Comment 38 for bug 1763273

After several weekends of testing, I believe I can report with high confidence that the kernel update to 4.17-rc2 fixes the second of the two problems; specifically, we no longer see kernel crashes after using Alt-SysRq-k to recover from frozen/hanging blank screens.

However, the unable-to-unblank problem remains; after normal screen blanking, about 50% of the time we are unable to recover by moving the cursor or typing a key. Instead, only Alt-SysRq-k allows us to recover back to a guest login screen.

There doesn't seem to be much in the system logs that I can find, except possibly this:

May 20 20:41:04 Comprm8 gnome-session[7919]: gnome-session-binary[7919]: GLib-GIO-CRITICAL: g_dbus_connection_call_internal: assertion 'object_path != NULL && g_variant_is_object_path (object_path)' failed
May 20 20:41:04 Comprm8 gnome-session-binary[7919]: GLib-GIO-CRITICAL: g_dbus_connection_call_internal: assertion 'object_path != NULL && g_variant_is_object_path (object_path)' failed

Some seemingly similar bug reports from out in the wild:

https://askubuntu.com/questions/795014/ubuntu-16-04-occasionally-hangs-with-screen-off-after-switching-ttys-or-turning
https://askubuntu.com/questions/949764/ubuntu-hangs-when-unlocking-screen

Can you recommend any approaches to help debug the root cause of this problem, presumably in X and/or the radeon driver?