RFR: 8376195: Convert ThreadLocalAllocBuffer to use Atomic<T>

[Kim Barrett]

On Fri, 23 Jan 2026 12:35:03 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review the change to use `Atomic<T>` in `ThreadLocalAllocBuffer`.
> 
> Testing: gha
> 
> Thanks,
>   Thomas

src/hotspot/share/gc/shared/threadLocalAllocBuffer.hpp line 51:

> 49:   friend class JVMCIVMStructs;
> 50: private:
> 51:   Atomic<HeapWord*> _start;                      // address of TLAB

[pre-existing] I don't understand why `_start` is atomic but other members set by `initialize` are not.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29386#discussion_r2724702445