linux-kernel - Re: DRM Error on Acer Aspire One

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Message-Id: <20100511153217.5c7661d7.akpm@linux-foundation.org>
Date:	Tue, 11 May 2010 15:32:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Airlie <airlied@...il.com>
Cc:	Chris Wilson <chris@...is-wilson.co.uk>,
	Jaswinder Singh Rajput <jaswinderlinux@...il.com>,
	dri-devel@...ts.freedesktop.org, Dave Airlie <airlied@...ux.ie>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Keith Packard <keithp@...thp.com>,
	Eric Anholt <eric@...olt.net>, Ingo Molnar <mingo@...e.hu>
Subject: Re: DRM Error on Acer Aspire One

On Wed, 12 May 2010 08:22:49 +1000
Dave Airlie <airlied@...il.com> wrote:

> On Wed, May 12, 2010 at 5:57 AM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> > On Tue, 11 May 2010 12:10:01 -0700, Andrew Morton <akpm@...ux-foundation.org> wrote:
> >> On Tue, 11 May 2010 19:52:31 +0100
> >> Chris Wilson <chris@...is-wilson.co.uk> wrote:
> >>
> >> > On Tue, 11 May 2010 11:35:55 -0400, Andrew Morton <akpm@...ux-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@...is-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.
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