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
58void _flockfile_debug_stub(FILE *, char *, int);
59int _ftrylockfile(FILE *);
60
61void
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 */
82void
83_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
84{
85	_flockfile(fp);
86}
87
88int
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
109void
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