1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Requirements: 34 * 35 * 1. The thread safe mechanism should be lightweight so the library can 36 * be used by non-threaded applications without unreasonable overhead. 37 * 38 * 2. There should be no dependency on a thread engine for non-threaded 39 * applications. 40 * 41 * 3. There should be no dependency on any particular thread engine. 42 * 43 * 4. The library should be able to be compiled without support for thread 44 * safety. 45 * 46 * 47 * Rationale: 48 * 49 * One approach for thread safety is to provide discrete versions of the 50 * library: one thread safe, the other not. The disadvantage of this is 51 * that libc is rather large, and two copies of a library which are 99%+ 52 * identical is not an efficient use of resources. 53 * 54 * Another approach is to provide a single thread safe library. However, 55 * it should not add significant run time or code size overhead to non- 56 * threaded applications. 57 * 58 * Since the NetBSD C library is used in other projects, it should be 59 * easy to replace the mutual exclusion primitives with ones provided by 60 * another system. Similarly, it should also be easy to remove all 61 * support for thread safety completely if the target environment does 62 * not support threads. 63 * 64 * 65 * Implementation Details: 66 * 67 * The mutex primitives used by the library (mutex_t, mutex_lock, etc.) 68 * are macros which expand to the corresponding primitives provided by 69 * the thread engine or to nothing. The latter is used so that code is 70 * not unreasonably cluttered with #ifdefs when all thread safe support 71 * is removed. 72 * 73 * The mutex macros can be directly mapped to the mutex primitives from 74 * pthreads, however it should be reasonably easy to wrap another mutex 75 * implementation so it presents a similar interface. 76 * 77 * Stub implementations of the mutex functions are provided with *weak* 78 * linkage. These functions simply return success. When linked with a 79 * thread library (i.e. -lpthread), the functions will override the 80 * stubs. 81 */ 82 83 #include <pthread.h> 84 #include <pthread_np.h> 85 #include "libc_private.h" 86 87 #define mutex_t pthread_mutex_t 88 #define cond_t pthread_cond_t 89 #define rwlock_t pthread_rwlock_t 90 #define once_t pthread_once_t 91 92 #define thread_key_t pthread_key_t 93 #define MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER 94 #define RWLOCK_INITIALIZER PTHREAD_RWLOCK_INITIALIZER 95 #define ONCE_INITIALIZER PTHREAD_ONCE_INIT 96 97 #define mutex_init(m, a) _pthread_mutex_init(m, a) 98 #define mutex_lock(m) if (__isthreaded) \ 99 _pthread_mutex_lock(m) 100 #define mutex_unlock(m) if (__isthreaded) \ 101 _pthread_mutex_unlock(m) 102 #define mutex_trylock(m) (__isthreaded ? 0 : _pthread_mutex_trylock(m)) 103 104 #define cond_init(c, a, p) _pthread_cond_init(c, a) 105 #define cond_signal(m) if (__isthreaded) \ 106 _pthread_cond_signal(m) 107 #define cond_broadcast(m) if (__isthreaded) \ 108 _pthread_cond_broadcast(m) 109 #define cond_wait(c, m) if (__isthreaded) \ 110 _pthread_cond_wait(c, m) 111 112 #define rwlock_init(l, a) _pthread_rwlock_init(l, a) 113 #define rwlock_rdlock(l) if (__isthreaded) \ 114 _pthread_rwlock_rdlock(l) 115 #define rwlock_wrlock(l) if (__isthreaded) \ 116 _pthread_rwlock_wrlock(l) 117 #define rwlock_unlock(l) if (__isthreaded) \ 118 _pthread_rwlock_unlock(l) 119 120 #define thr_keycreate(k, d) _pthread_key_create(k, d) 121 #define thr_setspecific(k, p) _pthread_setspecific(k, p) 122 #define thr_getspecific(k) _pthread_getspecific(k) 123 #define thr_sigsetmask(f, n, o) _pthread_sigmask(f, n, o) 124 125 #define thr_once(o, i) _pthread_once(o, i) 126 #define thr_self() _pthread_self() 127 #define thr_exit(x) _pthread_exit(x) 128 #define thr_main() _pthread_main_np() 129