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cbbce82209
In commit c1221321b7
sched: Allow wait_on_bit_action() functions to support a timeout
I suggested that a "wait_on_bit_timeout()" interface would not meet my
need. This isn't true - I was just over-engineering.
Including a 'private' field in wait_bit_key instead of a focused
"timeout" field was just premature generalization. If some other
use is ever found, it can be generalized or added later.
So this patch renames "private" to "timeout" with a meaning "stop
waiting when "jiffies" reaches or passes "timeout",
and adds two of the many possible wait..bit..timeout() interfaces:
wait_on_page_bit_killable_timeout(), which is the one I want to use,
and out_of_line_wait_on_bit_timeout() which is a reasonably general
example. Others can be added as needed.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
559 lines
16 KiB
C
559 lines
16 KiB
C
/*
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* Generic waiting primitives.
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*
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* (C) 2004 Nadia Yvette Chambers, Oracle
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*/
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#include <linux/init.h>
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#include <linux/export.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, const char *name, 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_and_name(&q->lock, key, name);
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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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* The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
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* wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
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* number) then we wake all the non-exclusive tasks and one exclusive task.
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*
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* There are circumstances in which we can try to wake a task which has already
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* started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
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* zero in this (rare) case, and we handle it by continuing to scan the queue.
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*/
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static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
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int nr_exclusive, int wake_flags, void *key)
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{
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wait_queue_t *curr, *next;
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list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
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unsigned flags = curr->flags;
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if (curr->func(curr, mode, wake_flags, key) &&
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(flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
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break;
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}
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}
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/**
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* __wake_up - wake up threads blocked on a waitqueue.
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* @q: the waitqueue
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* @mode: which threads
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* @nr_exclusive: how many wake-one or wake-many threads to wake up
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* @key: is directly passed to the wakeup function
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*
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* It may be assumed that this function implies a write memory barrier before
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* changing the task state if and only if any tasks are woken up.
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*/
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void __wake_up(wait_queue_head_t *q, unsigned int mode,
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int nr_exclusive, void *key)
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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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__wake_up_common(q, mode, nr_exclusive, 0, key);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL(__wake_up);
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/*
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* Same as __wake_up but called with the spinlock in wait_queue_head_t held.
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*/
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void __wake_up_locked(wait_queue_head_t *q, unsigned int mode, int nr)
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{
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__wake_up_common(q, mode, nr, 0, NULL);
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}
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EXPORT_SYMBOL_GPL(__wake_up_locked);
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void __wake_up_locked_key(wait_queue_head_t *q, unsigned int mode, void *key)
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{
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__wake_up_common(q, mode, 1, 0, key);
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}
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EXPORT_SYMBOL_GPL(__wake_up_locked_key);
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/**
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* __wake_up_sync_key - wake up threads blocked on a waitqueue.
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* @q: the waitqueue
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* @mode: which threads
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* @nr_exclusive: how many wake-one or wake-many threads to wake up
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* @key: opaque value to be passed to wakeup targets
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*
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* The sync wakeup differs that the waker knows that it will schedule
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* away soon, so while the target thread will be woken up, it will not
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* be migrated to another CPU - ie. the two threads are 'synchronized'
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* with each other. This can prevent needless bouncing between CPUs.
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*
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* On UP it can prevent extra preemption.
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*
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* It may be assumed that this function implies a write memory barrier before
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* changing the task state if and only if any tasks are woken up.
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*/
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void __wake_up_sync_key(wait_queue_head_t *q, unsigned int mode,
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int nr_exclusive, void *key)
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{
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unsigned long flags;
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int wake_flags = 1; /* XXX WF_SYNC */
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if (unlikely(!q))
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return;
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if (unlikely(nr_exclusive != 1))
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wake_flags = 0;
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spin_lock_irqsave(&q->lock, flags);
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__wake_up_common(q, mode, nr_exclusive, wake_flags, key);
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spin_unlock_irqrestore(&q->lock, flags);
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}
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EXPORT_SYMBOL_GPL(__wake_up_sync_key);
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/*
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* __wake_up_sync - see __wake_up_sync_key()
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*/
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void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
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{
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__wake_up_sync_key(q, mode, nr_exclusive, NULL);
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}
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EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
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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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long prepare_to_wait_event(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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if (signal_pending_state(state, current))
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return -ERESTARTSYS;
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wait->private = current;
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wait->func = autoremove_wake_function;
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spin_lock_irqsave(&q->lock, flags);
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if (list_empty(&wait->task_list)) {
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if (wait->flags & WQ_FLAG_EXCLUSIVE)
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__add_wait_queue_tail(q, wait);
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else
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__add_wait_queue(q, wait);
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}
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set_current_state(state);
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spin_unlock_irqrestore(&q->lock, flags);
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return 0;
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}
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EXPORT_SYMBOL(prepare_to_wait_event);
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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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* @mode: 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 no one 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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wait_bit_action_f *action, 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);
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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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wait_bit_action_f *action, 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 out_of_line_wait_on_bit_timeout(
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void *word, int bit, wait_bit_action_f *action,
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unsigned mode, unsigned long timeout)
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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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wait.key.timeout = jiffies + timeout;
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return __wait_on_bit(wq, &wait, action, mode);
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}
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EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
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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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wait_bit_action_f *action, 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);
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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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wait_bit_action_f *action, 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_atomic(), 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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/*
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* Manipulate the atomic_t address to produce a better bit waitqueue table hash
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* index (we're keying off bit -1, but that would produce a horrible hash
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* value).
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*/
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static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
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{
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if (BITS_PER_LONG == 64) {
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unsigned long q = (unsigned long)p;
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return bit_waitqueue((void *)(q & ~1), q & 1);
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}
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return bit_waitqueue(p, 0);
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}
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static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
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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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atomic_t *val = key->flags;
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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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atomic_read(val) != 0)
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return 0;
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return autoremove_wake_function(wait, mode, sync, key);
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}
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/*
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* To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
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* the actions of __wait_on_atomic_t() are permitted return codes. Nonzero
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|
* return codes halt waiting and return.
|
|
*/
|
|
static __sched
|
|
int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
|
|
int (*action)(atomic_t *), unsigned mode)
|
|
{
|
|
atomic_t *val;
|
|
int ret = 0;
|
|
|
|
do {
|
|
prepare_to_wait(wq, &q->wait, mode);
|
|
val = q->key.flags;
|
|
if (atomic_read(val) == 0)
|
|
break;
|
|
ret = (*action)(val);
|
|
} while (!ret && atomic_read(val) != 0);
|
|
finish_wait(wq, &q->wait);
|
|
return ret;
|
|
}
|
|
|
|
#define DEFINE_WAIT_ATOMIC_T(name, p) \
|
|
struct wait_bit_queue name = { \
|
|
.key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p), \
|
|
.wait = { \
|
|
.private = current, \
|
|
.func = wake_atomic_t_function, \
|
|
.task_list = \
|
|
LIST_HEAD_INIT((name).wait.task_list), \
|
|
}, \
|
|
}
|
|
|
|
__sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
|
|
unsigned mode)
|
|
{
|
|
wait_queue_head_t *wq = atomic_t_waitqueue(p);
|
|
DEFINE_WAIT_ATOMIC_T(wait, p);
|
|
|
|
return __wait_on_atomic_t(wq, &wait, action, mode);
|
|
}
|
|
EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
|
|
|
|
/**
|
|
* wake_up_atomic_t - Wake up a waiter on a atomic_t
|
|
* @p: The atomic_t being waited on, a kernel virtual address
|
|
*
|
|
* Wake up anyone waiting for the atomic_t to go to zero.
|
|
*
|
|
* Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
|
|
* check is done by the waiter's wake function, not the by the waker itself).
|
|
*/
|
|
void wake_up_atomic_t(atomic_t *p)
|
|
{
|
|
__wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
|
|
}
|
|
EXPORT_SYMBOL(wake_up_atomic_t);
|
|
|
|
__sched int bit_wait(struct wait_bit_key *word)
|
|
{
|
|
if (signal_pending_state(current->state, current))
|
|
return 1;
|
|
schedule();
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(bit_wait);
|
|
|
|
__sched int bit_wait_io(struct wait_bit_key *word)
|
|
{
|
|
if (signal_pending_state(current->state, current))
|
|
return 1;
|
|
io_schedule();
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(bit_wait_io);
|
|
|
|
__sched int bit_wait_timeout(struct wait_bit_key *word)
|
|
{
|
|
unsigned long now = ACCESS_ONCE(jiffies);
|
|
if (signal_pending_state(current->state, current))
|
|
return 1;
|
|
if (time_after_eq(now, word->timeout))
|
|
return -EAGAIN;
|
|
schedule_timeout(word->timeout - now);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(bit_wait_timeout);
|
|
|
|
__sched int bit_wait_io_timeout(struct wait_bit_key *word)
|
|
{
|
|
unsigned long now = ACCESS_ONCE(jiffies);
|
|
if (signal_pending_state(current->state, current))
|
|
return 1;
|
|
if (time_after_eq(now, word->timeout))
|
|
return -EAGAIN;
|
|
io_schedule_timeout(word->timeout - now);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
|