Integrated: 8274196: Crashes in VM_HeapDumper::work after JDK-8252842

[Lin Zang]

On Fri, 24 Sep 2021 13:13:39 GMT, Lin Zang <lzang at openjdk.org> wrote:

> The root cause for crash in ZGC is that the JNIHandles are processed before object iteration. And ZGC would update the JNIHandles at object iteration with read barrier. So the crash is cause by accessing the invalid address which can be dummy info after zgc, and hence crash.
> 
> The lock rank issue can be fixed because the related mutexes are acquired in safepoint. so the safepoint_check_required could be safepoint_check_always.
> 
> The Epsilon issue is caused by wrong _num_dumper_thread calculated when the gang==NULL.

This pull request has now been integrated.

Changeset: bfd61634
Author:    Lin Zang <lzang at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/bfd616347126a802c641326a6be5a14c4cd7af90
Stats:     22 lines in 3 files changed: 5 ins; 13 del; 4 mod

8274196: Crashes in VM_HeapDumper::work after JDK-8252842
8274245: sun/tools/jmap/BasicJMapTest.java Mutex rank failures

Reviewed-by: coleenp, pliden, cjplummer

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PR: https://git.openjdk.java.net/jdk/pull/5681