Summary: Closed a timing hole during which concurrent full gc requests can be missed. The hole can increase the latency of the response to a full gc request by up to the value of CMSWaitDuration. If CMSWaitDuration=0 is, as currently, interpreted as an unbounded wait, suitable in certain tuning scenarios, the application can potentially hang. Made two obscure tunables, including CMSWaitDuration, manageable.
Reviewed-by: jcoomes, tonyp