RFR: 8249004: Reduce ThreadsListHandle overhead in relation to direct handshakes [v12]

[Coleen Phillimore]

On Fri, 5 Nov 2021 15:43:37 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> A fix to reduce ThreadsListHandle overhead in relation to handshakes and
>> we add sanity checks for ThreadsListHandles higher in the call stack.
>> 
>> This fix was tested with Mach5 Tier[1-8]; Tier8 is still running.
>
> Daniel D. Daugherty has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8249004.cr4.patch

Thanks for the offline comments.  I still think refactoring is_JavaThread_protected would be a lot nicer but that's my opinion and you don't have to change it.

-------------

Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4677