1 /*

     2  * Copyright 2009 D.E. Shaw.  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 /**

    25  * @test

    26  * @bug 6912517

    27  * @summary JIT bug compiles out (and stops running) code that needs to be run.  Causes NPE.

    28  *

    29  * @run main/othervm -Xbatch -XX:CompileThreshold=100 -XX:+IgnoreUnrecognizedVMOptions -XX:-UseCompressedOops Test

    30  */

    31 

    32 /**

    33  * Highlights a bug with the JIT compiler.

    34  * @author Matt Bruce m b r u c e __\at/__ g m a i l DOT c o m

    35  */

    36 public class Test implements Runnable

    37 {

    38     private final Thread myThread;

    39     private Thread       myInitialThread;

    40     private boolean      myShouldCheckThreads;

    41 

    42     /**

    43      * Sets up the running thread, and starts it.

    44      */

    45     public Test(int id)

    46     {

    47         myThread = new Thread(this);

    48         myThread.setName("Runner: " + id);

    49         myThread.start();

    50         myShouldCheckThreads = false;

    51     }

    52 

    53     /**

    54      * @param shouldCheckThreads the shouldCheckThreads to set

    55      */

    56     public void setShouldCheckThreads(boolean shouldCheckThreads)

    57     {

    58         myShouldCheckThreads = shouldCheckThreads;

    59     }

    60 

    61     /**

    62      * Starts up the two threads with enough delay between them for JIT to

    63      * kick in.

    64      * @param args

    65      * @throws InterruptedException

    66      */

    67     public static void main(String[] args) throws InterruptedException

    68     {

    69         // let this run for a bit, so the "run" below is JITTed.

    70         for (int id = 0; id < 20; id++) {

    71             System.out.println("Starting thread: " + id);

    72             Test bug = new Test(id);

    73             bug.setShouldCheckThreads(true);

    74             Thread.sleep(2500);

    75         }

    76     }

    77 

    78     /**

    79      * @see java.lang.Runnable#run()

    80      */

    81     public void run()

    82     {

    83         long runNumber = 0;

    84         while (true) {

    85             // run hot for a little while, give JIT time to kick in to this loop.

    86             // then run less hot.

    87             if (runNumber > 15000) {

    88                 try {

    89                     Thread.sleep(5);

    90                 }

    91                 catch (InterruptedException e) {

    92                     e.printStackTrace();

    93                 }

    94             }

    95             runNumber++;

    96             ensureProperCallingThread();

    97         }

    98     }

    99 

   100     private void ensureProperCallingThread()

   101     {

   102         // this should never be null.  but with the JIT bug, it will be.

   103         // JIT BUG IS HERE ==>>>>>

   104         if (myShouldCheckThreads) {

   105             if (myInitialThread == null) {

   106                 myInitialThread = Thread.currentThread();

   107             }

   108             else if (myInitialThread != Thread.currentThread()) {

   109                 System.out.println("Not working: " + myInitialThread.getName());

   110             }

   111         }

   112     }

   113 }