RFR: 8374678: ZGC: Convert zForwarding to use Atomic<T> [v2]

[Stefan Karlsson]

On Wed, 14 Jan 2026 09:36:37 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> Convert usages of AtomicAccess to Atomic<T> in zForwarding.
>> 
>> `_ref_count` is unused by the SA. There is currently no implementation of Atomic<T> in SA.
>> 
>> Testing:
>>  * GHA
>>  * Tier 1-2 with ZGC linux x64 and linux aarch64
>>  * Stress tests with ZGC linux x64 and linux aarch64
>
> Axel Boldt-Christmas 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 three additional commits since the last revision:
> 
>  - Use compare_set
>  - Merge remote-tracking branch 'upstream_jdk/master' into JDK-8374678
>  - ZGC: Convert zForwarding to use Atomic<T>

Marked as reviewed by stefank (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/29220#pullrequestreview-3659903614