1 /*
2 * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 *
25 */
26
27 #include "namespace.h"
28 #include <pthread.h>
29 #include "un-namespace.h"
30
31 #include "thr_private.h"
32
33 #define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT
34 #define ONCE_DONE PTHREAD_DONE_INIT
35 #define ONCE_IN_PROGRESS 0x02
36 #define ONCE_MASK 0x03
37
38 static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER;
39 static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;
40
41 /*
42 * POSIX:
43 * The pthread_once() function is not a cancellation point. However,
44 * if init_routine is a cancellation point and is canceled, the effect
45 * on once_control shall be as if pthread_once() was never called.
46 */
47
48 static void
once_cancel_handler(void * arg)49 once_cancel_handler(void *arg)
50 {
51 pthread_once_t *once_control = arg;
52
53 _pthread_mutex_lock(&once_lock);
54 once_control->__state = ONCE_NEVER_DONE;
55 _pthread_mutex_unlock(&once_lock);
56 _pthread_cond_broadcast(&once_cv);
57 }
58
59 int
_pthread_once(pthread_once_t * once_control,void (* init_routine)(void))60 _pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
61 {
62 int wakeup = 0;
63
64 _thr_check_init();
65
66 if (once_control->__state == ONCE_DONE)
67 return (0);
68 _pthread_mutex_lock(&once_lock);
69 while (*(volatile int *)&(once_control->__state) == ONCE_IN_PROGRESS)
70 _pthread_cond_wait(&once_cv, &once_lock);
71 /*
72 * If previous thread was canceled, then the state still
73 * could be ONCE_NEVER_DONE, we need to check it again.
74 */
75 if (*(volatile int *)&(once_control->__state) == ONCE_NEVER_DONE) {
76 once_control->__state = ONCE_IN_PROGRESS;
77 _pthread_mutex_unlock(&once_lock);
78 _pthread_cleanup_push(once_cancel_handler, once_control);
79 init_routine();
80 _pthread_cleanup_pop(0);
81 _pthread_mutex_lock(&once_lock);
82 once_control->__state = ONCE_DONE;
83 wakeup = 1;
84 }
85 _pthread_mutex_unlock(&once_lock);
86 if (wakeup)
87 _pthread_cond_broadcast(&once_cv);
88 return (0);
89 }
90
91 __strong_reference(_pthread_once, pthread_once);
92