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