[Intel-gfx] [PATCH] drm/i915: Allow userspace to request no-error-capture upon GPU hangs

[Chris Wilson]

On Wed, Dec 16, 2015 at 09:54:47AM +0100, Daniel Vetter wrote:
> On Fri, Dec 11, 2015 at 10:18:35PM +0000, Chris Wilson wrote:
> > igt likes to inject GPU hangs into its command streams. However, as we
> > expect these hangs, we don't actually want them recorded in the dmesg
> > output or stored in the i915_error_state (usually). To accomodate this
> > allow userspace to set a flag on the context that any hang emanating
> > from that context will not be recorded. We still do the error capture
> > (otherwise how do we find the guilty context and know its intent?) as
> > part of the reason for random GPU hang injection is to exercise the race
> > conditions between the error capture and normal execution.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> Hm, I do like that we exercise the full paths all the time, increasing
> chances for fireworks. What's the motivation here? Is there some
> substantial speed-up?

No, since we keep doing the error-capture (we have to, we haven't fixed
the bugs in it yet!), the only benefits are:

(a) Reduce dmesg spam during igt
(b) simulating hangs doesn't leave an error-state around, or rather, we
don't leave the simulated error state and igt doesn't eat a *genuine* hang
that occurred during or before the test.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre