git.sesse.net Git - bcachefs-tools-debian/blob - linux/wait.c

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