RFR: 8256830: misc tests failed with "assert(env->is_enabled(JVMTI_EVENT_OBJECT_FREE)) failed: checking" [v2]

[Coleen Phillimore]

> The ServiceThread cleaning used a stale ObjectFree state when calling remove_dead_entries, because another thread had concurrently set is_enabled to false.  Add a lock around setting/resetting the lock event state and retest the state under a lock.  Ran the test 100s of time without failure, where otherwise it fails very quickly.
> Tested with tier2,3 and running tiers 4,5,6 in progress.
> Thanks to Kim for his previous feedback.

Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:

  Make enable events lock unconditionally if tagmap present.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1439/files
  - new: https://git.openjdk.java.net/jdk/pull/1439/files/1d9e6bef..ca1715b9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1439&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1439&range=00-01

  Stats: 8 lines in 1 file changed: 0 ins; 6 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1439.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1439/head:pull/1439

PR: https://git.openjdk.java.net/jdk/pull/1439