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
7struct once_work {
8 struct work_struct work;
9 struct static_key_true *key;
10};
11
12static 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
22static 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
35static DEFINE_SPINLOCK(once_lock);
36
37bool __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}
53EXPORT_SYMBOL(__do_once_start);
54
55void __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}
63EXPORT_SYMBOL(__do_once_done);
64