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![Peter Zijlstra](/assets/img/avatar_default.png)
Give waitqueue spinlocks their own lockdep classes when they are initialised from init_waitqueue_head(). This means that struct wait_queue::func functions can operate other waitqueues. This is used by CacheFiles to catch the page from a backing fs being unlocked and to wake up another thread to take a copy of it. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Takashi Iwai <tiwai@suse.de> Cc: linux-cachefs@redhat.com Cc: torvalds@osdl.org Cc: akpm@linux-foundation.org LKML-Reference: <20090810113305.17284.81508.stgit@warthog.procyon.org.uk> Signed-off-by: Ingo Molnar <mingo@elte.hu>
289 lines
8.2 KiB
C
289 lines
8.2 KiB
C
/*
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* Generic waiting primitives.
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*
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* (C) 2004 William Irwin, Oracle
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*/
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/wait.h>
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#include <linux/hash.h>
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void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *key)
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{
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spin_lock_init(&q->lock);
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lockdep_set_class(&q->lock, key);
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INIT_LIST_HEAD(&q->task_list);
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}
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EXPORT_SYMBOL(__init_waitqueue_head);
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void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
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{
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unsigned long flags;
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wait->flags &= ~WQ_FLAG_EXCLUSIVE;
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spin_lock_irqsave(&q->lock, flags);
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__add_wait_queue(q, wait);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(add_wait_queue);
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void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
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{
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unsigned long flags;
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wait->flags |= WQ_FLAG_EXCLUSIVE;
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spin_lock_irqsave(&q->lock, flags);
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__add_wait_queue_tail(q, wait);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(add_wait_queue_exclusive);
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void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
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{
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unsigned long flags;
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spin_lock_irqsave(&q->lock, flags);
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__remove_wait_queue(q, wait);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(remove_wait_queue);
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/*
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* Note: we use "set_current_state()" _after_ the wait-queue add,
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* because we need a memory barrier there on SMP, so that any
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* wake-function that tests for the wait-queue being active
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* will be guaranteed to see waitqueue addition _or_ subsequent
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* tests in this thread will see the wakeup having taken place.
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*
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* The spin_unlock() itself is semi-permeable and only protects
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* one way (it only protects stuff inside the critical region and
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* stops them from bleeding out - it would still allow subsequent
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* loads to move into the critical region).
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*/
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void
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prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
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{
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unsigned long flags;
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wait->flags &= ~WQ_FLAG_EXCLUSIVE;
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spin_lock_irqsave(&q->lock, flags);
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if (list_empty(&wait->task_list))
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__add_wait_queue(q, wait);
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set_current_state(state);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(prepare_to_wait);
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void
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prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
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{
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unsigned long flags;
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wait->flags |= WQ_FLAG_EXCLUSIVE;
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spin_lock_irqsave(&q->lock, flags);
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if (list_empty(&wait->task_list))
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__add_wait_queue_tail(q, wait);
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set_current_state(state);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(prepare_to_wait_exclusive);
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/*
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* finish_wait - clean up after waiting in a queue
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* @q: waitqueue waited on
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* @wait: wait descriptor
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*
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* Sets current thread back to running state and removes
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* the wait descriptor from the given waitqueue if still
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* queued.
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*/
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void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
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{
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unsigned long flags;
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__set_current_state(TASK_RUNNING);
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/*
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* We can check for list emptiness outside the lock
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* IFF:
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* - we use the "careful" check that verifies both
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* the next and prev pointers, so that there cannot
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* be any half-pending updates in progress on other
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* CPU's that we haven't seen yet (and that might
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* still change the stack area.
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* and
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* - all other users take the lock (ie we can only
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* have _one_ other CPU that looks at or modifies
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* the list).
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*/
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if (!list_empty_careful(&wait->task_list)) {
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spin_lock_irqsave(&q->lock, flags);
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list_del_init(&wait->task_list);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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}
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EXPORT_SYMBOL(finish_wait);
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/*
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* abort_exclusive_wait - abort exclusive waiting in a queue
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* @q: waitqueue waited on
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* @wait: wait descriptor
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* @state: runstate of the waiter to be woken
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* @key: key to identify a wait bit queue or %NULL
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*
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* Sets current thread back to running state and removes
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* the wait descriptor from the given waitqueue if still
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* queued.
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*
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* Wakes up the next waiter if the caller is concurrently
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* woken up through the queue.
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*
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* This prevents waiter starvation where an exclusive waiter
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* aborts and is woken up concurrently and noone wakes up
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* the next waiter.
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*/
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void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
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unsigned int mode, void *key)
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{
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unsigned long flags;
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__set_current_state(TASK_RUNNING);
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spin_lock_irqsave(&q->lock, flags);
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if (!list_empty(&wait->task_list))
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list_del_init(&wait->task_list);
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else if (waitqueue_active(q))
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__wake_up_locked_key(q, mode, key);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(abort_exclusive_wait);
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int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
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{
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int ret = default_wake_function(wait, mode, sync, key);
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if (ret)
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list_del_init(&wait->task_list);
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return ret;
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}
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EXPORT_SYMBOL(autoremove_wake_function);
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int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
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{
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struct wait_bit_key *key = arg;
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struct wait_bit_queue *wait_bit
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= container_of(wait, struct wait_bit_queue, wait);
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if (wait_bit->key.flags != key->flags ||
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wait_bit->key.bit_nr != key->bit_nr ||
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test_bit(key->bit_nr, key->flags))
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return 0;
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else
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return autoremove_wake_function(wait, mode, sync, key);
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}
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EXPORT_SYMBOL(wake_bit_function);
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/*
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* To allow interruptible waiting and asynchronous (i.e. nonblocking)
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* waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
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* permitted return codes. Nonzero return codes halt waiting and return.
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*/
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int __sched
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__wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
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int (*action)(void *), unsigned mode)
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{
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int ret = 0;
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do {
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prepare_to_wait(wq, &q->wait, mode);
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if (test_bit(q->key.bit_nr, q->key.flags))
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ret = (*action)(q->key.flags);
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} while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
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finish_wait(wq, &q->wait);
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return ret;
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}
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EXPORT_SYMBOL(__wait_on_bit);
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int __sched out_of_line_wait_on_bit(void *word, int bit,
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int (*action)(void *), unsigned mode)
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{
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wait_queue_head_t *wq = bit_waitqueue(word, bit);
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DEFINE_WAIT_BIT(wait, word, bit);
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return __wait_on_bit(wq, &wait, action, mode);
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}
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EXPORT_SYMBOL(out_of_line_wait_on_bit);
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int __sched
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__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
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int (*action)(void *), unsigned mode)
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{
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do {
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int ret;
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prepare_to_wait_exclusive(wq, &q->wait, mode);
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if (!test_bit(q->key.bit_nr, q->key.flags))
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continue;
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ret = action(q->key.flags);
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if (!ret)
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continue;
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abort_exclusive_wait(wq, &q->wait, mode, &q->key);
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return ret;
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} while (test_and_set_bit(q->key.bit_nr, q->key.flags));
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finish_wait(wq, &q->wait);
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return 0;
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}
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EXPORT_SYMBOL(__wait_on_bit_lock);
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int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
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int (*action)(void *), unsigned mode)
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{
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wait_queue_head_t *wq = bit_waitqueue(word, bit);
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DEFINE_WAIT_BIT(wait, word, bit);
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return __wait_on_bit_lock(wq, &wait, action, mode);
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}
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EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
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void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
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{
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struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
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if (waitqueue_active(wq))
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__wake_up(wq, TASK_NORMAL, 1, &key);
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}
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EXPORT_SYMBOL(__wake_up_bit);
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/**
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* wake_up_bit - wake up a waiter on a bit
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* @word: the word being waited on, a kernel virtual address
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* @bit: the bit of the word being waited on
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*
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* There is a standard hashed waitqueue table for generic use. This
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* is the part of the hashtable's accessor API that wakes up waiters
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* on a bit. For instance, if one were to have waiters on a bitflag,
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* one would call wake_up_bit() after clearing the bit.
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*
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* In order for this to function properly, as it uses waitqueue_active()
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* internally, some kind of memory barrier must be done prior to calling
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* this. Typically, this will be smp_mb__after_clear_bit(), but in some
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* cases where bitflags are manipulated non-atomically under a lock, one
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* may need to use a less regular barrier, such fs/inode.c's smp_mb(),
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* because spin_unlock() does not guarantee a memory barrier.
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*/
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void wake_up_bit(void *word, int bit)
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{
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__wake_up_bit(bit_waitqueue(word, bit), word, bit);
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}
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EXPORT_SYMBOL(wake_up_bit);
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wait_queue_head_t *bit_waitqueue(void *word, int bit)
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{
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const int shift = BITS_PER_LONG == 32 ? 5 : 6;
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const struct zone *zone = page_zone(virt_to_page(word));
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unsigned long val = (unsigned long)word << shift | bit;
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return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
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}
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EXPORT_SYMBOL(bit_waitqueue);
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