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 synchronized public String toString() { 91 System.out.println("Calling toString\n"); 92 return mStr; 93 } 94 }