Function registerMemoryEvent

libcontainer/notify_linux.go:20–61

(cgDir, evName, arg string)

)

func registerMemoryEvent(cgDir, evName, arg string) (<-chan struct{}, error) {
	evFile, err := os.Open(filepath.Join(cgDir, evName))
	if err != nil {
		return nil, err
	}
	fd, err := unix.Eventfd(0, unix.EFD_CLOEXEC)
	if err != nil {
		evFile.Close()
		return nil, err
	}

	eventfd := os.NewFile(uintptr(fd), "eventfd")

	eventControlPath := filepath.Join(cgDir, "cgroup.event_control")
	data := fmt.Sprintf("%d %d %s", eventfd.Fd(), evFile.Fd(), arg)
	if err := os.WriteFile(eventControlPath, []byte(data), 0o700); err != nil {
		eventfd.Close()
		evFile.Close()
		return nil, err
	}
	ch := make(chan struct{})
	go func() {
		defer func() {
			eventfd.Close()
			evFile.Close()
			close(ch)
		}()
		buf := make([]byte, 8)
		for {
			if _, err := eventfd.Read(buf); err != nil {
				return
			}
			// When a cgroup is destroyed, an event is sent to eventfd.
			// So if the control path is gone, return instead of notifying.
			if _, err := os.Lstat(eventControlPath); errors.Is(err, os.ErrNotExist) {
				return
			}
			ch <- struct{}{}
		}
	}()
	return ch, nil
}

// notifyOnOOM returns channel on which you can expect event about OOM,
// if process died without OOM this channel will be closed.