Re: [PATCH] Document Linux's memory barriers

[Robert Hancock]

Alan Cox wrote:
> On Maw, 2006-03-07 at 22:24 +0100, Andi Kleen wrote:
> > > But on most arches those accesses do indeed seem to happen in-order.  On
> > > i386 and x86_64, it's a natural consequence of program store ordering.
> > Not true for reads on x86.
>
> You must have a strange kernel Andi. Mine marks them as volatile
> unsigned char * references.

Well, that and the fact that IO memory should be mapped as uncacheable 
in the MTRRs should ensure that readl and writel won't be reordered on 
i386 and x86_64.. except in the case where CONFIG_UNORDERED_IO is 
enabled on x86_64 which can reorder writes since it uses nontemporal 
stores..

--
Robert Hancock      Saskatoon, SK, Canada
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Home Page: http://www.roberthancock.com/

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