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@xxxxxxx>
>
> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
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
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