On Thu, 13 Mar 2025 13:34:51 GMT, Dmitry Chuyko <dchu...@openjdk.org> wrote:
> Please review a tiny fix in the ForkJoinPool. Since JDK 9 (JDK-8134852 [1]) > in one case when TC subfield in ctl field is decremented, the applied masking > (UMASK, upper bits) may not preserve neighbor RC subfield sometimes. In JDKs > prior to 19 FJP may stop executing tasks, which requires a long running > application restart [2]. Since 19 it is even harder to reproduce because of > the separate parallelism field. > > The fix is to replace 'UMASK & (c - TC_UNIT)' with '(c & RC_MASK) | ((c - > TC_UNIT) & TC_MASK)' which preserves the RC part of the compareAndSetCtl() > candidate argument. On 17u and 11u that repairs known tests and applications. > This PR is for the mainline, and I intend to backport it to 21u, 17u and 11u. > > [1] https://bugs.openjdk.org/browse/JDK-8134852 > [2] https://bugs.openjdk.org/browse/JDK-8330017 The issue looks valid to me and the fix looks good. Would be nice if another reviewer can double check. ------------- Marked as reviewed by liach (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/24034#pullrequestreview-2691756966
