138 lines
4.1 KiB
C
138 lines
4.1 KiB
C
/* $NetBSD: pthread_barrier.c,v 1.19 2009/01/29 21:19:35 ad Exp $ */
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/*-
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* Copyright (c) 2001, 2003, 2006, 2007, 2009 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 Nathan J. Williams, by Jason R. Thorpe, and by Andrew Doran.
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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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*
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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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#include <sys/cdefs.h>
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__RCSID("$NetBSD: pthread_barrier.c,v 1.19 2009/01/29 21:19:35 ad Exp $");
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#include <errno.h>
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#include "pthread.h"
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#include "pthread_int.h"
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int
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pthread_barrier_init(pthread_barrier_t *barrier,
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const pthread_barrierattr_t *attr, unsigned int count)
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{
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if (attr != NULL && attr->ptba_magic != _PT_BARRIERATTR_MAGIC)
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return EINVAL;
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if (count == 0)
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return EINVAL;
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barrier->ptb_magic = _PT_BARRIER_MAGIC;
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PTQ_INIT(&barrier->ptb_waiters);
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barrier->ptb_initcount = count;
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barrier->ptb_curcount = 0;
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barrier->ptb_generation = 0;
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return 0;
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}
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int
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pthread_barrier_destroy(pthread_barrier_t *barrier)
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{
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if (barrier->ptb_magic != _PT_BARRIER_MAGIC)
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return EINVAL;
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if (barrier->ptb_curcount != 0)
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return EBUSY;
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return 0;
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}
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int
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pthread_barrier_wait(pthread_barrier_t *barrier)
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{
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pthread_mutex_t *interlock;
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pthread_t self;
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unsigned int gen;
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if (barrier->ptb_magic != _PT_BARRIER_MAGIC)
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return EINVAL;
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/*
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* A single arbitrary thread is supposed to return
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* PTHREAD_BARRIER_SERIAL_THREAD, and everone else
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* is supposed to return 0. Since pthread_barrier_wait()
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* is not a cancellation point, this is trivial; we
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* simply elect that the thread that causes the barrier
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* to be satisfied gets the special return value. Note
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* that this final thread does not actually need to block,
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* but instead is responsible for waking everyone else up.
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*/
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self = pthread__self();
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interlock = pthread__hashlock(barrier);
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pthread_mutex_lock(interlock);
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if (barrier->ptb_curcount + 1 == barrier->ptb_initcount) {
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barrier->ptb_generation++;
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barrier->ptb_curcount = 0;
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pthread__unpark_all(&barrier->ptb_waiters, self,
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interlock);
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pthread_mutex_unlock(interlock);
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return PTHREAD_BARRIER_SERIAL_THREAD;
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}
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barrier->ptb_curcount++;
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gen = barrier->ptb_generation;
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for (;;) {
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PTQ_INSERT_TAIL(&barrier->ptb_waiters, self, pt_sleep);
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self->pt_sleepobj = &barrier->ptb_waiters;
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(void)pthread__park(self, interlock, &barrier->ptb_waiters,
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NULL, 0, __UNVOLATILE(&interlock->ptm_waiters));
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if (__predict_true(gen != barrier->ptb_generation)) {
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break;
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}
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pthread_mutex_lock(interlock);
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if (gen != barrier->ptb_generation) {
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pthread_mutex_unlock(interlock);
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break;
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}
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}
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return 0;
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}
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int
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pthread_barrierattr_init(pthread_barrierattr_t *attr)
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{
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attr->ptba_magic = _PT_BARRIERATTR_MAGIC;
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return 0;
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}
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int
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pthread_barrierattr_destroy(pthread_barrierattr_t *attr)
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{
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if (attr->ptba_magic != _PT_BARRIERATTR_MAGIC)
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return EINVAL;
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attr->ptba_magic = _PT_BARRIERATTR_DEAD;
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return 0;
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}
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