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 "namespace.h" 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <pthread.h> 44 #include "un-namespace.h" 45 46 #include "local.h" 47 48 49 /* 50 * Weak symbols for externally visible functions in this file: 51 */ 52 __weak_reference(_flockfile, flockfile); 53 __weak_reference(_flockfile_debug_stub, _flockfile_debug); 54 __weak_reference(_ftrylockfile, ftrylockfile); 55 __weak_reference(_funlockfile, funlockfile); 56 57 void _flockfile_debug_stub(FILE *, char *, int); 58 int _ftrylockfile(FILE *); 59 60 void 61 _flockfile(FILE *fp) 62 { 63 pthread_t curthread = _pthread_self(); 64 65 if (fp->_fl_owner == curthread) 66 fp->_fl_count++; 67 else { 68 /* 69 * Make sure this mutex is treated as a private 70 * internal mutex: 71 */ 72 _pthread_mutex_lock(&fp->_fl_mutex); 73 fp->_fl_owner = curthread; 74 fp->_fl_count = 1; 75 } 76 } 77 78 /* 79 * This can be overriden by the threads library if it is linked in. 80 */ 81 void 82 _flockfile_debug_stub(FILE *fp, char *fname, int lineno) 83 { 84 _flockfile(fp); 85 } 86 87 int 88 _ftrylockfile(FILE *fp) 89 { 90 pthread_t curthread = _pthread_self(); 91 int ret = 0; 92 93 if (fp->_fl_owner == curthread) 94 fp->_fl_count++; 95 /* 96 * Make sure this mutex is treated as a private 97 * internal mutex: 98 */ 99 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) { 100 fp->_fl_owner = curthread; 101 fp->_fl_count = 1; 102 } 103 else 104 ret = -1; 105 return (ret); 106 } 107 108 void 109 _funlockfile(FILE *fp) 110 { 111 pthread_t curthread = _pthread_self(); 112 113 /* 114 * Check if this file is owned by the current thread: 115 */ 116 if (fp->_fl_owner == curthread) { 117 /* 118 * Check if this thread has locked the FILE 119 * more than once: 120 */ 121 if (fp->_fl_count > 1) 122 /* 123 * Decrement the count of the number of 124 * times the running thread has locked this 125 * file: 126 */ 127 fp->_fl_count--; 128 else { 129 /* 130 * The running thread will release the 131 * lock now: 132 */ 133 fp->_fl_count = 0; 134 fp->_fl_owner = NULL; 135 _pthread_mutex_unlock(&fp->_fl_mutex); 136 } 137 } 138 } 139