def check_posix_lock(filename):
        ''' check if POSIX lock (fcntl/lockf) is held on filename '''
        lockfile = None
        try:
            lockfile = open(filename, 'w')
            fcntl.lockf(lockfile, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except BlockingIOError:
            return True
        except:
            pass
        finally:
            if lockfile:
                lockfile.close()
        return False