On Wed, Jan 02, 2019 at 05:16:54PM +0100, Christian Brauner wrote: > + /* > + * Stop the child so we can inspect whether we have > + * recycled pid PID_RECYCLE. > + */ > + close(pipe_fds[0]); > + ret = kill(recycled_pid, SIGSTOP); > + close(pipe_fds[1]); > + if (ret) { > + (void)wait_for_pid(recycled_pid); > + _exit(PIDFD_ERROR); > + } Sorry for being late to the party, but I wonder if this whole thing couldn't be simplified with /proc/sys/kenrel/ns_last_pid? Tycho