For readability reasons do not describe the behavior of concurrent processes by means of concurrent state machines if these processes need to by synchronized. Instead, each process should be captured by individual function blocks (Activities). The process synchronization then should be performed “hardwired.”
Nevertheless, if concurrent state machines are used and the broadcasting mechanism is used for synchronization, they should be restricted for readability reasons to one chart level.
Functions (Activities), which are always active should be explicitly visualized in the control activity as concurrent processes (see the Visualization of Concurrent Processes in a Control Activity and the Feature Model: Seat Heating figures) with a respective Static Reaction (refer to State Transitions).