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 * $FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.16 2008/04/17 22:17:53 jhb Exp $
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 <pthread.h>
42 #include "un-namespace.h"
43
44 #include "local.h"
45
46 void _flockfile_debug_stub(FILE *, char *, int);
47 int _ftrylockfile(FILE *);
48
49 void
_flockfile(FILE * fp)50 _flockfile(FILE *fp)
51 {
52 pthread_t curthread = _pthread_self();
53
54 if (fp->_fl_owner == curthread)
55 fp->_fl_count++;
56 else {
57 /*
58 * Make sure this mutex is treated as a private
59 * internal mutex:
60 */
61 _pthread_mutex_lock(&fp->_fl_mutex);
62 fp->_fl_owner = curthread;
63 fp->_fl_count = 1;
64 }
65 }
66
67 /*
68 * This can be overridden by the threads library if it is linked in.
69 */
70 void
_flockfile_debug_stub(FILE * fp,char * fname __unused,int lineno __unused)71 _flockfile_debug_stub(FILE *fp, char *fname __unused, int lineno __unused)
72 {
73 _flockfile(fp);
74 }
75
76 int
_ftrylockfile(FILE * fp)77 _ftrylockfile(FILE *fp)
78 {
79 pthread_t curthread = _pthread_self();
80 int ret = 0;
81
82 if (fp->_fl_owner == curthread)
83 fp->_fl_count++;
84 /*
85 * Make sure this mutex is treated as a private
86 * internal mutex:
87 */
88 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
89 fp->_fl_owner = curthread;
90 fp->_fl_count = 1;
91 }
92 else
93 ret = -1;
94 return (ret);
95 }
96
97 void
_funlockfile(FILE * fp)98 _funlockfile(FILE *fp)
99 {
100 pthread_t curthread = _pthread_self();
101
102 /*
103 * Check if this file is owned by the current thread:
104 */
105 if (fp->_fl_owner == curthread) {
106 /*
107 * Check if this thread has locked the FILE
108 * more than once:
109 */
110 if (fp->_fl_count > 1) {
111 /*
112 * Decrement the count of the number of
113 * times the running thread has locked this
114 * file:
115 */
116 fp->_fl_count--;
117 } else {
118 /*
119 * The running thread will release the
120 * lock now:
121 */
122 fp->_fl_count = 0;
123 fp->_fl_owner = NULL;
124 _pthread_mutex_unlock(&fp->_fl_mutex);
125 }
126 }
127 }
128
129 /*
130 * Weak symbols for externally visible functions in this file:
131 */
132 __weak_reference(_flockfile, flockfile);
133 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
134 __weak_reference(_ftrylockfile, ftrylockfile);
135 __weak_reference(_funlockfile, funlockfile);
136