Hello Sabarinathan > It has got an indefinite while loop > so I want to make the module sleep for few milli seconds > if i use sleep, it said unresolved symbol sleep To make your module sleep....you mean, to make your own created process sleep, right? If you are sure that you want to sleep for certai period, try to check schedule_timeout() (i believe it is declared on include/linux/sched.h) if yo are trying to sleep when waiting for something, try to study about completion variable. it is declared on include/linux/completion.h regards Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/