Re: Memory Barrier Definitions

[justincarlson@cmu.edu]

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On Tue, 2002-05-07 at 16:27, Alan Cox wrote:
> and our current heirarchy is a little bit more squashed than that. I'd 
> agree. We actually hit a corner case of this on the IDT winchip x86 where
> we run relaxed store ordering and have to define wmb() as a locked add of
> zero to the top of stack - which does have a penalty that isnt needed
> for CPU ordering.
> 
> How much of this impacts Mips64 ?

In terms of the MIPS{32|64} ISA, the current primitives seem fine;
there's only 1 option defined in the ISA:  'sync'.  Order for all
off-cache accesses is guaranteed around a sync.

It gets a bit more complicated when you talk about what particular
implementations do, and ordering rules for uncached vs cached accesses,
but to the best of my knowledge there aren't any fundamental problems as
described for the PPC.

-Justin


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