1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * <linux/swait.h> (simple wait queues ) implementation: |
4 | */ |
5 | |
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(list: &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 | */ |
21 | void swake_up_locked(struct swait_queue_head *q, int wake_flags) |
22 | { |
23 | struct swait_queue *curr; |
24 | |
25 | if (list_empty(head: &q->task_list)) |
26 | return; |
27 | |
28 | curr = list_first_entry(&q->task_list, typeof(*curr), task_list); |
29 | try_to_wake_up(tsk: curr->task, TASK_NORMAL, wake_flags); |
30 | list_del_init(entry: &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 | */ |
41 | void swake_up_all_locked(struct swait_queue_head *q) |
42 | { |
43 | while (!list_empty(head: &q->task_list)) |
44 | swake_up_locked(q, 0); |
45 | } |
46 | |
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 | */ |
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(list: &q->task_list, head: &tmp); |
68 | while (!list_empty(head: &tmp)) { |
69 | curr = list_first_entry(&tmp, typeof(*curr), task_list); |
70 | |
71 | wake_up_state(tsk: curr->task, TASK_NORMAL); |
72 | list_del_init(entry: &curr->task_list); |
73 | |
74 | if (list_empty(head: &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 | |
84 | void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait) |
85 | { |
86 | wait->task = current; |
87 | if (list_empty(head: &wait->task_list)) |
88 | list_add_tail(new: &wait->task_list, head: &q->task_list); |
89 | } |
90 | |
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 | |
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(entry: &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 | |
125 | void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait) |
126 | { |
127 | __set_current_state(TASK_RUNNING); |
128 | if (!list_empty(head: &wait->task_list)) |
129 | list_del_init(entry: &wait->task_list); |
130 | } |
131 | |
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(head: &wait->task_list)) { |
139 | raw_spin_lock_irqsave(&q->lock, flags); |
140 | list_del_init(entry: &wait->task_list); |
141 | raw_spin_unlock_irqrestore(&q->lock, flags); |
142 | } |
143 | } |
144 | EXPORT_SYMBOL(finish_swait); |
145 | |