segfault when switching user

[anatoly techtonik]

When switching to another user lightdm hangs after entering password. Cursor just can't enter the field again. Dmesg shows the following:

...
[ 67.824062] hub 2-0:1.0: unable to enumerate USB device on port 2
[17534.653543] show_signal_msg: 36 callbacks suppressed
[17534.653553] lightdm[4737]: segfault at 0 ip (null) sp b5dff14c error 4 in libglib-2.0.so.0.3000.0[110000+f7000]
[17534.666035] init: lightdm main process (886) killed by SEGV signal
[17685.206223] compiz[1674]: segfault at 0 ip b6bdb4f7 sp bfc713d0 error 6 in libnvidia-glcore.so.280.13[b5b2d000+18a0000]
[17807.583211] init: tty1 main process ended, respawning
[17809.882622] init: tty1 main process ended, respawning

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: lightdm 1.0.1-0ubuntu6
ProcVersionSignature: Ubuntu 2.6.38-11.50-generic 2.6.38.8
Uname: Linux 2.6.38-11-generic i686
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu3
Architecture: i386
CheckboxSubmission: b346f016d264f3ef62407d5e29c198a2
CheckboxSystem: daed2f3d6643b4a84b4520a2427f8c2b
Date: Fri Oct 14 15:57:05 2011
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: lightdm
UpgradeStatus: Upgraded to oneiric on 2011-10-02 (12 days ago)

[Launchpad Janitor (janitor)]

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

[tatabow (tatabow)]

I do reproduce the bug too with a migrated Ubuntu from 11.04 (not a fresh install).

A workaround is to switch back to gdm using the command :
sudo dpkg-reconfigure gdm

Back to gdm all is fine so it's definitely a lightgdm bug.

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please try to obtain a backtrace following the instructions at http://wiki.ubuntu.com/DebuggingProgramCrash and upload the backtrace (as an attachment) to the bug report. This will greatly help us in tracking down your problem.

Could you also add your lightdm.log log to the bug?

[Sebastien Bacher (seb128)]

thanks, rktesser I'm not sure the original bug is the same as yours bug your issue is bug #829221 and has to do with samba credential, you should subscribe to that bug, there is a patch to test there as well

[Michael Satke (n9447354)]

Chaps,
I experience the same bug. In GUI mode, switching users causes lightdm to crash exactly the way anatoly techtonic described this.

Falling back to gdm can not be a solution, lightdm is really nice!

I have 64-bit standard oneiric installation (generic kernel 3.0.0-12) on a laptop (HP 625, CPU: AMD Athlon II P360 dual core, RAM 4 GiB, hdd 230 GiB).

I hope this bug can be forgot soon.

[anatoly techtonik (techtonik)]

Switched to gdm with:

$ sudo dpkg-reconfigure gdm

Now switched back:

$ sudo dpkg-reconfigure gdm
Please be sure to run "dpkg --configure lightdm".
$ sudo dpkg --configure lightgdm
dpkg: warning: there's no installed package matching lightgdm

I'll report back if bug appears one again.

[anatoly techtonik (techtonik)]

My lightgdm.log. Still hangs when I try to switch user after suspend. However, `dmesg` doesn't contain lightgdm segfaults.

-- cut dmesg --
...
[ 2391.853754] show_signal_msg: 45 callbacks suppressed
[ 2391.853760] compiz[1659]: segfault at 0 ip b69074f7 sp bfc67c30 error 6 in libnvidia-glcore.so.280.13[b5859000+18a0000]
-- ----

-- cut x-0.log --

X.Org X Server 1.10.4
Release Date: 2011-08-19
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-29-server i686 Ubuntu
Current Operating System: Linux host 2.6.38-11-generic #50-Ubuntu SMP Mon Sep 12 21:18:14 UTC 2011 i686
Kernel command line: root=UUID=00b0c18b-3e0b-4bec-96ab-b0ab4604afff ro splash vga=786
Build Date: 19 October 2011 05:09:41AM
xorg-server 2:1.10.4-1ubuntu4.2 (For technical support please see http://www.ubuntu.com/support)
Current version of pixman: 0.22.2
 Before reporting problems, check http://wiki.x.org
 to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
 (++) from command line, (!!) notice, (II) informational,
 (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Sat Nov 5 09:43:24 2011
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
(EE) Failed to load module "nv" (module does not exist, 0)

[anatoly techtonik (techtonik)]

Found segfault from lightdm earlier in kern.log

...
[ 9708.067796] PM: resume of devices complete after 833.337 msecs
[ 9708.067989] PM: resume devices took 0.832 seconds
[ 9708.068022] PM: Finishing wakeup.
[ 9708.068024] Restarting tasks ...
...
[ 9738.905189] show_signal_msg: 36 callbacks suppressed
[ 9738.905198] lightdm[7093]: segfault at 0 ip (null) sp b5dfd14c error 4 in libglib-2.0.so.0.3000.0[110000+f7000]
[ 9738.907571] init: lightdm main process (907) killed by SEGV signal

[Michael Satke (n9447354)]

After a routine update of my linux kernel to the generic 3.0.0-13, this bug has gone for my part. User switching works fine as I was used to in Natty. Whatever happened, my computers work well again.

[anatoly techtonik (techtonik)]

I don't care about segfaults anymore. That bugs me is that "lightdm" hangs after resuming from suspend, so I have to restart it every time manually.

[tatabow (tatabow)]

I confirm that the routine update of my linux kernel has fixed this bug for me.

[Launchpad Janitor (janitor)]

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

[cancan101 (agrothberg)]

When I switched to gdm from lightdm, the issue still seemed to happen. I see the segfault when switching users (and I think to tty1 and then back)

[cancan101 (agrothberg)]

I wonder if this is relevant: http://www.nvnews.net/vbulletin/showthread.php?t=168598 ? I think the segfault might also happen in nvidia-settings when I change the resolution / screen offsets.

[Robert Ancell (robert-ancell)]

Closing assumed fixed.

[vkapas (vkapas)]

I can confirm bug. There is still no fixes. In my case active user session crashed every 5-6-th login (PC has 2 users) after entering passwords with this:

kernel: [213870.238364] compiz[2577]: segfault at 0 ip 00007f6f2adb1530 sp 00007fff39517d40 error 6 in libnvidia-glcore.so.352.63[7f6f29568000+19fd000]

Ubuntu 14.04.4 with last updates
kernel 3.13.0-85-generic
compiz 1:0.9.11.3+14.04.20150313-0ubuntu1
lightdm 1.10.6-0ubuntu1