title: How to implement mutex in iOS app
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/11070947/gcd-how-to-write-and-read-to-variable-from-two-threads">GCD : How to write and read to variable from two threads</a>  </p>
  </blockquote>
  
  
  
  <p>I am developing a iOS app in which i am using sqlite database.I have to perform multithreading  but on sqlite database I am able to do only one thing at a time.So I need to implement concept of semaphore .So plz help me</p>