upgrading systemd to v237-3ubuntu10.43 on Ubuntu 18.04 LTS i386 causes lightdm to crash

[Wladimir Mutel]

Reproduction :
 take a bog-standard system with Intel CPU and Intel graphics (mobo like Foxconn 45GM/45CM/45CM-S or ECS 945GCT-M2 with Intel E4500, or ASRock G41C-VS/G41M-VS3/G31M-S with Intel E3300/E3400, or Asrock P4I45GL with Intel Pentium4 2.40GHz) ;
 install Lubuntu 18.04 i386 on it ;
 install all latest upgrades including systemd packages of version 237-3ubuntu10.43 ;
 reboot and watch black screen with blinking text cursor

Fix :
 switch into text console or log in as sudo-capable user over the network
 look at lightdm crashes in dmesg
 download past version of systemd packages (237-3ubuntu10.42)
 install them by dpkg
 reboot and enjoy your graphic screen again

[Sebastien Bacher (seb128)]

Thank you for your bug report, what lightdm greeter do you use? It's similar to bug #1902879. Also doesn't lubuntu use sddm as its login manager?

[Wladimir Mutel (mwg)]

I found it happens on non-Intel CPUs and VGAs as well.
Like, Gigabyte M61PME-S2 with Sempron LE-1200

[Wladimir Mutel (mwg)]

Lubuntu 18.04 is based on LXDE, not LXQt, and so it uses lightdm, not sddm.
greeter is lightdm-gtk-greeter, which causes traps in libglib like these :

ноя 04 16:50:48 user-desktop kernel: traps: lightdm-gtk-gre[673] trap int3 ip:b6f929d0 sp:bf9e9e20 error:0 in libglib-2.0.so.0.5600.4[b6f44000+12e000]
ноя 04 16:50:52 user-desktop kernel: traps: lightdm-gtk-gre[736] trap int3 ip:b6fe49d0 sp:bfbcfcd0 error:0 in libglib-2.0.so.0.5600.4[b6f96000+12e000]
ноя 04 16:50:54 user-desktop kernel: traps: lightdm-gtk-gre[798] trap int3 ip:b70149d0 sp:bf839010 error:0 in libglib-2.0.so.0.5600.4[b6fc6000+12e000]
ноя 04 16:50:56 user-desktop kernel: traps: lightdm-gtk-gre[860] trap int3 ip:b70669d0 sp:bf9a2f40 error:0 in libglib-2.0.so.0.5600.4[b7018000+12e000]
ноя 04 16:50:57 user-desktop kernel: traps: lightdm-gtk-gre[922] trap int3 ip:b701a9d0 sp:bfe9c750 error:0 in libglib-2.0.so.0.5600.4[b6fcc000+12e000]
ноя 04 16:50:59 user-desktop kernel: traps: lightdm-gtk-gre[984] trap int3 ip:b6fa19d0 sp:bfb4dcb0 error:0 in libglib-2.0.so.0.5600.4[b6f53000+12e000]

[Sebastien Bacher (seb128)]

thanks for the reply and sorry for the confusion, I was reading the focal manifest when I saw sddm. That's the same issue than bug #1890394 that was backported now to older series and a regression from bug #1830746. SRU for lightdm-gtk-greeter/bionic is coming

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.