If you're using futexes across processes (or any other cross-process state), one generic approach is for a watchdog process to keep a SOCK_STREAM or SOCK_SEQPAC

If you're using futexes across processes (or any other cross-process state), one generic approach is for a watchdog process to keep a SOCK_STREAM or SOCK_SEQPACKET Unix domain socket open for each process so it can reliably detect when a process crashes and clean up its per-process state.