JDK-8220295 added the following tests to exclusiveAccess.dirs to deal with some sporadic and poorly understood test failures:

 sun/tools/jstatd
 sun/tools/jcmd
 sun/tools/jhsdb
 sun/tools/jhsdb/heapconfig
 sun/tools/jinfo
 sun/tools/jmap
 sun/tools/jps
 sun/tools/jstack
 sun/tools/jstat
 com/sun/tools/attach

For the most part this is all of our tests that use the Attach API, and the issue being worked around seemed to be related to VirtualMachine.list(). There have been a few fixes in this area since then that may have resolved the issues that were being seen. In particular: JDK-8205654, JDK-8220175, and JDK-8223600. For the reason we should see how well these tests now run concurrently.

Also, jhsdb never should have been added to the list since it does not use the Attach API.