Hi. It is known that no semaphore synchronization should be used inside an interrupt handler. Anyway, I am looking at a freeBSD device driver (written by a profesionist) and there are semaphores inside an interrupt handler's subroutine. Since I should port to linux that driver, I ask you how can I reach such synchronization under linux; I tried to use semaphores inside my handler but I got complains, and I don't want to break the law, so no semaphores for me. The scenario is the following: firmware downloader { while(fw_blocks--){ /* the call below will cause an interrupt */ load_block(); /* sleep unitl the int handler ackn's the previous operation, and prevent ANY int. handler operations until the process goes actually to sleep through the following call */ sleep(); } } int handler { if(the process is NOT asleep) wait(); wake up the process. } NOTE: I am on a 2.6.10 in order to be closely tutored by LDD3.