Warning at drivers/gpu/drm/drm_atomic_helper.c

[Daniel Vetter]

On Mon, Jan 23, 2017 at 09:51:55AM -0200, Fabio Estevam wrote:
> On Mon, Jan 23, 2017 at 1:15 AM, Marek Vasut <marex at denx.de> wrote:
> 
> > IMHO this will no longer handle the fences correctly and you'll see
> > rendering artifacts sometimes.
> 
> Ok, for 4.9.x stable we cannot apply your 782ea2a493ba90800 ("drm/imx: Switch
> to drm_fb_cma_prepare_fb() helper") as it depends on many things that
> only show up on 4.10-rc1, so we need to provide a different fix for
> 4.9.x.
> 
> What I did not figure out so far is why are we getting sometimes the
> WARN_ON(!plane_state->fb); inside drm_atomic_helper_wait_for_fences()?
> 
> The way to reproduce this issue on 4.9.x:
> 
> 1. Start kmscube
> 2. Stop kmscube with CTRL + C
> 
> Repeate this sequence several times (10 to 20 times) and the
> WARN_ON(!plane_state->fb) will trigger about 20% of the times.

Sorry, my brain was still offline when I wrote that reply (I blame jetlag
...). Since this is all in 4.10 I'm not really sure what we should be
doing now. I also have no idea why it's blowing up on ->fb sometimes.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch