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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the 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   */
22  public final class DeadLockProofWorker {
23  
24      /**
25       * An <em>internal use only</em> thread-local variable that tells the
26       * {@link Executor} that this worker acquired a worker thread from.
27       */
28      public static final ThreadLocal<Executor> PARENT = new ThreadLocal<Executor>();
29  
30      public static void start(final Executor parent, final Runnable runnable) {
31          if (parent == null) {
32              throw new NullPointerException("parent");
33          }
34          if (runnable == null) {
35              throw new NullPointerException("runnable");
36          }
37  
38          parent.execute(new Runnable() {
39              public void run() {
40                  PARENT.set(parent);
41                  try {
42                      runnable.run();
43                  } finally {
44                      PARENT.remove();
45                  }
46              }
47          });
48      }
49  
50      private DeadLockProofWorker() {
51      }
52  }