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1   /*
2    * Copyright 2009 Red Hat, Inc.
3    *
4    * Red Hat licenses this file to you under the Apache License, version 2.0
5    * (the "License"); you may not use this file except in compliance with the
6    * License.  You may obtain a copy of the License at:
7    *
8    *    http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.util.internal;
17  
18  import java.util.concurrent.Executor;
19  
20  /**
21   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
22   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
23   */
24  public final class DeadLockProofWorker {
25  
26      /**
27       * An <em>internal use only</em> thread-local variable that tells the
28       * {@link Executor} that this worker acquired a worker thread from.
29       */
30      public static final ThreadLocal<Executor> PARENT = new ThreadLocal<Executor>();
31  
32      public static void start(final Executor parent, final Runnable runnable) {
33          if (parent == null) {
34              throw new NullPointerException("parent");
35          }
36          if (runnable == null) {
37              throw new NullPointerException("runnable");
38          }
39  
40          parent.execute(new Runnable() {
41              public void run() {
42                  PARENT.set(parent);
43                  try {
44                      runnable.run();
45                  } finally {
46                      PARENT.remove();
47                  }
48              }
49          });
50      }
51  
52      private DeadLockProofWorker() {
53          super();
54      }
55  }