// Continue reload.
$one_worker_pid = current(self::$_pidsToRestart);     <====只取了需要resetart的進程里的一個
// Send reload signal to a worker process.
posix_kill($one_worker_pid, SIGUSR1);
// If the process does not exit after self::KILL_WORKER_TIMER_TIME seconds try to kill it.
Timer::add(self::KILL_WORKER_TIMER_TIME, 'posix_kill', array($one_worker_pid, SIGKILL), false);