Re: [PATCH 0/6] drm/i915: Avoid stuck page flip waiters on GPU reset

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jan 29, 2013 at 06:13:32PM +0200, ville.syrjala@linux.intel.com wrote:
> Someone mentioned on irc that intel_crtc_wait_for_pending_flips() was
> getting stuck in some cases. This rang a bell since I was poking around
> that stuff last year.
> 
> The issue that I'm trying to fix here is processes getting stuck in D
> state when a GPU reset happens while page flips have been scheduled.
> 
> Testing is easy 1) fire up 'glxgears -fullscreen', run 'gem_hang 0',
> try to VT switch. Without this series X and some kworker soon get stuck
> in D state and you're left with a useless box. With the patch set, you
> wait a while, the GPU hangcheck kicks in, and you get your console back.

Broken record maintainer request: Can you please bake that into an i-g-t?
I think (hope) that running one of the delayed flip tests vs. the hangman
(gem_hang is a bit evil since it can kill boxes for real) should do the
trick. Then maybe also run one of the wf-vblank tests vs. hangman to check
that we cancel those correctly, too.

> The irc discussion was apparently about [1], but since the dmesg there 
> doesn't show a GPU hang, I don't see this patch set fixing it. Frankly,
> I have no idea what's happening there.
> 
> Additional work after this would involve sending out pending page flip
> events. Currently if you don't do the VT switch after a hang, glxgears
> remains stuck because the X server didn't get the page flip event from
> the kernel. Also we should probably do an explicit intel_pipe_set_base()
> with the current fb, to make sure we show the correct fb after the hang.
> But I'm not going to touch these right now. Actually I'm hoping someone
> else will volunteer for these tasks ;)

Hm ... I guess we need to walk the file_priv event list somewhere an fire
them all off, indicating somehow that things went kaboom. I think we
should aim for a drm generic way to singal those even.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch