1#include <linux/sched.h>
  2#include <linux/swait.h>
  3
  4void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
  5			     struct lock_class_key *key)
  6{
  7	raw_spin_lock_init(&q->lock);
  8	lockdep_set_class_and_name(&q->lock, key, name);
  9	INIT_LIST_HEAD(&q->task_list);
 10}
 11EXPORT_SYMBOL(__init_swait_queue_head);
 12
 13/*
 14 * The thing about the wake_up_state() return value; I think we can ignore it.
 15 *
 16 * If for some reason it would return 0, that means the previously waiting
 17 * task is already running, so it will observe condition true (or has already).
 18 */
 19void swake_up_locked(struct swait_queue_head *q)
 20{
 21	struct swait_queue *curr;
 22
 23	if (list_empty(&q->task_list))
 24		return;
 25
 26	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
 27	wake_up_process(curr->task);
 28	list_del_init(&curr->task_list);
 29}
 30EXPORT_SYMBOL(swake_up_locked);
 31
 32void swake_up(struct swait_queue_head *q)
 33{
 34	unsigned long flags;
 35
 36	if (!swait_active(q))
 37		return;
 38
 39	raw_spin_lock_irqsave(&q->lock, flags);
 40	swake_up_locked(q);
 41	raw_spin_unlock_irqrestore(&q->lock, flags);
 42}
 43EXPORT_SYMBOL(swake_up);
 44
 45/*
 46 * Does not allow usage from IRQ disabled, since we must be able to
 47 * release IRQs to guarantee bounded hold time.
 48 */
 49void swake_up_all(struct swait_queue_head *q)
 50{
 51	struct swait_queue *curr;
 52	LIST_HEAD(tmp);
 53
 54	if (!swait_active(q))
 55		return;
 56
 57	raw_spin_lock_irq(&q->lock);
 58	list_splice_init(&q->task_list, &tmp);
 59	while (!list_empty(&tmp)) {
 60		curr = list_first_entry(&tmp, typeof(*curr), task_list);
 61
 62		wake_up_state(curr->task, TASK_NORMAL);
 63		list_del_init(&curr->task_list);
 64
 65		if (list_empty(&tmp))
 66			break;
 67
 68		raw_spin_unlock_irq(&q->lock);
 69		raw_spin_lock_irq(&q->lock);
 70	}
 71	raw_spin_unlock_irq(&q->lock);
 72}
 73EXPORT_SYMBOL(swake_up_all);
 74
 75void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
 76{
 77	wait->task = current;
 78	if (list_empty(&wait->task_list))
 79		list_add(&wait->task_list, &q->task_list);
 80}
 81
 82void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
 83{
 84	unsigned long flags;
 85
 86	raw_spin_lock_irqsave(&q->lock, flags);
 87	__prepare_to_swait(q, wait);
 88	set_current_state(state);
 89	raw_spin_unlock_irqrestore(&q->lock, flags);
 90}
 91EXPORT_SYMBOL(prepare_to_swait);
 92
 93long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
 94{
 95	if (signal_pending_state(state, current))
 96		return -ERESTARTSYS;
 97
 98	prepare_to_swait(q, wait, state);
 99
100	return 0;
101}
102EXPORT_SYMBOL(prepare_to_swait_event);
103
104void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
105{
106	__set_current_state(TASK_RUNNING);
107	if (!list_empty(&wait->task_list))
108		list_del_init(&wait->task_list);
109}
110
111void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
112{
113	unsigned long flags;
114
115	__set_current_state(TASK_RUNNING);
116
117	if (!list_empty_careful(&wait->task_list)) {
118		raw_spin_lock_irqsave(&q->lock, flags);
119		list_del_init(&wait->task_list);
120		raw_spin_unlock_irqrestore(&q->lock, flags);
121	}
122}
123EXPORT_SYMBOL(finish_swait);