RFR: 8266936: Add a finalization JFR event

[Brent Christian]

On Tue, 18 May 2021 21:40:57 GMT, Istvan Neuwirth <github.com+6502015+ineuwirth 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.

Good idea, thanks.

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

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