Hi, I have experienced similar symptoms in realtime programs (LinuxCNC). We have a control thread which sometimes does operations like system(), and one or more realtime threads. There, we changed from using system() to using posix_spawn and it appears to have resolved the problem. However, I don't have any explanation as to why this is the case. On the specific version of glibc I have, posix_spawn uses vfork and system uses clone; other syscalls like rt_sigaction are taken in the system case but not the posix_spawn case. Jeff
