hg: shenandoah/jdk10/hotspot: System.gc() with ExplicitGCInvokesConcurrent should block

[ashipile at redhat.com]

Changeset: 02e85b3c09d3
Author:    shade
Date:      2017-09-06 17:59 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk10/hotspot/rev/02e85b3c09d3

System.gc() with ExplicitGCInvokesConcurrent should block

! src/share/vm/gc/shenandoah/shenandoahConcurrentThread.cpp
! src/share/vm/gc/shenandoah/shenandoahConcurrentThread.hpp
! src/share/vm/gc/shenandoah/shenandoahHeap.cpp
! test/gc/shenandoah/options/TestExplicitGC.java