git: openjdk/mobile: 8230594: Allow direct handshakes without VMThread intervention

[duke]

Changeset: b25bb17b
Author:    Patricio Chilano Mateo <pchilanomate at openjdk.org>
Date:      2020-01-22 16:46:46 +0000
URL:       https://git.openjdk.java.net/mobile/commit/b25bb17b

8230594: Allow direct handshakes without VMThread intervention

Introduce direct handshakes and enable it for biased locking revocations.

Reviewed-by: dholmes, dcubed, coleenp, rehn

! src/hotspot/share/runtime/biasedLocking.cpp
! src/hotspot/share/runtime/handshake.cpp
! src/hotspot/share/runtime/handshake.hpp
! src/hotspot/share/runtime/mutexLocker.cpp
! src/hotspot/share/runtime/safepoint.cpp
! src/hotspot/share/runtime/safepointMechanism.inline.hpp
! src/hotspot/share/runtime/thread.cpp
! src/hotspot/share/runtime/thread.hpp
+ test/hotspot/jtreg/runtime/handshake/HandshakeDirectTest.java