Single byte Atomic::cmpxchg implementation

[Erik Österlund]

> On 11 sep 2014, at 14:16, "David Holmes" <david.holmes at oracle.com> wrote:
> 
>> On 11/09/2014 9:46 PM, Erik Österlund wrote:
>> Sorry, I seem to have looked at defined(ARM) + zero where __kernel_cmpxchg is the implementation of choice rather than the AArch64-port specific code. Perhaps somebody else is responsible for that...
> 
> Yes the zero port is separate again. The kernel helper is needed on ARMv5.

Yes. This is why I previously said my ARM fix would only make sense on ARM >= 6 with MP. :)
Then if it's worth the hassle of maintaining it is a different question. I merely suggested improvements on other platforms than x86 which I was asked to do! Will simply let the Andrews do what they like on that one! :)

/Erik