RFR: 8298377: JfrVframeStream causes deadlocks in ZGC [v2]

Wed Jan 18 12:50:10 UTC 2023

On Wed, 18 Jan 2023 12:44:29 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> > > Question: does the "start_processing()" call ever reach a malloc, directly or indirectly? If so, it is problematic to call from the sampler thread.
> > 
> > 
> > It does allocate a stack iterator with malloc if it really did need to start processing and it was not yet started. So yes. Would you mind explaining why using malloc is problematic?
> 
> The problem is that the suspendee can be holding the malloc lock. Please see https://bugs.openjdk.org/browse/JDK-8274298 for an example situation.

Right - that makes sense. But I thought the processing is poked here before we suspend the target thread? Or did I read the code wrong?

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PR: https://git.openjdk.org/jdk/pull/11586