Meanwhile, On The Signaling Side...

To signal a condition variable, we use 'pthread_cond_signal' (to wake a single waiting thread), or 'pthread_cond_broadcast' (to signal all threads that might be waiting on this condition variable):

 /* lock the mutex */
 if (pthread_mutex_lock(&mutex) != 0) {
  /* handle error... */
 }
 
 /* perform the operation on which we wish */
 /* to notify the other thread...          */
 ...

 /* signal the condition variable. */
 if (pthread_cond_signal(&cond) != 0) {
   perror("help help help! pthread_cond_signal failed:");
   exit(1);
 }

 /* finally, unlock the mutex. */
 if (pthread_mutex_unlock(&mutex) != 0) {
   /* handle error... */
 }