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("$FreeBSD$");
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
60void _flockfile_debug_stub(FILE *, char *, int);
61int _ftrylockfile(FILE *);
62
63void
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 */
84void
85_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
86{
87	_flockfile(fp);
88}
89
90int
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
111void
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