RFR: 8369178: G1: Use NMethodMarkingScope and ThreadsClaimTokenScope in G1RootProcessor

[Thomas Schatzl]

On Mon, 6 Oct 2025 12:20:42 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> Replace `StrongRootsScope` with `ThreadsClaimTokenScope` and `MarkingNMethodClosure` in `G1RootProcessor ` to be more precise with what is needed and why.
> 
> - `MarkingNMethodClosure` is used in `G1FullGCMarkTask`, so we also need `NMethodMarkingScope`.
> - `active_workers ` is guaranteed to be `> 0`
> 
> Passes tier1 and tier2 (fastdebug).

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/27644#pullrequestreview-3315062162