Write a parallel program in c for implement producer consumer problem using mutex

#include <stdio.h>

#include <stdlib.h>

#include <pthread.h>

void *functionC();

pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;

int  counter = 0;

main()

{

   int rc1, rc2;

   pthread_t thread1, thread2;

   /* Create independent threads each of which will execute functionC */

   if( (rc1=pthread_create( &thread1, NULL, &functionC, NULL)) )

   {

      printf("Thread creation failed: %d\n", rc1);

   }

   if( (rc2=pthread_create( &thread2, NULL, &functionC, NULL)) )

   {

      printf("Thread creation failed: %d\n", rc2);

   }

   /* Wait till threads are complete before main continues. Unless we  */

   /* wait we run the risk of executing an exit which will terminate   */

   /* the process and all threads before the threads have completed.   */

   pthread_join( thread1, NULL);

   pthread_join( thread2, NULL);

   exit(0);

}

void *functionC()

{

   pthread_mutex_lock( &mutex1 );

   counter++;

   printf("Counter value: %d\n",counter);

   pthread_mutex_unlock( &mutex1 );

}