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 void _flockfile_debug_stub(FILE *, char *, int); 59 int _ftrylockfile(FILE *); 60 61 void 62 _flockfile(FILE *fp) 63 { 64 pthread_t curthread = _pthread_self(); 65 66 if (fp->_fl_owner == curthread) 67 fp->_fl_count++; 68 else { 69 /* 70 * Make sure this mutex is treated as a private 71 * internal mutex: 72 */ 73 _pthread_mutex_lock(&fp->_fl_mutex); 74 fp->_fl_owner = curthread; 75 fp->_fl_count = 1; 76 } 77 } 78 79 /* 80 * This can be overriden by the threads library if it is linked in. 81 */ 82 void 83 _flockfile_debug_stub(FILE *fp, char *fname, int lineno) 84 { 85 _flockfile(fp); 86 } 87 88 int 89 _ftrylockfile(FILE *fp) 90 { 91 pthread_t curthread = _pthread_self(); 92 int ret = 0; 93 94 if (fp->_fl_owner == curthread) 95 fp->_fl_count++; 96 /* 97 * Make sure this mutex is treated as a private 98 * internal mutex: 99 */ 100 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) { 101 fp->_fl_owner = curthread; 102 fp->_fl_count = 1; 103 } 104 else 105 ret = -1; 106 return (ret); 107 } 108 109 void 110 _funlockfile(FILE *fp) 111 { 112 pthread_t curthread = _pthread_self(); 113 114 /* 115 * Check if this file is owned by the current thread: 116 */ 117 if (fp->_fl_owner == curthread) { 118 /* 119 * Check if this thread has locked the FILE 120 * more than once: 121 */ 122 if (fp->_fl_count > 1) 123 /* 124 * Decrement the count of the number of 125 * times the running thread has locked this 126 * file: 127 */ 128 fp->_fl_count--; 129 else { 130 /* 131 * The running thread will release the 132 * lock now: 133 */ 134 fp->_fl_count = 0; 135 fp->_fl_owner = NULL; 136 _pthread_mutex_unlock(&fp->_fl_mutex); 137 } 138 } 139 } 140