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("$FreeBSD$"); 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 68 void 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 */ 89 void 90 _flockfile_debug_stub(FILE *fp, char *fname, int lineno) 91 { 92 _flockfile(fp); 93 } 94 95 int 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 } 115 116 void 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