Memory barriers and spin_unlock safety

David Howells dhowells at
Sat Mar 4 07:17:07 EST 2006

Linus Torvalds <torvalds at> wrote:

> Note that _normal_ writes never need an SFENCE, because they are ordered 
> by the core.
> The reason to use SFENCE is because of _special_ writes.

I suspect, then, that x86_64 should not have an SFENCE for smp_wmb(), and that
only io_wmb() should have that.


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