RFR: 8368086: G1: Use ThreadsClaimTokenScope in G1CMRemarkTask

[Stefan Karlsson]

On Fri, 19 Sep 2025 09:16:47 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Replace `StrongRootsScope` with `ThreadsClaimTokenScope` in `G1ConcurrentMark::finalize_marking` to be more precise with what is actually needed and why.
> 
> Test: tier1

One difference between the two code paths is the check to see if the number of threads are > 0. Are we guaranteed that active_workers are > 0 here?

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PR Review: https://git.openjdk.org/jdk/pull/27385#pullrequestreview-3244202432