/* Simple pthread example with semaphores         */
/* To compile me for Linux, type:                 */
/*    gcc -o filename filename.c -lpthread        */
/* To execute, type:  filename                    */

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

void * simple1(void *);
void * simple2(void *);

#define NUM_THREADS 2
pthread_t tid[NUM_THREADS];      /* array of thread IDs */
sem_t semA, semB;

main( int argc, char *argv[] ) 
{
  int i, ret;

  sem_init(&semA, 0, 0);
  sem_init(&semB, 0, 0);

  pthread_create(&tid[0], NULL, simple1, NULL);
  pthread_create(&tid[1], NULL, simple2, NULL);
  for ( i = 0; i < NUM_THREADS; i++)
    pthread_join(tid[i], NULL);

  printf("\nmain() reporting that all %d threads have terminated\n", i);

}  /* main */

  

void * simple1(void * parm)
{
   printf("Thread 1 here, before the barrier.\n");
   sem_post(&semB);
   sem_wait(&semA);
   printf("Thread 1 after the barrier.\n");
}    

void * simple2(void * parm)
{
   printf("Thread 2 here, before the barrier.\n");
   sem_post(&semA);
   sem_wait(&semB);
   printf("Thread 2 after the barrier.\n");
}