Re: [PATCH] drm/i915: Don't die in wait_for_pending_flips

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 19 May 2014 17:18:40 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Mon, May 19, 2014 at 08:06:06AM -0700, Jesse Barnes wrote:
> > On Mon, 19 May 2014 16:09:35 +0200
> > Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > 
> > > We can apperently miss them, but breaking the entire driver hampers
> > > testing. So bail out after one minute, our customerary "this is a lost
> > > cause" timeout.
> > > 
> > > References: https://bugs.freedesktop.org/show_bug.cgi?id=78383
> > > Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 0f8f9bcb3012..6eca24d8b282 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -3284,8 +3284,9 @@ static void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc)
> > >  
> > >  	WARN_ON(waitqueue_active(&dev_priv->pending_flip_queue));
> > >  
> > > -	wait_event(dev_priv->pending_flip_queue,
> > > -		   !intel_crtc_has_pending_flip(crtc));
> > > +	WARN_ON(wait_event_timeout(dev_priv->pending_flip_queue,
> > > +				   !intel_crtc_has_pending_flip(crtc),
> > > +				   60*HZ) == 0);
> > >  
> > >  	mutex_lock(&dev->struct_mutex);
> > >  	intel_finish_fb(crtc->primary->fb);
> > 
> > Updating our page flip ioctl man page (hah!) with the timeout info
> > would be good, in case people like Mario queue flips for after lunch. :)
> 
> We don't do that in the kernel though, we only ever queue flips for the
> next vblank after rendering completed. Completed rendering we can detect
> (and have 60s timeouts in other places where the hangcheck isn't
> guaranteed to be around already), the additional vblank is negligible imo.
> 
> Of course if we add support for flip queues in the kernel we might need to
> cancel outstanding flips properly when we kill the crtc, like we already
> do for vblank events.
> 
> So imo no need to document anything.

Ah right so we'd only be affected here by ridiculous refresh rates...
so yeah should be fine.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center