title: Does @synchronized block a whole thread
body: <p>Say you do</p>
  
  <pre><code>MyLock *lock = [[MyLock new] autorelease];
  @synchronized(lock) {
      NSLog(@"Hello World");
  //some very long process
  }
  </code></pre>
  
  <p>In the main thread. Does that mean till //some very long process is done, the main thread is locked? If some other thread call</p>
  
  <pre><code>    //Update on the main thread
      dispatch_sync(dispatch_get_main_queue(), ^{
          //Do some updates
      });
  </code></pre>
  
  <p>That some updates will never be called? Am I correct?</p>