title: pthread_rwlock_rdlock() and pthread_rwlock_wrlock()
body: <p>I can't understand a thing in the specification of the behaviour of these functions.   </p>
  
  <p>Imagine this scenario:<br>
  T1,T2 and T3 are the names of the threads.<br>
  Execute operations in series.    </p>
  
  <pre><code>    T1 calls pthread_rwlock_rdlock().
      T2 calls pthread_rwlock_wrlock() and wait because 
      rwlock is hold by T1.
      T3 calls pthread_rwlock_rdlock().
      T1 calls pthread_rwlock_unlock().
  </code></pre>
  
  <p>What's up next?</p>
  
  <p>The specification says this:<br>
  "The calling thread acquires the read lock if a writer does not hold the lock and there are no writers blocked on the lock"</p>
  
  <p>I can't undestand if T3 will take the rwlock before T2.<br>
  I hope yes.<br>
  Can you solve my problem?</p>