RFR: 8281615: Deadlock caused by jdwp agent [v4]

[David Holmes]

On Tue, 15 Feb 2022 20:17:09 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> I am not sure classTrack_activate() has the problem, but it is called outside of initialization, inside debug loop ... so I assume that event callback might happen.
>
> I agree. This code is called when the debug agent receives a CLASS_UNLOAD EventRequest (which the debug agent handles by requesting JVMTI GC_FINISH events). So there is nothing that prevents `classTrack_processUnloads()` from being called at the same time.

In that case the `classTrack_processUnloads` is racing with the `classTrack_activate` call. I would not expect it to be possible to generate an event in relation to this before things have been "activated". But moving on ...

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PR: https://git.openjdk.java.net/jdk/pull/7461