1 /* 2 * Copyright (c) 2017, Red Hat 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 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 import java.lang.reflect.Field; 25 26 /** 27 * @test 28 * @bug 8175887 29 * @summary C1 value numbering handling of Unsafe.get*Volatile is incorrect 30 * @modules java.base/jdk.internal.misc:+open 31 * @run main/othervm -XX:TieredStopAtLevel=1 UnsafeVolatileGuardTest 32 */ 33 public class UnsafeVolatileGuardTest { 34 volatile static private int a; 35 static private int b; 36 37 static final jdk.internal.misc.Unsafe UNSAFE; 38 39 static final Object BASE; 40 static final long OFFSET; 41 42 static { 43 try { 44 Field f = jdk.internal.misc.Unsafe.class.getDeclaredField("theUnsafe"); 45 f.setAccessible(true); 46 UNSAFE = (jdk.internal.misc.Unsafe) f.get(null); 47 } catch (Exception e) { 48 throw new RuntimeException("Unable to get Unsafe instance.", e); 49 } 50 51 try { 52 Field f = UnsafeVolatileGuardTest.class.getDeclaredField("a"); 53 BASE = UNSAFE.staticFieldBase(f); 54 OFFSET = UNSAFE.staticFieldOffset(f); 55 } catch (Exception e) { 56 throw new RuntimeException(e); 57 } 58 } 59 60 public static void main(String [] args) throws Exception { 61 for (int i = 0; i < 100; i++) { 62 new Thread() { 63 64 @Override 65 public void run() { 66 int tt = b; // makes the JVM CSE the value of b 67 68 while (UNSAFE.getIntVolatile(BASE, OFFSET) == 0) {} // burn 69 if (b == 0) { 70 System.out.println("error"); 71 System.exit(1); // fail hard 72 } 73 } 74 75 }.start(); 76 } 77 78 b = 1; 79 a = 1; 80 } 81 }