Public bug reported: 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) ** Affects: unity-settings-daemon (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1370720 Title: unity-settings-daemon can deadlock if a modeset fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity-settings-daemon/+bug/1370720/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
