Comment # 19 on bug 1079416 from Boian Berberov

I will find out later this week.  So far it still occurs with 4.16.12-2-default

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Jun 17 13:59:13 linux-qjvs sddm[1916]: Error from greeter session: "Process
crashed"
Jun 17 13:59:13 linux-qjvs sddm[1916]: Auth: sddm-helper crashed (exit code 15)
Jun 17 13:59:13 linux-qjvs sddm[1916]: Error from greeter session: "Process
crashed"
Jun 17 13:59:13 linux-qjvs sddm[1916]: Auth: sddm-helper exited with 15
Jun 17 13:59:13 linux-qjvs sddm[1916]: Greeter stopped.
...
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_flip_done
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CONNECTOR:48:LVDS-1] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [PLANE:28:primary A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_flip_done
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CONNECTOR:48:LVDS-1] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [PLANE:28:primary A] flip_done timed out
Jun 17 14:00:36 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_flip_done
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
...
Jun 17 14:00:36 linux-qjvs sddm[1916]: Signal received: SIGTERM
Jun 17 14:00:36 linux-qjvs sddm[1916]: Socket server stopping...
Jun 17 14:00:36 linux-qjvs sddm[1916]: Socket server stopped.
Jun 17 14:00:36 linux-qjvs sddm[1916]: Display server stopping...
...
Jun 17 14:00:46 linux-qjvs sddm[1916]: QProcess: Destroyed while process
("/usr/bin/X") is still running.
Jun 17 14:00:47 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CRTC:37:pipe A] flip_done timed out
Jun 17 14:00:57 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [CONNECTOR:48:LVDS-1] flip_done timed out
Jun 17 14:01:08 linux-qjvs kernel: [drm:drm_atomic_helper_wait_for_dependencies
[drm_kms_helper]] *ERROR* [PLANE:28:primary A] flip_done timed out
============================================================

I see Leap 15.0 has kernel 4.12.14.  I'll see if I can install that on
Tumbleweed side-by-side.