RFR: 8280832: Update usage docs for NonblockingQueue [v2]

[David Holmes]

On Thu, 10 Feb 2022 05:54:43 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this update of the usage and implementation comments for
>> NonblockingQueue to discuss the ABA issue in push/append operations.
>
> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
> 
>   walulyai review

src/hotspot/share/utilities/nonblockingQueue.inline.hpp line 122:

> 120:     // concurrent try_pop could take old_tail before our update, it gets
> 121:     // recycled and re-added to the end, and then we successfully cmpxchg,
> 122:     // rendering the list in _tail circular.

Suggestions:

1. start the new comment on a new line
2.  "Note that ABA would be possible if a concurrent try_pop takes old_tail before our update, ...

Cheers,
David

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PR: https://git.openjdk.java.net/jdk/pull/7393