RFR: 8266936: Add a finalization JFR event

[Istvan Neuwirth]

On Tue, 18 May 2021 20:55:10 GMT, Brent Christian <bchristi at openjdk.org> wrote:

> Please review this enhancement to add a new JFR event, generated whenever a finalizer is run.
> (The makeup is similar to the Deserialization event, [JDK-8261160](https://bugs.openjdk.java.net/browse/JDK-8261160).)
> 
> The event's only datum (beyond those common to all jfr events) is the class of the object that was finalized.
> 
> The Category for the event:
> `"Java Virtual Machine" / "GC" / "Finalization"`
> is what made sense to me, even though the event is generated from library code.
> 
> Along with the new regtest, I added a run mode to the basic finalizer test to enable jfr.
> Automated testing looks good so far.
> 
> Thanks,
> -Brent

test/jdk/jdk/jfr/event/gc/finalization/TestFinalizerEvent.java line 48:

> 46: 
> 47: public class TestFinalizerEvent {
> 48:     static boolean finalizerRun = false;

Should not this be a `volatile` field? (Or alternatively, using `AtomicBoolean`). As the `finalize` is invoked on the finalizer thread, the other thread executing the test might not see the change.

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PR: https://git.openjdk.java.net/jdk/pull/4101