conditionVariable {
  int queueSize = 0;
  semaphore lock;
  semaphore waiting;
  
  wait() {
     lock.acquire();
     queueSize++;
     lock.release();
     waiting.down();
  }
  
  signal() {
     lock.acquire();
     while (queueSize > 0){
        queueSize--;
        waiting.up();
     }
     lock.release();
  }
}