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/*
* Generic waiting primitives.
*
* (C) 2004 Nadia Yvette Chambers, Oracle
*/
#include <linux/init.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/wait.h>
#include <linux/hash.h>
void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key)
{
spin_lock_init(&q->lock);
lockdep_set_class_and_name(&q->lock, key, name);
INIT_LIST_HEAD(&q->task_list);
}
EXPORT_SYMBOL(__init_waitqueue_head);
void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
{
unsigned long flags;
wait->flags &= ~WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue(q, wait);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(add_wait_queue);
void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
{
unsigned long flags;
wait->flags |= WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&q->lock, flags);
__add_wait_queue_tail(q, wait);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(add_wait_queue_exclusive);
void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__remove_wait_queue(q, wait);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(remove_wait_queue);
/*
* Note: we use "set_current_state()" _after_ the wait-queue add,
* because we need a memory barrier there on SMP, so that any
* wake-function that tests for the wait-queue being active
* will be guaranteed to see waitqueue addition _or_ subsequent
* tests in this thread will see the wakeup having taken place.
*
* The spin_unlock() itself is semi-permeable and only protects
* one way (it only protects stuff inside the critical region and
* stops them from bleeding out - it would still allow subsequent
* loads to move into the critical region).
*/
void
prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state)
{
unsigned long flags;
wait->flags &= ~WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list))
__add_wait_queue(q, wait);
set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(prepare_to_wait);
void
prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
{
unsigned long flags;
wait->flags |= WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list))
__add_wait_queue_tail(q, wait);
set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(prepare_to_wait_exclusive);
long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state)
{
unsigned long flags;
if (signal_pending_state(state, current))
return -ERESTARTSYS;
wait->private = current;
wait->func = autoremove_wake_function;
spin_lock_irqsave(&q->lock, flags);
if (list_empty(&wait->task_list)) {
if (wait->flags & WQ_FLAG_EXCLUSIVE)
__add_wait_queue_tail(q, wait);
else
__add_wait_queue(q, wait);
}
set_current_state(state);
spin_unlock_irqrestore(&q->lock, flags);
return 0;
}
EXPORT_SYMBOL(prepare_to_wait_event);
/**
* finish_wait - clean up after waiting in a queue
* @q: waitqueue waited on
* @wait: wait descriptor
*
* Sets current thread back to running state and removes
* the wait descriptor from the given waitqueue if still
* queued.
*/
void finish_wait(wait_queue_head_t *q, wait_queue_t *wait)
{
unsigned long flags;
__set_current_state(TASK_RUNNING);
/*
* We can check for list emptiness outside the lock
* IFF:
* - we use the "careful" check that verifies both
* the next and prev pointers, so that there cannot
* be any half-pending updates in progress on other
* CPU's that we haven't seen yet (and that might
* still change the stack area.
* and
* - all other users take the lock (ie we can only
* have _one_ other CPU that looks at or modifies
* the list).
*/
if (!list_empty_careful(&wait->task_list)) {
spin_lock_irqsave(&q->lock, flags);
list_del_init(&wait->task_list);
spin_unlock_irqrestore(&q->lock, flags);
}
}
EXPORT_SYMBOL(finish_wait);
/**
* abort_exclusive_wait - abort exclusive waiting in a queue
* @q: waitqueue waited on
* @wait: wait descriptor
* @mode: runstate of the waiter to be woken
* @key: key to identify a wait bit queue or %NULL
*
* Sets current thread back to running state and removes
* the wait descriptor from the given waitqueue if still
* queued.
*
* Wakes up the next waiter if the caller is concurrently
* woken up through the queue.
*
* This prevents waiter starvation where an exclusive waiter
* aborts and is woken up concurrently and no one wakes up
* the next waiter.
*/
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
unsigned int mode, void *key)
{
unsigned long flags;
__set_current_state(TASK_RUNNING);
spin_lock_irqsave(&q->lock, flags);
if (!list_empty(&wait->task_list))
list_del_init(&wait->task_list);
else if (waitqueue_active(q))
__wake_up_locked_key(q, mode, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(abort_exclusive_wait);
int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
int ret = default_wake_function(wait, mode, sync, key);
if (ret)
list_del_init(&wait->task_list);
return ret;
}
EXPORT_SYMBOL(autoremove_wake_function);
int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
{
struct wait_bit_key *key = arg;
struct wait_bit_queue *wait_bit
= container_of(wait, struct wait_bit_queue, wait);
if (wait_bit->key.flags != key->flags ||
wait_bit->key.bit_nr != key->bit_nr ||
test_bit(key->bit_nr, key->flags))
return 0;
else
return autoremove_wake_function(wait, mode, sync, key);
}
EXPORT_SYMBOL(wake_bit_function);
/*
* To allow interruptible waiting and asynchronous (i.e. nonblocking)
* waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
* permitted return codes. Nonzero return codes halt waiting and return.
*/
int __sched
__wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q,
int (*action)(void *), unsigned mode)
{
int ret = 0;
do {
prepare_to_wait(wq, &q->wait, mode);
if (test_bit(q->key.bit_nr, q->key.flags))
ret = (*action)(q->key.flags);
} while (test_bit(q->key.bit_nr, q->key.flags) && !ret);
finish_wait(wq, &q->wait);
return ret;
}
EXPORT_SYMBOL(__wait_on_bit);
int __sched out_of_line_wait_on_bit(void *word, int bit,
int (*action)(void *), unsigned mode)
{
wait_queue_head_t *wq = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wait, word, bit);
return __wait_on_bit(wq, &wait, action, mode);
}
EXPORT_SYMBOL(out_of_line_wait_on_bit);
int __sched
__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
int (*action)(void *), unsigned mode)
{
do {
int ret;
prepare_to_wait_exclusive(wq, &q->wait, mode);
if (!test_bit(q->key.bit_nr, q->key.flags))
continue;
ret = action(q->key.flags);
if (!ret)
continue;
abort_exclusive_wait(wq, &q->wait, mode, &q->key);
return ret;
} while (test_and_set_bit(q->key.bit_nr, q->key.flags));
finish_wait(wq, &q->wait);
return 0;
}
EXPORT_SYMBOL(__wait_on_bit_lock);
int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
int (*action)(void *), unsigned mode)
{
wait_queue_head_t *wq = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wait, word, bit);
return __wait_on_bit_lock(wq, &wait, action, mode);
}
EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit)
{
struct
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