Created attachment 139785 [details] Xorg.log There are ubuntu mate-16.04 with mainline 4.16.7 kernel and oibaf ppa, option "power off monitor when system idle" in DE settings enabled and GLMatrix screensaver are used. By default dpms works, but adding /usr/share/X11/xorg.conf.d/20-nouveau.conf with content : Section "Module" Load "dri3" EndSection Section "Device" Identifier "Device0" Driver "nouveau" Option "DRI" "3" EndSection cause a issue: after monitor wake up there are only one frame from screensaver and mouse cursor over it (mouse work). System does not hang - is possible to switch to virtual console, DE seems to think that all rigth (after some mouse click there new folders appeares on a desktop) and X can be restarted without problem.
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