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SubjectRe: Uses for memory barriers
Alan Stern wrote:
> On Wed, 20 Sep 2006, Nick Piggin wrote:

>>I don't think that need be the case if one of the CPUs that has written
>>the variable forwards the store to a subsequent load before it reaches
>>the cache coherency (I could be wrong here). So if that is the case, then
>>your above example would be correct.
>
>
> I don't understand your comment. Are you saying it's possible for two
> CPUs to observe the same two writes and see them occurring in opposite
> orders?

If store forwarding is able to occur outside cache coherency protocol,
then I don't see why not. I would also be interested to know if this
is the case on real systems.

--
SUSE Labs, Novell Inc.
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