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
once_deferred(struct work_struct * w)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
once_disable_jump(struct static_key_true * key)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
__do_once_start(bool * done,unsigned long * flags)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
__do_once_done(bool * done,struct static_key_true * once_key,unsigned long * flags)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