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>
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;
> }
>
>
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