thr_once.c (bb535300dd871731b2542594a917bc2892479ca0) thr_once.c (a091d823ad89a36935ba6e5568c4720a35f9a99b)
1/*
2 * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
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

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26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $FreeBSD$
33 */
1/*
2 * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
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

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26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $FreeBSD$
33 */
34
35#include "namespace.h"
34#include <pthread.h>
36#include <pthread.h>
37#include "un-namespace.h"
38
35#include "thr_private.h"
36
37__weak_reference(_pthread_once, pthread_once);
38
39#include "thr_private.h"
40
41__weak_reference(_pthread_once, pthread_once);
42
43#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT
44#define ONCE_DONE PTHREAD_DONE_INIT
45#define ONCE_IN_PROGRESS 0x02
46#define ONCE_MASK 0x03
47
48static pthread_mutex_t once_lock = PTHREAD_MUTEX_INITIALIZER;
49static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER;
50
51/*
52 * POSIX:
53 * The pthread_once() function is not a cancellation point. However,
54 * if init_routine is a cancellation point and is canceled, the effect
55 * on once_control shall be as if pthread_once() was never called.
56 */
57
58static void
59once_cancel_handler(void *arg)
60{
61 pthread_once_t *once_control = arg;
62
63 _pthread_mutex_lock(&once_lock);
64 once_control->state = ONCE_NEVER_DONE;
65 _pthread_mutex_unlock(&once_lock);
66 _pthread_cond_broadcast(&once_cv);
67}
68
39int
69int
40_pthread_once(pthread_once_t * once_control, void (*init_routine) (void))
70_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
41{
71{
42 if (once_control->state == PTHREAD_NEEDS_INIT) {
43 if (_thread_initial == NULL)
44 _thread_init();
45 pthread_mutex_lock(&(once_control->mutex));
46 if (once_control->state == PTHREAD_NEEDS_INIT) {
47 init_routine();
48 once_control->state = PTHREAD_DONE_INIT;
49 }
50 pthread_mutex_unlock(&(once_control->mutex));
72 int wakeup = 0;
73
74 if (once_control->state == ONCE_DONE)
75 return (0);
76 _pthread_mutex_lock(&once_lock);
77 while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
78 _pthread_cond_wait(&once_cv, &once_lock);
79 /*
80 * If previous thread was canceled, then the state still
81 * could be ONCE_NEVER_DONE, we need to check it again.
82 */
83 if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
84 once_control->state = ONCE_IN_PROGRESS;
85 _pthread_mutex_unlock(&once_lock);
86 _pthread_cleanup_push(once_cancel_handler, once_control);
87 init_routine();
88 _pthread_cleanup_pop(0);
89 _pthread_mutex_lock(&once_lock);
90 once_control->state = ONCE_DONE;
91 wakeup = 1;
51 }
92 }
93 _pthread_mutex_unlock(&once_lock);
94 if (wakeup)
95 _pthread_cond_broadcast(&once_cv);
52 return (0);
53}
96 return (0);
97}
98