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 /**
 274  * abort_exclusive_wait - abort exclusive waiting in a queue
 275  * @q: waitqueue waited on
 276  * @wait: wait descriptor
 277  * @key: key to identify a wait bit queue or %NULL
 278  *
 279  * Sets current thread back to running state and removes
 280  * the wait descriptor from the given waitqueue if still
 281  * queued.
 282  *
 283  * Wakes up the next waiter if the caller is concurrently
 284  * woken up through the queue.
 285  *
 286  * This prevents waiter starvation where an exclusive waiter
 287  * aborts and is woken up concurrently and no one wakes up
 288  * the next waiter.
 289  */
 290 void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key)
 291 {
 292         unsigned long flags;
 293
 294         __set_current_state(TASK_RUNNING);
 295         spin_lock_irqsave(&q->lock, flags);
 296         if (!list_empty(&wait->task_list))
 297                 list_del_init(&wait->task_list);
 298         else if (waitqueue_active(q))
 299                 __wake_up_locked_key(q, TASK_NORMAL, key);
 300         spin_unlock_irqrestore(&q->lock, flags);
 301 }
 302 EXPORT_SYMBOL(abort_exclusive_wait);
 303
 304 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 305 {
 306         int ret = default_wake_function(wait, mode, sync, key);
 307
 308         if (ret)
 309                 list_del_init(&wait->task_list);
 310         return ret;
 311 }
 312 EXPORT_SYMBOL(autoremove_wake_function);
 313
 314 static inline bool is_kthread_should_stop(void)
 315 {
 316         return (current->flags & PF_KTHREAD) && kthread_should_stop();
 317 }
 318
 319 /*
 320  * DEFINE_WAIT_FUNC(wait, woken_wake_func);
 321  *
 322  * add_wait_queue(&wq, &wait);
 323  * for (;;) {
 324  *     if (condition)
 325  *         break;
 326  *
 327  *     p->state = mode;                         condition = true;
 328  *     smp_mb(); // A                           smp_wmb(); // C
 329  *     if (!wait->flags & WQ_FLAG_WOKEN)        wait->flags |= WQ_FLAG_WOKEN;
 330  *         schedule()                           try_to_wake_up();
 331  *     p->state = TASK_RUNNING;             ~~~~~~~~~~~~~~~~~~
 332  *     wait->flags &= ~WQ_FLAG_WOKEN;           condition = true;
 333  *     smp_mb() // B                            smp_wmb(); // C
 334  *                                              wait->flags |= WQ_FLAG_WOKEN;
 335  * }
 336  * remove_wait_queue(&wq, &wait);
 337  *
 338  */
 339 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
 340 {
 341         set_current_state(mode); /* A */
 342         /*
 343          * The above implies an smp_mb(), which matches with the smp_wmb() from
 344          * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
 345          * also observe all state before the wakeup.
 346          */
 347         if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
 348                 timeout = schedule_timeout(timeout);
 349         __set_current_state(TASK_RUNNING);
 350
 351         /*
 352          * The below implies an smp_mb(), it too pairs with the smp_wmb() from
 353          * woken_wake_function() such that we must either observe the wait
 354          * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
 355          * an event.
 356          */
 357         smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
 358
 359         return timeout;
 360 }
 361 EXPORT_SYMBOL(wait_woken);
 362
 363 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 364 {
 365         /*
 366          * Although this function is called under waitqueue lock, LOCK
 367          * doesn't imply write barrier and the users expects write
 368          * barrier semantics on wakeup functions.  The following
 369          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 370          * and is paired with smp_store_mb() in wait_woken().
 371          */
 372         smp_wmb(); /* C */
 373         wait->flags |= WQ_FLAG_WOKEN;
 374
 375         return default_wake_function(wait, mode, sync, key);
 376 }
 377 EXPORT_SYMBOL(woken_wake_function);
 378
 379 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 380 {
 381         struct wait_bit_key *key = arg;
 382         struct wait_bit_queue *wait_bit
 383                 = container_of(wait, struct wait_bit_queue, wait);
 384
 385         if (wait_bit->key.flags != key->flags ||
 386                         wait_bit->key.bit_nr != key->bit_nr ||
 387                         test_bit(key->bit_nr, key->flags))
 388                 return 0;
 389         else
 390                 return autoremove_wake_function(wait, mode, sync, key);
 391 }
 392 EXPORT_SYMBOL(wake_bit_function);
 393
 394 /*
 395  * To allow interruptible waiting and asynchronous (i.e. nonblocking)
 396  * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
 397  * permitted return codes. Nonzero return codes halt waiting and return.
 398  */
 399 int __sched
 400 __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
 401               wait_bit_action_f *action, unsigned mode)
 402 {
 403         int ret = 0;
 404
 405         do {
 406                 prepare_to_wait(wq, &q->wait, mode);
 407                 if (test_bit(q->key.bit_nr, q->key.flags))
 408                         ret = (*action)(&q->key, mode);
 409         } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
 410         finish_wait(wq, &q->wait);
 411         return ret;
 412 }
 413 EXPORT_SYMBOL(__wait_on_bit);
 414
 415 int __sched out_of_line_wait_on_bit(void *word, int bit,
 416                                     wait_bit_action_f *action, unsigned mode)
 417 {
 418         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 419         DEFINE_WAIT_BIT(wait, word, bit);
 420
 421         return __wait_on_bit(wq, &wait, action, mode);
 422 }
 423 EXPORT_SYMBOL(out_of_line_wait_on_bit);
 424
 425 int __sched out_of_line_wait_on_bit_timeout(
 426         void *word, int bit, wait_bit_action_f *action,
 427         unsigned mode, unsigned long timeout)
 428 {
 429         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 430         DEFINE_WAIT_BIT(wait, word, bit);
 431
 432         wait.key.timeout = jiffies + timeout;
 433         return __wait_on_bit(wq, &wait, action, mode);
 434 }
 435 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
 436
 437 int __sched
 438 __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
 439                         wait_bit_action_f *action, unsigned mode)
 440 {
 441         do {
 442                 int ret;
 443
 444                 prepare_to_wait_exclusive(wq, &q->wait, mode);
 445                 if (!test_bit(q->key.bit_nr, q->key.flags))
 446                         continue;
 447                 ret = action(&q->key, mode);
 448                 if (!ret)
 449                         continue;
 450                 abort_exclusive_wait(wq, &q->wait, &q->key);
 451                 return ret;
 452         } while (test_and_set_bit(q->key.bit_nr, q->key.flags));
 453         finish_wait(wq, &q->wait);
 454         return 0;
 455 }
 456 EXPORT_SYMBOL(__wait_on_bit_lock);
 457
 458 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
 459                                          wait_bit_action_f *action, unsigned mode)
 460 {
 461         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 462         DEFINE_WAIT_BIT(wait, word, bit);
 463
 464         return __wait_on_bit_lock(wq, &wait, action, mode);
 465 }
 466 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
 467
 468 void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
 469 {
 470         struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
 471         if (waitqueue_active(wq))
 472                 __wake_up(wq, TASK_NORMAL, 1, &key);
 473 }
 474 EXPORT_SYMBOL(__wake_up_bit);
 475
 476 /**
 477  * wake_up_bit - wake up a waiter on a bit
 478  * @word: the word being waited on, a kernel virtual address
 479  * @bit: the bit of the word being waited on
 480  *
 481  * There is a standard hashed waitqueue table for generic use. This
 482  * is the part of the hashtable's accessor API that wakes up waiters
 483  * on a bit. For instance, if one were to have waiters on a bitflag,
 484  * one would call wake_up_bit() after clearing the bit.
 485  *
 486  * In order for this to function properly, as it uses waitqueue_active()
 487  * internally, some kind of memory barrier must be done prior to calling
 488  * this. Typically, this will be smp_mb__after_atomic(), but in some
 489  * cases where bitflags are manipulated non-atomically under a lock, one
 490  * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
 491  * because spin_unlock() does not guarantee a memory barrier.
 492  */
 493 void wake_up_bit(void *word, int bit)
 494 {
 495         __wake_up_bit(bit_waitqueue(word, bit), word, bit);
 496 }
 497 EXPORT_SYMBOL(wake_up_bit);
 498
 499 wait_queue_head_t *bit_waitqueue(void *word, int bit)
 500 {
 501         const int shift = BITS_PER_LONG == 32 ? 5 : 6;
 502         const struct zone *zone = page_zone(virt_to_page(word));
 503         unsigned long val = (unsigned long)word << shift | bit;
 504
 505         return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
 506 }
 507 EXPORT_SYMBOL(bit_waitqueue);
 508
 509 /*
 510  * Manipulate the atomic_t address to produce a better bit waitqueue table hash
 511  * index (we're keying off bit -1, but that would produce a horrible hash
 512  * value).
 513  */
 514 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
 515 {
 516         if (BITS_PER_LONG == 64) {
 517                 unsigned long q = (unsigned long)p;
 518                 return bit_waitqueue((void *)(q & ~1), q & 1);
 519         }
 520         return bit_waitqueue(p, 0);
 521 }
 522
 523 static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
 524                                   void *arg)
 525 {
 526         struct wait_bit_key *key = arg;
 527         struct wait_bit_queue *wait_bit
 528                 = container_of(wait, struct wait_bit_queue, wait);
 529         atomic_t *val = key->flags;
 530
 531         if (wait_bit->key.flags != key->flags ||
 532             wait_bit->key.bit_nr != key->bit_nr ||
 533             atomic_read(val) != 0)
 534                 return 0;
 535         return autoremove_wake_function(wait, mode, sync, key);
 536 }
 537
 538 /*
 539  * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
 540  * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
 541  * return codes halt waiting and return.
 542  */
 543 static __sched
 544 int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
 545                        int (*action)(atomic_t *), unsigned mode)
 546 {
 547         atomic_t *val;
 548         int ret = 0;
 549
 550         do {
 551                 prepare_to_wait(wq, &q->wait, mode);
 552                 val = q->key.flags;
 553                 if (atomic_read(val) == 0)
 554                         break;
 555                 ret = (*action)(val);
 556         } while (!ret && atomic_read(val) != 0);
 557         finish_wait(wq, &q->wait);
 558         return ret;
 559 }
 560
 561 #define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
 562         struct wait_bit_queue name = {                                  \
 563                 .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
 564                 .wait   = {                                             \
 565                         .private        = current,                      \
 566                         .func           = wake_atomic_t_function,       \
 567                         .task_list      =                               \
 568                                 LIST_HEAD_INIT((name).wait.task_list),  \
 569                 },                                                      \
 570         }
 571
 572 __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
 573                                          unsigned mode)
 574 {
 575         wait_queue_head_t *wq = atomic_t_waitqueue(p);
 576         DEFINE_WAIT_ATOMIC_T(wait, p);
 577
 578         return __wait_on_atomic_t(wq, &wait, action, mode);
 579 }
 580 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
 581
 582 /**
 583  * wake_up_atomic_t - Wake up a waiter on a atomic_t
 584  * @p: The atomic_t being waited on, a kernel virtual address
 585  *
 586  * Wake up anyone waiting for the atomic_t to go to zero.
 587  *
 588  * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
 589  * check is done by the waiter's wake function, not the by the waker itself).
 590  */
 591 void wake_up_atomic_t(atomic_t *p)
 592 {
 593         __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
 594 }
 595 EXPORT_SYMBOL(wake_up_atomic_t);
 596
 597 __sched int bit_wait(struct wait_bit_key *word, int mode)
 598 {
 599         schedule();
 600         if (signal_pending_state(mode, current))
 601                 return -EINTR;
 602         return 0;
 603 }
 604 EXPORT_SYMBOL(bit_wait);
 605
 606 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
 607 {
 608         io_schedule();
 609         if (signal_pending_state(mode, current))
 610                 return -EINTR;
 611         return 0;
 612 }
 613 EXPORT_SYMBOL(bit_wait_io);
 614
 615 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
 616 {
 617         unsigned long now = READ_ONCE(jiffies);
 618         if (time_after_eq(now, word->timeout))
 619                 return -EAGAIN;
 620         schedule_timeout(word->timeout - now);
 621         if (signal_pending_state(mode, current))
 622                 return -EINTR;
 623         return 0;
 624 }
 625 EXPORT_SYMBOL_GPL(bit_wait_timeout);
 626
 627 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
 628 {
 629         unsigned long now = READ_ONCE(jiffies);
 630         if (time_after_eq(now, word->timeout))
 631                 return -EAGAIN;
 632         io_schedule_timeout(word->timeout - now);
 633         if (signal_pending_state(mode, current))
 634                 return -EINTR;
 635         return 0;
 636 }
 637 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);