[LightDM] Xorg does not terminate since r2441

[Martin Vogt]

Hello,

recently lightdm was updated in my linux distribution and I was unable to
logout from my desktop.
The Xorg server does not terminate and does not switches back to the X11
chooser.

Xorg is started with:

>/usr/lib/xorg/Xorg :1 -dpi 100 -terminate -indirect x11chooser


[1] The lightdm.log file gives a critical signal emit error for r2441 in
the moment I exit my desktop:

>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Session stopped
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Stopping display server, no
sessions require it
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Display server stopped
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Active display server
stopped, starting greeter
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Stopping; failed to start a
greeter
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Stopping
>lightdm[19287]: [+35.97s] DEBUG: Seat (null): Stopped
>lightdm[19287]: [+35.97s] WARNING: instance with invalid (NULL) class
pointer
>lightdm[19287]: [+35.97s] CRITICAL: g_signal_emit_valist: assertion
'G_TYPE_CHECK_INSTANCE (instance)' failed

The relevant code section is in seat.c:

>   /* Stop the display server if no-longer required */
>   if (display_server && !display_server_get_is_stopping (display_server)
&&
>        !SEAT_GET_CLASS (seat)->display_server_is_used (seat,
display_server))
>    {
>       l_debug (seat, "Stopping display server, no sessions require it");
>       display_server_stop (display_server);
>    }
>
>   g_signal_emit (seat, signals[SESSION_REMOVED], 0, session);
>   g_object_unref (session);



The attached patch fixes the problem for me, but I don't know how commit
2441 has caused it.
The display_server_stop() will call seat_stop() which will finalize/frees
the seat class in both cases (r2440+1)
Thus r2440 should have the same behaviour [1] as r2441, but r2440 works
fine.

regards,

Martin
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