if(call_stack_setter != null)
if(deadlock_detection && call_stack_setter == null) { call_stack_setter=new CallStackSetter();
    void startScheduler() {        if(scheduler == null) {            scheduler=new Scheduler();            if(call_stack_setter != null)                scheduler.setListener(call_stack_setter);            if(concurrent_processing)                scheduler.setConcurrentProcessing(concurrent_processing);            scheduler.start();        }    }