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);