[jdk11u-dev] RFR: 8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool [v6]

[duke]

On Fri, 26 Sep 2025 16:33:48 GMT, Dmitry Chuyko <dchuyko at openjdk.org> wrote:

>> This a backport of JDK-8351933 [0] (PR [1]) for 11u. At one of code paths the TC subfield of ctl field is decremented and the result is not masked correctly. The target code is in runWorker() instead of tryTrim()/awaitWork() and the surrounding code is different from the current master, as well as the original mask name. The core change is the same, candidate for CTL.compareAndSet is constructed using '(RC_MASK & c) | (TC_MASK & (c - TC_UNIT))' instead of '(UC_MASK & (c - TC_UNIT))' to correctly preserve the RC subfield.
>> 
>> [0] https://bugs.openjdk.org/browse/JDK-8351933
>> [1] https://github.com/openjdk/jdk/pull/24034
>
> Dmitry Chuyko 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 six additional commits since the last revision:
> 
>  - Merge branch 'openjdk:master' into JDK-8351936
>  - Merge branch 'openjdk:master' into JDK-8351936
>  - Merge branch 'openjdk:master' into JDK-8351936
>  - Merge branch 'openjdk:master' into JDK-8351936
>  - Merge branch 'openjdk:master' into JDK-8351936
>  - RC_MASK and TC_MASK instead of UC_MASK

@dchuyko 
Your change (at version 4efbfb6daf0ff264cdebc05b5387574dff556a1a) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk11u-dev/pull/3012#issuecomment-3351253475