lib/libc/include/reentrant.h

   1 /*-
   2  * Copyright (c) 1997,98 The NetBSD Foundation, Inc.
   3  * All rights reserved.
   4  *
   5  * This code is derived from software contributed to The NetBSD Foundation
   6  * by J.T. Conklin.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *        This product includes software developed by the NetBSD
  19  *        Foundation, Inc. and its contributors.
  20  * 4. Neither the name of The NetBSD Foundation nor the names of its
  21  *    contributors may be used to endorse or promote products derived
  22  *    from this software without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  25  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  26  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  27  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  28  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  29  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  30  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  31  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  32  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  33  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  34  * POSSIBILITY OF SUCH DAMAGE.
  35  *
  36  * $FreeBSD: src/lib/libc/include/reentrant.h,v 1.3 2004/02/25 21:03:45 green Exp $
  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 #include <pthread.h>
  91 #include <pthread_np.h>
  92 #include "libc_private.h"
  93
  94 #define mutex_t                 pthread_mutex_t
  95 #define cond_t                  pthread_cond_t
  96 #define rwlock_t                pthread_rwlock_t
  97 #define once_t                  pthread_once_t
  98
  99 #define thread_key_t            pthread_key_t
 100 #define MUTEX_INITIALIZER       PTHREAD_MUTEX_INITIALIZER
 101 #define RWLOCK_INITIALIZER      PTHREAD_RWLOCK_INITIALIZER
 102 #define ONCE_INITIALIZER        PTHREAD_ONCE_INIT
 103
 104 #define mutex_init(m, a)        _pthread_mutex_init(m, a)
 105 #define mutex_lock(m)           if (__isthreaded) \
 106                                 _pthread_mutex_lock(m)
 107 #define mutex_unlock(m)         if (__isthreaded) \
 108                                 _pthread_mutex_unlock(m)
 109 #define mutex_trylock(m)        (__isthreaded ? 0 : _pthread_mutex_trylock(m))
 110
 111 #define cond_init(c, a, p)      _pthread_cond_init(c, a)
 112 #define cond_signal(m)          if (__isthreaded) \
 113                                 _pthread_cond_signal(m)
 114 #define cond_broadcast(m)       if (__isthreaded) \
 115                                 _pthread_cond_broadcast(m)
 116 #define cond_wait(c, m)         if (__isthreaded) \
 117                                 _pthread_cond_wait(c, m)
 118
 119 #define rwlock_init(l, a)       _pthread_rwlock_init(l, a)
 120 #define rwlock_rdlock(l)        if (__isthreaded) \
 121                                 _pthread_rwlock_rdlock(l)
 122 #define rwlock_wrlock(l)        if (__isthreaded) \
 123                                 _pthread_rwlock_wrlock(l)
 124 #define rwlock_unlock(l)        if (__isthreaded) \
 125                                 _pthread_rwlock_unlock(l)
 126
 127 #define thr_keycreate(k, d)     _pthread_key_create(k, d)
 128 #define thr_setspecific(k, p)   _pthread_setspecific(k, p)
 129 #define thr_getspecific(k)      _pthread_getspecific(k)
 130 #define thr_sigsetmask(f, n, o) _pthread_sigmask(f, n, o)
 131
 132 #define thr_once(o, i)          _pthread_once(o, i)
 133 #define thr_self()              _pthread_self()
 134 #define thr_exit(x)             _pthread_exit(x)
 135 #define thr_main()              _pthread_main_np()