thr_once.c revision 303709
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 * $FreeBSD: stable/10/lib/libthr/thread/thr_once.c 303709 2016-08-03 10:23:42Z kib $
27 *
28 */
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 = arg;
54
55	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_NEVER_DONE))
56		return;
57	atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
58	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
59}
60
61int
62_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
63{
64	struct pthread *curthread;
65	int state;
66
67	_thr_check_init();
68
69	for (;;) {
70		state = once_control->state;
71		if (state == ONCE_DONE)
72			return (0);
73		if (state == ONCE_NEVER_DONE) {
74			if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_IN_PROGRESS))
75				break;
76		} else if (state == ONCE_IN_PROGRESS) {
77			if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_WAIT))
78				_thr_umtx_wait_uint(&once_control->state, ONCE_WAIT, NULL, 0);
79		} else if (state == ONCE_WAIT) {
80			_thr_umtx_wait_uint(&once_control->state, state, NULL, 0);
81		} else
82			return (EINVAL);
83        }
84
85	curthread = _get_curthread();
86	THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
87	init_routine();
88	THR_CLEANUP_POP(curthread, 0);
89	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_DONE))
90		return (0);
91	atomic_store_rel_int(&once_control->state, ONCE_DONE);
92	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
93	return (0);
94}
95