diff --git a/include/system/graphics.h b/include/system/graphics.h
index d39bd4e..77cd337 100644
--- a/include/system/graphics.h
+++ b/include/system/graphics.h
@@ -19,6 +19,20 @@
 
 __BEGIN_DECLS
 
+/*
+ * If the HAL needs to create service threads to handle graphics related
+ * tasks, these threads need to run at HAL_PRIORITY_URGENT_DISPLAY priority
+ * if they can block the main rendering thread in any way.
+ *
+ * the priority of the current thread can be set with:
+ *
+ *      #include <sys/resource.h>
+ *      setpriority(PRIO_PROCESS, 0, HAL_PRIORITY_URGENT_DISPLAY);
+ *
+ */
+
+#define HAL_PRIORITY_URGENT_DISPLAY     (-8)
+
 /**
  * pixel format definitions
  */