RFR: 8373723: Deadlock with JvmtiTagMap::flush_object_free_events() [v2]

[Leonid Mesnik]

> The JvmtiTagMap::flush_object_free_events() method might be called from different threads.
> The thread waits using lock until other thread posting events. The locking thread is in vm state doesn't allowing safepoints. While other thread posting events might request safepoints.
> 
> The fix is to block thread to allow safepoints while waiting on the lock.

Leonid Mesnik has updated the pull request incrementally with one additional commit since the last revision:

  applid David's suggestion

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28839/files
  - new: https://git.openjdk.org/jdk/pull/28839/files/3035f2b4..6790f159

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28839&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28839&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28839.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28839/head:pull/28839

PR: https://git.openjdk.org/jdk/pull/28839