RFR: 8323631: JfrTypeSet::write_klass can enqueue a CLD klass that is unloading

[Erik Gahlin]

On Mon, 15 Jan 2024 22:42:51 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> Greetings,
> 
> [JDK-8316241](https://bugs.openjdk.org/browse/JDK-8316241) introduced a bug where a CLD klass that may be in the process of being unloaded can erroneously get enqueued (because it does not go through the proper registration for unloading). This is a result of the attempt to make artefact tagging deep, by transitively marking (and enqueuing) CLD klasses.
> 
> However, during class unloading, it is possible that a CLD klass is itself being unloaded. There must be a check for this situation so that klasses being unloaded are not enqueued.
> 
> Testing: jdk_jfr, stress testing
> 
> Thanks
> Markus

Marked as reviewed by egahlin (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/17434#pullrequestreview-1822490945