1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
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, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the author nor the names of any co-contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 /*
33 * POSIX stdio FILE locking functions. These assume that the locking
34 * is only required at FILE structure level, not at file descriptor
35 * level too.
36 *
37 */
38
39 #include "namespace.h"
40 #include <stdio.h>
41 #include <stdlib.h>
42 #include <string.h>
43 #include <pthread.h>
44 #include "un-namespace.h"
45
46 #include "local.h"
47
48
49 /*
50 * Weak symbols for externally visible functions in this file:
51 */
52 __weak_reference(_flockfile, flockfile);
53 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
54 __weak_reference(_ftrylockfile, ftrylockfile);
55 __weak_reference(_funlockfile, funlockfile);
56
57 void _flockfile_debug_stub(FILE *, char *, int);
58 int _ftrylockfile(FILE *);
59
60 void
_flockfile(FILE * fp)61 _flockfile(FILE *fp)
62 {
63 pthread_t curthread = _pthread_self();
64
65 if (fp->_fl_owner == curthread)
66 fp->_fl_count++;
67 else {
68 /*
69 * Make sure this mutex is treated as a private
70 * internal mutex:
71 */
72 _pthread_mutex_lock(&fp->_fl_mutex);
73 fp->_fl_owner = curthread;
74 fp->_fl_count = 1;
75 }
76 }
77
78 /*
79 * This can be overriden by the threads library if it is linked in.
80 */
81 void
_flockfile_debug_stub(FILE * fp,char * fname,int lineno)82 _flockfile_debug_stub(FILE *fp, char *fname, int lineno)
83 {
84 _flockfile(fp);
85 }
86
87 int
_ftrylockfile(FILE * fp)88 _ftrylockfile(FILE *fp)
89 {
90 pthread_t curthread = _pthread_self();
91 int ret = 0;
92
93 if (fp->_fl_owner == curthread)
94 fp->_fl_count++;
95 /*
96 * Make sure this mutex is treated as a private
97 * internal mutex:
98 */
99 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
100 fp->_fl_owner = curthread;
101 fp->_fl_count = 1;
102 }
103 else
104 ret = -1;
105 return (ret);
106 }
107
108 void
_funlockfile(FILE * fp)109 _funlockfile(FILE *fp)
110 {
111 pthread_t curthread = _pthread_self();
112
113 /*
114 * Check if this file is owned by the current thread:
115 */
116 if (fp->_fl_owner == curthread) {
117 /*
118 * Check if this thread has locked the FILE
119 * more than once:
120 */
121 if (fp->_fl_count > 1)
122 /*
123 * Decrement the count of the number of
124 * times the running thread has locked this
125 * file:
126 */
127 fp->_fl_count--;
128 else {
129 /*
130 * The running thread will release the
131 * lock now:
132 */
133 fp->_fl_count = 0;
134 fp->_fl_owner = NULL;
135 _pthread_mutex_unlock(&fp->_fl_mutex);
136 }
137 }
138 }
139