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