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[Aaron Plattner <aplattner@xxxxxxxxxx>]

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

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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:
  New

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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