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 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
 208 {
 209         unsigned long flags;
 210
 211         if (signal_pending_state(state, current))
 212                 return -ERESTARTSYS;
 213
 214         wait->private = current;
 215         wait->func = autoremove_wake_function;
 216
 217         spin_lock_irqsave(&q->lock, flags);
 218         if (list_empty(&wait->task_list)) {
 219                 if (wait->flags & WQ_FLAG_EXCLUSIVE)
 220                         __add_wait_queue_tail(q, wait);
 221                 else
 222                         __add_wait_queue(q, wait);
 223         }
 224         set_current_state(state);
 225         spin_unlock_irqrestore(&q->lock, flags);
 226
 227         return 0;
 228 }
 229 EXPORT_SYMBOL(prepare_to_wait_event);
 230
 231 /**
 232  * finish_wait - clean up after waiting in a queue
 233  * @q: waitqueue waited on
 234  * @wait: wait descriptor
 235  *
 236  * Sets current thread back to running state and removes
 237  * the wait descriptor from the given waitqueue if still
 238  * queued.
 239  */
 240 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
 241 {
 242         unsigned long flags;
 243
 244         __set_current_state(TASK_RUNNING);
 245         /*
 246          * We can check for list emptiness outside the lock
 247          * IFF:
 248          *  - we use the "careful" check that verifies both
 249          *    the next and prev pointers, so that there cannot
 250          *    be any half-pending updates in progress on other
 251          *    CPU's that we haven't seen yet (and that might
 252          *    still change the stack area.
 253          * and
 254          *  - all other users take the lock (ie we can only
 255          *    have _one_ other CPU that looks at or modifies
 256          *    the list).
 257          */
 258         if (!list_empty_careful(&wait->task_list)) {
 259                 spin_lock_irqsave(&q->lock, flags);
 260                 list_del_init(&wait->task_list);
 261                 spin_unlock_irqrestore(&q->lock, flags);
 262         }
 263 }
 264 EXPORT_SYMBOL(finish_wait);
 265
 266 /**
 267  * abort_exclusive_wait - abort exclusive waiting in a queue
 268  * @q: waitqueue waited on
 269  * @wait: wait descriptor
 270  * @mode: runstate of the waiter to be woken
 271  * @key: key to identify a wait bit queue or %NULL
 272  *
 273  * Sets current thread back to running state and removes
 274  * the wait descriptor from the given waitqueue if still
 275  * queued.
 276  *
 277  * Wakes up the next waiter if the caller is concurrently
 278  * woken up through the queue.
 279  *
 280  * This prevents waiter starvation where an exclusive waiter
 281  * aborts and is woken up concurrently and no one wakes up
 282  * the next waiter.
 283  */
 284 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
 285                         unsigned int mode, void *key)
 286 {
 287         unsigned long flags;
 288
 289         __set_current_state(TASK_RUNNING);
 290         spin_lock_irqsave(&q->lock, flags);
 291         if (!list_empty(&wait->task_list))
 292                 list_del_init(&wait->task_list);
 293         else if (waitqueue_active(q))
 294                 __wake_up_locked_key(q, mode, key);
 295         spin_unlock_irqrestore(&q->lock, flags);
 296 }
 297 EXPORT_SYMBOL(abort_exclusive_wait);
 298
 299 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 300 {
 301         int ret = default_wake_function(wait, mode, sync, key);
 302
 303         if (ret)
 304                 list_del_init(&wait->task_list);
 305         return ret;
 306 }
 307 EXPORT_SYMBOL(autoremove_wake_function);
 308
 309 static inline bool is_kthread_should_stop(void)
 310 {
 311         return (current->flags & PF_KTHREAD) && kthread_should_stop();
 312 }
 313
 314 /*
 315  * DEFINE_WAIT_FUNC(wait, woken_wake_func);
 316  *
 317  * add_wait_queue(&wq, &wait);
 318  * for (;;) {
 319  *     if (condition)
 320  *         break;
 321  *
 322  *     p->state = mode;                         condition = true;
 323  *     smp_mb(); // A                           smp_wmb(); // C
 324  *     if (!wait->flags & WQ_FLAG_WOKEN)        wait->flags |= WQ_FLAG_WOKEN;
 325  *         schedule()                           try_to_wake_up();
 326  *     p->state = TASK_RUNNING;             ~~~~~~~~~~~~~~~~~~
 327  *     wait->flags &= ~WQ_FLAG_WOKEN;           condition = true;
 328  *     smp_mb() // B                            smp_wmb(); // C
 329  *                                              wait->flags |= WQ_FLAG_WOKEN;
 330  * }
 331  * remove_wait_queue(&wq, &wait);
 332  *
 333  */
 334 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
 335 {
 336         set_current_state(mode); /* A */
 337         /*
 338          * The above implies an smp_mb(), which matches with the smp_wmb() from
 339          * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
 340          * also observe all state before the wakeup.
 341          */
 342         if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
 343                 timeout = schedule_timeout(timeout);
 344         __set_current_state(TASK_RUNNING);
 345
 346         /*
 347          * The below implies an smp_mb(), it too pairs with the smp_wmb() from
 348          * woken_wake_function() such that we must either observe the wait
 349          * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
 350          * an event.
 351          */
 352         smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
 353
 354         return timeout;
 355 }
 356 EXPORT_SYMBOL(wait_woken);
 357
 358 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 359 {
 360         /*
 361          * Although this function is called under waitqueue lock, LOCK
 362          * doesn't imply write barrier and the users expects write
 363          * barrier semantics on wakeup functions.  The following
 364          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 365          * and is paired with smp_store_mb() in wait_woken().
 366          */
 367         smp_wmb(); /* C */
 368         wait->flags |= WQ_FLAG_WOKEN;
 369
 370         return default_wake_function(wait, mode, sync, key);
 371 }
 372 EXPORT_SYMBOL(woken_wake_function);
 373
 374 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 375 {
 376         struct wait_bit_key *key = arg;
 377         struct wait_bit_queue *wait_bit
 378                 = container_of(wait, struct wait_bit_queue, wait);
 379
 380         if (wait_bit->key.flags != key->flags ||
 381                         wait_bit->key.bit_nr != key->bit_nr ||
 382                         test_bit(key->bit_nr, key->flags))
 383                 return 0;
 384         else
 385                 return autoremove_wake_function(wait, mode, sync, key);
 386 }
 387 EXPORT_SYMBOL(wake_bit_function);
 388
 389 /*
 390  * To allow interruptible waiting and asynchronous (i.e. nonblocking)
 391  * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
 392  * permitted return codes. Nonzero return codes halt waiting and return.
 393  */
 394 int __sched
 395 __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
 396               wait_bit_action_f *action, unsigned mode)
 397 {
 398         int ret = 0;
 399
 400         do {
 401                 prepare_to_wait(wq, &q->wait, mode);
 402                 if (test_bit(q->key.bit_nr, q->key.flags))
 403                         ret = (*action)(&q->key, mode);
 404         } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
 405         finish_wait(wq, &q->wait);
 406         return ret;
 407 }
 408 EXPORT_SYMBOL(__wait_on_bit);
 409
 410 int __sched out_of_line_wait_on_bit(void *word, int bit,
 411                                     wait_bit_action_f *action, unsigned mode)
 412 {
 413         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 414         DEFINE_WAIT_BIT(wait, word, bit);
 415
 416         return __wait_on_bit(wq, &wait, action, mode);
 417 }
 418 EXPORT_SYMBOL(out_of_line_wait_on_bit);
 419
 420 int __sched out_of_line_wait_on_bit_timeout(
 421         void *word, int bit, wait_bit_action_f *action,
 422         unsigned mode, unsigned long timeout)
 423 {
 424         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 425         DEFINE_WAIT_BIT(wait, word, bit);
 426
 427         wait.key.timeout = jiffies + timeout;
 428         return __wait_on_bit(wq, &wait, action, mode);
 429 }
 430 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
 431
 432 int __sched
 433 __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
 434                         wait_bit_action_f *action, unsigned mode)
 435 {
 436         do {
 437                 int ret;
 438
 439                 prepare_to_wait_exclusive(wq, &q->wait, mode);
 440                 if (!test_bit(q->key.bit_nr, q->key.flags))
 441                         continue;
 442                 ret = action(&q->key, mode);
 443                 if (!ret)
 444                         continue;
 445                 abort_exclusive_wait(wq, &q->wait, mode, &q->key);
 446                 return ret;
 447         } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
 448         finish_wait(wq, &q->wait);
 449         return 0;
 450 }
 451 EXPORT_SYMBOL(__wait_on_bit_lock);
 452
 453 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
 454                                          wait_bit_action_f *action, unsigned mode)
 455 {
 456         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 457         DEFINE_WAIT_BIT(wait, word, bit);
 458
 459         return __wait_on_bit_lock(wq, &wait, action, mode);
 460 }
 461 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
 462
 463 void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
 464 {
 465         struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
 466         if (waitqueue_active(wq))
 467                 __wake_up(wq, TASK_NORMAL, 1, &key);
 468 }
 469 EXPORT_SYMBOL(__wake_up_bit);
 470
 471 /**
 472  * wake_up_bit - wake up a waiter on a bit
 473  * @word: the word being waited on, a kernel virtual address
 474  * @bit: the bit of the word being waited on
 475  *
 476  * There is a standard hashed waitqueue table for generic use. This
 477  * is the part of the hashtable's accessor API that wakes up waiters
 478  * on a bit. For instance, if one were to have waiters on a bitflag,
 479  * one would call wake_up_bit() after clearing the bit.
 480  *
 481  * In order for this to function properly, as it uses waitqueue_active()
 482  * internally, some kind of memory barrier must be done prior to calling
 483  * this. Typically, this will be smp_mb__after_atomic(), but in some
 484  * cases where bitflags are manipulated non-atomically under a lock, one
 485  * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
 486  * because spin_unlock() does not guarantee a memory barrier.
 487  */
 488 void wake_up_bit(void *word, int bit)
 489 {
 490         __wake_up_bit(bit_waitqueue(word, bit), word, bit);
 491 }
 492 EXPORT_SYMBOL(wake_up_bit);
 493
 494 wait_queue_head_t *bit_waitqueue(void *word, int bit)
 495 {
 496         const int shift = BITS_PER_LONG == 32 ? 5 : 6;
 497         const struct zone *zone = page_zone(virt_to_page(word));
 498         unsigned long val = (unsigned long)word << shift | bit;
 499
 500         return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
 501 }
 502 EXPORT_SYMBOL(bit_waitqueue);
 503
 504 /*
 505  * Manipulate the atomic_t address to produce a better bit waitqueue table hash
 506  * index (we're keying off bit -1, but that would produce a horrible hash
 507  * value).
 508  */
 509 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
 510 {
 511         if (BITS_PER_LONG == 64) {
 512                 unsigned long q = (unsigned long)p;
 513                 return bit_waitqueue((void *)(q & ~1), q & 1);
 514         }
 515         return bit_waitqueue(p, 0);
 516 }
 517
 518 static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
 519                                   void *arg)
 520 {
 521         struct wait_bit_key *key = arg;
 522         struct wait_bit_queue *wait_bit
 523                 = container_of(wait, struct wait_bit_queue, wait);
 524         atomic_t *val = key->flags;
 525
 526         if (wait_bit->key.flags != key->flags ||
 527             wait_bit->key.bit_nr != key->bit_nr ||
 528             atomic_read(val) != 0)
 529                 return 0;
 530         return autoremove_wake_function(wait, mode, sync, key);
 531 }
 532
 533 /*
 534  * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
 535  * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
 536  * return codes halt waiting and return.
 537  */
 538 static __sched
 539 int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
 540                        int (*action)(atomic_t *), unsigned mode)
 541 {
 542         atomic_t *val;
 543         int ret = 0;
 544
 545         do {
 546                 prepare_to_wait(wq, &q->wait, mode);
 547                 val = q->key.flags;
 548                 if (atomic_read(val) == 0)
 549                         break;
 550                 ret = (*action)(val);
 551         } while (!ret && atomic_read(val) != 0);
 552         finish_wait(wq, &q->wait);
 553         return ret;
 554 }
 555
 556 #define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
 557         struct wait_bit_queue name = {                                  \
 558                 .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
 559                 .wait   = {                                             \
 560                         .private        = current,                      \
 561                         .func           = wake_atomic_t_function,       \
 562                         .task_list      =                               \
 563                                 LIST_HEAD_INIT((name).wait.task_list),  \
 564                 },                                                      \
 565         }
 566
 567 __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
 568                                          unsigned mode)
 569 {
 570         wait_queue_head_t *wq = atomic_t_waitqueue(p);
 571         DEFINE_WAIT_ATOMIC_T(wait, p);
 572
 573         return __wait_on_atomic_t(wq, &wait, action, mode);
 574 }
 575 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
 576
 577 /**
 578  * wake_up_atomic_t - Wake up a waiter on a atomic_t
 579  * @p: The atomic_t being waited on, a kernel virtual address
 580  *
 581  * Wake up anyone waiting for the atomic_t to go to zero.
 582  *
 583  * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
 584  * check is done by the waiter's wake function, not the by the waker itself).
 585  */
 586 void wake_up_atomic_t(atomic_t *p)
 587 {
 588         __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
 589 }
 590 EXPORT_SYMBOL(wake_up_atomic_t);
 591
 592 __sched int bit_wait(struct wait_bit_key *word, int mode)
 593 {
 594         schedule();
 595         if (signal_pending_state(mode, current))
 596                 return -EINTR;
 597         return 0;
 598 }
 599 EXPORT_SYMBOL(bit_wait);
 600
 601 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
 602 {
 603         io_schedule();
 604         if (signal_pending_state(mode, current))
 605                 return -EINTR;
 606         return 0;
 607 }
 608 EXPORT_SYMBOL(bit_wait_io);
 609
 610 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
 611 {
 612         unsigned long now = READ_ONCE(jiffies);
 613         if (time_after_eq(now, word->timeout))
 614                 return -EAGAIN;
 615         schedule_timeout(word->timeout - now);
 616         if (signal_pending_state(mode, current))
 617                 return -EINTR;
 618         return 0;
 619 }
 620 EXPORT_SYMBOL_GPL(bit_wait_timeout);
 621
 622 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
 623 {
 624         unsigned long now = READ_ONCE(jiffies);
 625         if (time_after_eq(now, word->timeout))
 626                 return -EAGAIN;
 627         io_schedule_timeout(word->timeout - now);
 628         if (signal_pending_state(mode, current))
 629                 return -EINTR;
 630         return 0;
 631 }
 632 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);