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