pthread_barrier_init.c

/*
 * pthread_barrier_init.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_init (pthread_barrier_t * barrier,
		      const pthread_barrierattr_t * attr, unsigned int count)
{
  pthread_barrier_t b;

  if (barrier == NULL || count == 0)
    {
      return EINVAL;
    }

  if (NULL != (b = (pthread_barrier_t) calloc (1, sizeof (*b))))
    {
      b->pshared = (attr != NULL && *attr != NULL
		    ? (*attr)->pshared : PTHREAD_PROCESS_PRIVATE);

      b->nCurrentBarrierHeight = b->nInitialBarrierHeight = count;
      b->iStep = 0;

      /*
       * Two semaphores are used in the same way as two stepping
       * stones might be used in crossing a stream. Once all
       * threads are safely on one stone, the other stone can
       * be moved ahead, and the threads can start moving to it.
       * If some threads decide to eat their lunch before moving
       * then the other threads have to wait.
       */
      if (0 == sem_init (&(b->semBarrierBreeched[0]), b->pshared, 0))
	{
	  if (0 == sem_init (&(b->semBarrierBreeched[1]), b->pshared, 0))
	    {
	      *barrier = b;
	      return 0;
	    }
	  (void) sem_destroy (&(b->semBarrierBreeched[0]));
	}
      (void) free (b);
    }

  return ENOMEM;
}