RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning

[Patricio Chilano Mateo]

On Sat, 26 Oct 2024 05:39:32 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> test/jdk/java/lang/reflect/callerCache/ReflectionCallerCacheTest.java line 30:
>> 
>>> 28:  *         by reflection API
>>> 29:  * @library /test/lib/
>>> 30:  * @requires vm.compMode != "Xcomp"
>> 
>> If there is a problem with this test running with -Xcomp and virtual threads, maybe it should be handled as a separate bug fix.
>
> JBS has several issues related to ReflectionCallerCacheTest.java and -Xcomp, going back several releases. It seems some nmethod is keeping objects alive and is preventing class unloading in this test. The refactoring of j.l.ref in JDK 19 to workaround pinning issues made it go away. There is some minimal revert in this PR to deal with the potential for preemption when polling a reference queue and it seems the changes to this Java code have brought back the issue. So it's excluded from -Xcomp again.  Maybe it would be better to add it to ProblemList-Xcomp.txt instead? That would allow it to link to one of the JSB issue on this issue.

I added the test to `test/jdk/ProblemList-Xcomp.txt` instead with a reference to 8332028.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1831604339