1 /* $NetBSD: reentrant.h,v 1.5 1998/09/14 11:03:05 kleink Exp $ */ 2 3 /*- 4 * Copyright (c) 1997,98 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by J.T. Conklin. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 /* 40 * Requirements: 41 * 42 * 1. The thread safe mechanism should be lightweight so the library can 43 * be used by non-threaded applications without unreasonable overhead. 44 * 45 * 2. There should be no dependency on a thread engine for non-threaded 46 * applications. 47 * 48 * 3. There should be no dependency on any particular thread engine. 49 * 50 * 4. The library should be able to be compiled without support for thread 51 * safety. 52 * 53 * 54 * Rationale: 55 * 56 * One approach for thread safety is to provide discrete versions of the 57 * library: one thread safe, the other not. The disadvantage of this is 58 * that libc is rather large, and two copies of a library which are 99%+ 59 * identical is not an efficent use of resources. 60 * 61 * Another approach is to provide a single thread safe library. However, 62 * it should not add significant run time or code size overhead to non- 63 * threaded applications. 64 * 65 * Since the NetBSD C library is used in other projects, it should be 66 * easy to replace the mutual exclusion primitives with ones provided by 67 * another system. Similarly, it should also be easy to remove all 68 * support for thread safety completely if the target environment does 69 * not support threads. 70 * 71 * 72 * Implementation Details: 73 * 74 * The mutex primitives used by the library (mutex_t, mutex_lock, etc.) 75 * are macros which expand to the cooresponding primitives provided by 76 * the thread engine or to nothing. The latter is used so that code is 77 * not unreasonably cluttered with #ifdefs when all thread safe support 78 * is removed. 79 * 80 * The mutex macros can be directly mapped to the mutex primitives from 81 * pthreads, however it should be reasonably easy to wrap another mutex 82 * implementation so it presents a similar interface. 83 * 84 * Stub implementations of the mutex functions are provided with *weak* 85 * linkage. These functions simply return success. When linked with a 86 * thread library (i.e. -lpthread), the functions will override the 87 * stubs. 88 */ 89 90 /* FIXME: Using _REENT during integration testing. It should be changed 91 to _REENTRANT once pthread engine is available */ 92 93 #ifdef _REENT 94 95 #include <pthread.h> 96 97 #define mutex_t pthread_mutex_t 98 #define MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER 99 100 #define mutex_init(m, a) pthread_mutex_init(m, a) 101 #define mutex_lock(m) pthread_mutex_lock(m) 102 #define mutex_unlock(m) pthread_mutex_unlock(m) 103 104 #define rwlock_t pthread_rwlock_t 105 #define RWLOCK_INITIALIZER PTHREAD_RWLOCK_INITIALIZER 106 107 #define rwlock_init(l, a) pthread_rwlock_init(l, a) 108 #define rwlock_rdlock(l) pthread_rwlock_rdlock(l) 109 #define rwlock_wrlock(l) pthread_rwlock_wrlock(l) 110 #define rwlock_unlock(l) pthread_rwlock_unlock(l) 111 112 #define FLOCKFILE(fp) flockfile(fp) 113 #define FUNLOCKFILE(fp) funlockfile(fp) 114 115 #else 116 117 #define mutex_init(m, a) 118 #define mutex_lock(m) 119 #define mutex_unlock(m) 120 121 #define rwlock_init(l, a) 122 #define rwlock_rdlock(l) 123 #define rwlock_wrlock(l) 124 #define rwlock_unlock(l) 125 126 #define FLOCKFILE(fp) 127 #define FUNLOCKFILE(fp) 128 129 #endif 130