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

[David Holmes]

On Fri, 30 Jul 2021 00:08:55 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> A trivial follow-up to:
>> 
>> JDK-8271251 JavaThread::java_suspend() fails with "fatal error: Illegal threadstate encountered: 6"
>> 
>> that adds a stronger sanity check of thread state when polling for safepoint/handshakes.
>> 
>> This fix was used to test @pchilano's fix for JDK-8271251 in my JDK17 Mach5
>> Tier[1-8] runs for JDK-8271251. It has also been tested with Mach5 Tier[1-3]
>> for jdk/jdk (JDK18).
>
> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
> 
>   dholmes CR

Marked as reviewed by dholmes (Reviewer).

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