/* * 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"intpthread_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);}