1 /*

     2  * Copyright (c) 2005, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 /* @test

    25    @bug 4905777

    26    @summary PrintStream.println(Object) oversynchronized, can deadlock

    27    @key randomness

    28 */

    29 

    30 import java.io.PrintStream;

    31 

    32 public class OversynchronizedTest extends Thread {

    33     private static TestObj testObj = new TestObj("This is a test.");

    34     private static int loopNum = 100;

    35 

    36     public void run() {

    37         for(int i=0; i<loopNum; i++) {

    38             testObj.test();

    39 

    40             //passing an object to System.out.println might cause deadlock

    41             //if the object has a synchronized toString() method.

    42             //using System.out.println(testObj.toString()) won't have a problem

    43            System.out.println(testObj);

    44         }

    45     }

    46 

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

    48         // should no NullPointerException

    49         System.out.println((Object)null);

    50 

    51         // over synch test

    52         int num = 5;

    53 

    54         OversynchronizedTest[] t = new OversynchronizedTest[num];

    55         for(int i=0; i<num; i++) {

    56             t[i] = new OversynchronizedTest();

    57             t[i].start();

    58         }

    59 

    60         for(int i=0; i <num; i++) {

    61             t[i].join();

    62         }

    63 

    64         System.out.println("Test completed.");

    65     }

    66 }

    67 

    68 class TestObj {

    69     String mStr;

    70 

    71     TestObj(String str) {

    72         mStr = str;

    73     }

    74 

    75     synchronized void test() {

    76         try {

    77             long t = Math.round(Math.random()*10);

    78             Thread.currentThread().sleep(t);

    79         } catch (InterruptedException e) {

    80             // jtreg timeout?

    81             // Only jtreg will interrupt this thread so it knows what to do:

    82             e.printStackTrace();

    83         }

    84 

    85         //the following line might cause hang if there is System.out.println(testObj)

    86         //called by other threads.

    87         System.out.println("In test().");

    88     }

    89 

    90     public synchronized String toString() {

    91         System.out.println("Calling toString\n");

    92         return mStr;

    93     }

    94 }