1 /*
2 * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
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, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the author nor the names of any co-contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*
31 * POSIX stdio FILE locking functions. These assume that the locking
32 * is only required at FILE structure level, not at file descriptor
33 * level too.
34 *
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
39
40 #include "namespace.h"
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44 #include <pthread.h>
45 #include "un-namespace.h"
46
47 #include "local.h"
48
49
50 /*
51 * Weak symbols for externally visible functions in this file:
52 */
53 __weak_reference(_flockfile, flockfile);
54 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
55 __weak_reference(_ftrylockfile, ftrylockfile);
56 __weak_reference(_funlockfile, funlockfile);
57
58 void _flockfile_debug_stub(FILE *, char *, int);
59 int _ftrylockfile(FILE *);
60
61 void
_flockfile(FILE * fp)62 _flockfile(FILE *fp)
63 {
64 pthread_t curthread = _pthread_self();
65
66 if (fp->_fl_owner == curthread)
67 fp->_fl_count++;
68 else {
69 /*
70 * Make sure this mutex is treated as a private
71 * internal mutex:
72 */
73 _pthread_mutex_lock(&fp->_fl_mutex);
74 fp->_fl_owner = curthread;
75 fp->_fl_count = 1;
76 }
77 }
78
79 /*
80 * This can be overriden by the threads library if it is linked in.
81 */
82 void
_flockfile_debug_stub(FILE * fp,char * fname,int lineno)83 _flockfile_debug_stub(FILE *fp, char *fname, int lineno)
84 {
85 _flockfile(fp);
86 }
87
88 int
_ftrylockfile(FILE * fp)89 _ftrylockfile(FILE *fp)
90 {
91 pthread_t curthread = _pthread_self();
92 int ret = 0;
93
94 if (fp->_fl_owner == curthread)
95 fp->_fl_count++;
96 /*
97 * Make sure this mutex is treated as a private
98 * internal mutex:
99 */
100 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
101 fp->_fl_owner = curthread;
102 fp->_fl_count = 1;
103 }
104 else
105 ret = -1;
106 return (ret);
107 }
108
109 void
_funlockfile(FILE * fp)110 _funlockfile(FILE *fp)
111 {
112 pthread_t curthread = _pthread_self();
113
114 /*
115 * Check if this file is owned by the current thread:
116 */
117 if (fp->_fl_owner == curthread) {
118 /*
119 * Check if this thread has locked the FILE
120 * more than once:
121 */
122 if (fp->_fl_count > 1)
123 /*
124 * Decrement the count of the number of
125 * times the running thread has locked this
126 * file:
127 */
128 fp->_fl_count--;
129 else {
130 /*
131 * The running thread will release the
132 * lock now:
133 */
134 fp->_fl_count = 0;
135 fp->_fl_owner = NULL;
136 _pthread_mutex_unlock(&fp->_fl_mutex);
137 }
138 }
139 }
140