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/*
 * 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 internal use only thread-local variable that tells the
     * {@link Executor} that this worker acquired a worker thread from.
     */
    public static final ThreadLocal PARENT = new ThreadLocal();

    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() {
    }
}