RFR: 8373941: Epsilon: Robust counter updates in early VM phases [v2]

[Thomas Schatzl]

On Fri, 9 Jan 2026 09:08:06 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See more details in the bug. This PR makes the counters updated on allocation path more robust. New regression test captures the original failure (intermittently). This would be also backported to JDK 26.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 server fastdebug, `gc/epsilon`, 100x
>>  - [x] Linux x86_64 server fastdebug, `runtime/cds/appcds/TestEpsilonGCWithCDS.java`, 100x
>>  - [x] Linux x86_64 server fastdebug, `gc/epsilon/TestInitAllocs.java`, 1000x
>
> Aleksey Shipilev 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:
> 
>  - Merge branch 'master' into JDK-8373941-epsilon-robust-counter-updates
>  - Typos
>  - Fix

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/29061#pullrequestreview-3643697000