Re: [gnome-flashback] Gnome FB Meta on F22 fails to start locally

[Yaakov Selkowitz <yselkowi redhat com>]

On Mon, 2015-08-10 at 12:09 +0300, Alberts Muktupāvels wrote:
> On Mon, Aug 10, 2015 at 9:32 AM, Yaakov Selkowitz wrote:
> > I had the same issue on a Lenovo Thinkpad T540p.  gnome-flashback
> > crashes in flashback_monitor_manager_read_current_config(), and I 
> > was
> > able to work around it by setting the org.gnome.gnome-flashback 
> > display
> > -config key to false (at the price of losing the Display control 
> > panel
> > functionality).
> >
> > As for a proper fix, please let me know if you need any further
> > information to help diagnose the issue.
> gdb output? And if you can please test with git master - there was 
> changes in display code.

Still crashes with git master.

Backtrace from systemd-coredump:

#0  0x0000000000421f44 read_current_config (gnome-flashback)
#1  0x0000000000423757 flashback_monitor_manager_read_current_config
(gnome-flashback)
#2  0x00000000004223d5 flashback_monitor_manager_constructed (gnome
-flashback)
#3  0x00000037dc015627 g_object_new_internal (libgobject-2.0.so.0)
#4  0x00000037dc016f45 g_object_new_valist (libgobject-2.0.so.0)
#5  0x00000037dc0172b1 g_object_new (libgobject-2.0.so.0)
#6  0x00000000004228c4 flashback_monitor_manager_new (gnome-flashback)
#7  0x000000000041a92b flashback_display_config_init (gnome-flashback)
#8  0x00000037dc03256b g_type_create_instance (libgobject-2.0.so.0)
#9  0x00000037dc0150ab g_object_new_internal (libgobject-2.0.so.0)
#10 0x00000037dc016991 g_object_newv (libgobject-2.0.so.0)
#11 0x00000037dc0172c4 g_object_new (libgobject-2.0.so.0)
#12 0x000000000041a991 flashback_display_config_new (gnome-flashback)
#13 0x000000000041231f settings_changed (gnome-flashback)
#14 0x0000000000412c9c flashback_application_init (gnome-flashback)
#15 0x00000037dc03256b g_type_create_instance (libgobject-2.0.so.0)
#16 0x00000037dc0150ab g_object_new_internal (libgobject-2.0.so.0)
#17 0x00000037dc016991 g_object_newv (libgobject-2.0.so.0)
#18 0x00000037dc0172c4 g_object_new (libgobject-2.0.so.0)
#19 0x0000000000412d35 flashback_application_new (gnome-flashback)
#20 0x0000000000412f1d main (gnome-flashback)
#21 0x00000037d9020700 __libc_start_main (libc.so.6)
#22 0x0000000000411df9 _start (gnome-flashback)

$ addr2line -Cfpe /usr/bin/gnome-flashback 0x421f44
read_current_config at gnome-flashback/libdisplay-config/flashback
-monitor-manager.c:1296

which is:

          meta_output->preferred_mode = meta_output->modes[0];

Adding some g_warning calls shows that on the first run of
read_current_config(), meta_output->n_modes and manager->n_modes are
both 1, but on subsequent calls they are 0 and 1 respectively, which
leads to this NULL reference.

This is a Lenovo ThinkPad T540p running F22.

-- 
Yaakov Selkowitz
Associate Software Engineer, ARM
Red Hat, Inc.