1. 17 Mar, 2016 1 commit
    • Lyude's avatar
      drm/i915: Fix race condition in intel_dp_destroy_mst_connector() · 1f771755
      Lyude authored
      After unplugging a DP MST display from the system, we have to go through
      and destroy all of the DRM connectors associated with it since none of
      them are valid anymore. Unfortunately, intel_dp_destroy_mst_connector()
      doesn't do a good enough job of ensuring that throughout the destruction
      process that no modesettings can be done with the connectors. As it is
      right now, intel_dp_destroy_mst_connector() works like this:
      
      * Take all modeset locks
      * Clear the configuration of the crtc on the connector, if there is one
      * Drop all modeset locks, this is required because of circular
        dependency issues that arise with trying to remove the connector from
        sysfs with modeset locks held
      * Unregister the connector
      * Take all modeset locks, again
      * Do the rest of the required cleaning for destroying the connector
      * Finally drop all modeset locks for good
      
      This only works sometimes. During the destruction process, it's very
      possible that a userspace application will attempt to do a modesetting
      using the connector. When we drop the modeset locks, an ioctl handler
      such as drm_mode_setcrtc has the oppurtunity to take all of the modeset
      locks from us. When this happens, one thing leads to another and
      eventually we end up committing a mode with the non-existent connector:
      
      	[drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* failed to enable link training
      	[drm:intel_dp_aux_ch] dp_aux_ch timeout status 0x7cf0001f
      	[drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization
      	[drm:intel_dp_aux_ch] dp_aux_ch timeout status 0x7cf0001f
      	[drm:intel_mst_pre_enable_dp [i915]] *ERROR* failed to allocate vcpi
      
      And in some cases, such as with the T460s using an MST dock, this
      results in breaking modesetting and/or panicking the system.
      
      To work around this, we now unregister the connector at the very
      beginning of intel_dp_destroy_mst_connector(), grab all the modesetting
      locks, and then hold them until we finish the rest of the function.
      
      CC: stable@vger.kernel.org
      Signed-off-by: default avatarLyude <cpaul@redhat.com>
      Signed-off-by: default avatarRob Clark <rclark@redhat.com>
      Reviewed-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
      Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      Link: http://patchwork.freedesktop.org/patch/msgid/1458155884-13877-1-git-send-email-cpaul@redhat.com
      1f771755
  2. 16 Mar, 2016 28 commits
  3. 15 Mar, 2016 1 commit
  4. 14 Mar, 2016 10 commits