MMIO and gcc re-ordering issue

[Jes Sorensen]

Jesse Barnes wrote:
> Now, in hindsight, using a PIO write set & test flag approach in 
> writeX/spin_unlock (ala powerpc) might have been a better approach, but iirc 
> that never came up in the discussion, probably because we were focused on PCI 
> posting and not uncached vs. cached ordering.

Hi Jesse,

I am going to take a stab at implementing this so we can see how much
of an impact it will have.

Cheers,
Jes