Just a reminder. Thanks. On 06/09/2017 05:30 PM, Andrey Grodzovsky wrote: > Problem: > While running IGT kms_atomic_transition test suite i encountered > a hang in drmHandleEvent immidietly follwoing 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 singnaled. > This point to a bug in IGT but also DRM should gracefully > fail such scenario so no hang on user side will happen. > > Fix: > Explicitly fail by failing atomic_commit early in > drm_mode_atomic_commit where such problem can be identified. > > Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky at amd.com> > --- > drivers/gpu/drm/drm_atomic.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c > index a567310..32eae1c 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; > } > > @@ -2179,6 +2188,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev, > drm_mode_object_unreference(obj); > } > > + > + > ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state, > &num_fences); > if (ret)