Index: kernel/generic/src/ipc/sysipc.c
===================================================================
--- kernel/generic/src/ipc/sysipc.c	(revision 56d5c7f65d38f337974902681786c185542a8079)
+++ kernel/generic/src/ipc/sysipc.c	(revision b11ee8872cb2061cd04c3ebb8c53931f45068af2)
@@ -937,4 +937,9 @@
 	 * copy whole call->data, not only call->data.args */
 	if (STRUCT_TO_USPACE(calldata, &call->data)) {
+		/* XXX
+		 * To avoid deadlocks in synchronous calls
+		 * this should be replaced by discarding
+		 * the call and notifying the caller.
+		 */
 		return 0;
 	}