[jdk11u-dev] RFR: 8260589: Crash in JfrTraceIdLoadBarrier::load(_jclass*)

[Denghui Dong]

On Thu, 1 Jul 2021 07:29:14 GMT, Denghui Dong <ddong at openjdk.org> wrote:

>> Could I have a review of this backport that fixes a crash problem?
>> 
>> Although there are many conflicts, I think it's necessary to backport it to 11u since the problem is very easy to reproduce.
>> 
>> And I hope JFR's folks could review it.
>> 
>> In addition to the different context of modified files, I think the following items we should review carefully:
>> 
>> 1. use MaxJfrEventId + 100 instead of LAST_TYPE_ID + 1 as the klass id of void.class
>> 2. jdk 11 doesn't support jfr streaming, so I removed the call `JfrTraceIdEpoch::set_changed_tag_state()` in `load_primitive`
>> 3. the Class in jdk 11 doesn't have the field 'hidden', so I removed `writer->write<bool>(false);` in `write_primitive`
>> 4. there are many differences in the API of JfrTraceId between 11u and tip
>> 
>> Thanks,
>> Denghui
>
> @mgronlun @egahlin 
> Sorry for messaging you directly.
> Could you help review this backport when you have time?
> This problem is easy to trigger.
> 
> Thanks,
> Denghui

> Hi @D-D-H,
> Unfortunately I can't comment so much on the actual changes in JFR coding. However, I ran your patch through our testing and couldn't spot any regressions. So I'm approving it. However, I think it would be good if Markus or Erik (or any other JFR expert) could throw an eye on it.

Thank you.
Yes, I also think this backport should be reviewed properly by JFR folks.

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PR: https://git.openjdk.java.net/jdk11u-dev/pull/47