1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * <linux/swait.h> (simple wait queues ) implementation:
4  */
5 
__init_swait_queue_head(struct swait_queue_head * q,const char * name,struct lock_class_key * key)6 void __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 }
13 EXPORT_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  */
swake_up_locked(struct swait_queue_head * q,int wake_flags)21 void 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 }
32 EXPORT_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  */
swake_up_all_locked(struct swait_queue_head * q)41 void 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 
swake_up_one(struct swait_queue_head * q)47 void 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 }
55 EXPORT_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  */
swake_up_all(struct swait_queue_head * q)61 void 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 }
82 EXPORT_SYMBOL(swake_up_all);
83 
__prepare_to_swait(struct swait_queue_head * q,struct swait_queue * wait)84 void __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 
prepare_to_swait_exclusive(struct swait_queue_head * q,struct swait_queue * wait,int state)91 void 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 }
100 EXPORT_SYMBOL(prepare_to_swait_exclusive);
101 
prepare_to_swait_event(struct swait_queue_head * q,struct swait_queue * wait,int state)102 long 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 }
123 EXPORT_SYMBOL(prepare_to_swait_event);
124 
__finish_swait(struct swait_queue_head * q,struct swait_queue * wait)125 void __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 
finish_swait(struct swait_queue_head * q,struct swait_queue * wait)132 void 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 }
144 EXPORT_SYMBOL(finish_swait);
145