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_one(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_one);
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
72static void __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_tail(&wait->task_list, &q->task_list);
77}
78
79void prepare_to_swait_exclusive(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_exclusive);
89
90long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
91{
92 unsigned long flags;
93 long ret = 0;
94
95 raw_spin_lock_irqsave(&q->lock, flags);
96 if (signal_pending_state(state, current)) {
97 /*
98 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
99 * must not see us.
100 */
101 list_del_init(&wait->task_list);
102 ret = -ERESTARTSYS;
103 } else {
104 __prepare_to_swait(q, wait);
105 set_current_state(state);
106 }
107 raw_spin_unlock_irqrestore(&q->lock, flags);
108
109 return ret;
110}
111EXPORT_SYMBOL(prepare_to_swait_event);
112
113void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
114{
115 __set_current_state(TASK_RUNNING);
116 if (!list_empty(&wait->task_list))
117 list_del_init(&wait->task_list);
118}
119
120void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
121{
122 unsigned long flags;
123
124 __set_current_state(TASK_RUNNING);
125
126 if (!list_empty_careful(&wait->task_list)) {
127 raw_spin_lock_irqsave(&q->lock, flags);
128 list_del_init(&wait->task_list);
129 raw_spin_unlock_irqrestore(&q->lock, flags);
130 }
131}
132EXPORT_SYMBOL(finish_swait);
133