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 This pull request has now been integrated. Changeset: fed34e46 Author: Dmitry Chuyko <dchu...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/fed34e46b89bc9b0462d9b5f5e5ab5516fe18c6e Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod 8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool Reviewed-by: dl, alanb, liach ------------- PR: https://git.openjdk.org/jdk/pull/24034
