[jdk17u-dev] RFR: 8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool [v2]

[Dmitry Chuyko]

> This a backport of JDK-8351933 [0] (PR [1]) for 17u. At one of code paths the TC subfield of ctl field is decremented and the result is not masked correctly. As a result, the FJP may stop executing tasks [2]. The target code is in awaitWork() instead of tryTrim() 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 compareAndSetCtl() is constructed using '(c & RC_MASK) | ((c - TC_UNIT) & TC_MASK)' 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
> [2] https://bugs.openjdk.org/browse/JDK-8330017

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 two additional commits since the last revision:

 - Merge branch 'openjdk:master' into JDK-8351935
 - RC_MASK and TC_MASK instead of UC_MASK

-------------

Changes:
  - all: https://git.openjdk.org/jdk17u-dev/pull/3354/files
  - new: https://git.openjdk.org/jdk17u-dev/pull/3354/files/3bd11db2..7fbe301f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3354&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3354&range=00-01

  Stats: 122497 lines in 1962 files changed: 70563 ins; 39977 del; 11957 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3354.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3354/head:pull/3354

PR: https://git.openjdk.org/jdk17u-dev/pull/3354