Memory barriers and spin_unlock safety

[Benjamin Herrenschmidt]

On Sat, 2006-03-04 at 21:58 +1100, Paul Mackerras wrote:
> Benjamin Herrenschmidt writes:
> 
> > Actually, the ppc's full barrier (sync) will generate bus traffic, and I
> > think in some case eieio barriers can propagate to the chipset to
> > enforce ordering there too depending on some voodoo settings and wether
> > the storage space is cacheable or not.
> 
> Eieio has to go to the PCI host bridge because it is supposed to
> prevent write-combining, both in the host bridge and in the CPU.

That can be disabled with HID bits tho ;)

Ben.