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

Fri Sep 24 15:48:05 UTC 2021

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.

@linzang and @coleenp - I've ProblemListed the test via:

JDK-8274294 ProblemList sun/tools/jmap/BasicJMapTest.java

to give you folks time to sort thru the details.

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