Thank you Maksim for the information.
I have very, very, very simple design.
So for my design the use of notify()/notifyAll() in the lock method was an absolute nonsense. In the unlock() method I have used notifyAll().
Of course, I agree with you that calling notifyAll() from lock doesn't make sense, but the fact that you got 100% while calling notifyAll() in unlock() (as other people) confirms that the "consumes no CPU cycle" requirement may be loosely interpreted.
Regards,
Phil.