100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/*
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* Copyright (c) 2005, David Xu <davidxu@freebsd.org>
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* All rights reserved.
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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 unmodified, this list of conditions, and the following
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* 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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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*/
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#include "namespace.h"
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#include <pthread.h>
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#include "un-namespace.h"
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#include "thr_private.h"
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__weak_reference(_pthread_once, pthread_once);
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#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT
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#define ONCE_DONE PTHREAD_DONE_INIT
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#define ONCE_IN_PROGRESS 0x02
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#define ONCE_MASK 0x03
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static pthread_mutex_t _thr_once_lock = PTHREAD_MUTEX_INITIALIZER;
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static pthread_cond_t _thr_once_cv = PTHREAD_COND_INITIALIZER;
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/*
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* POSIX:
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* The pthread_once() function is not a cancellation point. However,
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* if init_routine is a cancellation point and is canceled, the effect
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* on once_control shall be as if pthread_once() was never called.
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*/
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static void
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once_cancel_handler(void *arg)
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{
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pthread_once_t *once_control = arg;
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_pthread_mutex_lock(&_thr_once_lock);
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once_control->state = ONCE_NEVER_DONE;
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_pthread_mutex_unlock(&_thr_once_lock);
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_pthread_cond_broadcast(&_thr_once_cv);
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}
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int
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_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
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{
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int wakeup = 0;
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if (once_control->state == ONCE_DONE)
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return (0);
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_pthread_mutex_lock(&_thr_once_lock);
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while (*(volatile int *)&(once_control->state) == ONCE_IN_PROGRESS)
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_pthread_cond_wait(&_thr_once_cv, &_thr_once_lock);
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/*
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* If previous thread was canceled, then the state still
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* could be ONCE_NEVER_DONE, we need to check it again.
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*/
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if (*(volatile int *)&(once_control->state) == ONCE_NEVER_DONE) {
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once_control->state = ONCE_IN_PROGRESS;
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_pthread_mutex_unlock(&_thr_once_lock);
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_pthread_cleanup_push(once_cancel_handler, once_control);
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init_routine();
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_pthread_cleanup_pop(0);
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_pthread_mutex_lock(&_thr_once_lock);
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once_control->state = ONCE_DONE;
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wakeup = 1;
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}
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_pthread_mutex_unlock(&_thr_once_lock);
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if (wakeup)
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_pthread_cond_broadcast(&_thr_once_cv);
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return (0);
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}
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void
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_thr_once_init()
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{
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_thr_once_lock = PTHREAD_MUTEX_INITIALIZER;
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_thr_once_cv = PTHREAD_COND_INITIALIZER;
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}
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