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