#include <pthread.h>
#include <stdio.h>

void * task(void * data)
{
 pthread_mutex_t * mtx=(pthread_mutex_t *)data;
 int n;
 fprintf(stderr,"begin task() in %d\n",
                (int)pthread_self()); /* ugly cast ! */

 for(n=0;n<2;n++)
 {
  unsigned long i;
  pthread_mutex_lock(mtx); /* begin critical section */
  fprintf(stderr,"  thread %d -->\n",
                (int)pthread_self()); /* ugly cast ! */
  for(i=0;i<10*1000*1000;i++) {}
  fprintf(stderr,"  thread %d <--\n",
                (int)pthread_self()); /* ugly cast ! */
  pthread_mutex_unlock(mtx); /* end critical section */
 }

 fprintf(stderr,"end task() in %d\n",
                (int)pthread_self()); /* ugly cast ! */

 return((void *)0);
}

int main(void)
{
 pthread_mutex_t mtx=PTHREAD_MUTEX_INITIALIZER;
 pthread_t th[3];
 int i;
 void * result;

 for(i=0;i<3;i++)
 {
  if(pthread_create(&th[i],(pthread_attr_t *)0,task,&mtx))
    { fprintf(stderr,"Pb create\n"); return(1); }
 }

 for(i=0;i<3;i++)
 {
  if(pthread_join(th[i],&result))
    { fprintf(stderr,"Pb join\n"); return(1); }
 }

 if(pthread_mutex_destroy(&mtx))
 { fprintf(stderr,"Pb mutex destroy\n"); return(1); }

 return(0);
}