process.c:497
static VALUE
detach_process_watcer(pid_p)
    int *pid_p;
{
    int cpid, status;

    for (;;) {
	cpid = rb_waitpid(*pid_p, &status, WNOHANG);
	if (cpid == -1) return Qnil;
	rb_thread_sleep(1);
    }
}
