RFR: 8256474: Migrate Mutex _owner accesses to use Atomic operations

[Coleen Phillimore]

On Mon, 23 Nov 2020 23:08:28 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

Looks good to me.

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Marked as reviewed by coleenp (Reviewer).

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