RFR: 8355726: LinkedBlockingDeque fixes and improvements [v6]

[kabutz]

On Mon, 9 Jun 2025 13:11:34 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> What would you like to do if the invariant fails inside linkFirst() and linkLast()? Should we throw an AssertionError each time?
>
> No, I was more thinking keeping it as it was: (return true/false from linkFirst / linkLast depending on whether it passes the capacity check or not)

I've made the changes you suggested and it is indeed better. Thanks @viktorklang-ora

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PR Review Comment: https://git.openjdk.org/jdk/pull/24925#discussion_r2136077386