Hi Friends I am new to linux kernal I found this in a kernal code while just browsing. Can any one explain this semaphores with a good example. static struct semaphore cmd_semaphore = MUTEX; down(&cmd_semaphore); up(&cmd_semaphore); Thanx Deepti Get 250 color business cards for FREE! at Lycos Mail http://mail.lycos.com/freemail/vistaprint_index.html