1// SPDX-License-Identifier: GPL-2.0
2/*
3 * <linux/swait.h> (simple wait queues ) implementation:
4 */
5
6void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
7			     struct lock_class_key *key)
8{
9	raw_spin_lock_init(&q->lock);
10	lockdep_set_class_and_name(&q->lock, key, name);
11	INIT_LIST_HEAD(&q->task_list);
12}
13EXPORT_SYMBOL(__init_swait_queue_head);
14
15/*
16 * The thing about the wake_up_state() return value; I think we can ignore it.
17 *
18 * If for some reason it would return 0, that means the previously waiting
19 * task is already running, so it will observe condition true (or has already).
20 */
21void swake_up_locked(struct swait_queue_head *q, int wake_flags)
22{
23	struct swait_queue *curr;
24
25	if (list_empty(&q->task_list))
26		return;
27
28	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
29	try_to_wake_up(curr->task, TASK_NORMAL, wake_flags);
30	list_del_init(&curr->task_list);
31}
32EXPORT_SYMBOL(swake_up_locked);
33
34/*
35 * Wake up all waiters. This is an interface which is solely exposed for
36 * completions and not for general usage.
37 *
38 * It is intentionally different from swake_up_all() to allow usage from
39 * hard interrupt context and interrupt disabled regions.
40 */
41void swake_up_all_locked(struct swait_queue_head *q)
42{
43	while (!list_empty(&q->task_list))
44		swake_up_locked(q, 0);
45}
46
47void swake_up_one(struct swait_queue_head *q)
48{
49	unsigned long flags;
50
51	raw_spin_lock_irqsave(&q->lock, flags);
52	swake_up_locked(q, 0);
53	raw_spin_unlock_irqrestore(&q->lock, flags);
54}
55EXPORT_SYMBOL(swake_up_one);
56
57/*
58 * Does not allow usage from IRQ disabled, since we must be able to
59 * release IRQs to guarantee bounded hold time.
60 */
61void swake_up_all(struct swait_queue_head *q)
62{
63	struct swait_queue *curr;
64	LIST_HEAD(tmp);
65
66	raw_spin_lock_irq(&q->lock);
67	list_splice_init(&q->task_list, &tmp);
68	while (!list_empty(&tmp)) {
69		curr = list_first_entry(&tmp, typeof(*curr), task_list);
70
71		wake_up_state(curr->task, TASK_NORMAL);
72		list_del_init(&curr->task_list);
73
74		if (list_empty(&tmp))
75			break;
76
77		raw_spin_unlock_irq(&q->lock);
78		raw_spin_lock_irq(&q->lock);
79	}
80	raw_spin_unlock_irq(&q->lock);
81}
82EXPORT_SYMBOL(swake_up_all);
83
84void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
85{
86	wait->task = current;
87	if (list_empty(&wait->task_list))
88		list_add_tail(&wait->task_list, &q->task_list);
89}
90
91void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
92{
93	unsigned long flags;
94
95	raw_spin_lock_irqsave(&q->lock, flags);
96	__prepare_to_swait(q, wait);
97	set_current_state(state);
98	raw_spin_unlock_irqrestore(&q->lock, flags);
99}
100EXPORT_SYMBOL(prepare_to_swait_exclusive);
101
102long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
103{
104	unsigned long flags;
105	long ret = 0;
106
107	raw_spin_lock_irqsave(&q->lock, flags);
108	if (signal_pending_state(state, current)) {
109		/*
110		 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
111		 * must not see us.
112		 */
113		list_del_init(&wait->task_list);
114		ret = -ERESTARTSYS;
115	} else {
116		__prepare_to_swait(q, wait);
117		set_current_state(state);
118	}
119	raw_spin_unlock_irqrestore(&q->lock, flags);
120
121	return ret;
122}
123EXPORT_SYMBOL(prepare_to_swait_event);
124
125void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
126{
127	__set_current_state(TASK_RUNNING);
128	if (!list_empty(&wait->task_list))
129		list_del_init(&wait->task_list);
130}
131
132void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
133{
134	unsigned long flags;
135
136	__set_current_state(TASK_RUNNING);
137
138	if (!list_empty_careful(&wait->task_list)) {
139		raw_spin_lock_irqsave(&q->lock, flags);
140		list_del_init(&wait->task_list);
141		raw_spin_unlock_irqrestore(&q->lock, flags);
142	}
143}
144EXPORT_SYMBOL(finish_swait);
145