RFR: 8271348: Add stronger sanity check of thread state when polling for safepoint/handshakes [v2]

[Daniel D.Daugherty]

On Fri, 30 Jul 2021 16:46:06 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   dholmes CR
>
> LGTM!
> 
> Thanks,
> Patricio

Since @pchilano  is listed as the Contributor, I need another (R)eviewer.
I can't be listed as a (R)eviewer because I created the PR. @dholmes-ora,
if you are okay with the latest version (and my replies), that would work.

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PR: https://git.openjdk.java.net/jdk/pull/4936