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 33 /* 34 * POSIX stdio FILE locking functions. These assume that the locking 35 * is only required at FILE structure level, not at file descriptor 36 * level too. 37 * 38 */ 39 40 #include <sys/cdefs.h> 41 __FBSDID("$FreeBSD$"); 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 __weak_reference(_flockfile, flockfile); 57 __weak_reference(_flockfile_debug_stub, _flockfile_debug); 58 __weak_reference(_ftrylockfile, ftrylockfile); 59 __weak_reference(_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 71 void 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 */ 92 void 93 _flockfile_debug_stub(FILE *fp, char *fname, int lineno) 94 { 95 _flockfile(fp); 96 } 97 98 int 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 } 118 119 void 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