// Create a worker thread if we don't have one. If the system
// is interrupted, we only create a worker task if there
// are threads that need to be completed. If the system is
// shutting down, we never create a new worker.
if (!shutting_down_scheduler) {
// Create a worker thread if we don't have one. If the system
// is interrupted, we only create a worker task if there
// are threads that need to be completed. If the system is
// shutting down, we never create a new worker.
if (!shutting_down_scheduler) {