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