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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          super();
    52      }
    53  }