Re: 2.6.13-rc3: cache flush missing from somewhere

[Catalin Marinas]

Russell King <rmk+lkml@xxxxxxxxxxxxxxxx> wrote:
> On Mon, Aug 01, 2005 at 01:24:04PM +0100, Catalin Marinas wrote:
>> "David S. Miller" <davem@xxxxxxxxxxxxx> wrote:
>> > If one cpu stores, does it get picked up in the other cpu's I-cache?
>> 
>> It only gets picked up by the other CPU's D-cache (which is fully
>> coherent between cores). The I-cache needs to be invalidated on each
>> CPU.
>
> Are you sure about this requirement?  I see no evidence of it in Harry's
> patch set.

I asked the people that know more about this architecture than me and
they confirmed that this is a requirement. I will double check
tomorrow with the people that did the initial Linux support.

I haven't checked the original patch but it might work (by luck)
without the I-cache invalidation (and without stressing it too
much). This is because you might do a full mm flush when a process
exits and the I-cache would be clean for newly allocated pages (only
the D-cache needs flushing). If you don't overload memory, you don't
get pages swapped-out/removed and the code in a page for a given
process might remain unchanged until the process exits.

-- 
Catalin

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