1 /*

     2  * Copyright 2004 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  */

    23 

    24 // See bug 5094825 / ClassLoadDeadlock.sh

    25 

    26 import java.net.*;

    27 

    28 import java.security.*;

    29 

    30 public class ClassLoaderDeadlock {

    31 

    32     public static void main(String[] args) throws Exception {

    33         // create a new classloader

    34         URL url = new URL("file:provider/");

    35         final DelayClassLoader cl = new DelayClassLoader(url);

    36 

    37         // install a provider on the custom class loader as the most prefered provider

    38         Class clazz = cl.loadClass("HashProvider");

    39         Provider p = (Provider)clazz.newInstance();

    40         Security.insertProviderAt(p, 1);

    41 

    42         // add a delay in class loading for reproducability

    43         cl.delay = 1000;

    44 

    45         new Thread() {

    46             public void run() {

    47                 try {

    48                     // load a random system class

    49                     // this locks the DelayClassLoader and after the delay the system class loader

    50                     Class c1 = cl.loadClass("java.lang.String");

    51                     System.out.println(c1);

    52                 } catch (Exception e) {

    53                     e.printStackTrace();

    54                 }

    55             }

    56         }.start();

    57 

    58         // make sure the other thread got a chance to run and grab the lock

    59         Thread.sleep(200);

    60 

    61         // load a random class from a signed JAR file to trigger JAR signature verification

    62         // locks system class loader first and then tries to lock DelayClassLoader to load the hashes

    63         // DEADLOCK HAPPENS HERE

    64         Class c2 = Class.forName("com.abc.Tst1");

    65 

    66         // NOT REACHED

    67         System.out.println(c2);

    68 

    69         System.out.println("OK");

    70     }

    71 

    72     static class DelayClassLoader extends URLClassLoader {

    73 

    74         volatile int delay;

    75 

    76         DelayClassLoader(URL url) {

    77             super(new URL[] {url});

    78         }

    79 

    80         protected synchronized Class loadClass(String name, boolean resolve) throws ClassNotFoundException {

    81             System.out.println("-loadClass(" + name + "," + resolve + ")");

    82             try {

    83                 // delay so that we hold the lock for a longer period

    84                 // makes it much easier to reproduce

    85                 Thread.sleep(delay);

    86             } catch (InterruptedException e) { e.printStackTrace(); }

    87             return super.loadClass(name, resolve);

    88         }

    89     }

    90 

    91 }