Re: g33: GPU hangs

[Chris Wilson]

On Thu, 01 Dec 2011 13:30:18 +0100, Jiri Slaby <jslaby@xxxxxxx> wrote:
> Hi,
> 
> both yesterday and today, my GPU hung. Both happened when I opened
> google front page in firefox.
> 
> I'm running 3.2.0-rc3-next-20111130. Given it happened twice in the past
> 24 hours, it looks like a regression from next-20111124. Or is this a
> userspace issue (I might updated some packages)?
> 
> i915_error_state dumps from the two hangs are here:
> http://www.fi.muni.cz/~xslaby/sklad/panics/915_error_state_0
> http://www.fi.muni.cz/~xslaby/sklad/panics/915_error_state_second

Both error states contain the same bug: a fence register in conflict
with the command stream. The batch is using the buffer at 0x03d0000 
as an untiled 40x40 rgba buffer with pitch 192. However, a fence
register is programmed to
  fence[3] = 03d00001
    valid, x-tiled, pitch: 512, start: 0x03d00000, size: 1048576

Also note that buffer is also not listed as currently active, so
presumably we reused the buffer as tiled (and so reprogrammed the
fence registered) before the GPU retired the batch. That sounds eerily
similar to this bug: