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         long ret = 0;
 203
 204         wait->private = current;
 205         wait->func = autoremove_wake_function;
 206
 207         spin_lock_irqsave(&q->lock, flags);
 208         if (unlikely(signal_pending_state(state, current))) {
 209                 /*
 210                  * Exclusive waiter must not fail if it was selected by wakeup,
 211                  * it should "consume" the condition we were waiting for.
 212                  *
 213                  * The caller will recheck the condition and return success if
 214                  * we were already woken up, we can not miss the event because
 215                  * wakeup locks/unlocks the same q->lock.
 216                  *
 217                  * But we need to ensure that set-condition + wakeup after that
 218                  * can't see us, it should wake up another exclusive waiter if
 219                  * we fail.
 220                  */
 221                 list_del_init(&wait->task_list);
 222                 ret = -ERESTARTSYS;
 223         } else {
 224                 if (list_empty(&wait->task_list)) {
 225                         if (wait->flags & WQ_FLAG_EXCLUSIVE)
 226                                 __add_wait_queue_tail(q, wait);
 227                         else
 228                                 __add_wait_queue(q, wait);
 229                 }
 230                 set_current_state(state);
 231         }
 232         spin_unlock_irqrestore(&q->lock, flags);
 233
 234         return ret;
 235 }
 236 EXPORT_SYMBOL(prepare_to_wait_event);
 237
 238 /**
 239  * finish_wait - clean up after waiting in a queue
 240  * @q: waitqueue waited on
 241  * @wait: wait descriptor
 242  *
 243  * Sets current thread back to running state and removes
 244  * the wait descriptor from the given waitqueue if still
 245  * queued.
 246  */
 247 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
 248 {
 249         unsigned long flags;
 250
 251         __set_current_state(TASK_RUNNING);
 252         /*
 253          * We can check for list emptiness outside the lock
 254          * IFF:
 255          *  - we use the "careful" check that verifies both
 256          *    the next and prev pointers, so that there cannot
 257          *    be any half-pending updates in progress on other
 258          *    CPU's that we haven't seen yet (and that might
 259          *    still change the stack area.
 260          * and
 261          *  - all other users take the lock (ie we can only
 262          *    have _one_ other CPU that looks at or modifies
 263          *    the list).
 264          */
 265         if (!list_empty_careful(&wait->task_list)) {
 266                 spin_lock_irqsave(&q->lock, flags);
 267                 list_del_init(&wait->task_list);
 268                 spin_unlock_irqrestore(&q->lock, flags);
 269         }
 270 }
 271 EXPORT_SYMBOL(finish_wait);
 272
 273 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 274 {
 275         int ret = default_wake_function(wait, mode, sync, key);
 276
 277         if (ret)
 278                 list_del_init(&wait->task_list);
 279         return ret;
 280 }
 281 EXPORT_SYMBOL(autoremove_wake_function);
 282
 283 static inline bool is_kthread_should_stop(void)
 284 {
 285         return (current->flags & PF_KTHREAD) && kthread_should_stop();
 286 }
 287
 288 /*
 289  * DEFINE_WAIT_FUNC(wait, woken_wake_func);
 290  *
 291  * add_wait_queue(&wq, &wait);
 292  * for (;;) {
 293  *     if (condition)
 294  *         break;
 295  *
 296  *     p->state = mode;                         condition = true;
 297  *     smp_mb(); // A                           smp_wmb(); // C
 298  *     if (!wait->flags & WQ_FLAG_WOKEN)        wait->flags |= WQ_FLAG_WOKEN;
 299  *         schedule()                           try_to_wake_up();
 300  *     p->state = TASK_RUNNING;             ~~~~~~~~~~~~~~~~~~
 301  *     wait->flags &= ~WQ_FLAG_WOKEN;           condition = true;
 302  *     smp_mb() // B                            smp_wmb(); // C
 303  *                                              wait->flags |= WQ_FLAG_WOKEN;
 304  * }
 305  * remove_wait_queue(&wq, &wait);
 306  *
 307  */
 308 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
 309 {
 310         set_current_state(mode); /* A */
 311         /*
 312          * The above implies an smp_mb(), which matches with the smp_wmb() from
 313          * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
 314          * also observe all state before the wakeup.
 315          */
 316         if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
 317                 timeout = schedule_timeout(timeout);
 318         __set_current_state(TASK_RUNNING);
 319
 320         /*
 321          * The below implies an smp_mb(), it too pairs with the smp_wmb() from
 322          * woken_wake_function() such that we must either observe the wait
 323          * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
 324          * an event.
 325          */
 326         smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
 327
 328         return timeout;
 329 }
 330 EXPORT_SYMBOL(wait_woken);
 331
 332 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 333 {
 334         /*
 335          * Although this function is called under waitqueue lock, LOCK
 336          * doesn't imply write barrier and the users expects write
 337          * barrier semantics on wakeup functions.  The following
 338          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 339          * and is paired with smp_store_mb() in wait_woken().
 340          */
 341         smp_wmb(); /* C */
 342         wait->flags |= WQ_FLAG_WOKEN;
 343
 344         return default_wake_function(wait, mode, sync, key);
 345 }
 346 EXPORT_SYMBOL(woken_wake_function);
 347
 348 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 349 {
 350         struct wait_bit_key *key = arg;
 351         struct wait_bit_queue *wait_bit
 352                 = container_of(wait, struct wait_bit_queue, wait);
 353
 354         if (wait_bit->key.flags != key->flags ||
 355                         wait_bit->key.bit_nr != key->bit_nr ||
 356                         test_bit(key->bit_nr, key->flags))
 357                 return 0;
 358         else
 359                 return autoremove_wake_function(wait, mode, sync, key);
 360 }
 361 EXPORT_SYMBOL(wake_bit_function);
 362
 363 /*
 364  * To allow interruptible waiting and asynchronous (i.e. nonblocking)
 365  * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
 366  * permitted return codes. Nonzero return codes halt waiting and return.
 367  */
 368 int __sched
 369 __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
 370               wait_bit_action_f *action, unsigned mode)
 371 {
 372         int ret = 0;
 373
 374         do {
 375                 prepare_to_wait(wq, &q->wait, mode);
 376                 if (test_bit(q->key.bit_nr, q->key.flags))
 377                         ret = (*action)(&q->key, mode);
 378         } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
 379         finish_wait(wq, &q->wait);
 380         return ret;
 381 }
 382 EXPORT_SYMBOL(__wait_on_bit);
 383
 384 int __sched out_of_line_wait_on_bit(void *word, int bit,
 385                                     wait_bit_action_f *action, unsigned mode)
 386 {
 387         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 388         DEFINE_WAIT_BIT(wait, word, bit);
 389
 390         return __wait_on_bit(wq, &wait, action, mode);
 391 }
 392 EXPORT_SYMBOL(out_of_line_wait_on_bit);
 393
 394 int __sched out_of_line_wait_on_bit_timeout(
 395         void *word, int bit, wait_bit_action_f *action,
 396         unsigned mode, unsigned long timeout)
 397 {
 398         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 399         DEFINE_WAIT_BIT(wait, word, bit);
 400
 401         wait.key.timeout = jiffies + timeout;
 402         return __wait_on_bit(wq, &wait, action, mode);
 403 }
 404 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
 405
 406 int __sched
 407 __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
 408                         wait_bit_action_f *action, unsigned mode)
 409 {
 410         int ret = 0;
 411
 412         for (;;) {
 413                 prepare_to_wait_exclusive(wq, &q->wait, mode);
 414                 if (test_bit(q->key.bit_nr, q->key.flags)) {
 415                         ret = action(&q->key, mode);
 416                         /*
 417                          * See the comment in prepare_to_wait_event().
 418                          * finish_wait() does not necessarily takes wq->lock,
 419                          * but test_and_set_bit() implies mb() which pairs with
 420                          * smp_mb__after_atomic() before wake_up_page().
 421                          */
 422                         if (ret)
 423                                 finish_wait(wq, &q->wait);
 424                 }
 425                 if (!test_and_set_bit(q->key.bit_nr, q->key.flags)) {
 426                         if (!ret)
 427                                 finish_wait(wq, &q->wait);
 428                         return 0;
 429                 } else if (ret) {
 430                         return ret;
 431                 }
 432         }
 433 }
 434 EXPORT_SYMBOL(__wait_on_bit_lock);
 435
 436 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
 437                                          wait_bit_action_f *action, unsigned mode)
 438 {
 439         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 440         DEFINE_WAIT_BIT(wait, word, bit);
 441
 442         return __wait_on_bit_lock(wq, &wait, action, mode);
 443 }
 444 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
 445
 446 void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
 447 {
 448         struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
 449         if (waitqueue_active(wq))
 450                 __wake_up(wq, TASK_NORMAL, 1, &key);
 451 }
 452 EXPORT_SYMBOL(__wake_up_bit);
 453
 454 /**
 455  * wake_up_bit - wake up a waiter on a bit
 456  * @word: the word being waited on, a kernel virtual address
 457  * @bit: the bit of the word being waited on
 458  *
 459  * There is a standard hashed waitqueue table for generic use. This
 460  * is the part of the hashtable's accessor API that wakes up waiters
 461  * on a bit. For instance, if one were to have waiters on a bitflag,
 462  * one would call wake_up_bit() after clearing the bit.
 463  *
 464  * In order for this to function properly, as it uses waitqueue_active()
 465  * internally, some kind of memory barrier must be done prior to calling
 466  * this. Typically, this will be smp_mb__after_atomic(), but in some
 467  * cases where bitflags are manipulated non-atomically under a lock, one
 468  * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
 469  * because spin_unlock() does not guarantee a memory barrier.
 470  */
 471 void wake_up_bit(void *word, int bit)
 472 {
 473         __wake_up_bit(bit_waitqueue(word, bit), word, bit);
 474 }
 475 EXPORT_SYMBOL(wake_up_bit);
 476
 477 wait_queue_head_t *bit_waitqueue(void *word, int bit)
 478 {
 479         const int shift = BITS_PER_LONG == 32 ? 5 : 6;
 480         const struct zone *zone = page_zone(virt_to_page(word));
 481         unsigned long val = (unsigned long)word << shift | bit;
 482
 483         return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
 484 }
 485 EXPORT_SYMBOL(bit_waitqueue);
 486
 487 /*
 488  * Manipulate the atomic_t address to produce a better bit waitqueue table hash
 489  * index (we're keying off bit -1, but that would produce a horrible hash
 490  * value).
 491  */
 492 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
 493 {
 494         if (BITS_PER_LONG == 64) {
 495                 unsigned long q = (unsigned long)p;
 496                 return bit_waitqueue((void *)(q & ~1), q & 1);
 497         }
 498         return bit_waitqueue(p, 0);
 499 }
 500
 501 static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
 502                                   void *arg)
 503 {
 504         struct wait_bit_key *key = arg;
 505         struct wait_bit_queue *wait_bit
 506                 = container_of(wait, struct wait_bit_queue, wait);
 507         atomic_t *val = key->flags;
 508
 509         if (wait_bit->key.flags != key->flags ||
 510             wait_bit->key.bit_nr != key->bit_nr ||
 511             atomic_read(val) != 0)
 512                 return 0;
 513         return autoremove_wake_function(wait, mode, sync, key);
 514 }
 515
 516 /*
 517  * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
 518  * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
 519  * return codes halt waiting and return.
 520  */
 521 static __sched
 522 int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
 523                        int (*action)(atomic_t *), unsigned mode)
 524 {
 525         atomic_t *val;
 526         int ret = 0;
 527
 528         do {
 529                 prepare_to_wait(wq, &q->wait, mode);
 530                 val = q->key.flags;
 531                 if (atomic_read(val) == 0)
 532                         break;
 533                 ret = (*action)(val);
 534         } while (!ret && atomic_read(val) != 0);
 535         finish_wait(wq, &q->wait);
 536         return ret;
 537 }
 538
 539 #define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
 540         struct wait_bit_queue name = {                                  \
 541                 .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
 542                 .wait   = {                                             \
 543                         .private        = current,                      \
 544                         .func           = wake_atomic_t_function,       \
 545                         .task_list      =                               \
 546                                 LIST_HEAD_INIT((name).wait.task_list),  \
 547                 },                                                      \
 548         }
 549
 550 __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
 551                                          unsigned mode)
 552 {
 553         wait_queue_head_t *wq = atomic_t_waitqueue(p);
 554         DEFINE_WAIT_ATOMIC_T(wait, p);
 555
 556         return __wait_on_atomic_t(wq, &wait, action, mode);
 557 }
 558 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
 559
 560 /**
 561  * wake_up_atomic_t - Wake up a waiter on a atomic_t
 562  * @p: The atomic_t being waited on, a kernel virtual address
 563  *
 564  * Wake up anyone waiting for the atomic_t to go to zero.
 565  *
 566  * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
 567  * check is done by the waiter's wake function, not the by the waker itself).
 568  */
 569 void wake_up_atomic_t(atomic_t *p)
 570 {
 571         __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
 572 }
 573 EXPORT_SYMBOL(wake_up_atomic_t);
 574
 575 __sched int bit_wait(struct wait_bit_key *word, int mode)
 576 {
 577         schedule();
 578         if (signal_pending_state(mode, current))
 579                 return -EINTR;
 580         return 0;
 581 }
 582 EXPORT_SYMBOL(bit_wait);
 583
 584 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
 585 {
 586         io_schedule();
 587         if (signal_pending_state(mode, current))
 588                 return -EINTR;
 589         return 0;
 590 }
 591 EXPORT_SYMBOL(bit_wait_io);
 592
 593 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
 594 {
 595         unsigned long now = READ_ONCE(jiffies);
 596         if (time_after_eq(now, word->timeout))
 597                 return -EAGAIN;
 598         schedule_timeout(word->timeout - now);
 599         if (signal_pending_state(mode, current))
 600                 return -EINTR;
 601         return 0;
 602 }
 603 EXPORT_SYMBOL_GPL(bit_wait_timeout);
 604
 605 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
 606 {
 607         unsigned long now = READ_ONCE(jiffies);
 608         if (time_after_eq(now, word->timeout))
 609                 return -EAGAIN;
 610         io_schedule_timeout(word->timeout - now);
 611         if (signal_pending_state(mode, current))
 612                 return -EINTR;
 613         return 0;
 614 }
 615 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);