reentrant.h revision 330446 
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 *
17 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
18 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
19 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
21 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27 * POSSIBILITY OF SUCH DAMAGE.
28 *
29 * $FreeBSD: stable/11/lib/libc/include/reentrant.h 330446 2018-03-05 06:59:30Z eadler $
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