1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
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 "namespace.h"
30 #include <pthread.h>
31 #include "un-namespace.h"
32
33 #include "thr_private.h"
34
35 __weak_reference(_thr_once, pthread_once);
36 __weak_reference(_thr_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
50 static void
once_cancel_handler(void * arg)51 once_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
63 int
_thr_once(pthread_once_t * once_control,void (* init_routine)(void))64 _thr_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