1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the author nor the names of any co-contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 /* 33 * POSIX stdio FILE locking functions. These assume that the locking 34 * is only required at FILE structure level, not at file descriptor 35 * level too. 36 * 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "namespace.h" 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <pthread.h> 47 #include "un-namespace.h" 48 49 #include "local.h" 50 51 52 /* 53 * Weak symbols for externally visible functions in this file: 54 */ 55 __weak_reference(_flockfile, flockfile); 56 __weak_reference(_flockfile_debug_stub, _flockfile_debug); 57 __weak_reference(_ftrylockfile, ftrylockfile); 58 __weak_reference(_funlockfile, funlockfile); 59 60 void _flockfile_debug_stub(FILE *, char *, int); 61 int _ftrylockfile(FILE *); 62 63 void 64 _flockfile(FILE *fp) 65 { 66 pthread_t curthread = _pthread_self(); 67 68 if (fp->_fl_owner == curthread) 69 fp->_fl_count++; 70 else { 71 /* 72 * Make sure this mutex is treated as a private 73 * internal mutex: 74 */ 75 _pthread_mutex_lock(&fp->_fl_mutex); 76 fp->_fl_owner = curthread; 77 fp->_fl_count = 1; 78 } 79 } 80 81 /* 82 * This can be overriden by the threads library if it is linked in. 83 */ 84 void 85 _flockfile_debug_stub(FILE *fp, char *fname, int lineno) 86 { 87 _flockfile(fp); 88 } 89 90 int 91 _ftrylockfile(FILE *fp) 92 { 93 pthread_t curthread = _pthread_self(); 94 int ret = 0; 95 96 if (fp->_fl_owner == curthread) 97 fp->_fl_count++; 98 /* 99 * Make sure this mutex is treated as a private 100 * internal mutex: 101 */ 102 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) { 103 fp->_fl_owner = curthread; 104 fp->_fl_count = 1; 105 } 106 else 107 ret = -1; 108 return (ret); 109 } 110 111 void 112 _funlockfile(FILE *fp) 113 { 114 pthread_t curthread = _pthread_self(); 115 116 /* 117 * Check if this file is owned by the current thread: 118 */ 119 if (fp->_fl_owner == curthread) { 120 /* 121 * Check if this thread has locked the FILE 122 * more than once: 123 */ 124 if (fp->_fl_count > 1) 125 /* 126 * Decrement the count of the number of 127 * times the running thread has locked this 128 * file: 129 */ 130 fp->_fl_count--; 131 else { 132 /* 133 * The running thread will release the 134 * lock now: 135 */ 136 fp->_fl_count = 0; 137 fp->_fl_owner = NULL; 138 _pthread_mutex_unlock(&fp->_fl_mutex); 139 } 140 } 141 } 142