drm/i915/selftests: Flush the context worker

When cleaning up the mock device, remember to flush the context worker
to free the residual GEM contexts before shutting down the device.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/802
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191230165821.3840449-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -1172,15 +1172,15 @@ void i915_gem_driver_remove(struct drm_i915_private *dev_priv)
 
 void i915_gem_driver_release(struct drm_i915_private *dev_priv)
 {
+	i915_gem_driver_release__contexts(dev_priv);
+
 	intel_gt_driver_release(&dev_priv->gt);
 
 	intel_wa_list_free(&dev_priv->gt_wa_list);
 
 	intel_uc_cleanup_firmwares(&dev_priv->gt.uc);
 	i915_gem_cleanup_userptr(dev_priv);
 
-	i915_gem_driver_release__contexts(dev_priv);
-
 	i915_gem_drain_freed_objects(dev_priv);
 
 	WARN_ON(!list_empty(&dev_priv->gem.contexts.list));

drivers/gpu/drm/i915/selftests/mock_gem_device.c

@@ -58,6 +58,8 @@ static void mock_device_release(struct drm_device *dev)
 	mock_device_flush(i915);
 	intel_gt_driver_remove(&i915->gt);
 
+	i915_gem_driver_release__contexts(i915);
+
 	i915_gem_drain_workqueue(i915);
 	i915_gem_drain_freed_objects(i915);