Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64...
[platform/kernel/linux-rpi.git] / lib / once.c
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 *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_key_slow_dec(work->key);
19         kfree(work);
20 }
21
22 static void once_disable_jump(struct static_key *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 *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);