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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 | #include <linux/module.h> | |
7 | ||
8 | struct once_work { | |
9 | struct work_struct work; | |
10 | struct static_key_true *key; | |
11 | struct module *module; | |
12 | }; | |
13 | ||
14 | static void once_deferred(struct work_struct *w) | |
15 | { | |
16 | struct once_work *work; | |
17 | ||
18 | work = container_of(w, struct once_work, work); | |
19 | BUG_ON(!static_key_enabled(work->key)); | |
20 | static_branch_disable(work->key); | |
21 | module_put(work->module); | |
22 | kfree(work); | |
23 | } | |
24 | ||
25 | static void once_disable_jump(struct static_key_true *key, struct module *mod) | |
26 | { | |
27 | struct once_work *w; | |
28 | ||
29 | w = kmalloc(sizeof(*w), GFP_ATOMIC); | |
30 | if (!w) | |
31 | return; | |
32 | ||
33 | INIT_WORK(&w->work, once_deferred); | |
34 | w->key = key; | |
35 | w->module = mod; | |
36 | __module_get(mod); | |
37 | schedule_work(&w->work); | |
38 | } | |
39 | ||
40 | static DEFINE_SPINLOCK(once_lock); | |
41 | ||
42 | bool __do_once_start(bool *done, unsigned long *flags) | |
43 | __acquires(once_lock) | |
44 | { | |
45 | spin_lock_irqsave(&once_lock, *flags); | |
46 | if (*done) { | |
47 | spin_unlock_irqrestore(&once_lock, *flags); | |
48 | /* Keep sparse happy by restoring an even lock count on | |
49 | * this lock. In case we return here, we don't call into | |
50 | * __do_once_done but return early in the DO_ONCE() macro. | |
51 | */ | |
52 | __acquire(once_lock); | |
53 | return false; | |
54 | } | |
55 | ||
56 | return true; | |
57 | } | |
58 | EXPORT_SYMBOL(__do_once_start); | |
59 | ||
60 | void __do_once_done(bool *done, struct static_key_true *once_key, | |
61 | unsigned long *flags, struct module *mod) | |
62 | __releases(once_lock) | |
63 | { | |
64 | *done = true; | |
65 | spin_unlock_irqrestore(&once_lock, *flags); | |
66 | once_disable_jump(once_key, mod); | |
67 | } | |
68 | EXPORT_SYMBOL(__do_once_done); |