RFR(S) 8067331: Zero: Atomic::xchg and Atomic::xchg_ptr need full memory barrier

[David Holmes]

Can we get a second hotspot review please - this is quite straight forward.

Thanks,
David

On 5/01/2015 12:21 PM, David Holmes wrote:
> Hi Severin,
>
> Sorry this slipped through the cracks before the holidays.
>
> On 16/12/2014 1:09 AM, Severin Gehwolf wrote:
>> Hi,
>>
>> Could someone please review and sponsor the following change?
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8067331
>> webrev:
>> http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8067331/webrev.02/
>>
>> The issue is that all atomic operations are expected to be full memory
>> barriers, but two implementations of the Zero variant JVM - Atomic::xchg
>> and Atomic::xchg_ptr - use GCC's built-in __sync_lock_test_and_set which
>> is an acquire barrier only. The fix adds full memory barriers manually
>> for those.
>>
>> Thoughts?
>
> Looks completely consistent with what I just saw in the aarch64 port code.
>
> I can sponsor this but we still need a second review.
>
> Thanks,
> David
>
>> Cheers,
>> Severin
>>