blob: 6e52801eefac21e0dbdfe8383eef85964befe605 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
|
/***
This file is part of PulseAudio.
Copyright 2006 Lennart Poettering
PulseAudio is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License,
or (at your option) any later version.
PulseAudio is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
***/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <pulsecore/macro.h>
#include "once.h"
/* See http://www.hpl.hp.com/research/linux/atomic_ops/example.php4 for the
* reference algorithm used here. */
bool pa_once_begin(pa_once *control) {
pa_mutex *m;
pa_assert(control);
if (pa_atomic_load(&control->done))
return false;
/* Caveat: We have to make sure that the once func has completed
* before returning, even if the once func is not actually
* executed by us. Hence the awkward locking. */
m = pa_static_mutex_get(&control->mutex, false, false);
pa_mutex_lock(m);
if (pa_atomic_load(&control->done)) {
pa_mutex_unlock(m);
return false;
}
return true;
}
void pa_once_end(pa_once *control) {
pa_mutex *m;
pa_assert(control);
pa_assert(!pa_atomic_load(&control->done));
pa_atomic_store(&control->done, 1);
m = pa_static_mutex_get(&control->mutex, false, false);
pa_mutex_unlock(m);
}
/* Not reentrant -- how could it be? */
void pa_run_once(pa_once *control, pa_once_func_t func) {
pa_assert(control);
pa_assert(func);
if (pa_once_begin(control)) {
func();
pa_once_end(control);
}
}
|
