8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool

[dchuyko]

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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

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Progress

• [x] Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue
• [ ] JDK-8351933 needs maintainer approval

Issue

• JDK-8351933: Inaccurate masking of TC subfield decrement in ForkJoinPool (Bug - P4 - Requested)

Reviewers

• Paul Hohensee (@phohensee - Reviewer)

Reviewing

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