1 /* 2 * Copyright (c) 2020, 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 25 /* 26 * @test HandshakeDirectTest 27 * @summary This test tries to stress direct handshakes between threads. 28 * @library /testlibrary /test/lib 29 * @build HandshakeDirectTest 30 * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+SafepointALot -XX:BiasedLockingDecayTime=100000000 -XX:BiasedLockingBulkRebiasThreshold=1000000 -XX:BiasedLockingBulkRevokeThreshold=1000000 HandshakeDirectTest 31 */ 32 33 import java.util.concurrent.atomic.AtomicInteger; 34 import java.util.concurrent.ThreadLocalRandom; 35 import java.util.concurrent.Semaphore; 36 import java.io.*; 37 38 public class HandshakeDirectTest implements Runnable { 39 static final int WORKING_THREADS = 32; 40 static final int DIRECT_HANDSHAKES_MARK = 50000; 41 static Thread[] workingThreads = new Thread[WORKING_THREADS]; 42 static Semaphore[] handshakeSem = new Semaphore[WORKING_THREADS]; 43 static Object[] locks = new Object[WORKING_THREADS]; 44 static boolean[] isBiased = new boolean[WORKING_THREADS]; 45 static AtomicInteger handshakeCount = new AtomicInteger(0); 46 47 @Override 48 public void run() { 49 int me = Integer.parseInt(Thread.currentThread().getName()); 50 51 while (true) { 52 try { 53 if (!isBiased[me]) { 54 handshakeSem[me].acquire(); 55 synchronized(locks[me]) { 56 isBiased[me] = true; 57 } 58 handshakeSem[me].release(); 59 } 60 61 // Handshake directly some other worker 62 int handshakee = ThreadLocalRandom.current().nextInt(0, WORKING_THREADS-1); 63 if (handshakee == me) { 64 handshakee = handshakee != 0 ? handshakee - 1 : handshakee + 1; 65 } 66 handshakeSem[handshakee].acquire(); 67 if (isBiased[handshakee]) { 68 // Revoke biased lock 69 synchronized(locks[handshakee]) { 70 handshakeCount.incrementAndGet(); 71 } 72 // Create new lock to be biased 73 locks[handshakee] = new Object(); 74 isBiased[handshakee] = false; 75 } 76 handshakeSem[handshakee].release(); 77 if (handshakeCount.get() >= DIRECT_HANDSHAKES_MARK) { 78 break; 79 } 80 } catch(InterruptedException ie) { 81 throw new Error("Unexpected interrupt"); 82 } 83 } 84 } 85 86 public static void main(String... args) throws Exception { 87 HandshakeDirectTest test = new HandshakeDirectTest(); 88 89 // Initialize semaphores 90 for (int i = 0; i < WORKING_THREADS; i++) { 91 handshakeSem[i] = new Semaphore(1); 92 } 93 94 // Initialize locks 95 for (int i = 0; i < WORKING_THREADS; i++) { 96 locks[i] = new Object(); 97 } 98 99 // Fire-up working threads. 100 for (int i = 0; i < WORKING_THREADS; i++) { 101 workingThreads[i] = new Thread(test, Integer.toString(i)); 102 workingThreads[i].setDaemon(true); 103 workingThreads[i].start(); 104 } 105 106 // Wait until the desired number of direct handshakes is reached 107 workingThreads[0].join(); 108 } 109 }