diff --git a/sys/dev/drm/radeon/radeon_irq_kms.c b/sys/dev/drm/radeon/radeon_irq_kms.c
--- a/sys/dev/drm/radeon/radeon_irq_kms.c
+++ b/sys/dev/drm/radeon/radeon_irq_kms.c
@@ -103,9 +103,10 @@
 	struct drm_mode_config *mode_config = &dev->mode_config;
 	struct drm_connector *connector;
 
-	/* this should take a mutex */
+	mutex_lock(&mode_config->mutex);
 	list_for_each_entry(connector, &mode_config->connector_list, head)
 		radeon_connector_hotplug(connector);
+	mutex_unlock(&mode_config->mutex);
 }
 /**
  * radeon_driver_irq_preinstall_kms - drm irq preinstall callback