title: how uevents get triggered in kernel
body: <p>uevents has been sent from kernel space to user space through netlink socket.</p>
  
  <p>In kernel, there must be something trigger uevent. </p>
  
  <p>I guess there are two possibilities:</p>
  
  <ol>
  <li><p>Hardware interrupt - this means, once hardware interruption happened, kernel sends event to user space to signal that there is some events happened.</p></li>
  <li><p>software polling - this means, there is always a daemon to check these file system to see if there is anything changed. If so, then update these info to upper layer.</p></li>
  </ol>
  
  <p>Could anyone provide your feedback?</p>
  
  <p>Thanks</p>