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/*
* pthread_barrier_wait.c
*
* Description:
* This translation unit implements barrier primitives.
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2005 Pthreads-win32 contributors
*
* Contact Email: rpj@callisto.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "pthread.h"
#include "implement.h"
int
pthread_barrier_wait (pthread_barrier_t * barrier)
{
int result;
int step;
pthread_barrier_t b;
if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
{
return EINVAL;
}
b = *barrier;
step = b->iStep;
if (0 == InterlockedDecrement ((long *) &(b->nCurrentBarrierHeight)))
{
/* Must be done before posting the semaphore. */
b->nCurrentBarrierHeight = b->nInitialBarrierHeight;
/*
* There is no race condition between the semaphore wait and post
* because we are using two alternating semas and all threads have
* entered barrier_wait and checked nCurrentBarrierHeight before this
* barrier's sema can be posted. Any threads that have not quite
* entered sem_wait below when the multiple_post has completed
* will nevertheless continue through the semaphore (barrier)
* and will not be left stranded.
*/
result = (b->nInitialBarrierHeight > 1
? sem_post_multiple (&(b->semBarrierBreeched[step]),
b->nInitialBarrierHeight - 1) : 0);
}
else
{
/*
* Use the non-cancelable version of sem_wait().
*/
result = ptw32_semwait (&(b->semBarrierBreeched[step]));
}
/*
* The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD.
* This also sets up the alternate semaphore as the next barrier.
*/
if (0 == result)
{
result = ((PTW32_INTERLOCKED_LONG) step ==
PTW32_INTERLOCKED_COMPARE_EXCHANGE ((PTW32_INTERLOCKED_LPLONG)
& (b->iStep),
(PTW32_INTERLOCKED_LONG)
(1L - step),
(PTW32_INTERLOCKED_LONG)
step) ?
PTHREAD_BARRIER_SERIAL_THREAD : 0);
}
return (result);
}
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