Well, I saw this occasionally on my dual core laptop when working on the RWLock.  A notify() before a target does a wait() is ineffective and it would wait indefinitely after the notify(5) call.  This isn't a "proper" fix (I had another, more complex, where we would keep a counter for the number of successful "waiters" and wait for that to reach the target value) but it is in the spirit of many of these tests, where we rely on _wait() to be sufficient to reach a certain state.