = page_zone(virt_to_page(word));
 491         unsigned long val = (unsigned long)word << shift | bit;
 492
 493         return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
 494 }
 495 EXPORT_SYMBOL(bit_waitqueue);
 496
 497 /*
 498  * Manipulate the atomic_t address to produce a better bit waitqueue table hash
 499  * index (we're keying off bit -1, but that would produce a horrible hash
 500  * value).
 501  */
 502 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
 503 {
 504         if (BITS_PER_LONG == 64) {
 505                 unsigned long q = (unsigned long)p;
 506                 return bit_waitqueue((void *)(q & ~1), q & 1);
 507         }
 508         return bit_waitqueue(p, 0);
 509 }
 510
 511 static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
 512                                   void *arg)
 513 {
 514         struct wait_bit_key *key = arg;
 515         struct wait_bit_queue *wait_bit
 516                 = container_of(wait, struct wait_bit_queue, wait);
 517         atomic_t *val = key->flags;
 518
 519         if (wait_bit->key.flags != key->flags ||
 520             wait_bit->key.bit_nr != key->bit_nr ||
 521             atomic_read(val) != 0)
 522                 return 0;
 523         return autoremove_wake_function(wait, mode, sync, key);
 524 }
 525
 526 /*
 527  * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
 528  * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
 529  * return codes halt waiting and return.
 530  */
 531 static __sched
 532 int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
 533                        int (*action)(atomic_t *), unsigned mode)
 534 {
 535         atomic_t *val;
 536         int ret = 0;
 537
 538         do {
 539                 prepare_to_wait(wq, &q->wait, mode);
 540                 val = q->key.flags;
 541                 if (atomic_read(val) == 0)
 542                         break;
 543                 ret = (*action)(val);
 544         } while (!ret && atomic_read(val) != 0);
 545         finish_wait(wq, &q->wait);
 546         return ret;
 547 }
 548
 549 #define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
 550         struct wait_bit_queue name = {                                  \
 551                 .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
 552                 .wait   = {                                             \
 553                         .private        = current,                      \
 554                         .func           = wake_atomic_t_function,       \
 555                         .task_list      =                               \
 556                                 LIST_HEAD_INIT((name).wait.task_list),  \
 557                 },                                                      \
 558         }
 559
 560 __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
 561                                          unsigned mode)
 562 {
 563         wait_queue_head_t *wq = atomic_t_waitqueue(p);
 564         DEFINE_WAIT_ATOMIC_T(wait, p);
 565
 566         return __wait_on_atomic_t(wq, &wait, action, mode);
 567 }
 568 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
 569
 570 /**
 571  * wake_up_atomic_t - Wake up a waiter on a atomic_t
 572  * @p: The atomic_t being waited on, a kernel virtual address
 573  *
 574  * Wake up anyone waiting for the atomic_t to go to zero.
 575  *
 576  * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
 577  * check is done by the waiter's wake function, not the by the waker itself).
 578  */
 579 void wake_up_atomic_t(atomic_t *p)
 580 {
 581         __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
 582 }
 583 EXPORT_SYMBOL(wake_up_atomic_t);
 584
 585 __sched int bit_wait(struct wait_bit_key *word)
 586 {
 587         if (signal_pending_state(current->state, current))
 588                 return 1;
 589         schedule();
 590         return 0;
 591 }
 592 EXPORT_SYMBOL(bit_wait);
 593
 594 __sched int bit_wait_io(struct wait_bit_key *word)
 595 {
 596         if (signal_pending_state(current->state, current))
 597                 return 1;
 598         io_schedule();
 599         return 0;
 600 }
 601 EXPORT_SYMBOL(bit_wait_io);
 602
 603 __sched int bit_wait_timeout(struct wait_bit_key *word)
 604 {
 605         unsigned long now = READ_ONCE(jiffies);
 606         if (signal_pending_state(current->state, current))
 607                 return 1;
 608         if (time_after_eq(now, word->timeout))
 609                 return -EAGAIN;
 610         schedule_timeout(word->timeout - now);
 611         return 0;
 612 }
 613 EXPORT_SYMBOL_GPL(bit_wait_timeout);
 614
 615 __sched int bit_wait_io_timeout(struct wait_bit_key *word)
 616 {
 617         unsigned long now = READ_ONCE(jiffies);
 618         if (signal_pending_state(current->state, current))
 619                 return 1;
 620         if (time_after_eq(now, word->timeout))
 621                 return -EAGAIN;
 622         io_schedule_timeout(word->timeout - now);
 623         return 0;
 624 }
 625 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);