Re: [rfc] data race in page table setup/walking?

[Hugh Dickins <hugh@veritas.com>]

On Thu, 1 May 2008, Nick Piggin wrote:
> On Wed, Apr 30, 2008 at 12:14:51PM +0100, Hugh Dickins wrote:
> > On Wed, 30 Apr 2008, Nick Piggin wrote:
> > > 
> > > Actually, aside, all those smp_wmb() things in pgtable-3level.h can
> > > probably go away if we cared: because we could be sneaky and leverage
> > > the assumption that top and bottom will always be in the same cacheline
> > > and thus should be shielded from memory consistency problems :)
> > 
> > I've sometimes wondered along those lines.  But it would need
> > interrupts disabled, wouldn't it?  And could SMM mess it up?
> > And what about another CPU taking the cacheline to modify it
> > in between our two accesses?
> 
> Nothing more than could not already happen with the smp_wmb in there,
> AFAIKS.

Yes, one does wonder just what I was wondering ;)

Hugh

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