glibc/linuxthreads/Examples/ex9.c

/* Tests for pthread_barrier_* functions.
   Copyright (C) 2000 Free Software Foundation, Inc.
   Contributed by Kaz Kylheku <kaz@ashi.footprints.net>, 2000.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <error.h>
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

#define NUM_THREADS 10
#define NUM_ITERS   500

static void *thread (void *);
static pthread_barrier_t barrier;

int
main (void)
{
  pthread_t th;
  int i;

  if (pthread_barrier_init (&barrier, NULL, NUM_THREADS + 1) != 0)
    error (EXIT_FAILURE, 0, "cannot initialize barrier");

  for (i = 0; i < NUM_THREADS; i++)
    {
      if (pthread_create (&th, NULL, thread, NULL) != 0)
	error (EXIT_FAILURE, 0, "cannot create thread");
    }

  (void) thread (NULL);
  /* notreached */
  return 0;
}


static void *
thread (void *arg)
{
  int i;
  pthread_t self = pthread_self ();
  static pthread_t last_serial_thread;
  static int linecount; /* protected by flockfile(stdout) */

  for (i = 0; i < NUM_ITERS; i++)
    {
      switch (pthread_barrier_wait (&barrier))
	{
	case 0:
	  flockfile (stdout);
	  printf ("%04d: non-serial thread %lu\n", ++linecount, 
		  (unsigned long) self);
	  funlockfile (stdout);
	  break;
	case PTHREAD_BARRIER_SERIAL_THREAD:
	  flockfile (stdout);
	  printf ("%04d: serial thread %lu\n", ++linecount, 
		  (unsigned long) self);
	  funlockfile (stdout);
	  last_serial_thread = self;
	  break;
	default:
	  /* Huh? */
	  error (EXIT_FAILURE, 0, "unexpected return value from barrier wait");
	}
    }

  if (pthread_equal (self, last_serial_thread))
  {
    flockfile (stdout);
    printf ("%04d: last serial thread %lu terminating process\n", 
	    ++linecount, (unsigned long) self);
    funlockfile (stdout);
    exit (0);
  }

  pthread_exit(NULL);
}