/* * 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). */voidprepare_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); voidprepare_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); /** * 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 wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);	if (waitqueue_active(wq))		__wake_up(wq, TASK_NORMAL, 1, &key);}EXPORT_SYMBOL(__wake_up_bit); /** * wake_up_bit - wake up a waiter on a bit * @word: the word being waited on, a kernel virtual address * @bit: the bit of the word being waited on * * There is a standard hashed waitqueue table for generic use. This * is the part of the hashtable's accessor API that wakes up waiters * on a bit. For instance, if one were to have waiters on a bitflag, * one would call wake_up_bit() after clearing the bit. * * In order for this to function properly, as it uses waitqueue_active() * internally, some kind of memory barrier must be done prior to calling * this. Typically, this will be smp_mb__after_clear_bit(), but in some * cases where bitflags are manipulated non-atomically under a lock, one * may need to use a less regular barrier, such fs/inode.c's smp_mb(), * because spin_unlock() does not guarantee a memory barrier. */void wake_up_bit(void *word, int bit){	__wake_up_bit(bit_waitqueue(word, bit), word, bit);}EXPORT_SYMBOL(wake_up_bit); wait_queue_head_t *bit_waitqueue(void *word, int bit){	const int shift = BITS_PER_LONG == 32 ? 5 : 6;	const struct zone *zone = page_zone(virt_to_page(word));	unsigned long val = (unsigned long)word << shift | bit; 	return &zone->wait_table[hash_long(val, zone->wait_table_bits)];}EXPORT_SYMBOL(bit_waitqueue);