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      1 /*	$NetBSD: flockfile.c,v 1.11 2012/03/15 18:22:30 christos 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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: flockfile.c,v 1.11 2012/03/15 18:22:30 christos Exp $");
     35 #endif /* LIBC_SCCS and not lint */
     36 
     37 #include "namespace.h"
     38 
     39 #include <assert.h>
     40 #include <errno.h>
     41 #include <stdio.h>
     42 #include <string.h>
     43 #include "reentrant.h"
     44 #include "local.h"
     45 
     46 #ifdef __weak_alias
     47 __weak_alias(flockfile,_flockfile)
     48 __weak_alias(ftrylockfile,_ftrylockfile)
     49 __weak_alias(funlockfile,_funlockfile)
     50 #endif
     51 
     52 #ifdef _REENTRANT
     53 /*
     54  * XXX This code makes the assumption that a thr_t (pthread_t) is a
     55  * XXX pointer.
     56  */
     57 
     58 void
     59 flockfile(FILE *fp)
     60 {
     61 
     62 	__flockfile_internal(fp, 0);
     63 }
     64 
     65 int
     66 ftrylockfile(FILE *fp)
     67 {
     68 	int retval;
     69 
     70 	if (__isthreaded == 0)
     71 		return 0;
     72 
     73 	retval = 0;
     74 	mutex_lock(&_LOCK(fp));
     75 
     76 	if (_LOCKOWNER(fp) == thr_self()) {
     77 		_LOCKCOUNT(fp)++;
     78 	} else if (_LOCKOWNER(fp) == NULL) {
     79 		_LOCKOWNER(fp) = thr_self();
     80 		_LOCKCOUNT(fp) = 1;
     81 	} else
     82 		retval = -1;
     83 
     84 	mutex_unlock(&_LOCK(fp));
     85 
     86 	return retval;
     87 }
     88 
     89 void
     90 funlockfile(FILE *fp)
     91 {
     92 
     93 	__funlockfile_internal(fp, 0);
     94 }
     95 
     96 void
     97 __flockfile_internal(FILE *fp, int internal)
     98 {
     99 
    100 	if (__isthreaded == 0)
    101 		return;
    102 
    103 	mutex_lock(&_LOCK(fp));
    104 
    105 	if (_LOCKOWNER(fp) == thr_self()) {
    106 		_LOCKCOUNT(fp)++;
    107 		if (internal)
    108 			_LOCKINTERNAL(fp)++;
    109 	} else {
    110 		/* danger! cond_wait() is a cancellation point. */
    111 		int oldstate;
    112 		thr_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
    113 		while (_LOCKOWNER(fp) != NULL)
    114 			cond_wait(&_LOCKCOND(fp), &_LOCK(fp));
    115 		thr_setcancelstate(oldstate, NULL);
    116 		_LOCKOWNER(fp) = thr_self();
    117 		_LOCKCOUNT(fp) = 1;
    118 		if (internal)
    119 			_LOCKINTERNAL(fp) = 1;
    120 	}
    121 
    122 	if (_LOCKINTERNAL(fp) == 1)
    123 		/* stash cancellation state and disable */
    124 		thr_setcancelstate(PTHREAD_CANCEL_DISABLE,
    125 		    &_LOCKCANCELSTATE(fp));
    126 
    127 	mutex_unlock(&_LOCK(fp));
    128 }
    129 
    130 void
    131 __funlockfile_internal(FILE *fp, int internal)
    132 {
    133 
    134 	if (__isthreaded == 0)
    135 		return;
    136 
    137 	mutex_lock(&_LOCK(fp));
    138 
    139 	if (internal) {
    140 		_LOCKINTERNAL(fp)--;
    141 		if (_LOCKINTERNAL(fp) == 0)
    142 			thr_setcancelstate(_LOCKCANCELSTATE(fp), NULL);
    143 	}
    144 
    145 	_LOCKCOUNT(fp)--;
    146 	if (_LOCKCOUNT(fp) == 0) {
    147 		_LOCKOWNER(fp) = NULL;
    148 		cond_signal(&_LOCKCOND(fp));
    149 	}
    150 
    151 	mutex_unlock(&_LOCK(fp));
    152 }
    153 
    154 #else /* _REENTRANT */
    155 
    156 void
    157 flockfile(FILE *fp)
    158 {
    159 	/* LINTED deliberate lack of effect */
    160 	(void)fp;
    161 
    162 	return;
    163 }
    164 
    165 int
    166 ftrylockfile(FILE *fp)
    167 {
    168 	/* LINTED deliberate lack of effect */
    169 	(void)fp;
    170 
    171 	return 0;
    172 }
    173 
    174 void
    175 funlockfile(FILE *fp)
    176 {
    177 	/* LINTED deliberate lack of effect */
    178 	(void)fp;
    179 
    180 	return;
    181 }
    182 
    183 #endif /* _REENTRANT */
    184