summaryrefslogtreecommitdiff
path: root/kernel/sched/swait.c
blob: 66b59ac77c2209fd9fccd92c8ae0c660e7428e4d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
// SPDX-License-Identifier: GPL-2.0
/*
 * <linux/swait.h> (simple wait queues ) implementation:
 */
#include "sched.h"

void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
			     struct lock_class_key *key)
{
	raw_spin_lock_init(&q->lock);
	lockdep_set_class_and_name(&q->lock, key, name);
	INIT_LIST_HEAD(&q->task_list);
}
EXPORT_SYMBOL(__init_swait_queue_head);

/*
 * The thing about the wake_up_state() return value; I think we can ignore it.
 *
 * If for some reason it would return 0, that means the previously waiting
 * task is already running, so it will observe condition true (or has already).
 */
void swake_up_locked(struct swait_queue_head *q)
{
	struct swait_queue *curr;

	if (list_empty(&q->task_list))
		return;

	curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
	wake_up_process(curr->task);
	list_del_init(&curr->task_list);
}
EXPORT_SYMBOL(swake_up_locked);

void swake_up_one(struct swait_queue_head *q)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&q->lock, flags);
	swake_up_locked(q);
	raw_spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(swake_up_one);

/*
 * Does not allow usage from IRQ disabled, since we must be able to
 * release IRQs to guarantee bounded hold time.
 */
void swake_up_all(struct swait_queue_head *q)
{
	struct swait_queue *curr;
	LIST_HEAD(tmp);

	raw_spin_lock_irq(&q->lock);
	list_splice_init(&q->task_list, &tmp);
	while (!list_empty(&tmp)) {
		curr = list_first_entry(&tmp, typeof(*curr), task_list);

		wake_up_state(curr->task, TASK_NORMAL);
		list_del_init(&curr->task_list);

		if (list_empty(&tmp))
			break;

		raw_spin_unlock_irq(&q->lock);
		raw_spin_lock_irq(&q->lock);
	}
	raw_spin_unlock_irq(&q->lock);
}
EXPORT_SYMBOL(swake_up_all);

static void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
{
	wait->task = current;
	if (list_empty(&wait->task_list))
		list_add_tail(&wait->task_list, &q->task_list);
}

void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&q->lock, flags);
	__prepare_to_swait(q, wait);
	set_current_state(state);
	raw_spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(prepare_to_swait_exclusive);

long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
{
	unsigned long flags;
	long ret = 0;

	raw_spin_lock_irqsave(&q->lock, flags);
	if (unlikely(signal_pending_state(state, current))) {
		/*
		 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
		 * must not see us.
		 */
		list_del_init(&wait->task_list);
		ret = -ERESTARTSYS;
	} else {
		__prepare_to_swait(q, wait);
		set_current_state(state);
	}
	raw_spin_unlock_irqrestore(&q->lock, flags);

	return ret;
}
EXPORT_SYMBOL(prepare_to_swait_event);

void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
{
	__set_current_state(TASK_RUNNING);
	if (!list_empty(&wait->task_list))
		list_del_init(&wait->task_list);
}

void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
{
	unsigned long flags;

	__set_current_state(TASK_RUNNING);

	if (!list_empty_careful(&wait->task_list)) {
		raw_spin_lock_irqsave(&q->lock, flags);
		list_del_init(&wait->task_list);
		raw_spin_unlock_irqrestore(&q->lock, flags);
	}
}
EXPORT_SYMBOL(finish_swait);