thr_once.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2005, David Xu <davidxu@freebsd.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice unmodified, this list of conditions, and the following
12 *    disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include <sys/cdefs.h>
30__FBSDID("$FreeBSD: stable/11/lib/libthr/thread/thr_once.c 330897 2018-03-14 03:19:51Z eadler $");
31
32#include "namespace.h"
33#include <pthread.h>
34#include "un-namespace.h"
35
36#include "thr_private.h"
37
38__weak_reference(_pthread_once, pthread_once);
39
40#define ONCE_NEVER_DONE		PTHREAD_NEEDS_INIT
41#define ONCE_DONE		PTHREAD_DONE_INIT
42#define	ONCE_IN_PROGRESS	0x02
43#define ONCE_WAIT		0x03
44
45/*
46 * POSIX:
47 * The pthread_once() function is not a cancellation point. However,
48 * if init_routine is a cancellation point and is canceled, the effect
49 * on once_control shall be as if pthread_once() was never called.
50 */
51
52static void
53once_cancel_handler(void *arg)
54{
55	pthread_once_t *once_control;
56
57	once_control = arg;
58	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
59	    ONCE_NEVER_DONE))
60		return;
61	atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
62	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
63}
64
65int
66_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
67{
68	struct pthread *curthread;
69	int state;
70
71	_thr_check_init();
72
73	for (;;) {
74		state = once_control->state;
75		if (state == ONCE_DONE) {
76			atomic_thread_fence_acq();
77			return (0);
78		}
79		if (state == ONCE_NEVER_DONE) {
80			if (atomic_cmpset_int(&once_control->state, state,
81			    ONCE_IN_PROGRESS))
82				break;
83		} else if (state == ONCE_IN_PROGRESS) {
84			if (atomic_cmpset_int(&once_control->state, state,
85			    ONCE_WAIT))
86				_thr_umtx_wait_uint(&once_control->state,
87				    ONCE_WAIT, NULL, 0);
88		} else if (state == ONCE_WAIT) {
89			_thr_umtx_wait_uint(&once_control->state, state,
90			    NULL, 0);
91		} else
92			return (EINVAL);
93        }
94
95	curthread = _get_curthread();
96	THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
97	init_routine();
98	THR_CLEANUP_POP(curthread, 0);
99	if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS,
100	    ONCE_DONE))
101		return (0);
102	atomic_store_rel_int(&once_control->state, ONCE_DONE);
103	_thr_umtx_wake(&once_control->state, INT_MAX, 0);
104	return (0);
105}
106