tree 2dada0828636c2dc8e40e0f34b2b3f01e6caa0a5
parent ba1e9e73c07bffc046f651414db43aeee9953d15
author Alex Light <allight@google.com> 1521762610 -0700
committer Alex Light <allight@google.com> 1521839975 -0700

Remove unneeded ScopedGCCriticalSections from openjdkjvmti.

We used ScopedGCCriticalSections in many parts of the openjdkjvmti
often unnecessarily.

We removed a totally unneeded GCCriticalSection that was acquired when
modifying the instrumentation listeners.

We also removed RequestGCSafeSynchronousCheckpoint and the change to
use GcRoots instead.  We added RequestGCSafeSynchronousCheckpoint as a
way to prevent the GC from running when we are doing some JVMTI
operations on other threads.  This could interact with running GCs in
non-trivial ways, potentially causing deadlocks in some situations.
This changes the code to instead use read-barriers and GcRoots to
ensure that we do not read data from the wrong gc space.

In order for this to work correctly we need to make sure that we are
only ever reading the GcRoots from the thread that eventually needs
the reference. This required some re-writing of the checkpoint
closures since they would often just call AddLocalReference on
non-local Thread objects.

Changes to Thread::RequestSynchronousCheckpoint and art::Barrier were
needed in order to allow this all to work since we needed to ensure
that the requesting thread did not suspend as the checkpoint was being
run.

This is a partial revert of commit 7585b91bfc77b8.

Bug: 67838964
Bug: 76003243

Test: use gapid
Test: ./test.py --host -j50
Test: ./art/tools/run-libjdwp-tests.sh --mode=host

Change-Id: I26d871089829639eccb973cecc315194f7bcf681