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 <sys/cdefs.h>
40 __FBSDID("$FreeBSD: stable/12/lib/libc/stdio/_flock_stub.c 326025 2017-11-20 19:49:47Z pfg $");
41
42 #include "namespace.h"
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <string.h>
46 #include <pthread.h>
47 #include "un-namespace.h"
48
49 #include "local.h"
50
51
52 /*
53 * Weak symbols for externally visible functions in this file:
54 */
55 __weak_reference(_flockfile, flockfile);
56 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
57 __weak_reference(_ftrylockfile, ftrylockfile);
58 __weak_reference(_funlockfile, funlockfile);
59
60 void _flockfile_debug_stub(FILE *, char *, int);
61 int _ftrylockfile(FILE *);
62
63 void
_flockfile(FILE * fp)64 _flockfile(FILE *fp)
65 {
66 pthread_t curthread = _pthread_self();
67
68 if (fp->_fl_owner == curthread)
69 fp->_fl_count++;
70 else {
71 /*
72 * Make sure this mutex is treated as a private
73 * internal mutex:
74 */
75 _pthread_mutex_lock(&fp->_fl_mutex);
76 fp->_fl_owner = curthread;
77 fp->_fl_count = 1;
78 }
79 }
80
81 /*
82 * This can be overriden by the threads library if it is linked in.
83 */
84 void
_flockfile_debug_stub(FILE * fp,char * fname,int lineno)85 _flockfile_debug_stub(FILE *fp, char *fname, int lineno)
86 {
87 _flockfile(fp);
88 }
89
90 int
_ftrylockfile(FILE * fp)91 _ftrylockfile(FILE *fp)
92 {
93 pthread_t curthread = _pthread_self();
94 int ret = 0;
95
96 if (fp->_fl_owner == curthread)
97 fp->_fl_count++;
98 /*
99 * Make sure this mutex is treated as a private
100 * internal mutex:
101 */
102 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
103 fp->_fl_owner = curthread;
104 fp->_fl_count = 1;
105 }
106 else
107 ret = -1;
108 return (ret);
109 }
110
111 void
_funlockfile(FILE * fp)112 _funlockfile(FILE *fp)
113 {
114 pthread_t curthread = _pthread_self();
115
116 /*
117 * Check if this file is owned by the current thread:
118 */
119 if (fp->_fl_owner == curthread) {
120 /*
121 * Check if this thread has locked the FILE
122 * more than once:
123 */
124 if (fp->_fl_count > 1)
125 /*
126 * Decrement the count of the number of
127 * times the running thread has locked this
128 * file:
129 */
130 fp->_fl_count--;
131 else {
132 /*
133 * The running thread will release the
134 * lock now:
135 */
136 fp->_fl_count = 0;
137 fp->_fl_owner = NULL;
138 _pthread_mutex_unlock(&fp->_fl_mutex);
139 }
140 }
141 }
142