Bug#838050: gnome-shell: gdm doesn't start due to a problem with gnome-shell crashing in libwacom2

[Erik Tews]

Am Samstag, den 17.09.2016, 09:37 +0200 schrieb Michael Biebl:
> Am 17.09.2016 um 01:09 schrieb Erik Tews:
> 
> > 
> > After startup, gdm doesn't show up and just shows a grey screen.
> > Looking at syslog reveals the reason:
> > 
> > syslog:Sep 16 23:27:25 matte kernel: [  172.983123] gnome-
> > shell[3206]: segfault 
> > at 10 ip 00007f8e7c85d6c4 sp 00007ffd151d0a80 error 4 in
> > libwacom.so.2.4.6[7f8e7
> > c85a000+9000]
> > 
> > Since I haven't updated libwacom2 in the last 2 weeks, but gnome-
> > shell was recently updated, I assume this is due to a problem in
> > gnome-shell.
> > 
> > There is also a temporary fix, just run: rmmod wacom, and then
> > restart gdm, and you can use it again, of course without the
> > touchscreen.
> > 
> > Unfortunately, in upstream, I cannot see any kind of commit between
> > 3.21.92 and 3.21.91 that might cause such a problem.
> 
> Can you downgrade gnome-shell (and gnome-shell-common) to version
> 3.21.91-2 (from testing), reboot and test if the problem is still
> reproducible?
> 
> If not, does downgrading libmutter0i, mutter-common, mutter to
> 3.21.91-2
> fix the problem?

Just downgrading gnome-shell with the dependencies didn't help, but
downgrading mutter and some related packages with gnome-shell solved
the problem. Right now I have the following versions of those packages,
everything else is on Debian unstable:

ii  gdm3                                    3.21.90-1                amd64                    GNOME Display Manager
ii  gir1.2-gdm-1.0                          3.21.90-1                amd64                    GObject introspection data for the GNOME Display Manager
ii  gir1.2-mutter-3.0:amd64                 3.21.91-2                amd64                    GObject introspection data for Mutter
ii  gnome-session                           3.20.2-1                 all                      GNOME Session Manager - GNOME 3 session
ii  gnome-session-bin                       3.20.2-1                 amd64                    GNOME Session Manager - Minimal runtime
ii  gnome-session-common                    3.20.2-1                 all                      GNOME Session Manager - common files
ii  gnome-shell                             3.21.91-2                amd64                    graphical shell for the GNOME desktop
ii  gnome-shell-common                      3.21.91-2                all                      common files for the GNOME graphical shell
ii  gnome-shell-extensions                  3.21.91-1                all                      Extensions to extend functionality of GNOME Shell
ii  libgdm1                                 3.21.90-1                amd64                    GNOME Display Manager (shared library)
ii  libmutter0i:amd64                       3.21.91-2                amd64                    window manager library from the Mutter window manager
ii  linux-base                              4.4                      all                      Linux image base package
ii  mutter                                  3.21.91-2                amd64                    lightweight GTK+ window manager
ii  mutter-common                           3.21.91-2                all                      shared files for the Mutter window manager

And gdm with gnome-shell works fine with wacom.

I also looked at the upstream git commits for mutter, but didn't find
an obvious one that causes the problem.

Is there any nice way of getting a stack backtrace when gnome-shell
launched by gdm crashes so that I can see how the call looks like and
through which library it went?

Erik
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