RFR: 8256474: Migrate Mutex _owner accesses to use Atomic operations [v3]

[Coleen Phillimore]

On Tue, 24 Nov 2020 22:39:08 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Simple update to move away from volatile fields and use Atomic::load/store on racy accesses.
>> 
>> Thanks,
>> David
>
> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Restore volatile modifier

Still looks good to me.

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Marked as reviewed by coleenp (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1402