blob: 05c8604627eb0ae085913a91a17013604e83f359
1 | #include <linux/slab.h> |
2 | #include <linux/spinlock.h> |
3 | #include <linux/once.h> |
4 | #include <linux/random.h> |
5 | |
6 | struct once_work { |
7 | struct work_struct work; |
8 | struct static_key *key; |
9 | }; |
10 | |
11 | static void once_deferred(struct work_struct *w) |
12 | { |
13 | struct once_work *work; |
14 | |
15 | work = container_of(w, struct once_work, work); |
16 | BUG_ON(!static_key_enabled(work->key)); |
17 | static_key_slow_dec(work->key); |
18 | kfree(work); |
19 | } |
20 | |
21 | static void once_disable_jump(struct static_key *key) |
22 | { |
23 | struct once_work *w; |
24 | |
25 | w = kmalloc(sizeof(*w), GFP_ATOMIC); |
26 | if (!w) |
27 | return; |
28 | |
29 | INIT_WORK(&w->work, once_deferred); |
30 | w->key = key; |
31 | schedule_work(&w->work); |
32 | } |
33 | |
34 | static DEFINE_SPINLOCK(once_lock); |
35 | |
36 | bool __do_once_start(bool *done, unsigned long *flags) |
37 | __acquires(once_lock) |
38 | { |
39 | spin_lock_irqsave(&once_lock, *flags); |
40 | if (*done) { |
41 | spin_unlock_irqrestore(&once_lock, *flags); |
42 | /* Keep sparse happy by restoring an even lock count on |
43 | * this lock. In case we return here, we don't call into |
44 | * __do_once_done but return early in the DO_ONCE() macro. |
45 | */ |
46 | __acquire(once_lock); |
47 | return false; |
48 | } |
49 | |
50 | return true; |
51 | } |
52 | EXPORT_SYMBOL(__do_once_start); |
53 | |
54 | void __do_once_done(bool *done, struct static_key *once_key, |
55 | unsigned long *flags) |
56 | __releases(once_lock) |
57 | { |
58 | *done = true; |
59 | spin_unlock_irqrestore(&once_lock, *flags); |
60 | once_disable_jump(once_key); |
61 | } |
62 | EXPORT_SYMBOL(__do_once_done); |
63 |