1/* 2 * Copyright (c) 2009, 2010, 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 * @test 26 * @bug 6823609 27 * @summary Selector.select can hangs on Windows for cases where a helper thread 28 * becomes redudant but a new helper is immediately needed. 29 */ 30 31import java.nio.channels.*; 32import java.io.IOException; 33 34public class HelperSlowToDie { 35 private static final int CHANNELS_PER_THREAD = 1023; 36 private static final int TEST_ITERATIONS = 200; 37 private static volatile boolean done; 38 39 public static void main(String[] args) throws IOException { 40 if (!System.getProperty("os.name").startsWith("Windows")) { 41 System.out.println("Test skipped as it verifies a Windows specific bug"); 42 return; 43 } 44 45 Selector sel = Selector.open(); 46 47 // register channels 48 SocketChannel[] channels = new SocketChannel[CHANNELS_PER_THREAD]; 49 for (int i=0; i<CHANNELS_PER_THREAD; i++) { 50 SocketChannel sc = SocketChannel.open(); 51 sc.configureBlocking(false); 52 sc.register(sel, SelectionKey.OP_CONNECT); 53 channels[i] = sc; 54 } 55 sel.selectNow(); 56 57 // Start threads to swamp all cores but one. This improves the chances 58 // of duplicating the bug. 59 Runnable busy = new Runnable() { 60 public void run() { 61 while (!done) ; // no nothing 62 } 63 }; 64 int ncores = Runtime.getRuntime().availableProcessors(); 65 for (int i=0; i<ncores-1; i++) 66 new Thread(busy).start(); 67 68 // Loop changing the number of channels from 1023 to 1024 and back. 69 for (int i=0; i<TEST_ITERATIONS; i++) { 70 SocketChannel sc = SocketChannel.open(); 71 sc.configureBlocking(false); 72 sc.register(sel, SelectionKey.OP_CONNECT); 73 sel.selectNow(); // cause helper to spin up 74 sc.close(); 75 sel.selectNow(); // cause helper to retire 76 } 77 78 // terminate busy threads 79 done = true; 80 81 // clean-up 82 for (int i=0; i<CHANNELS_PER_THREAD; i++) { 83 channels[i].close(); 84 } 85 sel.close(); 86 } 87} 88