RFR: 8253180: ZGC: Implementation of JEP 376: ZGC: Concurrent Thread-Stack Processing [v5]

[Erik Österlund]

On Thu, 24 Sep 2020 12:49:06 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Erik Österlund has updated the pull request with a new target base due to a merge or a rebase. The pull request now
>> contains seven commits:
>>  - Review: Per CR 1
>>  - Merge branch 'master' into 8253180_conc_stack_scanning
>>  - Review: Albert CR 1
>>  - Review: SteafanK CR 2
>>  - Merge branch 'master' into 8253180_conc_stack_scanning
>>  - Review: SteafanK CR 1
>>  - 8253180: ZGC: Implementation of JEP 376: ZGC: Concurrent Thread-Stack Processing
>
> I looked at the runtime code and it is nicely non-invasive, and makes sense where there are changes.

I uploaded an incremental change to re-instate the separate verification of the thread head vs frames that I had
before. Stefan wanted it merged into one function unless I could remember why I had split it. I did not remember why,
but now I do. Updated with comments this time to describe why this is split (the exception oop must be fixed before
fiddling with the frames).

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PR: https://git.openjdk.java.net/jdk/pull/296