title: readers-writers ( readers starvation )
body: <p>It said in Wikipedia that the code below "adds the constraint that no thread shall be allowed to starve" and I can't understand it why there is no starvation.
  for example : what if there are many writers arrive before any readers and the first writer took a very long time to finish his writing then r maybe reach some big minus number lets say -12345 and after it readers begin to arrive along with writers, and somehow the operating system always choose writer to take the semaphore and not reader, in that case the readers would be starve, is that right or am I wrong ? 
  link : <a href="http://en.wikipedia.org/wiki/Readers%E2%80%93writers_problem" rel="nofollow">readers-writers problem</a></p>
  
  <p>look at the third readers-writers problem in the link.</p>
  
  <p>code : </p>
  
  <pre><code>int readcount; // (initial value = 0)
  semaphore mutex_rdcnt, r, w; // ( initial value = 1 ) 
  //READER
      wait(r);
        wait(mutex_rdcnt);
          readcount++;
          if (readcount == 1)
            wait(w);
        signal(mutex_rdcnt);          
      signal(r);
  
      // reading is performed 
  
      wait(mutex_rdcnt);
        readcount--;
        if (readcount == 0)
          signal(w);
      signal(mutex_rdcnt);  
  //WRITER
      wait(r);
      wait(w);
  
       // writing is performed
  
      signal(w);  
      signal(r);
  </code></pre>