Such kind of situations are very common where you are relatively new, handling software for a safety critical system and entire production line is shut down due

Such kind of situations are very common where you are relatively new, handling software for a safety critical system and entire production line is shut down due to some exception occurring in large complex hard-real time multithreaded s/w module developed by some past ghost employee who has forgot to comment the code with no documentation available and the plant manager is banging your head for downtime loss!