title: For Linux RCU, during the grace period, is it possible that a new writer update the new data?
body: <p>I am new to Linux and studying RCU section. I saw there is a grace period during operation. Just want to know if some new writer want to update the data during a grace period, is it possible? I guess there are two ways:</p>
  
  <ol>
  <li><p>During a grace period, it comes with write-lock</p></li>
  <li><p>RCU can work on RCU, which means it creates a new RCU on the old RCU, waits for new RCU to finish and then the old RCU go to end of a grace period.</p></li>
  </ol>
  
  <p>Which way is correct for Linux?</p>