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 * $FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.16 2008/04/17 22:17:53 jhb Exp $ 30 * $DragonFly: src/lib/libc/stdio/_flock_stub.c,v 1.10 2005/07/23 23:14:44 joerg Exp $ 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 "namespace.h" 41 #include <stdio.h> 42 #include <pthread.h> 43 #include "un-namespace.h" 44 45 #include "local.h" 46 #include "priv_stdio.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 58 _flockfile(FILE *fp) 59 { 60 pthread_t curthread = _pthread_self(); 61 62 if (fp->_fl_owner == curthread) 63 fp->_fl_count++; 64 else { 65 /* 66 * Make sure this mutex is treated as a private 67 * internal mutex: 68 */ 69 _pthread_mutex_lock(&fp->_fl_mutex); 70 fp->_fl_owner = curthread; 71 fp->_fl_count = 1; 72 } 73 } 74 75 /* 76 * This can be overriden by the threads library if it is linked in. 77 */ 78 void 79 _flockfile_debug_stub(FILE *fp, char *fname __unused, int lineno __unused) 80 { 81 _flockfile(fp); 82 } 83 84 int 85 _ftrylockfile(FILE *fp) 86 { 87 pthread_t curthread = _pthread_self(); 88 int ret = 0; 89 90 if (fp->_fl_owner == curthread) 91 fp->_fl_count++; 92 /* 93 * Make sure this mutex is treated as a private 94 * internal mutex: 95 */ 96 else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) { 97 fp->_fl_owner = curthread; 98 fp->_fl_count = 1; 99 } 100 else 101 ret = -1; 102 return (ret); 103 } 104 105 void 106 _funlockfile(FILE *fp) 107 { 108 pthread_t curthread = _pthread_self(); 109 110 /* 111 * Check if this file is owned by the current thread: 112 */ 113 if (fp->_fl_owner == curthread) { 114 /* 115 * Check if this thread has locked the FILE 116 * more than once: 117 */ 118 if (fp->_fl_count > 1) { 119 /* 120 * Decrement the count of the number of 121 * times the running thread has locked this 122 * file: 123 */ 124 fp->_fl_count--; 125 } else { 126 /* 127 * The running thread will release the 128 * lock now: 129 */ 130 fp->_fl_count = 0; 131 fp->_fl_owner = NULL; 132 _pthread_mutex_unlock(&fp->_fl_mutex); 133 } 134 } 135 } 136