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flockfile.c revision 1.8 
      1 /*	$NetBSD: flockfile.c,v 1.8 2003/07/22 00:56:25 nathanw Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2002 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Nathan J. Williams.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 __RCSID("$NetBSD: flockfile.c,v 1.8 2003/07/22 00:56:25 nathanw Exp $");
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include "namespace.h"
     45 
     46 #include <assert.h>
     47 #include <errno.h>
     48 #include <stdio.h>
     49 #include <string.h>
     50 #include "reentrant.h"
     51 #include "local.h"
     52 
     53 #ifdef __weak_alias
     54 __weak_alias(flockfile,_flockfile)
     55 __weak_alias(ftrylockfile,_ftrylockfile)
     56 __weak_alias(funlockfile,_funlockfile)
     57 #endif
     58 
     59 #ifdef _REENTRANT
     60 /*
     61  * XXX This code makes the assumption that a thr_t (pthread_t) is a
     62  * XXX pointer.
     63  */
     64 
     65 extern int __isthreaded;
     66 
     67 void
     68 flockfile(FILE *fp)
     69 {
     70 
     71 	__flockfile_internal(fp, 0);
     72 }
     73 
     74 int
     75 ftrylockfile(FILE *fp)
     76 {
     77 	int retval;
     78 
     79 	if (__isthreaded == 0)
     80 		return 0;
     81 
     82 	retval = 0;
     83 	mutex_lock(&_LOCK(fp));
     84 
     85 	if (_LOCKOWNER(fp) == thr_self()) {
     86 		_LOCKCOUNT(fp)++;
     87 	} else if (_LOCKOWNER(fp) == NULL) {
     88 		_LOCKOWNER(fp) = thr_self();
     89 		_LOCKCOUNT(fp) = 1;
     90 	} else
     91 		retval = -1;
     92 
     93 	mutex_unlock(&_LOCK(fp));
     94 
     95 	return retval;
     96 }
     97 
     98 void
     99 funlockfile(FILE *fp)
    100 {
    101 
    102 	__funlockfile_internal(fp, 0);
    103 }
    104 
    105 void
    106 __flockfile_internal(FILE *fp, int internal)
    107 {
    108 
    109 	if (__isthreaded == 0)
    110 		return;
    111 
    112 	mutex_lock(&_LOCK(fp));
    113 
    114 	if (_LOCKOWNER(fp) == thr_self()) {
    115 		_LOCKCOUNT(fp)++;
    116 		if (internal)
    117 			_LOCKINTERNAL(fp)++;
    118 	} else {
    119 		/* danger! cond_wait() is a cancellation point. */
    120 		int oldstate;
    121 		thr_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
    122 		while (_LOCKOWNER(fp) != NULL)
    123 			cond_wait(&_LOCKCOND(fp), &_LOCK(fp));
    124 		thr_setcancelstate(oldstate, NULL);
    125 		_LOCKOWNER(fp) = thr_self();
    126 		_LOCKCOUNT(fp) = 1;
    127 		if (internal)
    128 			_LOCKINTERNAL(fp) = 1;
    129 	}
    130 
    131 	if (_LOCKINTERNAL(fp) == 1)
    132 		/* stash cancellation state and disable */
    133 		thr_setcancelstate(PTHREAD_CANCEL_DISABLE,
    134 		    &_LOCKCANCELSTATE(fp));
    135 
    136 	mutex_unlock(&_LOCK(fp));
    137 }
    138 
    139 void
    140 __funlockfile_internal(FILE *fp, int internal)
    141 {
    142 
    143 	if (__isthreaded == 0)
    144 		return;
    145 
    146 	mutex_lock(&_LOCK(fp));
    147 
    148 	if (internal) {
    149 		_LOCKINTERNAL(fp)--;
    150 		if (_LOCKINTERNAL(fp) == 0)
    151 			thr_setcancelstate(_LOCKCANCELSTATE(fp), NULL);
    152 	}
    153 
    154 	_LOCKCOUNT(fp)--;
    155 	if (_LOCKCOUNT(fp) == 0) {
    156 		_LOCKOWNER(fp) = NULL;
    157 		cond_signal(&_LOCKCOND(fp));
    158 	}
    159 
    160 	mutex_unlock(&_LOCK(fp));
    161 }
    162 
    163 #else /* _REENTRANT */
    164 
    165 void
    166 flockfile(FILE *fp)
    167 {
    168 	/* LINTED deliberate lack of effect */
    169 	(void)fp;
    170 
    171 	return;
    172 }
    173 
    174 int
    175 ftrylockfile(FILE *fp)
    176 {
    177 	/* LINTED deliberate lack of effect */
    178 	(void)fp;
    179 
    180 	return (0);
    181 }
    182 
    183 void
    184 funlockfile(FILE *fp)
    185 {
    186 	/* LINTED deliberate lack of effect */
    187 	(void)fp;
    188 
    189 	return;
    190 }
    191 
    192 #endif /* _REENTRANT */
    193