Ubuntu
lightdm package

lightdm crashed with SIGSEGV in g_child_watch_dispatch()

Bug #795324 reported by Eliah Kagan
28
This bug affects 2 people
Affects Status Importance Assigned to Milestone
lightdm (Ubuntu)
Invalid
Medium
Unassigned

Bug Description

Binary package hint: lightdm

On an Oneiric i386 system, I updated a number of packages yesterday (/var/log/dpkg.log attached compressed as dpkg.log.gz), and was given the choice between remaining with gdm (2.32.1-0ubuntu5) as my display manager, or switching to lightdm (0.3.7-0ubuntu1). I decided to try out lightdm. It appeared to work without problems, and defaulted to my default gdm session type as desired. But immediately after log in (to a unity-2d session), Apport informed me that lightdm had crashed with with SIGSEGV in g_child_watch_dispatch().

I don't have any more information, except that this bug looks similar to bug 795050, which is a SIGSEGV in a similar bug different dispatch function (g_main_context_dispatch()). But I did *not* also experience bug 795050. Also [UPDATE], bug 795050 has been fixed in lightdm 0.3.7-0ubuntu2, whereas this bug still occurs with that version.

ProblemType: Crash
DistroRelease: Ubuntu 11.10
Package: lightdm 0.3.7-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.39-3.10-generic 2.6.39
Uname: Linux 2.6.39-3-generic i686
Architecture: i386
Date: Wed Jun 8 19:14:16 2011
ExecutablePath: /usr/bin/lightdm
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Alpha i386 (20110604)
ProcCmdline: lightdm
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
SegvAnalysis:
 Segfault happened at: 0x804bb73: mov 0x20(%eax),%eax
 PC (0x0804bb73) ok
 source "0x20(%eax)" (0xaaaaaaca) not located in a known VMA region (needed readable region)!
 destination "%eax" ok
SegvReason: reading unknown VMA
Signal: 11
SourcePackage: lightdm
StacktraceTop:
 ?? ()
 g_child_watch_dispatch (source=0x9c7fbc0, callback=0x804bb10, user_data=0x9c81000) at /build/buildd/glib2.0-2.29.4/./glib/gmain.c:4471
 g_main_dispatch (context=0x9c5b850) at /build/buildd/glib2.0-2.29.4/./glib/gmain.c:2477
 g_main_context_dispatch (context=0x9c5b850) at /build/buildd/glib2.0-2.29.4/./glib/gmain.c:3050
 g_main_context_iterate (context=0x9c5b850, block=1448320, dispatch=1, self=<value optimized out>) at /build/buildd/glib2.0-2.29.4/./glib/gmain.c:3128
Title: lightdm crashed with SIGSEGV in g_child_watch_dispatch()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

See original description
Revision history for this message
Eliah Kagan (degeneracypressure) wrote :
Revision history for this message
Eliah Kagan (degeneracypressure) wrote :

This is .xsession-errors from the session I logged into using lightdm (so far, this is the only session ever on this machine that has been logged into via lightdm).

Revision history for this message
Eliah Kagan (degeneracypressure) wrote :

This is .xsession-errors.old, documenting the previous session, for comparison (or in case it contains useful other information).

Revision history for this message
Jean-Baptiste Lallement (jibel) wrote :

Could you try lightdm 0.3.7-0ubuntu2? It fixed many crashers for me.

Changed in lightdm (Ubuntu):
status: New → Incomplete
Revision history for this message
Eliah Kagan (degeneracypressure) wrote :

I have successfully produced this crash again with lightdm 0.3.7-0ubuntu2, as requested. I've filed a new report (private duplicate bug 796521) from that crash. I'm removing the CoreDump.gz attachment in this bug and marking it public (I've looked over the data in the other files and it doesn't look like login credentials, and since it's my system, I can choose to take on that minimal level of risk). Hopefully that will make this bug easier to confirm and otherwise work on, while bug 796521 will still have all the automatically attached information (so perhaps "Apport retracing service" will be able to improve its stack trace). As with this bug, I've subscribed Jean-Baptiste Lallement and Robert Ancell to bug 796521 so they have full access to it even though it's private.

I have tried to produce this crash on another Oneiric i386 system on identical (virtual) hardware, so as to produce a complete bug report including core dump that I know doesn't contain any passwords I actually use on other machines. I have not succeeded, so far. So it seems that there is some undiscovered factor involved in determining whether or not this crash occurs.

Changed in lightdm (Ubuntu):
status: Incomplete → New
visibility: private → public
description: updated
description: updated
Eliah Kagan (degeneracypressure)
description: updated
Apport retracing service (apport)
tags: removed: need-i386-retrace
Revision history for this message
Pedro Villavicencio (pedro) wrote :

Lightdm 0.4.0 is on Oneiric right now, could you please give it a try with that version to se if you still can reproduce the issue? just set the bug to Confirmed if you're able to, thanks in advance!.

Changed in lightdm (Ubuntu):
importance: Undecided → Medium
status: New → Incomplete
Revision history for this message
Sebastien Bacher (seb128) wrote :

We are closing this bug report as it lacks the information, described in the previous comments, we need to investigate the problem further. However, please reopen it if you can give us the missing information and don't hesitate to submit bug reports in the future.

Changed in lightdm (Ubuntu):
status: Incomplete → Invalid
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