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List:       openjdk-serviceability-dev
Subject:    Integrated: 8276696: ParallelObjectIterator freed at the wrong time in VM_HeapDumper
From:       Erik =?UTF-8?B?w5ZzdGVybHVuZA==?= <eosterlund () openjdk ! java ! net>
Date:       2021-11-23 14:38:15
Message-ID: RU1WUNJVx1eqBs8mKDW0CaW5HtJGn7sFG7noGQsCAIQ=.538901b5-02a8-4bbf-896b-fa70b7424abf () github ! com
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On Mon, 22 Nov 2021 13:49:02 GMT, Erik Österlund <eosterlund@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.

This pull request has now been integrated.

Changeset: f4dc03ea
Author:    Erik Österlund <eosterlund@openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/f4dc03ea6de327425ff265c3d2ec16ea7b0e1634
                
Stats:     70 lines in 15 files changed: 35 ins; 11 del; 24 mod

8276696: ParallelObjectIterator freed at the wrong time in VM_HeapDumper

Reviewed-by: pliden, stefank

-------------

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


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