title: Possibility of deadlock with dispatch_async in asynchronous connection completion handler
body: <p>Is it possible that using <code>dispatch_async()</code> to the main queue inside an <code>NSURLConnection</code>'s asynchronous request completion handler can cause a deadlock?</p>
  
  <pre><code>NSOperationQueue *queue = [[NSOperationQueue alloc]init];
  [NSURLConnection sendAsynchronousRequest:request
                                     queue:queue
                         completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
       {
           if (!error) {
               dispatch_async(dispatch_get_main_queue(), ^{
                   // Alsways perform such code on the main queue/thread
                   /// At this point I update the UI
               });
  
           }
       }];
  </code></pre>
  
  <p>If yes, how can I solve it?</p>