RFR: 8366363: MemBaseline accesses VMT without using lock [v12]

[Johan Sjölen]

On Wed, 3 Sep 2025 09:12:44 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi,
>> 
>> The `MemBaseline` used to access the VMT instance directly without a lock. We fix that, and we switch from using a `LinkedList` to a copied `RegionsTree` instead.
>
> Johan Sjölen has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 16 commits:
> 
>  - Merge remote-tracking branch 'openjdk/master' into cleanup-membaseline
>  - Rename to _vma_allocations
>  - After a lot of casting
>  - Yup
>  - Some more ugly casts
>  - Aha, _root is typed as an IntrusiveRBNode
>  - Aha, missing include
>  - Wait, the VMATree is wrong?
>  - Rename
>  - It's const
>  - ... and 6 more: https://git.openjdk.org/jdk/compare/6dda2f6f...82df750b

Mach5 passes tier1 and tier2.

@caspernorrbin , @afshin-zafari , @Arraying , could you review this again?

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PR Comment: https://git.openjdk.org/jdk/pull/27003#issuecomment-3252209567