[PATCH] Document Linux's memory barriers

[Linus Torvalds]

On Thu, 9 Mar 2006, Linus Torvalds wrote:
> 
> So the fact that x86 SMP ops basically never guarantee any bus cycles 
> basically means that they are fundamentally no-ops when it comes to IO 
> serialization. That was really my only point.

Side note: of course, locked cycles _do_ "serialize" the core. So they'll 
stop at least the core write merging, and speculative reads. So they do 
have some impact on IO, but they have no way of impacting things like 
write posting etc that is outside the CPU.

			Linus