class Lock {
  private:
    int value = FREE;
    Queue waiting;
  public:
    void acquire();
    void release();
}

Lock::acquire() {
    TCB *chosenTCB;

    disableInterrupts();
    if (value == BUSY) {
        waiting.add(runningThread); 
        runningThread->state = #\waitingThreadState#;
        next = readyList.remove();
        thread_switch(runningThread, 
                      chosenTCB);  
        runningThread->state = #\runningThreadState#;
    } else {
        value = BUSY;
    }
    enableInterrupts();
}

Lock::release() {
// next thread to hold lock
    TCB *next; 

    disableInterrupts();
    if (waiting.notEmpty()) {
    // move one TCB from waiting 
    // to ready
        next = waiting.remove();
        next->state = #\readyThreadState#;
        readyList.add(next);
    } else {
        value = FREE;
    }
    enableInterrupts();
}