title: programe received signal SIGIO
body: <p>I see following error in my <code>Nginx</code>'s error.log,</p>
  
  <blockquote>
    <p>[notice] 12451#0: signal 29 (SIGIO) received</p>
  </blockquote>
  
  <p>I want to know in which case does a program receive a <code>SIGIO</code>?</p>