hg: jdk/sandbox: Implement allocation fencing

[thomas.stuefe at gmail.com]

Changeset: 5bd12b38d875
Author:    stuefe
Date:      2020-04-04 10:02 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/5bd12b38d875

Implement allocation fencing

+ src/hotspot/share/memory/metaspace/allocationGuard.hpp
! src/hotspot/share/memory/metaspace/classLoaderMetaspace.cpp
! src/hotspot/share/memory/metaspace/metachunk.cpp
! src/hotspot/share/memory/metaspace/metachunk.hpp
! src/hotspot/share/memory/metaspace/metaspaceCommon.cpp
! src/hotspot/share/memory/metaspace/metaspaceCommon.hpp
! src/hotspot/share/memory/metaspace/settings.cpp
! src/hotspot/share/memory/metaspace/settings.hpp
! src/hotspot/share/memory/metaspace/spaceManager.cpp
! src/hotspot/share/memory/metaspace/spaceManager.hpp
! src/hotspot/share/runtime/globals.hpp
! test/hotspot/gtest/metaspace/test_metachunk.cpp