I was trying some experiments with the kernel daemon. The experiment works as follows: A daemon sleeps in the background. User can enter a string through the proc interface. Whenever a string is entered, the daemon is woke. The daemon keeps a copy of the last entered string in a variable. Initially the variable is initialized to NULL. When the daemon wakes, it checks if the string entered is same as the previous one or a new string is entered. When the string is entered, in case the new or the old strings are NULL, or in case the entered string is same as the old string the daemon goes back to sleep (with the help of the function interruptible_sleep_on(). The problem I am facing is that when I enter the string the second time, the system stalls. I added some sleeps in the code and figured out that when the proc function wakes up the daemon, the system stalls. I have attached the module code with the mail. Any suggestion for the error would be a great help. Shubham