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 */ 28 29 import java.io.PrintStream; 30 31 public class OversynchronizedTest extends Thread { 32 private static TestObj testObj = new TestObj("This is a test."); 33 private static int loopNum = 100; 34 35 public void run() { 36 for(int i=0; i<loopNum; i++) { 37 testObj.test(); 38 39 //passing an object to System.out.println might cause deadlock 40 //if the object has a synchronized toString() method. 41 //using System.out.println(testObj.toString()) won't have a problem 42 System.out.println(testObj); 43 } 44 } 45 46 public static void main(String args[]) throws Exception { 47 // should no NullPointerException 48 System.out.println((Object)null); 49 50 // over synch test 51 int num = 5; 52 53 OversynchronizedTest[] t = new OversynchronizedTest[num]; 54 for(int i=0; i<num; i++) { 55 t[i] = new OversynchronizedTest(); 56 t[i].start(); 57 } 58 59 for(int i=0; i <num; i++) { 60 t[i].join(); 61 } 62 63 System.out.println("Test completed."); 64 } 65 } 66 67 class TestObj { 68 String mStr; 69 70 TestObj(String str) { 71 mStr = str; 72 } 73 74 synchronized void test() { 75 try { 76 long t = Math.round(Math.random()*10); 77 Thread.currentThread().sleep(t); 78 } catch (InterruptedException e) { 79 // jtreg timeout? 80 // Only jtreg will interrupt this thread so it knows what to do: 81 e.printStackTrace(); 82 } 83 84 //the following line might cause hang if there is System.out.println(testObj) 85 //called by other threads. 86 System.out.println("In test()."); 87 } 88 89 synchronized public String toString() { 90 System.out.println("Calling toString\n"); 91 return mStr; 92 } 93 }