RFR: 8249004: Reduce ThreadListHandle overhead in relation to direct handshakes [v4]

[Daniel D.Daugherty]

On Wed, 22 Sep 2021 03:57:21 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

>> A trivial fix to reduce ThreadListHandle overhead in relation to handshakes.
>> 
>> This refactoring was tested with Mach5 Tier[1-3].
>
> Daniel D. Daugherty has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8249004
>  - Merge branch 'master' into JDK-8249004
>  - Merge branch 'master' into JDK-8249004
>  - Merge branch 'master' into JDK-8249004
>  - 8249004: Reduce ThreadListHandle overhead in relation to direct handshakes

Rebased this project to the latest jdk/jdk baseline as of 2021.10.11 in the afternoon.

HOWEVER, I'm still working on the latest version of the fix so please do not review
this PR yet.

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