private final void contendedLock() {
            boolean waiting = false;
            for (int s;;) {
                if (((s = lockState) & ~WAITER) == 0) {
                    if (LOCKSTATE.compareAndSet(this, s, WRITER)) {
                        if (waiting)
                            waiter = null;
                        return;
                    }
                }
                else if ((s & WAITER) == 0) {
                    if (LOCKSTATE.compareAndSet(this, s, s | WAITER)) {
                        waiting = true;
                        waiter = Thread.currentThread();
                    }
                }
                else if (waiting)
                    LockSupport.park(this);
            }
        }
private final void contendedLock()