Messages in this thread | | | Subject | Re: [PATCH] Document Linux's memory barriers | From | Andi Kleen <> | Date | 08 Mar 2006 15:55:08 +0100 |
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Robert Hancock <hancockr@shaw.ca> writes:
> 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..
CONFIG_UNORDERED_IO is a failed experiment. I just removed it.
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