RFR: 8166607: G1 needs klass_or_null_acquire

[Kim Barrett]

> On Oct 18, 2016, at 4:53 AM, Erik Helin <erik.helin at oracle.com> wrote:
> 
> On 2016-10-13, Kim Barrett wrote:
>> So what I’d like is that you just pretend for now that the comment about the
>> ordering in oops_on_card_xxx is actually correct.
>> 
>> The change I’m working on for JDK-8166811 eliminates that ordering problem
>> completely, but depends heavily on the changes here.
> 
> I've discussed this with Thomas, what do you think about pushing the
> fix for JDK-8166811 at the same time as this one? This patch looks good
> AFAICS, but I'm worried that your code will be exposed slightly
> different to existing bug than the current code. Given that
> crashes/issues resulting from these kinds of bugs often are nightmarish
> to track down, I'm a bit hesitant to push these patches one by one.
> 
> What do you think?

Sure, I can do that.