class CV {
  private:
    Queue waiting;
  public:
    void wait(Lock *lock);
    void signal();
    void broadcast();
}

// Monitor lock is held by current thread.
void CV::wait(Lock *lock) {
    assert(lock.isHeld());
    waiting.add(myTCB); 
    // Switch to new thread and release lock.
    scheduler.suspend(&lock);
    lock->acquire();
}

// Monitor lock is held by current thread.
void CV::signal() {
    if (waiting.notEmpty()) {
        thread = waiting.remove();
        scheduler.makeReady(thread);
    }
}

void CV::broadcast() {
    while (waiting.notEmpty()) {
        thread = waiting.remove();
        scheduler.makeReady(thread);
    }
}