linux-kernel - Re: [PATCH v2] drm/core: Fail atomic IOCTL with no CRTC state but with signaling.

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Date:   Tue, 27 Jun 2017 09:37:40 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Harry Wentland <harry.wentland@....com>
Cc:     Andrey Grodzovsky <Andrey.Grodzovsky@....com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, maarten.lankhorst@...ux.intel.com,
        amd-gfx@...ts.freedesktop.org, seanpaul@...omium.org,
        daniel@...ll.ch
Subject: Re: [PATCH v2] drm/core: Fail atomic IOCTL with no CRTC state but
 with signaling.

On Mon, Jun 26, 2017 at 03:44:07PM -0400, Harry Wentland wrote:
> On 2017-06-20 01:57 PM, Andrey Grodzovsky wrote:
> > Problem : While running IGT kms_atomic_transition test suite i encountered
> > a hang in drmHandleEvent immediately following  an atomic_commit.
> > After dumping the atomic state I relized that in this case there was
> > not even one CRTC attached to the state and only disabled
> > planes. This probably due to a commit which hadn't changed any property
> > which would require attaching crtc state. This means drmHandleEvent
> > will never wake up from read since without CRTC in atomic state
> > the event fd will not be signaled.
> > 
> > Fix: Protect against this issue by failing atomic_commit early in
> > drm_mode_atomic_commit where such probelm can be identified.
> > 
> > v2:
> > Fix typos and extra newlines.
> > 
> > Change-Id: I3ee28ffae35fd1e8bfe553146c44da53da02e6f8
> > Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@....com>
> 
> Reviewed-by: Harry Wentland <harry.wentland@....com>

Stalling on this hoping for the igt patch. Does it exist already?
-Daniel

> 
> Harry
> 
> > ---
> >  drivers/gpu/drm/drm_atomic.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index a567310..48145bf 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1933,7 +1933,7 @@ static int prepare_crtc_signaling(struct drm_device *dev,
> >  {
> >  	struct drm_crtc *crtc;
> >  	struct drm_crtc_state *crtc_state;
> > -	int i, ret;
> > +	int i, c = 0, ret;
> >  
> >  	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY)
> >  		return 0;
> > @@ -1994,8 +1994,17 @@ static int prepare_crtc_signaling(struct drm_device *dev,
> >  
> >  			crtc_state->event->base.fence = fence;
> >  		}
> > +
> > +		c++;
> >  	}
> >  
> > +	/*
> > +	 * Having this flag means user mode pends on event which will never
> > +	 * reach due to lack of at least one CRTC for signaling
> > +	 */
> > +	if (c == 0 && (arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
> > +		return -EINVAL;
> > +
> >  	return 0;
> >  }
> >  
> > 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch