Deadlock in Java9.getDefaultImportClasses() ?

After updating Kubernetes from 1.27 to 1.28 one of our applications is not working anymore.

The application uses thymeleaf templating engine that uses groove under the hood. The application does not respond to request that require a template to be rendered. Looking at the stacktrace did not give us any hint what is causing this. In the profiler it looks like a lot of time is spent waiting in Java9.getDefaultImportClasses() method. We could not find any code in there or in ClassFinder.find() that looks like it could cause a dead lock.

When attaching the debugger and adding some break points in Java9.getDefaultImportClasses() it did work 🤷‍♂️.

The only thing that we could see that is different between a working setup and a non-working one is the updated Kubernetes with updated node images using a newer linux kernel. No idea how this could impact the code.

Does anyone have an idea what could cause this or what we could do to identify the cause of the dead lock?

I attached a screenshot of the profiler.

With regards,
Florian Mutter

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