Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE

Benjamin Herrenschmidt
2004-05-24T05:52:17Z

On Mon, 2004-05-24 at 15:38, Benjamin Herrenschmidt wrote:
> > Well, the original scenario triggering that from userland is, imho, so
> > broken, that we may just not care losing that dirty bit ... Oh well :)
> > Anyway, apply my patch. If pte is not present, this will have no effect,
> > if it is, it makes sure we never leave a stale HPTE in the hash, which
> > is fatal in far worse ways.
>
> Hrm... Or maybe I should just do in set_pte something like
>
> BUG_ON(pte_present(ptep))
>
> That would make me sleep better ;)

... And would not work in the case you mentioned where we set it with
the dirty bit set... for write protect, we have a separate function now,
though. But I'm a bit paranoid with those PTE manipulations, so I think
it would be better to play it the safe way and keep my original patch.

Ben.