[Modify] Lock it within the method

websocket-sharp/Net/HttpListener.cs

@@ -469,9 +469,9 @@ namespace WebSocketSharp.Net
       cleanup (force);
     }
 
-    // Must be called with a lock on _ctxQueue.
     private HttpListenerContext getContextFromQueue ()
     {
+      lock (_ctxQueueSync) {
         if (_ctxQueue.Count == 0)
           return null;
 
@@ -480,6 +480,7 @@ namespace WebSocketSharp.Net
 
         return ctx;
       }
+    }
 
     private void sendServiceUnavailable ()
     {
@@ -561,13 +562,11 @@ namespace WebSocketSharp.Net
 
       // Lock _waitQueue early to avoid race conditions.
       lock (_waitQueueSync) {
-        lock (_ctxQueueSync) {
         var ctx = getContextFromQueue ();
         if (ctx != null) {
           asyncResult.Complete (ctx, true);
           return asyncResult;
         }
-        }
 
         _waitQueue.Add (asyncResult);
       }