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1 | // SPDX-License-Identifier: GPL-2.0 | |
2 | #include <linux/slab.h> | |
3 | #include <linux/spinlock.h> | |
4 | #include <linux/once.h> | |
5 | #include <linux/random.h> | |
6 | ||
7 | struct once_work { | |
8 | struct work_struct work; | |
9 | struct static_key_true *key; | |
10 | }; | |
11 | ||
12 | static void once_deferred(struct work_struct *w) | |
13 | { | |
14 | struct once_work *work; | |
15 | ||
16 | work = container_of(w, struct once_work, work); | |
17 | BUG_ON(!static_key_enabled(work->key)); | |
18 | static_branch_disable(work->key); | |
19 | kfree(work); | |
20 | } | |
21 | ||
22 | static void once_disable_jump(struct static_key_true *key) | |
23 | { | |
24 | struct once_work *w; | |
25 | ||
26 | w = kmalloc(sizeof(*w), GFP_ATOMIC); | |
27 | if (!w) | |
28 | return; | |
29 | ||
30 | INIT_WORK(&w->work, once_deferred); | |
31 | w->key = key; | |
32 | schedule_work(&w->work); | |
33 | } | |
34 | ||
35 | static DEFINE_SPINLOCK(once_lock); | |
36 | ||
37 | bool __do_once_start(bool *done, unsigned long *flags) | |
38 | __acquires(once_lock) | |
39 | { | |
40 | spin_lock_irqsave(&once_lock, *flags); | |
41 | if (*done) { | |
42 | spin_unlock_irqrestore(&once_lock, *flags); | |
43 | /* Keep sparse happy by restoring an even lock count on | |
44 | * this lock. In case we return here, we don't call into | |
45 | * __do_once_done but return early in the DO_ONCE() macro. | |
46 | */ | |
47 | __acquire(once_lock); | |
48 | return false; | |
49 | } | |
50 | ||
51 | return true; | |
52 | } | |
53 | EXPORT_SYMBOL(__do_once_start); | |
54 | ||
55 | void __do_once_done(bool *done, struct static_key_true *once_key, | |
56 | unsigned long *flags) | |
57 | __releases(once_lock) | |
58 | { | |
59 | *done = true; | |
60 | spin_unlock_irqrestore(&once_lock, *flags); | |
61 | once_disable_jump(once_key); | |
62 | } | |
63 | EXPORT_SYMBOL(__do_once_done); |