swait.c

  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, int wake_flags)
 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	try_to_wake_up(curr->task, TASK_NORMAL, wake_flags);
 31	list_del_init(&curr->task_list);
 32}
 33EXPORT_SYMBOL(swake_up_locked);
 34
 35/*
 36 * Wake up all waiters. This is an interface which is solely exposed for
 37 * completions and not for general usage.
 38 *
 39 * It is intentionally different from swake_up_all() to allow usage from
 40 * hard interrupt context and interrupt disabled regions.
 41 */
 42void swake_up_all_locked(struct swait_queue_head *q)
 43{
 44	while (!list_empty(&q->task_list))
 45		swake_up_locked(q, 0);
 46}
 47
 48void swake_up_one(struct swait_queue_head *q)
 49{
 50	unsigned long flags;
 51
 52	raw_spin_lock_irqsave(&q->lock, flags);
 53	swake_up_locked(q, 0);
 54	raw_spin_unlock_irqrestore(&q->lock, flags);
 55}
 56EXPORT_SYMBOL(swake_up_one);
 57
 58/*
 59 * Does not allow usage from IRQ disabled, since we must be able to
 60 * release IRQs to guarantee bounded hold time.
 61 */
 62void swake_up_all(struct swait_queue_head *q)
 63{
 64	struct swait_queue *curr;
 65	LIST_HEAD(tmp);
 66
 67	raw_spin_lock_irq(&q->lock);
 68	list_splice_init(&q->task_list, &tmp);
 69	while (!list_empty(&tmp)) {
 70		curr = list_first_entry(&tmp, typeof(*curr), task_list);
 71
 72		wake_up_state(curr->task, TASK_NORMAL);
 73		list_del_init(&curr->task_list);
 74
 75		if (list_empty(&tmp))
 76			break;
 77
 78		raw_spin_unlock_irq(&q->lock);
 79		raw_spin_lock_irq(&q->lock);
 80	}
 81	raw_spin_unlock_irq(&q->lock);
 82}
 83EXPORT_SYMBOL(swake_up_all);
 84
 85void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
 86{
 87	wait->task = current;
 88	if (list_empty(&wait->task_list))
 89		list_add_tail(&wait->task_list, &q->task_list);
 90}
 91
 92void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
 93{
 94	unsigned long flags;
 95
 96	raw_spin_lock_irqsave(&q->lock, flags);
 97	__prepare_to_swait(q, wait);
 98	set_current_state(state);
 99	raw_spin_unlock_irqrestore(&q->lock, flags);
100}
101EXPORT_SYMBOL(prepare_to_swait_exclusive);
102
103long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
104{
105	unsigned long flags;
106	long ret = 0;
107
108	raw_spin_lock_irqsave(&q->lock, flags);
109	if (signal_pending_state(state, current)) {
110		/*
111		 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
112		 * must not see us.
113		 */
114		list_del_init(&wait->task_list);
115		ret = -ERESTARTSYS;
116	} else {
117		__prepare_to_swait(q, wait);
118		set_current_state(state);
119	}
120	raw_spin_unlock_irqrestore(&q->lock, flags);
121
122	return ret;
123}
124EXPORT_SYMBOL(prepare_to_swait_event);
125
126void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
127{
128	__set_current_state(TASK_RUNNING);
129	if (!list_empty(&wait->task_list))
130		list_del_init(&wait->task_list);
131}
132
133void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
134{
135	unsigned long flags;
136
137	__set_current_state(TASK_RUNNING);
138
139	if (!list_empty_careful(&wait->task_list)) {
140		raw_spin_lock_irqsave(&q->lock, flags);
141		list_del_init(&wait->task_list);
142		raw_spin_unlock_irqrestore(&q->lock, flags);
143	}
144}
145EXPORT_SYMBOL(finish_swait);