Bug#933842: crashes when switching monitor input under wayland

[Simon McVittie]

Control: tags -1 + moreinfo

On Sun, 04 Aug 2019 at 12:28:40 +0200, Stéphane Glondu wrote:
> Since recently, gnome-shell on wayland crashes when I switch the input
> of my monitor. This is a regression. And I don't observe the bug on
> X11.

Please try upgrading libmutter-3-0 and gir1.2-mutter-3 to 3.30.2-8
from unstable, then reboot (or at least log out from GNOME and back in)
to make sure that GNOME Shell is using the upgraded libraries.

This sounds like #932428, #932767 and #932781, which are believed to be
multiple reports of a mutter bug that was only a theoretical problem
in buster, but became a practical problem as a result of upgrading
from mesa 18.3.x to 19.1.x after buster was released: mesa 19.1.x is
more multi-threaded, which means mutter has to be more careful about
shutting things down in the right order to avoid a use-after-free on
monitor configuration changes or suspend.

If the problem persists even after you have upgraded, please install
systemd-coredump (or some other way to get core dumps, if you have
a favourite), along with GLib and libmutter debug symbols, and send a
backtrace from the crash to this bug report. I personally recommend
systemd-coredump, which collects core dumps system-wide, records
information about them in the systemd journal, and keeps the actual
core dump for a while (with automatic rotation/expiry) so that you can
load it into gdb and get a more complete backtrace. More information:
https://wiki.debian.org/HowToGetABacktrace#Core_dump

Because this is an intermittent problem (it doesn't *always* crash)
I'm waiting for more feedback before I close the bugs.

> I have no idea how to debug this. Is it possible to get gnome-shell
> stdout and stderr, or to run it from a ssh session (from another
> computer)?

On a system booted with systemd, gnome-shell's stdout and stderr should
end up in the systemd journal.

I don't know of a way to run gnome-shell in Wayland mode other than by
launching it from gdm.

    smcv