I have now tested the new kernel for two days, and unfortunately, after several user switches I got a blank screen again :-( However, the kernel does not output any errors. So it seems this bug is not kernel related.
Here is a log from lightdm, which is the only log I could find with an error: [+2816.49s] DEBUG: Seat seat0: Switching to user erling [+2816.49s] DEBUG: Seat seat0: Creating user session [+2816.49s] DEBUG: Session pid=3701: Started with service 'lightdm', username 'erling' [+2816.50s] DEBUG: Session pid=3701: Authentication complete with return value 7: Authentication failure [+2816.50s] DEBUG: Session pid=3701: Sending SIGTERM [+2816.50s] DEBUG: Seat seat0: Starting greeter to authenticate session [+2816.50s] DEBUG: Seat seat0: Creating greeter session [+2816.51s] DEBUG: Seat seat0: Creating display server of type x [+2816.51s] DEBUG: Using VT 9 [+2816.51s] DEBUG: Seat seat0: Starting local X display on VT 9 [+2816.51s] DEBUG: DisplayServer x-2: Logging to /var/log/lightdm/x-2.log [+2816.51s] DEBUG: DisplayServer x-2: Writing X server authority to /var/run/lightdm/root/:2 [+2816.51s] DEBUG: DisplayServer x-2: Launching X Server [+2816.51s] DEBUG: Launching process 3702: /usr/bin/X -core :2 -seat seat0 -auth /var/run/lightdm/root/:2 -nolisten tcp vt9 -novtswitch [+2816.51s] DEBUG: DisplayServer x-2: Waiting for ready signal from X server :2 [+2816.51s] DEBUG: Session pid=3701: Exited with return value 1 [+2816.51s] DEBUG: Seat seat0: Session stopped [+2816.66s] DEBUG: Seat seat0 changes active session to [+2816.92s] DEBUG: Got signal 10 from process 3702 [+2816.92s] DEBUG: DisplayServer x-2: Got signal from X server :2 [+2816.92s] DEBUG: DisplayServer x-2: Connecting to XServer :2 [+2816.92s] DEBUG: DisplayServer x-2: Error connecting to XServer :2 [+2817.20s] DEBUG: Got signal 10 from process 3702 [+2817.49s] DEBUG: Got signal 10 from process 3702 (Last three lines pops up when I tried to switch user and the bug appeared). I assume this is an X/lightdm bug? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1652644 Title: Switching users in Ubuntu/Ubuntu Gnome freezes graphics To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1652644/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
