NetBSD/lib/libpthread/pthread_barrier.c

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/* $NetBSD: pthread_barrier.c,v 1.19 2009/01/29 21:19:35 ad Exp $ */
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/*-
* Copyright (c) 2001, 2003, 2006, 2007, 2009 The NetBSD Foundation, Inc.
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* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Nathan J. Williams, by Jason R. Thorpe, and by Andrew Doran.
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*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
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#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_barrier.c,v 1.19 2009/01/29 21:19:35 ad Exp $");
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#include <errno.h>
#include "pthread.h"
#include "pthread_int.h"
int
pthread_barrier_init(pthread_barrier_t *barrier,
const pthread_barrierattr_t *attr, unsigned int count)
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{
if (attr != NULL && attr->ptba_magic != _PT_BARRIERATTR_MAGIC)
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return EINVAL;
if (count == 0)
return EINVAL;
barrier->ptb_magic = _PT_BARRIER_MAGIC;
PTQ_INIT(&barrier->ptb_waiters);
barrier->ptb_initcount = count;
barrier->ptb_curcount = 0;
barrier->ptb_generation = 0;
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return 0;
}
int
pthread_barrier_destroy(pthread_barrier_t *barrier)
{
if (barrier->ptb_magic != _PT_BARRIER_MAGIC)
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return EINVAL;
if (barrier->ptb_curcount != 0)
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return EBUSY;
return 0;
}
int
pthread_barrier_wait(pthread_barrier_t *barrier)
{
pthread_mutex_t *interlock;
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pthread_t self;
unsigned int gen;
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if (barrier->ptb_magic != _PT_BARRIER_MAGIC)
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return EINVAL;
/*
* A single arbitrary thread is supposed to return
* PTHREAD_BARRIER_SERIAL_THREAD, and everone else
* is supposed to return 0. Since pthread_barrier_wait()
* is not a cancellation point, this is trivial; we
* simply elect that the thread that causes the barrier
* to be satisfied gets the special return value. Note
* that this final thread does not actually need to block,
* but instead is responsible for waking everyone else up.
*/
self = pthread__self();
interlock = pthread__hashlock(barrier);
pthread_mutex_lock(interlock);
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if (barrier->ptb_curcount + 1 == barrier->ptb_initcount) {
barrier->ptb_generation++;
barrier->ptb_curcount = 0;
pthread__unpark_all(&barrier->ptb_waiters, self,
interlock);
pthread_mutex_unlock(interlock);
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return PTHREAD_BARRIER_SERIAL_THREAD;
}
barrier->ptb_curcount++;
gen = barrier->ptb_generation;
for (;;) {
PTQ_INSERT_TAIL(&barrier->ptb_waiters, self, pt_sleep);
self->pt_sleepobj = &barrier->ptb_waiters;
(void)pthread__park(self, interlock, &barrier->ptb_waiters,
NULL, 0, __UNVOLATILE(&interlock->ptm_waiters));
if (__predict_true(gen != barrier->ptb_generation)) {
break;
}
pthread_mutex_lock(interlock);
if (gen != barrier->ptb_generation) {
pthread_mutex_unlock(interlock);
break;
}
}
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return 0;
}
int
pthread_barrierattr_init(pthread_barrierattr_t *attr)
{
attr->ptba_magic = _PT_BARRIERATTR_MAGIC;
return 0;
}
int
pthread_barrierattr_destroy(pthread_barrierattr_t *attr)
{
if (attr->ptba_magic != _PT_BARRIERATTR_MAGIC)
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return EINVAL;
attr->ptba_magic = _PT_BARRIERATTR_DEAD;
return 0;
}