Created attachment 1271535 [details]
Screen shot after systemctl restart gdm

Description of problem:

On two different machines, I had some hangs with black screen and live mouse. On one machine, I had this almost systematically after screen blanking / screen lock, to the point that I disabled screen blanking entirely (I wish this machine could auto-lock, even if it does not contain any sensitive material). On another machine, it was after logging out to attempt to clear an issue with vino-server.

In both cases, I attempted to restart gdm with "systemctl restart gdm". I was unsuccessful every time (4 attempts total). In all cases, the restart fails, and you end up with a text console showing boot messages, see attachment. The last one is "Stopping User Manager for UID 42". Ctrl-Alt-Fn does not work at that stage.

Running systemctl status gdm shows gdm still running, an assertion and an error message with "too many open files". ps -ef | grep gdm shows that the original gdm process is still running, although I have no graphical login.

● gdm.service - GNOME Display Manager
   Loaded: loaded (/usr/lib/systemd/system/gdm.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2017-04-13 20:35:24 CEST; 1h 11min ago
 Main PID: 5025 (gdm)
    Tasks: 3 (limit: 4915)
   CGroup: /system.slice/gdm.service
           └─5025 /usr/sbin/gdm

Apr 13 20:38:00 muse.dinechin.org gdm[5025]: Unable to kill session worker process
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Child process -18189 was already dead.
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Child process 18181 was already dead.
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Unable to kill session worker process
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: GdmDisplay: display lasted 0.382937 seconds
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Could not start command '/usr/libexec/gdm-session-worker': Too many open files
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: GLib: g_child_watch_add_full: assertion 'pid > 0' failed
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Child process -18215 was already dead.
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Child process 18207 was already dead.
Apr 13 20:38:01 muse.dinechin.org gdm[5025]: Unable to kill session worker process

In all cases, the machine is "live" can be reached normally using ssh.

Using such a connection do to a "killall gdm" results in a flashing login screen alternating between login and boot console, see https://www.youtube.com/watch?v=hjpwRAz3vaw. Control-Alt-Fn does not work well at that stage either.

Version-Release number of selected component (if applicable):

gdm.x86_64                                             1:3.22.1-1.fc25                                             @anaconda



How reproducible: Always (in the screen blanking case)


Steps to Reproduce:
1. Wait until screen lock appears
2. Try to login
3. See that the screen is black with moving mouse cursor, but no login textbox
4. ssh to the machine, attempt "systemctl restart gdm"
5. ssh to the machine, attempt "killall gdm"

Actual results:

No clean way to restart gdm


Expected results:

gdm shuts down and restart, possible to login again.


Additional info:

Screen shot, see attachment.
Flashing screen, sss https://www.youtube.com/watch?v=hjpwRAz3vaw