Function newSignalHandler

signals.go:21–48

newSignalHandler returns a signal handler for processing SIGCHLD and SIGWINCH signals while still forwarding all other signals to the process. If notifySocket is present, use it to read systemd notifications from the container and forward them to notifySocketHost.

(enableSubreaper bool, notifySocket *notifySocket)

// If notifySocket is present, use it to read systemd notifications from the container and
// forward them to notifySocketHost.
func newSignalHandler(enableSubreaper bool, notifySocket *notifySocket) chan *signalHandler {
	if enableSubreaper {
		// set us as the subreaper before registering the signal handler for the container
		if err := system.SetSubreaper(1); err != nil {
			logrus.Warn(err)
		}
	}
	handler := make(chan *signalHandler)

	// Ensure that we have a large buffer size so that we do not miss any
	// signals in case we are not processing them fast enough.
	s := make(chan os.Signal, signalBufferSize)

	// signal.Notify is actually quite expensive, as it has to configure the
	// signal mask and add signal handlers for all signals (all ~65 of them).
	// So, defer this to a background thread while doing the rest of the io/tty
	// setup, except for SIGCHLD which is very important (see #5208).
	signal.Notify(s, unix.SIGCHLD)
	go func() {
		// handle all signals for the process.
		signal.Notify(s)
		handler <- &signalHandler{
			signals:      s,
			notifySocket: notifySocket,
		}
	}()
	return handler
}

// exit models a process exit status with the pid and
// exit status.