first condition:
Thread 1 Waits
Thread 2 Notifies

second condition:
Thread 2 Notifies
Thread 1 Should not wait and continue normal execution.

Thread 1:
lock(x);
if(!signaled)
{
    unlock(x); // ****************************
    // still small gap, how to avoid?
    cv.wait();
    signaled = false;
}
else unlock(x);

Thread 2:
lock(x);
signaled = true;
cv.notify();
unlock(x);