RFR: 8308978: regression with a deadlock involving FollowReferences [v3]

[Alex Menkov]

> The change fixes regression from JDK-8299414.
> There is a deadlock between JvmtiVTMSTransitionDisabler and EscapeBarrier when virtual threads are in mount/unmount transition:
> EscapeBarrier requests deoptimization which requires thread suspension.
> JvmtiVTMSTransitionDisabler ctor waits until all in progress VTMS transitions complete, but they cannot be completed as thread is suspended.
> To avoid the deadlock mount/unmount transitions should be completed before EscapeBarrier stuff.

Alex Menkov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Merge branch 'follow_ref_deadlock' of github.com:alexmenkov/jdk into follow_ref_deadlock
 - Merge branch 'openjdk:master' into follow_ref_deadlock
 - Merge branch 'follow_ref_deadlock' of github.com:alexmenkov/jdk into follow_ref_deadlock
 - fix
 - unproblem-list tests
 - fix
 - unproblem-list tests
 - fix

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14233/files
  - new: https://git.openjdk.org/jdk/pull/14233/files/b2df4fd6..8c3ed263

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14233&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14233&range=01-02

  Stats: 1647 lines in 164 files changed: 729 ins; 474 del; 444 mod
  Patch: https://git.openjdk.org/jdk/pull/14233.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14233/head:pull/14233

PR: https://git.openjdk.org/jdk/pull/14233