1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * <linux/swait.h> (simple wait queues ) implementation:
4 */
5 #include "sched.h"
6
__init_swait_queue_head(struct swait_queue_head * q,const char * name,struct lock_class_key * key)7 void __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 }
14 EXPORT_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 */
swake_up_locked(struct swait_queue_head * q)22 void 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 }
33 EXPORT_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 */
swake_up_all_locked(struct swait_queue_head * q)42 void swake_up_all_locked(struct swait_queue_head *q)
43 {
44 while (!list_empty(&q->task_list))
45 swake_up_locked(q);
46 }
47
swake_up_one(struct swait_queue_head * q)48 void 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);
54 raw_spin_unlock_irqrestore(&q->lock, flags);
55 }
56 EXPORT_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 */
swake_up_all(struct swait_queue_head * q)62 void 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 }
83 EXPORT_SYMBOL(swake_up_all);
84
__prepare_to_swait(struct swait_queue_head * q,struct swait_queue * wait)85 void __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
prepare_to_swait_exclusive(struct swait_queue_head * q,struct swait_queue * wait,int state)92 void 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 }
101 EXPORT_SYMBOL(prepare_to_swait_exclusive);
102
prepare_to_swait_event(struct swait_queue_head * q,struct swait_queue * wait,int state)103 long 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 }
124 EXPORT_SYMBOL(prepare_to_swait_event);
125
__finish_swait(struct swait_queue_head * q,struct swait_queue * wait)126 void __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
finish_swait(struct swait_queue_head * q,struct swait_queue * wait)133 void 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 }
145 EXPORT_SYMBOL(finish_swait);
146