Black screen when usc is installed

[Kai Mast]

I updated today and now my laptop is unusable with USC installed. The screen is just black.

The log file only contains the following:
dm_connection_start
Failed to read header

I have a radeon graphics card. Maybe the composition bypass is broken here?

[Kai Mast (kai-mast)]

Here is the lightdm log:

[+0.12s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.12s] DEBUG: Starting Light Display Manager 1.7.12, UID=0 PID=1155
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/10-ubuntu.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/10-unity-system-compositor.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-ubuntu.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-unity-greeter.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf.d/50-xserver-command.conf
[+0.12s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
[+0.12s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
[+0.12s] DEBUG: Registered seat module xlocal
[+0.12s] DEBUG: Registered seat module xremote
[+0.12s] DEBUG: Registered seat module unity
[+0.12s] DEBUG: Adding default seat
[+0.13s] DEBUG: Quitting Plymouth
[+0.17s] DEBUG: Using VT 7
[+0.17s] DEBUG: Seat: Logging to /var/log/lightdm/unity-system-compositor.log
[+0.17s] DEBUG: Launching process 1216: /usr/sbin/unity-system-compositor.sleep --from-dm-fd 9 --to-dm-fd 13 --vt 7
[+0.17s] DEBUG: Seat: Waiting for system compositor for 60s
[+0.17s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.17s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
[+2.74s] DEBUG: Seat: READY
[+2.74s] DEBUG: Seat: Compositor ready
[+2.74s] DEBUG: Seat: Starting
[+2.74s] DEBUG: Seat: Creating greeter session
[+2.77s] DEBUG: Seat: Setting XDG_SEAT=seat0
[+2.77s] DEBUG: Seat: Setting XDG_VTNR=7
[+2.77s] DEBUG: Seat: Creating display server of type x
[+2.77s] DEBUG: Seat: Starting X server on Unity compositor
[+2.77s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
[+2.77s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
[+2.77s] DEBUG: DisplayServer x-0: Launching X Server
[+2.77s] DEBUG: Launching process 1349: /usr/bin/X -core :0 -auth /var/run/lightdm/root/:0 -mir 0 -mirSocket /tmp/mir_socket -nolisten tcp
[+2.77s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
[+138.95s] DEBUG: Process 1349 terminated with signal 6
[+138.95s] DEBUG: DisplayServer x-0: X server stopped
[+138.95s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
[+138.95s] DEBUG: Seat: Display server stopped
[+138.95s] DEBUG: Seat: Stopping; greeter display server failed to start
[+138.95s] DEBUG: Seat: Stopping
[+138.95s] DEBUG: Sending signal 15 to process 1216
[+138.95s] DEBUG: Seat: Stopping session
[+138.95s] DEBUG: Seat: Session stopped
[+138.95s] DEBUG: Seat: Stopped
[+138.95s] DEBUG: Required seat has stopped
[+138.95s] DEBUG: Stopping display manager
[+138.95s] DEBUG: Display manager stopped
[+138.95s] DEBUG: Stopping daemon
[+138.95s] DEBUG: Exiting with return value 1

[Kai Mast (kai-mast)]

I think I found the actual issue in the X log:

Driver needs flags 1, incompatible with nested, deleting.
Driver needs flags 0, incompatible with nested, deleting.
Driver needs flags 0, incompatible with nested, deleting.
(II) [XMir] Using Radeon device from Mir.
(II) [KMS] Kernel modesetting enabled.
X: ../../../../include/privates.h:123: dixGetPrivateAddr: Assertion `key->initialized' failed.

[Daniel van Vugt (vanvugt)]

Indeed sounds like bug 1217637 so I'm going to mark this one as a duplicate.