drm i915 hangs on heavy io load

[Chris Wilson]

On Tue, 23 Oct 2012 14:38:30 +0900, Norbert Preining <preining at logic.at> wrote:
> Hi everyone,
> 
> (please Cc)
> 
> I am running 3.7-rc2 and got recently hit a few times (under rc1, too)
> by hanging drm i915 while doing large io operations.
[snip]
> 
> I captured the i915_error_state and uploaded it here:
> 	http://www.logic.at/people/preining/drm_i915_error_state.gz
> 
> The hangs have been normally initiated on svn up in a very big
> repository, or git checkout on a very big repository or so.
> 
> Other system is Debian/unstable. The above output and error state is
> from after a reboot without any suspends or other tricks inbetween,
> uptime 3.5h.

Looks like fallout from a missing ILK rc6 workaround - it looks like the
write to the ring tail never landed and so the command streamer hung.

See https://bugs.freedesktop.org/show_bug.cgi?id=55984 and
http://cgit.freedesktop.org/~danvet/drm/log/?h=ilk-wa-pile of which I
think
http://cgit.freedesktop.org/~danvet/drm/commit/?h=ilk-wa-pile&id=0d5fed2de763b49bb1a90140758153481f043757
is the missing ingredient.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre