test/jdk/java/lang/ClassLoader/deadlock/GetResource.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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 */

import java.util.Properties;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.BrokenBarrierException;
import java.io.IOException;
import java.net.URL;

/* @test
 * @bug 6977738 8029891
 * @summary Test ClassLoader.getResource() that should not deadlock
 #          if another thread is holding the system properties object
 *
 * @build GetResource
 * @run main GetResource
 */

public class GetResource {
    CyclicBarrier go = new CyclicBarrier(2);
    CyclicBarrier done = new CyclicBarrier(2);
    Thread t1, t2;
    public GetResource() {
        t1 = new Thread() {
            public void run() {
                Properties prop = System.getProperties();
                synchronized (prop) {
                    System.out.println("Thread 1 ready");
                    try {
                        go.await();
                        prop.put("property", "value");
                        prop.store(System.out, "");
                        done.await();   // keep holding the lock until t2 finishes
                    } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                    } catch (BrokenBarrierException e) {
                        throw new RuntimeException(e);
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }
                }
                System.out.println("Thread 1 exits");
            }
        };

        t2 = new Thread()  {
            public void run() {
                System.out.println("Thread 2 ready");
                try {
                    go.await();  // wait until t1 holds the lock of the system properties

                    URL u1 = Thread.currentThread().getContextClassLoader().getResource("unknownresource");
                    done.await();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                } catch (BrokenBarrierException e) {
                    throw new RuntimeException(e);
                }
                System.out.println("Thread 2 exits");
            }
        };
    }

    public void run() throws Exception {
        t1.start();
        t2.start();
        try {
            t1.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
            throw e;
        }
        try {
            t2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
            throw e;
        }
    }

    public static void main(String[] args) throws Exception {
        new GetResource().run();
    }
}