Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: unity-settings-daemon (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1370720
Title:
unity-settings-daemon can deadlock if a modeset fails
Status in unity-settings-daemon package in Ubuntu:
Confirmed
Bug description:
The system I used to reproduce this bug was a laptop with two display
devices (one DisplayPort, one DVI) connected to a docking station.
Dock the laptop. unity-settings-manager triggers a display change to
extended mode. Then, undock the laptop. The following sequence of
events triggers a deadlock:
1. The system generates an ACPI event that video.ko turns into a display
change hotkey press.
2. Something sees the display change hotkey event and calls
unity-settings-manager via dbus.
3. The X driver sees the DVI monitor go away and updates the RandR
configuration.
4. unity-settings-manager enters handle_fn_f7() and calls
gnome_rr_screen_refresh().
5. gnome_rr_screen_refresh() sees that the configuration changed and calls
the callbacks.
6. The X driver sees the DP monitor go away and updates the RandR
configuration.
7. on_randr_event() tries to reconfigure the desktop with the DVI monitor
disabled and the DP monitor enabled.
8. The RandR SetCrtcConfig call fails because it's trying to set a mode on a
disconnected output.
9. apply_configuration() calls error_message(), which tries to pop up a
dialog box.
Step #9 deadlocks because gnome_rr_screen_refresh() called
XGrabServer() in step #5.
Upstream gnome-settings-daemon fixed this with commit
0f7cbfed5e5e76824e057ce9c570fad66ba001c6.
https://git.gnome.org/browse/gnome-settings-daemon/commit/?id=0f7cbfed5e5e76824e057ce9c570fad66ba001c6
This change cherry-picks cleanly to unity-settings-daemon.
(as an aside, the video.ko display change hotkey events are entirely
pointless and probably deserve their own bug)
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