RFR: 8244679: JVM/TI GetCurrentContendedMonitor/contmon001 failed due to "(IsSameObject#3) unexpected monitor object: 0x000000562336DBA8"

[Robbin Ehn]

As the stack trace in the bug shows, we cannot load classes, since we may take a monitor.
Resulting in an unexpected result to GetCurrentContendedMonitor().
Trying to use some decent primitive, e.g. Wicket/Semaphore/.., without being implementation dependent means we must warm up every possible scenario, since it may use a new class.
Instead I here just use sleep + volatile for the barriers.

I cannot reproduce with these changes.

Chewing through T6 as most issues have been seen there.

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Commit messages:
 - Volatile and sleep

Changes: https://git.openjdk.java.net/jdk/pull/1177/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1177&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8244679
  Stats: 39 lines in 2 files changed: 25 ins; 5 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1177.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1177/head:pull/1177

PR: https://git.openjdk.java.net/jdk/pull/1177