140 lines
5.1 KiB
C
140 lines
5.1 KiB
C
/* $NetBSD: reentrant.h,v 1.8 2003/01/19 19:25:05 thorpej Exp $ */
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/*-
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* Copyright (c) 1997, 1998, 2003 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by J.T. Conklin, by Nathan J. Williams, and by Jason R. Thorpe.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Requirements:
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*
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* 1. The thread safe mechanism should be lightweight so the library can
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* be used by non-threaded applications without unreasonable overhead.
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*
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* 2. There should be no dependency on a thread engine for non-threaded
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* applications.
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*
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* 3. There should be no dependency on any particular thread engine.
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*
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* 4. The library should be able to be compiled without support for thread
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* safety.
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*
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*
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* Rationale:
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*
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* One approach for thread safety is to provide discrete versions of the
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* library: one thread safe, the other not. The disadvantage of this is
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* that libc is rather large, and two copies of a library which are 99%+
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* identical is not an efficent use of resources.
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*
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* Another approach is to provide a single thread safe library. However,
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* it should not add significant run time or code size overhead to non-
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* threaded applications.
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*
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* Since the NetBSD C library is used in other projects, it should be
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* easy to replace the mutual exclusion primitives with ones provided by
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* another system. Similarly, it should also be easy to remove all
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* support for thread safety completely if the target environment does
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* not support threads.
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*
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*
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* Implementation Details:
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*
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* The thread primitives used by the library (mutex_t, mutex_lock, etc.)
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* are macros which expand to the cooresponding primitives provided by
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* the thread engine or to nothing. The latter is used so that code is
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* not unreasonably cluttered with #ifdefs when all thread safe support
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* is removed.
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*
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* The thread macros can be directly mapped to the mutex primitives from
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* pthreads, however it should be reasonably easy to wrap another mutex
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* implementation so it presents a similar interface.
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*
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* The thread functions operate by dispatching to symbols which are, by
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* default, weak-aliased to no-op functions in thread-stub/thread-stub.c
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* (some uses of thread operations are conditional on __isthreaded, but
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* not all of them are).
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*
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* When the thread library is linked in, it provides strong-alias versions
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* of those symbols which dispatch to its own real thread operations.
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*
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* [This interface has been exposed to simplify making other libraries
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* thread-safe.]
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*/
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#ifdef _REENTRANT
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#include <threadlib.h>
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#define FLOCKFILE(fp) flockfile(fp)
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#define FUNLOCKFILE(fp) funlockfile(fp)
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#else /* _REENTRANT */
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#define mutex_init(m, a)
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#define mutex_lock(m)
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#define mutex_trylock(m)
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#define mutex_unlock(m)
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#define mutex_destroy(m)
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#define cond_init(c, t, a)
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#define cond_signal(c)
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#define cond_broadcast(c)
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#define cond_wait(c, m)
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#define cond_timedwait(c, m, t)
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#define cond_destroy(c)
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#define rwlock_init(l, a)
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#define rwlock_rdlock(l)
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#define rwlock_wrlock(l)
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#define rwlock_tryrdlock(l)
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#define rwlock_trywrlock(l)
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#define rwlock_unlock(l)
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#define rwlock_destroy(l)
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#define thr_keycreate(k, d)
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#define thr_setspecific(k, p)
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#define thr_getspecific(k)
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#define thr_keydelete(k)
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#define thr_once(o, f)
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#define thr_sigsetmask(f, n, o)
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#define thr_self()
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#define thr_errno()
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#define FLOCKFILE(fp)
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#define FUNLOCKFILE(fp)
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#endif /* _REENTRANT */
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