thr_once.c revision 303708 
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 unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/11/lib/libthr/thread/thr_once.c 303708 2016-08-03 10:18:52Z kib $");
29
30#include "namespace.h"
31#include <pthread.h>
32#include "un-namespace.h"
33
34#include "thr_private.h"
35
36__weak_reference(_pthread_once, pthread_once);
37
38#define ONCE_NEVER_DONE		PTHREAD_NEEDS_INIT
39#define ONCE_DONE		PTHREAD_DONE_INIT
40#define	ONCE_IN_PROGRESS	0x02
41#define ONCE_WAIT		0x03
42
43/*
44 * POSIX:
45 * The pthread_once() function is not a cancellation point. However,
46 * if init_routine is a cancellation point and is canceled, the effect
47 * on once_control shall be as if pthread_once() was never called.
48 */
49
50static void
51once_cancel_handler(void *arg)
52{
53	pthread_once_t *once_control;
54
55	once_control = arg;
56	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
57	    ONCE_NEVER_DONE))
58		return;
59	atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
60	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
61}
62
63int
64_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
65{
66	struct pthread *curthread;
67	int state;
68
69	_thr_check_init();
70
71	for (;;) {
72		state = once_control->state;
73		if (state == ONCE_DONE) {
74			atomic_thread_fence_acq();
75			return (0);
76		}
77		if (state == ONCE_NEVER_DONE) {
78			if (atomic_cmpset_int(&once_control->state, state,
79			    ONCE_IN_PROGRESS))
80				break;
81		} else if (state == ONCE_IN_PROGRESS) {
82			if (atomic_cmpset_int(&once_control->state, state,
83			    ONCE_WAIT))
84				_thr_umtx_wait_uint(&once_control->state,
85				    ONCE_WAIT, NULL, 0);
86		} else if (state == ONCE_WAIT) {
87			_thr_umtx_wait_uint(&once_control->state, state,
88			    NULL, 0);
89		} else
90			return (EINVAL);
91        }
92
93	curthread = _get_curthread();
94	THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
95	init_routine();
96	THR_CLEANUP_POP(curthread, 0);
97	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
98	    ONCE_DONE))
99		return (0);
100	atomic_store_rel_int(&once_control->state, ONCE_DONE);
101	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
102	return (0);
103}
104