[Intel-gfx] [PATCH] drm/i915: Try to stop rings before reset

[Daniel Vetter]

On Tue, Apr 29, 2014 at 6:07 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> On Tue, Apr 29, 2014 at 4:38 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>> This seems to make the hard machine hangs provoked by running
>> gem_reset_stats tests a lot less likely. At least on my snb here.
>>
>> v2: Don't DRM_ERROR when a reset is in progress in the stop_ring
>> function.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=74100
>> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> A bit a terse commit message ...
>
> The theory that lead me to this patch is that these hard hangs only
> started to show up with the endless batch chaining that
> gem_reset_stats does. All previous gpu reset testcase we have
> essentially reset the gpu while it is completely idle. If figured that
> trying to idle it first (by stopping the CS) can't hurt, and indeed it
> seems to help a lot.

Aside: This now survived about half a day of running piglit -t
gem_reset_stats in a loop (since just running gem_reset_stats doesn't
run the gpu_quiescent before/after each subtest using piglit is much
more hang-happy). Didn't hang after 70+ loops, so seems really solid
here.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch