On Mon, 22 Nov 2021 13:49:02 GMT, Erik Österlund <eosterl...@openjdk.org> wrote:

> The VM_HeapDumper code uses a C heap allocated ParallelObjectIterator. It is 
> constructed right before running a parallel operation with a work gang, but 
> freed in the destructor of the VM_HeapDumper. This means it is created on one 
> thread and deleted on another thread. This becomes a bit problematic when a 
> parallel object iterator implementation uses a ThreadsListHandle (which is 
> indeed the case for ZGC). This patch changes ParallelObjectIterator to be a 
> StackObj, carrying a ParallelObjectIteratorImpl object, which is never 
> exposed publicly. This ensures that construction and destruction of the 
> internal object iterator is scoped like RAII objects, hence complying with 
> how ThreadsListHandle is supposed to be used.

Looks good.

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Marked as reviewed by pliden (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6501

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