RFR: 8166583: Add oopDesc::klass_or_null_acquire()

[Kim Barrett]

> On Sep 23, 2016, at 3:10 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi Kim,
> 
> On Thu, 2016-09-22 at 16:51 -0400, 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.
>> 
> 
>   looks good.

Thanks.

> Is there a bug filed for fixing the "// Workaround for non-const
> load_acquire parameter." comment? I.e. it seems that actually more
> infrastructure changes are required that have been deferred for now.

Not yet; I’ve drafted it but not actually entered it into the system.  Planning to do that tomorrow.

I spent a little time working on it, and have a changeset that I think should cover
it, but I haven’t tested it except locally yet, and can’t test on some affected platforms.
It touches quite a few files, and is unfortunately less mechanical than one might wish.
It also doesn’t seem like something that needs to be done for JDK 9.  I’ll probably
add a pointer to a webrev when I submit the RFE.