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); |
64 | |