Jan Kiszka wrote:
> Jan Kiszka wrote:
> > Philippe Gerum wrote:
> >> On Tue, 2007-08-07 at 17:09 +0200, Gilles Chanteperdrix wrote:
> >>> On 8/7/07, Jan Kiszka <[EMAIL PROTECTED]> wrote:
> >>>> Gilles Chanteperdrix wrote:
> >>>>> The fact that you are in a hurry should not be an excuse to propose a
> >>>>> fix which is much worse than the bug itself.
> >>>> Please explain.
> >>> Using GFP_ATOMIC is not a good idea, because the kernel needs the
> >>> GFP_ATOMIC pools for allocation that take place from really atomic
> >>> contexts such as interruption handlers for instance. fork should not
> >>> be an atomic context.
> >>>
> >>> So the only reason I see why you propose this patch is because you are
> >>> in a hurry. Ok, before we fix this properly, you can use GFP_ATOMIC
> >>> locally, but please do not make
> >>> this an official patch.
> >>>
> >> I'm afraid you are both right. Draining pages from the atomic pool might
> >> starve truely atomic contexts, and releasing the lock guarding the
> >> pagetable pages for the source mm seems contradictory with what the
> >> current code tries to achieve in holding it.
> >>
> >> Here is a patch preallocating the page for the cow-breaking code, which
> >> relies on the lock breaking pattern already in place. Not exactly
> >> pretty, slightly tested here (UP, spinlock debug), but looks ok so far.
> >> Needs SMP testing before any attempt is made to merge it.
> >
> > Funny. I just finished my own patch of this kind and made it pass a
> > basic COW stress test here. Find it below, it is very similar. Will
> > now analyse yours to see which one looks nicer and/or is more correct.
>
> Yours is clearly nicer, but it required/allowed a few more cleanups.
> Find my variant attached (against our local 2.6.20 kernel).
>
> From my POV: problem solved. 8)
It seems you solved this problem before I even had a chance to have
a look at the code.
--
Gilles Chanteperdrix.
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