RFR: 8166583: Add oopDesc::klass_or_null_acquire()

[Kim Barrett]

> On Sep 22, 2016, at 6:27 PM, David Holmes <david.holmes at oracle.com> wrote:
> 
> Looks good.

Thanks.

> Thanks,
> David
> 
> On 23/09/2016 6:51 AM, Kim Barrett wrote:
>> Please review this addition of a new function to oopDesc.  This is a
>> variant of an existing function; the new function provides acquire
>> semantics to the access.
>> 
>> This is a subtask of JDK-8160369, providing additional infrastructure
>> needed to fix that bug.
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8166583
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8166583/webrev.00/
>> 
>> Testing:
>> Ran nightly tests with this being used by an in-development fix for
>> part of JDK-8160369.