RFR: 8310194: Generational ZGC: Lock-order asserts in JVMTI IterateThroughHeap

[Stefan Karlsson]

On Fri, 16 Jun 2023 11:52:51 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

> Generational ZGC changed the location where the heap object iterator called the visit function. It used to be called when the objects were popped and then followed, but it was changed so that the function where called immediately when the objects are marked. This gave the benefit that the verification code code show exactly what root had a broken object. Unfortunately, this change started to apply non-GC closure during the root iteration. This could lead to lock order issues, just like the one described in the JBS entry.
> 
> This fix moves the visit calls for non-GC closures back to the follow calls.

Thanks for reviewing!

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PR Comment: https://git.openjdk.org/jdk/pull/14518#issuecomment-1598821180