kernel - Fix condvar races
[dragonfly.git] / sys / kern / kern_condvar.c
1 #include <sys/condvar.h>
2 #include <sys/spinlock2.h>
3 #include <sys/systm.h>
4 #include <sys/lock.h>
5
6 void
7 cv_init(struct cv *c, const char *desc)
8 {
9         c->cv_desc = desc;
10         c->cv_waiters = 0;
11         spin_init(&c->cv_lock);
12 }
13
14 void
15 cv_destroy(struct cv *c)
16 {
17         spin_uninit(&c->cv_lock);
18 }
19
20 int
21 _cv_timedwait(struct cv *c, struct lock *lk, int timo, int wakesig)
22 {
23         int flags = wakesig ? PCATCH : 0;
24         int error;
25
26         /*
27          * Can interlock without critical section/spinlock as long
28          * as we don't block before calling *sleep().  PINTERLOCKED
29          * must be passed to the *sleep() to use the manual interlock
30          * (else a new one is created which opens a timing race).
31          */
32         tsleep_interlock(c, flags);
33
34         spin_lock(&c->cv_lock);
35         c->cv_waiters++;
36         spin_unlock(&c->cv_lock);
37
38         if (lk)
39                 error = lksleep(c, lk, flags | PINTERLOCKED, c->cv_desc, timo);
40         else
41                 error = tsleep(c, flags | PINTERLOCKED, c->cv_desc, timo);
42
43         return (error);
44 }
45
46 void
47 _cv_signal(struct cv *c, int broadcast)
48 {
49         spin_lock(&c->cv_lock);
50         if (c->cv_waiters == 0) {
51                 spin_unlock(&c->cv_lock);
52         } else if (broadcast) {
53                 c->cv_waiters = 0;
54                 spin_unlock(&c->cv_lock);       /* must unlock first */
55                 wakeup(c);
56         } else {
57                 c->cv_waiters--;
58                 spin_unlock(&c->cv_lock);       /* must unlock first */
59                 wakeup_one(c);
60         }
61 }
62
63 int
64 cv_has_waiters(const struct cv *c)
65 {
66         return (c->cv_waiters);
67 }