I hope we get all the possible methods listed now. I have used signals for years in my alsashmrec. One process reads A/D to a ring buffer and another process empties the ring buffer to the disk. The problem was how to make the disk process (non-RT process) to wait. When the disk process has no data in the ring buffer, it goes to sleep: kill((pid_t)diskpid,SIGSTOP); When the A/D process has written enough data to the ring buffer, it wakes up the disk process: kill((pid_t)diskpid,SIGCONT); Because A/D process uses smaller buffer size, the A/D process is executed multiple times before SIGCONT is sent. Juhana -- http://music.columbia.edu/mailman/listinfo/linux-graphics-dev for developers of open source graphics software