hg: jdk7/hotspot-gc/hotspot: 6992998: CMSWaitDuration=0 causes hangs with +ExplicitGCInvokesConcurrent

[y.s.ramakrishna at oracle.com]

Changeset: cd3ef3fd20dd
Author:    ysr
Date:      2010-10-21 17:29 -0700
URL:       http://hg.openjdk.java.net/jdk7/hotspot-gc/hotspot/rev/cd3ef3fd20dd

6992998: CMSWaitDuration=0 causes hangs with +ExplicitGCInvokesConcurrent
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

! src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.cpp
! src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp
! src/share/vm/runtime/globals.hpp