_flock_stub.c revision 165968 
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: head/lib/libc/stdio/_flock_stub.c 165968 2007-01-12 07:31:30Z imp $");
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
58/*
59 * We need to retain binary compatibility for a while.  So pretend
60 * that _lock is part of FILE * even though it is dereferenced off
61 * _extra now.  When we stop encoding the size of FILE into binaries
62 * this can be changed in stdio.h.  This will reduce the amount of
63 * code that has to change in the future (just remove this comment
64 * and #define).
65 */
66#define _lock _extra
67
68void
69_flockfile(FILE *fp)
70{
71	pthread_t curthread = _pthread_self();
72
73	if (fp->_lock->fl_owner == curthread)
74		fp->_lock->fl_count++;
75	else {
76		/*
77		 * Make sure this mutex is treated as a private
78		 * internal mutex:
79		 */
80		_pthread_mutex_lock(&fp->_lock->fl_mutex);
81		fp->_lock->fl_owner = curthread;
82		fp->_lock->fl_count = 1;
83	}
84}
85
86/*
87 * This can be overriden by the threads library if it is linked in.
88 */
89void
90_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
91{
92	_flockfile(fp);
93}
94
95int
96_ftrylockfile(FILE *fp)
97{
98	pthread_t curthread = _pthread_self();
99	int	ret = 0;
100
101	if (fp->_lock->fl_owner == curthread)
102		fp->_lock->fl_count++;
103	/*
104	 * Make sure this mutex is treated as a private
105	 * internal mutex:
106	 */
107	else if (_pthread_mutex_trylock(&fp->_lock->fl_mutex) == 0) {
108		fp->_lock->fl_owner = curthread;
109		fp->_lock->fl_count = 1;
110	}
111	else
112		ret = -1;
113	return (ret);
114}
115
116void
117_funlockfile(FILE *fp)
118{
119	pthread_t	curthread = _pthread_self();
120
121	/*
122	 * Check if this file is owned by the current thread:
123	 */
124	if (fp->_lock->fl_owner == curthread) {
125		/*
126		 * Check if this thread has locked the FILE
127		 * more than once:
128		 */
129		if (fp->_lock->fl_count > 1)
130			/*
131			 * Decrement the count of the number of
132			 * times the running thread has locked this
133			 * file:
134			 */
135			fp->_lock->fl_count--;
136		else {
137			/*
138			 * The running thread will release the
139			 * lock now:
140			 */
141			fp->_lock->fl_count = 0;
142			fp->_lock->fl_owner = NULL;
143			_pthread_mutex_unlock(&fp->_lock->fl_mutex);
144		}
145	}
146}
147