/*
    * Copyright 2009 Red Hat, Inc.
    *
    * Red Hat licenses this file to you under the Apache License, version 2.0
    * (the "License"); you may not use this file except in compliance with the
    * License.  You may obtain a copy of the License at:
    *
    *    http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package org.jboss.netty.util.internal;
  
  import java.util.concurrent.Executor;
  
  /**
   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
   */
  public final class DeadLockProofWorker {
  
      /**
       * An <em>internal use only</em> thread-local variable that tells the
       * {@link Executor} that this worker acquired a worker thread from.
       */
      public static final ThreadLocal<Executor> PARENT = new ThreadLocal<Executor>();
  
      public static void start(final Executor parent, final Runnable runnable) {
          if (parent == null) {
              throw new NullPointerException("parent");
          }
          if (runnable == null) {
              throw new NullPointerException("runnable");
          }
  
          parent.execute(new Runnable() {
              public void run() {
                  PARENT.set(parent);
                  try {
                      runnable.run();
                  } finally {
                      PARENT.remove();
                  }
              }
          });
      }
  
      private DeadLockProofWorker() {
          super();
      }
  }