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/signal.h>
   9 #include <linux/sched/debug.h>
  10 #include <linux/mm.h>
  11 #include <linux/wait.h>
  12 #include <linux/hash.h>
  13 #include <linux/kthread.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 /*
 161  * Note: we use "set_current_state()" _after_ the wait-queue add,
 162  * because we need a memory barrier there on SMP, so that any
 163  * wake-function that tests for the wait-queue being active
 164  * will be guaranteed to see waitqueue addition _or_ subsequent
 165  * tests in this thread will see the wakeup having taken place.
 166  *
 167  * The spin_unlock() itself is semi-permeable and only protects
 168  * one way (it only protects stuff inside the critical region and
 169  * stops them from bleeding out - it would still allow subsequent
 170  * loads to move into the critical region).
 171  */
 172 void
 173 prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
 174 {
 175         unsigned long flags;
 176
 177         wait->flags &= ~WQ_FLAG_EXCLUSIVE;
 178         spin_lock_irqsave(&q->lock, flags);
 179         if (list_empty(&wait->task_list))
 180                 __add_wait_queue(q, wait);
 181         set_current_state(state);
 182         spin_unlock_irqrestore(&q->lock, flags);
 183 }
 184 EXPORT_SYMBOL(prepare_to_wait);
 185
 186 void
 187 prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
 188 {
 189         unsigned long flags;
 190
 191         wait->flags |= WQ_FLAG_EXCLUSIVE;
 192         spin_lock_irqsave(&q->lock, flags);
 193         if (list_empty(&wait->task_list))
 194                 __add_wait_queue_tail(q, wait);
 195         set_current_state(state);
 196         spin_unlock_irqrestore(&q->lock, flags);
 197 }
 198 EXPORT_SYMBOL(prepare_to_wait_exclusive);
 199
 200 void init_wait_entry(wait_queue_t *wait, int flags)
 201 {
 202         wait->flags = flags;
 203         wait->private = current;
 204         wait->func = autoremove_wake_function;
 205         INIT_LIST_HEAD(&wait->task_list);
 206 }
 207 EXPORT_SYMBOL(init_wait_entry);
 208
 209 long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
 210 {
 211         unsigned long flags;
 212         long ret = 0;
 213
 214         spin_lock_irqsave(&q->lock, flags);
 215         if (unlikely(signal_pending_state(state, current))) {
 216                 /*
 217                  * Exclusive waiter must not fail if it was selected by wakeup,
 218                  * it should "consume" the condition we were waiting for.
 219                  *
 220                  * The caller will recheck the condition and return success if
 221                  * we were already woken up, we can not miss the event because
 222                  * wakeup locks/unlocks the same q->lock.
 223                  *
 224                  * But we need to ensure that set-condition + wakeup after that
 225                  * can't see us, it should wake up another exclusive waiter if
 226                  * we fail.
 227                  */
 228                 list_del_init(&wait->task_list);
 229                 ret = -ERESTARTSYS;
 230         } else {
 231                 if (list_empty(&wait->task_list)) {
 232                         if (wait->flags & WQ_FLAG_EXCLUSIVE)
 233                                 __add_wait_queue_tail(q, wait);
 234                         else
 235                                 __add_wait_queue(q, wait);
 236                 }
 237                 set_current_state(state);
 238         }
 239         spin_unlock_irqrestore(&q->lock, flags);
 240
 241         return ret;
 242 }
 243 EXPORT_SYMBOL(prepare_to_wait_event);
 244
 245 /*
 246  * Note! These two wait functions are entered with the
 247  * wait-queue lock held (and interrupts off in the _irq
 248  * case), so there is no race with testing the wakeup
 249  * condition in the caller before they add the wait
 250  * entry to the wake queue.
 251  */
 252 int do_wait_intr(wait_queue_head_t *wq, wait_queue_t *wait)
 253 {
 254         if (likely(list_empty(&wait->task_list)))
 255                 __add_wait_queue_tail(wq, wait);
 256
 257         set_current_state(TASK_INTERRUPTIBLE);
 258         if (signal_pending(current))
 259                 return -ERESTARTSYS;
 260
 261         spin_unlock(&wq->lock);
 262         schedule();
 263         spin_lock(&wq->lock);
 264         return 0;
 265 }
 266 EXPORT_SYMBOL(do_wait_intr);
 267
 268 int do_wait_intr_irq(wait_queue_head_t *wq, wait_queue_t *wait)
 269 {
 270         if (likely(list_empty(&wait->task_list)))
 271                 __add_wait_queue_tail(wq, wait);
 272
 273         set_current_state(TASK_INTERRUPTIBLE);
 274         if (signal_pending(current))
 275                 return -ERESTARTSYS;
 276
 277         spin_unlock_irq(&wq->lock);
 278         schedule();
 279         spin_lock_irq(&wq->lock);
 280         return 0;
 281 }
 282 EXPORT_SYMBOL(do_wait_intr_irq);
 283
 284 /**
 285  * finish_wait - clean up after waiting in a queue
 286  * @q: waitqueue waited on
 287  * @wait: wait descriptor
 288  *
 289  * Sets current thread back to running state and removes
 290  * the wait descriptor from the given waitqueue if still
 291  * queued.
 292  */
 293 void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
 294 {
 295         unsigned long flags;
 296
 297         __set_current_state(TASK_RUNNING);
 298         /*
 299          * We can check for list emptiness outside the lock
 300          * IFF:
 301          *  - we use the "careful" check that verifies both
 302          *    the next and prev pointers, so that there cannot
 303          *    be any half-pending updates in progress on other
 304          *    CPU's that we haven't seen yet (and that might
 305          *    still change the stack area.
 306          * and
 307          *  - all other users take the lock (ie we can only
 308          *    have _one_ other CPU that looks at or modifies
 309          *    the list).
 310          */
 311         if (!list_empty_careful(&wait->task_list)) {
 312                 spin_lock_irqsave(&q->lock, flags);
 313                 list_del_init(&wait->task_list);
 314                 spin_unlock_irqrestore(&q->lock, flags);
 315         }
 316 }
 317 EXPORT_SYMBOL(finish_wait);
 318
 319 int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 320 {
 321         int ret = default_wake_function(wait, mode, sync, key);
 322
 323         if (ret)
 324                 list_del_init(&wait->task_list);
 325         return ret;
 326 }
 327 EXPORT_SYMBOL(autoremove_wake_function);
 328
 329 static inline bool is_kthread_should_stop(void)
 330 {
 331         return (current->flags & PF_KTHREAD) && kthread_should_stop();
 332 }
 333
 334 /*
 335  * DEFINE_WAIT_FUNC(wait, woken_wake_func);
 336  *
 337  * add_wait_queue(&wq, &wait);
 338  * for (;;) {
 339  *     if (condition)
 340  *         break;
 341  *
 342  *     p->state = mode;                         condition = true;
 343  *     smp_mb(); // A                           smp_wmb(); // C
 344  *     if (!wait->flags & WQ_FLAG_WOKEN)        wait->flags |= WQ_FLAG_WOKEN;
 345  *         schedule()                           try_to_wake_up();
 346  *     p->state = TASK_RUNNING;             ~~~~~~~~~~~~~~~~~~
 347  *     wait->flags &= ~WQ_FLAG_WOKEN;           condition = true;
 348  *     smp_mb() // B                            smp_wmb(); // C
 349  *                                              wait->flags |= WQ_FLAG_WOKEN;
 350  * }
 351  * remove_wait_queue(&wq, &wait);
 352  *
 353  */
 354 long wait_woken(wait_queue_t *wait, unsigned mode, long timeout)
 355 {
 356         set_current_state(mode); /* A */
 357         /*
 358          * The above implies an smp_mb(), which matches with the smp_wmb() from
 359          * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must
 360          * also observe all state before the wakeup.
 361          */
 362         if (!(wait->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop())
 363                 timeout = schedule_timeout(timeout);
 364         __set_current_state(TASK_RUNNING);
 365
 366         /*
 367          * The below implies an smp_mb(), it too pairs with the smp_wmb() from
 368          * woken_wake_function() such that we must either observe the wait
 369          * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss
 370          * an event.
 371          */
 372         smp_store_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */
 373
 374         return timeout;
 375 }
 376 EXPORT_SYMBOL(wait_woken);
 377
 378 int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
 379 {
 380         /*
 381          * Although this function is called under waitqueue lock, LOCK
 382          * doesn't imply write barrier and the users expects write
 383          * barrier semantics on wakeup functions.  The following
 384          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
 385          * and is paired with smp_store_mb() in wait_woken().
 386          */
 387         smp_wmb(); /* C */
 388         wait->flags |= WQ_FLAG_WOKEN;
 389
 390         return default_wake_function(wait, mode, sync, key);
 391 }
 392 EXPORT_SYMBOL(woken_wake_function);
 393
 394 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 395 {
 396         struct wait_bit_key *key = arg;
 397         struct wait_bit_queue *wait_bit
 398                 = container_of(wait, struct wait_bit_queue, wait);
 399
 400         if (wait_bit->key.flags != key->flags ||
 401                         wait_bit->key.bit_nr != key->bit_nr ||
 402                         test_bit(key->bit_nr, key->flags))
 403                 return 0;
 404         else
 405                 return autoremove_wake_function(wait, mode, sync, key);
 406 }
 407 EXPORT_SYMBOL(wake_bit_function);
 408
 409 /*
 410  * To allow interruptible waiting and asynchronous (i.e. nonblocking)
 411  * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
 412  * permitted return codes. Nonzero return codes halt waiting and return.
 413  */
 414 int __sched
 415 __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
 416               wait_bit_action_f *action, unsigned mode)
 417 {
 418         int ret = 0;
 419
 420         do {
 421                 prepare_to_wait(wq, &q->wait, mode);
 422                 if (test_bit(q->key.bit_nr, q->key.flags))
 423                         ret = (*action)(&q->key, mode);
 424         } while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
 425         finish_wait(wq, &q->wait);
 426         return ret;
 427 }
 428 EXPORT_SYMBOL(__wait_on_bit);
 429
 430 int __sched out_of_line_wait_on_bit(void *word, int bit,
 431                                     wait_bit_action_f *action, unsigned mode)
 432 {
 433         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 434         DEFINE_WAIT_BIT(wait, word, bit);
 435
 436         return __wait_on_bit(wq, &wait, action, mode);
 437 }
 438 EXPORT_SYMBOL(out_of_line_wait_on_bit);
 439
 440 int __sched out_of_line_wait_on_bit_timeout(
 441         void *word, int bit, wait_bit_action_f *action,
 442         unsigned mode, unsigned long timeout)
 443 {
 444         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 445         DEFINE_WAIT_BIT(wait, word, bit);
 446
 447         wait.key.timeout = jiffies + timeout;
 448         return __wait_on_bit(wq, &wait, action, mode);
 449 }
 450 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
 451
 452 int __sched
 453 __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
 454                         wait_bit_action_f *action, unsigned mode)
 455 {
 456         int ret = 0;
 457
 458         for (;;) {
 459                 prepare_to_wait_exclusive(wq, &q->wait, mode);
 460                 if (test_bit(q->key.bit_nr, q->key.flags)) {
 461                         ret = action(&q->key, mode);
 462                         /*
 463                          * See the comment in prepare_to_wait_event().
 464                          * finish_wait() does not necessarily takes wq->lock,
 465                          * but test_and_set_bit() implies mb() which pairs with
 466                          * smp_mb__after_atomic() before wake_up_page().
 467                          */
 468                         if (ret)
 469                                 finish_wait(wq, &q->wait);
 470                 }
 471                 if (!test_and_set_bit(q->key.bit_nr, q->key.flags)) {
 472                         if (!ret)
 473                                 finish_wait(wq, &q->wait);
 474                         return 0;
 475                 } else if (ret) {
 476                         return ret;
 477                 }
 478         }
 479 }
 480 EXPORT_SYMBOL(__wait_on_bit_lock);
 481
 482 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
 483                                          wait_bit_action_f *action, unsigned mode)
 484 {
 485         wait_queue_head_t *wq = bit_waitqueue(word, bit);
 486         DEFINE_WAIT_BIT(wait, word, bit);
 487
 488         return __wait_on_bit_lock(wq, &wait, action, mode);
 489 }
 490 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
 491
 492 void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
 493 {
 494         struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
 495         if (waitqueue_active(wq))
 496                 __wake_up(wq, TASK_NORMAL, 1, &key);
 497 }
 498 EXPORT_SYMBOL(__wake_up_bit);
 499
 500 /**
 501  * wake_up_bit - wake up a waiter on a bit
 502  * @word: the word being waited on, a kernel virtual address
 503  * @bit: the bit of the word being waited on
 504  *
 505  * There is a standard hashed waitqueue table for generic use. This
 506  * is the part of the hashtable's accessor API that wakes up waiters
 507  * on a bit. For instance, if one were to have waiters on a bitflag,
 508  * one would call wake_up_bit() after clearing the bit.
 509  *
 510  * In order for this to function properly, as it uses waitqueue_active()
 511  * internally, some kind of memory barrier must be done prior to calling
 512  * this. Typically, this will be smp_mb__after_atomic(), but in some
 513  * cases where bitflags are manipulated non-atomically under a lock, one
 514  * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
 515  * because spin_unlock() does not guarantee a memory barrier.
 516  */
 517 void wake_up_bit(void *word, int bit)
 518 {
 519         __wake_up_bit(bit_waitqueue(word, bit), word, bit);
 520 }
 521 EXPORT_SYMBOL(wake_up_bit);
 522
 523 /*
 524  * Manipulate the atomic_t address to produce a better bit waitqueue table hash
 525  * index (we're keying off bit -1, but that would produce a horrible hash
 526  * value).
 527  */
 528 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
 529 {
 530         if (BITS_PER_LONG == 64) {
 531                 unsigned long q = (unsigned long)p;
 532                 return bit_waitqueue((void *)(q & ~1), q & 1);
 533         }
 534         return bit_waitqueue(p, 0);
 535 }
 536
 537 static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
 538                                   void *arg)
 539 {
 540         struct wait_bit_key *key = arg;
 541         struct wait_bit_queue *wait_bit
 542                 = container_of(wait, struct wait_bit_queue, wait);
 543         atomic_t *val = key->flags;
 544
 545         if (wait_bit->key.flags != key->flags ||
 546             wait_bit->key.bit_nr != key->bit_nr ||
 547             atomic_read(val) != 0)
 548                 return 0;
 549         return autoremove_wake_function(wait, mode, sync, key);
 550 }
 551
 552 /*
 553  * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
 554  * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
 555  * return codes halt waiting and return.
 556  */
 557 static __sched
 558 int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
 559                        int (*action)(atomic_t *), unsigned mode)
 560 {
 561         atomic_t *val;
 562         int ret = 0;
 563
 564         do {
 565                 prepare_to_wait(wq, &q->wait, mode);
 566                 val = q->key.flags;
 567                 if (atomic_read(val) == 0)
 568                         break;
 569                 ret = (*action)(val);
 570         } while (!ret && atomic_read(val) != 0);
 571         finish_wait(wq, &q->wait);
 572         return ret;
 573 }
 574
 575 #define DEFINE_WAIT_ATOMIC_T(name, p)                                   \
 576         struct wait_bit_queue name = {                                  \
 577                 .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),              \
 578                 .wait   = {                                             \
 579                         .private        = current,                      \
 580                         .func           = wake_atomic_t_function,       \
 581                         .task_list      =                               \
 582                                 LIST_HEAD_INIT((name).wait.task_list),  \
 583                 },                                                      \
 584         }
 585
 586 __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
 587                                          unsigned mode)
 588 {
 589         wait_queue_head_t *wq = atomic_t_waitqueue(p);
 590         DEFINE_WAIT_ATOMIC_T(wait, p);
 591
 592         return __wait_on_atomic_t(wq, &wait, action, mode);
 593 }
 594 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
 595
 596 /**
 597  * wake_up_atomic_t - Wake up a waiter on a atomic_t
 598  * @p: The atomic_t being waited on, a kernel virtual address
 599  *
 600  * Wake up anyone waiting for the atomic_t to go to zero.
 601  *
 602  * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
 603  * check is done by the waiter's wake function, not the by the waker itself).
 604  */
 605 void wake_up_atomic_t(atomic_t *p)
 606 {
 607         __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
 608 }
 609 EXPORT_SYMBOL(wake_up_atomic_t);
 610
 611 __sched int bit_wait(struct wait_bit_key *word, int mode)
 612 {
 613         schedule();
 614         if (signal_pending_state(mode, current))
 615                 return -EINTR;
 616         return 0;
 617 }
 618 EXPORT_SYMBOL(bit_wait);
 619
 620 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
 621 {
 622         io_schedule();
 623         if (signal_pending_state(mode, current))
 624                 return -EINTR;
 625         return 0;
 626 }
 627 EXPORT_SYMBOL(bit_wait_io);
 628
 629 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
 630 {
 631         unsigned long now = READ_ONCE(jiffies);
 632         if (time_after_eq(now, word->timeout))
 633                 return -EAGAIN;
 634         schedule_timeout(word->timeout - now);
 635         if (signal_pending_state(mode, current))
 636                 return -EINTR;
 637         return 0;
 638 }
 639 EXPORT_SYMBOL_GPL(bit_wait_timeout);
 640
 641 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
 642 {
 643         unsigned long now = READ_ONCE(jiffies);
 644         if (time_after_eq(now, word->timeout))
 645                 return -EAGAIN;
 646         io_schedule_timeout(word->timeout - now);
 647         if (signal_pending_state(mode, current))
 648                 return -EINTR;
 649         return 0;
 650 }
 651 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);