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Date: Tue, 11 May 2010 15:32:17 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Dave Airlie <airlied@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>,
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Subject: Re: DRM Error on Acer Aspire One
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On Wed, 12 May 2010 08:22:49 +1000
Dave Airlie <airlied@gmail.com> wrote:

> On Wed, May 12, 2010 at 5:57 AM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > On Tue, 11 May 2010 12:10:01 -0700, Andrew Morton <akpm@linux-foundation.org> wrote:
> >> On Tue, 11 May 2010 19:52:31 +0100
> >> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> >>
> >> > On Tue, 11 May 2010 11:35:55 -0400, Andrew Morton <akpm@linux-foundation.org> wrote:
> >> > > No, io_mapping_map_atomic_wc() cannot be used from [soft]irq context:
> >> > > it hardwires use of KM_USER0. __I suggest that io_mapping_create_wc(),
> >> > > io_mapping_map_atomic_wc() etc be changed so that the caller passes in the
> >> > > KM_foo kmap slot index.
> >> >
> >> > Argh, sorry for the noise, read the mail in the wrong order. Thanks for
> >> > the review. It would be sensible to go with your simpler patch whilst
> >> > io_mapping_map_atomic_wc() is improved.
> >>
> >> OK. __I'll be sending a bunch of fixes Linuswards in an hour or two.
> >> Should I include this?
> >
> > Yes.
> >
> > Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
> >
> 
> I'm not sure pushing this in at this point is a good idea, if I'm
> reading it correctly we've no idea what KM_IRQ is being used for,

It's used for taking kmaps from IRQ contexts.

> and
> this codepath is called from non-irq contexts just as much as irq
> contexts.

That's fine.  As long as we do a local_irq_disable(), KM_IRQ0 can be
used from both irq- and non-irq contexts.  All we need to do is to
ensure that some interrupt cannot come along on this CPU and corrupt
the slot.

> I'd rather we just backout the hangcheck stuff touching copies at all
> at this point, and try again doing it properly with a slow work or
> something for later.
> 
> Dave.