Some notes after helping to investigate this via IRC: The DDX is stuck in drmmode_set_mode_major during its attempt to unblank the display, because it is waiting for a pending page flip that is never delivered (based on the backtrace provided by Christoph, which I'm attaching for future reference).
** Attachment added: "Xserver-backtrace.txt" https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1577170/+attachment/4658778/+files/Xserver-backtrace.txt -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to xserver-xorg-video-ati in Ubuntu. https://bugs.launchpad.net/bugs/1577170 Title: screen cannot be turned back on after being switched off after some time of inactivity Status in xserver-xorg-video-ati package in Ubuntu: New Bug description: I did a fresh install of ubuntu 16.04 on my old dell computer in which there is an ati radeon X1300 graphics card. Whenever the screen turns off due to inactivity, it cannot be woken up by moving the mouse or by hitting a key. When I kill the Xorg process via ssh with another computer, the screen then comes to life again and I can log back in. When I remove the graphic card from the computer and use the built in graphic card instead, the bug doesn't occur. So I guess it is related to the radeon driver. Oddly enough, there is no problem waking the screen when I type "xset -display :0.0 dpms force off" in a terminal. Moreover typing gnome- screensaver-command -a in a terminal turns my screen off and after typing this line, the screen can be woken up by moving the mouse or by hitting a key. I'm confused. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1577170/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
