1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 import sun.misc.Unsafe; 18 19 import java.lang.reflect.Field; 20 21 public class Main { 22 private static Unsafe UNSAFE; 23 24 public static void main(String[] args) throws Exception { 25 setUp(); 26 27 ParkTester test = new ParkTester(); 28 29 System.out.println("Test starting"); 30 31 test.start(); 32 UNSAFE.unpark(test); 33 clearStack(10); 34 35 System.out.println("GC'ing"); 36 System.gc(); 37 System.runFinalization(); 38 System.gc(); 39 40 System.out.println("Asking thread to park"); 41 test.parkNow = true; 42 43 try { 44 // Give some time to the ParkTester thread to honor the park command. 45 Thread.sleep(3000); 46 } catch (InterruptedException ex) { 47 System.out.println("Main thread interrupted!"); 48 System.exit(1); 49 } 50 51 if (test.success) { 52 System.out.println("Test succeeded!"); 53 } else { 54 System.out.println("Test failed."); 55 } 56 } 57 58 /** 59 * Set up {@link #UNSAFE}. 60 */ 61 public static void setUp() throws Exception{ 62 /* 63 * Subvert the access check to get the unique Unsafe instance. 64 * We can do this because there's no security manager 65 * installed when running the test. 66 */ 67 Field field = null; 68 try { 69 field = Unsafe.class.getDeclaredField("THE_ONE"); 70 } catch (NoSuchFieldException e1) { 71 try { 72 field = Unsafe.class.getDeclaredField("theUnsafe"); 73 } catch (NoSuchFieldException e2) { 74 throw new RuntimeException("Failed to find THE_ONE or theUnsafe"); 75 } 76 } 77 field.setAccessible(true); 78 UNSAFE = (Unsafe) field.get(null); 79 } 80 81 /** 82 * Scribbles on the stack to help ensure we don't have a fake 83 * pointer that would keep would-be garbage alive. 84 */ 85 private static void clearStack(int depth) { 86 int a = 0; 87 int b = 0; 88 int c = 0; 89 int d = 0; 90 int e = 0; 91 int f = 0; 92 int g = 0; 93 int h = 0; 94 int i = 0; 95 int j = 0; 96 97 if (depth > 0) { 98 clearStack(depth - 1); 99 } 100 } 101 102 private static class ParkTester extends Thread { 103 public volatile boolean parkNow = false; 104 public volatile boolean success = false; 105 106 public void run() { 107 while (!parkNow) { 108 try { 109 Thread.sleep(500); 110 } catch (InterruptedException ex) { 111 // Ignore it. 112 } 113 } 114 115 long start = System.currentTimeMillis(); 116 UNSAFE.park(false, 500 * 1000000); // 500 msec 117 long elapsed = System.currentTimeMillis() - start; 118 119 if (elapsed > 200) { 120 System.out.println("park()ed for " + elapsed + " msec"); 121 success = false; 122 } else { 123 System.out.println("park() returned quickly"); 124 success = true; 125 } 126 } 127 } 128 } 129
