子进程为什么要重装信号处理器？

[code] // uninstall stop signal handler
pcntl_signal(SIGINT, SIG_IGN, false);
// uninstall graceful stop signal handler
pcntl_signal(SIGTERM, SIG_IGN, false);
// uninstall reload signal handler
pcntl_signal(SIGUSR1, SIG_IGN, false);
// uninstall graceful reload signal handler
pcntl_signal(SIGQUIT, SIG_IGN, false);
// uninstall status signal handler
pcntl_signal(SIGUSR2, SIG_IGN, false);
// reinstall stop signal handler
static::$globalEvent->add(SIGINT, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));
// reinstall graceful stop signal handler
static::$globalEvent->add(SIGTERM, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));
// reinstall reload signal handler
static::$globalEvent->add(SIGUSR1, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));
// reinstall graceful reload signal handler
static::$globalEvent->add(SIGQUIT, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));
// reinstall status signal handler
static::$globalEvent->add(SIGUSR2, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));
// reinstall connection status signal handler
static::$globalEvent->add(SIGIO, EventInterface::EV_SIGNAL, array('\Workerman\Worker', 'signalHandler'));[/code]1）为什么没有 pcntl_signal(SIGIO, SIG_IGN, false)； ？
2）重装信号处理器，似乎还是调用的 array('\Workerman\Worker', 'signalHandler')，为什么要重装？