RFR: 8280828: Improve invariants in NonblockingQueue::append [v2]

[Kim Barrett]

On Tue, 8 Feb 2022 12:08:51 GMT, Ivan Walulya <iwalulya at openjdk.org> wrote:

> Not part of this PR, but we need to add a comment about `push/append` being susceptible to ABA behavior as discovered in JDK-8273383.

See https://bugs.openjdk.java.net/browse/JDK-8280832

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PR: https://git.openjdk.java.net/jdk/pull/7250