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
57void _flockfile_debug_stub(FILE *, char *, int);
58int _ftrylockfile(FILE *);
59
60void
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 */
81void
82_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
83{
84	_flockfile(fp);
85}
86
87int
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
108void
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