Bug#681830: debug logs

Neil Williams codehelp at debian.org
Mon Jan 28 15:50:41 UTC 2013


On Sun, 27 Jan 2013 19:42:47 +0000
Neil Williams <codehelp at debian.org> wrote:

> I made a fresh Wheezy GNOME3 install on a desktop machine (so that the
> display could be disconnected more easily) and had the GDM3 welcome
> screen on display. 

I've now been able to reproduce this on a laptop, as long as it is the
main X session and not a virtualbox or similar, so that access is
preserved to the virtual terminals.

As requested, I've rebuilt gdm3 with the --enable-debug switch
to ./configure and repeated the test with a simple shell script
replacing /usr/bin/Xorg which is just sleep 4 ; exit 1

This should mean that anyone with an old Debian box can test this bug,
it just needs access to the virtual terminals. A simple
# mv /Xorg /usr/bin
# invoke-rc.d gdm3 start
to restore the system.

If the output in /var/log/gdm3 was more useful, it could possibly be
done inside a virtualbox instance, just by replacing /usr/bin/Xorg
with a suitable shell script which exits nonzero.

> I changed the shell script to avoid the 3 second timeout (which makes
> this much more manageable) and gdm3 just keeps respawning using
> gdm-simple-slave, incrementing the --display-id each time.

This behaviour (monitored via htop on a virtual terminal) was
reproduced - I left the test running until the ID was at least 12 or
higher before switching back to the virtual terminal which started gdm3
and killing it with Ctrl-C.

I've attached a tarball of all of the /var/log/gdm3/*greeter* log files
which were the only files in /var/log/gdm3/ which were not zero length
after the tests.

This test machine is an old laptop of mine which was upgraded to Wheezy
this morning and has a working (if clunky) X session normally.

> As mentioned on IRC, there is already some code to handle GdmDisplay
> respawning too fast. See on_display_status_changed() in
> gdm-local-display-factory.c.
> 
> I’m interested in logs with debugging enabled, especially stuff like
> “GdmLocalDisplayFactory: display status changed”.

I get no such matches in the attached logs, I'm afraid. Indeed, I don't
get any output from the logs during the re-spawning itself. Even
watching the files in /var/log/gdm3 with tail -f whilst the problem is
occurring shows no log entries being added during the restart
operations.

I have put commands into the /usr/bin/Xorg shell script replacement and
I can see that output being written to a test file, but no
corresponding entry is made either on the terminal running gdm3 or in
the files in /var/log/gdm3/

I have also tried with and without --fatal-warnings, with no effect.

This bug appears readily reproducible, assuming that
replacing /usr/bin/Xorg temporarily is a suitable mimic of the original
problem reported.

-- 


Neil Williams
=============
http://www.linux.codehelp.co.uk/

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