/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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;
  
  /**
   */
  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() {
      }
  }