failsafeXServer kicked in without (a real) reason?

When I came back to my laptop, after some `xset dpms force off`, my window manager (awesomeWM) behaved strange:
the modkey (super/windows key) was not recognized anymore - probably just all modifier keys (I still could type into the current window, but not switch).

Then I've noticed that there is failsafeXServer on VT2.
I've chosen the last option (drop me to a console login), and that killed the gnome-session which ran awesomeWM.

I've noticed this on ~02:55.

From the logs it seems like the failsafeXServer has been there since the last reboot already?

There were no "systemd" messages in the systemd journal for hours - e.g. because X might have crashed or something else would have triggered this.

It seems like for some reason the long-running failsafeXServer suddenly captured the input method somehow, and also the redrawing which wasn't happening in awesomeWM anymore.

It's a bit frustrating to have the X session being killed like this.

Let me know, if I should provide more information from logs etc.

For the time being I'll probably uninstall xdiagnose - it's not worth such trouble (for me).

❯❯ systemctl status failsafe-x.service -l
● failsafe-x.service - X.org diagnosis failsafe
   Loaded: loaded (/lib/systemd/system/failsafe-x.service; static; vendor preset: enabled)
   Active: inactive (dead) since Mo 2015-05-18 02:57:00 CEST; 45min ago
 Main PID: 5175 (code=killed, signal=TERM)
   Memory: 16.3M
   CGroup: /system.slice/failsafe-x.service

Mai 16 20:15:14 lenny.thequod.de org.a11y.atspi.Registry[5255]: SpiRegistry daemon is running with well-known name - org.a11y.atspi.Registry
Mai 16 20:15:14 lenny.thequod.de failsafeXServer[5175]: Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
Mai 18 02:56:48 lenny.thequod.de failsafeXServer[5175]: Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
Mai 18 02:57:00 lenny.thequod.de systemd[1]: Stopping X.org diagnosis failsafe...
Mai 18 02:57:00 lenny.thequod.de systemd[1]: Stopped X.org diagnosis failsafe.
Mai 18 02:57:02 lenny.thequod.de failsafeXServer[5175]: xinit: connection to X server lost
Mai 18 02:57:02 lenny.thequod.de org.a11y.atspi.Registry[5255]: XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":0"
Mai 18 02:57:02 lenny.thequod.de org.a11y.atspi.Registry[5255]: after 41 requests (41 known processed) with 0 events remaining.
Mai 18 02:57:02 lenny.thequod.de org.a11y.Bus[5250]: g_dbus_connection_real_closed: Remote peer vanished with error: Underlying GIOStream returned 0 bytes on an async read (g-io-error-quark, 0). Exiting.
Mai 18 02:57:02 lenny.thequod.de failsafeXServer[5175]: waiting for X server to shut down (II) Server terminated successfully (0). Closing log file.

❯❯ systemctl status failsafe-graphical.target
● failsafe-graphical.target - Graphical failsafe fallback
   Loaded: loaded (/lib/systemd/system/failsafe-graphical.target; static; vendor preset: enabled)
   Active: inactive (dead) since Mo 2015-05-18 02:57:00 CEST; 45min ago

Mai 16 20:15:12 lenny.thequod.de systemd[1]: Reached target Graphical failsafe fallback.
Mai 16 20:15:12 lenny.thequod.de systemd[1]: Starting Graphical failsafe fallback.
Mai 18 02:57:00 lenny.thequod.de systemd[1]: Stopped target Graphical failsafe fallback.
Mai 18 02:57:00 lenny.thequod.de systemd[1]: Stopping Graphical failsafe fallback.
---
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
DistroRelease: Ubuntu 15.04
InstallationDate: Installed on 2012-05-28 (1084 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
Package: xdiagnose 3.7.2
PackageArchitecture: all
ProcVersionSignature: Ubuntu 3.19.0-17.17-generic 3.19.6
Tags: vivid third-party-packages
Uname: Linux 3.19.0-17-generic x86_64
UpgradeStatus: Upgraded to vivid on 2015-05-14 (3 days ago)
UserGroups: adm cdrom davfs2 dialout dip docker fuse lastfm libvirtd lpadmin plugdev sambashare sudo wireshark www-data
_MarkForUpload: True