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

[Coleen Phillimore]

On Fri, 27 Nov 2020 08:46:40 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> David Holmes has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Restore volatile modifier
>
> src/hotspot/share/runtime/mutex.hpp line 90:
> 
>> 88:   // than the lock owner are inherently racy.
>> 89:   Thread* volatile _owner;
>> 90:   void raw_set_owner(Thread* new_owner) { Atomic::store(&_owner, new_owner); }
> 
> set_owner_relaxed might be a better name.  Your call...

Don't like 'relaxed'.  I'm not a huge fan of raw, since it's not raw here, but leave it.  It's fine.

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