1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * <linux/swait.h> (simple wait queues ) implementation:
  4 */
  5#include "sched.h"
  6
  7void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
  8			     struct lock_class_key *key)
  9{
 10	raw_spin_lock_init(&q->lock);
 11	lockdep_set_class_and_name(&q->lock, key, name);
 12	INIT_LIST_HEAD(&q->task_list);
 13}
 14EXPORT_SYMBOL(__init_swait_queue_head);
 15
 16/*
 17 * The thing about the wake_up_state() return value; I think we can ignore it.
 18 *
 19 * If for some reason it would return 0, that means the previously waiting
 20 * task is already running, so it will observe condition true (or has already).
 21 */
 22void swake_up_locked(struct swait_queue_head *q)
 23{
 24	struct swait_queue *curr;
 25
 26	if (list_empty(&q->task_list))
 27		return;
 28
 29	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
 30	wake_up_process(curr->task);
 31	list_del_init(&curr->task_list);
 32}
 33EXPORT_SYMBOL(swake_up_locked);
 34
 35void swake_up(struct swait_queue_head *q)
 36{
 37	unsigned long flags;
 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	raw_spin_lock_irq(&q->lock);
 55	list_splice_init(&q->task_list, &tmp);
 56	while (!list_empty(&tmp)) {
 57		curr = list_first_entry(&tmp, typeof(*curr), task_list);
 58
 59		wake_up_state(curr->task, TASK_NORMAL);
 60		list_del_init(&curr->task_list);
 61
 62		if (list_empty(&tmp))
 63			break;
 64
 65		raw_spin_unlock_irq(&q->lock);
 66		raw_spin_lock_irq(&q->lock);
 67	}
 68	raw_spin_unlock_irq(&q->lock);
 69}
 70EXPORT_SYMBOL(swake_up_all);
 71
 72void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
 73{
 74	wait->task = current;
 75	if (list_empty(&wait->task_list))
 76		list_add(&wait->task_list, &q->task_list);
 77}
 78
 79void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
 80{
 81	unsigned long flags;
 82
 83	raw_spin_lock_irqsave(&q->lock, flags);
 84	__prepare_to_swait(q, wait);
 85	set_current_state(state);
 86	raw_spin_unlock_irqrestore(&q->lock, flags);
 87}
 88EXPORT_SYMBOL(prepare_to_swait);
 89
 90long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
 91{
 92	if (signal_pending_state(state, current))
 93		return -ERESTARTSYS;
 94
 95	prepare_to_swait(q, wait, state);
 96
 97	return 0;
 98}
 99EXPORT_SYMBOL(prepare_to_swait_event);
100
101void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
102{
103	__set_current_state(TASK_RUNNING);
104	if (!list_empty(&wait->task_list))
105		list_del_init(&wait->task_list);
106}
107
108void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
109{
110	unsigned long flags;
111
112	__set_current_state(TASK_RUNNING);
113
114	if (!list_empty_careful(&wait->task_list)) {
115		raw_spin_lock_irqsave(&q->lock, flags);
116		list_del_init(&wait->task_list);
117		raw_spin_unlock_irqrestore(&q->lock, flags);
118	}
119}
120EXPORT_SYMBOL(finish_swait);