_flock_stub.c revision 73254 
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. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by John Birrell.
16 * 4. Neither the name of the author nor the names of any co-contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $FreeBSD: head/lib/libc/stdio/_flock_stub.c 73254 2001-03-01 05:22:14Z deischen $
33 *
34 */
35
36/*
37 * POSIX stdio FILE locking functions. These assume that the locking
38 * is only required at FILE structure level, not at file descriptor
39 * level too.
40 *
41 */
42
43#include "namespace.h"
44#include <stdio.h>
45#include <stdlib.h>
46#include <string.h>
47#include <pthread.h>
48#include "un-namespace.h"
49
50#include "local.h"
51
52
53/*
54 * Weak symbols for externally visible functions in this file:
55 */
56#pragma weak	flockfile=_flockfile
57#pragma weak	_flockfile_debug=_flockfile_debug_stub
58#pragma weak	ftrylockfile=_ftrylockfile
59#pragma weak	funlockfile=_funlockfile
60
61/*
62 * We need to retain binary compatibility for a while.  So pretend
63 * that _lock is part of FILE * even though it is dereferenced off
64 * _extra now.  When we stop encoding the size of FILE into binaries
65 * this can be changed in stdio.h.  This will reduce the amount of
66 * code that has to change in the future (just remove this comment
67 * and #define).
68 */
69#define _lock _extra
70
71void
72_flockfile(FILE *fp)
73{
74	pthread_t curthread = _pthread_self();
75
76	if (fp->_lock->fl_owner == curthread)
77		fp->_lock->fl_count++;
78	else {
79		/*
80		 * Make sure this mutex is treated as a private
81		 * internal mutex:
82		 */
83		_pthread_mutex_lock(&fp->_lock->fl_mutex);
84		fp->_lock->fl_owner = curthread;
85		fp->_lock->fl_count = 1;
86	}
87}
88
89/*
90 * This can be overriden by the threads library if it is linked in.
91 */
92void
93_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
94{
95	_flockfile(fp);
96}
97
98int
99_ftrylockfile(FILE *fp)
100{
101	pthread_t curthread = _pthread_self();
102	int	ret = 0;
103
104	if (fp->_lock->fl_owner == curthread)
105		fp->_lock->fl_count++;
106	/*
107	 * Make sure this mutex is treated as a private
108	 * internal mutex:
109	 */
110	else if (_pthread_mutex_trylock(&fp->_lock->fl_mutex) == 0) {
111		fp->_lock->fl_owner = curthread;
112		fp->_lock->fl_count = 1;
113	}
114	else
115		ret = -1;
116	return (ret);
117}
118
119void
120_funlockfile(FILE *fp)
121{
122	pthread_t	curthread = _pthread_self();
123
124	/*
125	 * Check if this file is owned by the current thread:
126	 */
127	if (fp->_lock->fl_owner == curthread) {
128		/*
129		 * Check if this thread has locked the FILE
130		 * more than once:
131		 */
132		if (fp->_lock->fl_count > 1)
133			/*
134			 * Decrement the count of the number of
135			 * times the running thread has locked this
136			 * file:
137			 */
138			fp->_lock->fl_count--;
139		else {
140			/*
141			 * The running thread will release the
142			 * lock now:
143			 */
144			fp->_lock->fl_count = 0;
145			fp->_lock->fl_owner = NULL;
146			_pthread_mutex_unlock(&fp->_lock->fl_mutex);
147		}
148	}
149}
150