i915 hang and large allocation (~3.7-rc4)

[Daniel Vetter]

On Mon, Nov 12, 2012 at 02:44:46PM -0800, Dave Hansen wrote:
> I've been seeing a little goofiness with i915 video under the 3.7-rc's.
> It looks like I'm seeing two separate issues.  One, that the video
> hardware hangs, spits some errors in dmesg, and then video acceleration
> seems to stop working.  Two, when it does this, apport goes digging in
> debugfs for information about the hang.  When it does this, something
> does an order-9 (2MB) kmalloc() which fails.
> 
> While debugfs is expected to be a _bit_ rickety, I do think order-9
> is a bit excessive for an in-kernel allocation, even a temporary
> one.  I'm not quite sure if it has done this for a long time, and I'm
> only hitting it now since I'm seeing a _separate_ i915 hang.
> 
> Relevant parts of dmesg, lspci, and kernel config are here:
> 
> 	http://sr71.net/~dave/linux/i915-wonky/

Ironlake gpu, so if this is a regression introduced in 3.7 and things work
normally in 3.6, it's likely that you're hitting a variant of

https://bugs.freedesktop.org/show_bug.cgi?id=55984

It'd be best if you can subscribe yourselfes there, so that all potential
testers are at the same place.

For the 2MB allocation, this is a known problem, unfortunately reworking
the dump code will be major work. Which is why it hasn't been done yet.
But fixing that is somewhere on our giant todo list.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch