1 /*
   2  * Copyright (c) 2008, 2012, 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.nio.ch;
  27 
  28 import java.util.concurrent.*;
  29 import java.security.AccessController;
  30 import java.security.PrivilegedAction;
  31 import sun.security.action.GetPropertyAction;
  32 import sun.security.action.GetIntegerAction;
  33 import jdk.internal.misc.InnocuousThread;
  34 
  35 /**
  36  * Encapsulates a thread pool associated with a channel group.
  37  */
  38 
  39 public class ThreadPool {
  40     private static final String DEFAULT_THREAD_POOL_THREAD_FACTORY =
  41         "java.nio.channels.DefaultThreadPool.threadFactory";
  42     private static final String DEFAULT_THREAD_POOL_INITIAL_SIZE =
  43         "java.nio.channels.DefaultThreadPool.initialSize";
  44 
  45     private final ExecutorService executor;
  46 
  47     // indicates if thread pool is fixed size
  48     private final boolean isFixed;
  49 
  50     // indicates the pool size (for a fixed thread pool configuratin this is
  51     // the maximum pool size; for other thread pools it is the initial size)
  52     private final int poolSize;
  53 
  54     private ThreadPool(ExecutorService executor,
  55                        boolean isFixed,
  56                        int poolSize)
  57     {
  58         this.executor = executor;
  59         this.isFixed = isFixed;
  60         this.poolSize = poolSize;
  61     }
  62 
  63     ExecutorService executor() {
  64         return executor;
  65     }
  66 
  67     boolean isFixedThreadPool() {
  68         return isFixed;
  69     }
  70 
  71     int poolSize() {
  72         return poolSize;
  73     }
  74 
  75     static ThreadFactory defaultThreadFactory() {
  76         if (System.getSecurityManager() == null) {
  77             return (Runnable r) -> {
  78                 Thread t = new Thread(r);
  79                 t.setDaemon(true);
  80                 return t;
  81             };
  82         } else {
  83             return (Runnable r) -> {
  84                 PrivilegedAction<Thread> action = () -> {
  85                     Thread t = InnocuousThread.newThread(r);
  86                     t.setDaemon(true);
  87                     return t;
  88                };
  89                return AccessController.doPrivileged(action);
  90            };
  91         }
  92     }
  93 
  94     private static class DefaultThreadPoolHolder {
  95         static final ThreadPool defaultThreadPool = createDefault();
  96     }
  97 
  98     // return the default (system-wide) thread pool
  99     static ThreadPool getDefault() {
 100         return DefaultThreadPoolHolder.defaultThreadPool;
 101     }
 102 
 103     // create thread using default settings (configured by system properties)
 104     static ThreadPool createDefault() {
 105         // default the number of fixed threads to the hardware core count
 106         int initialSize = getDefaultThreadPoolInitialSize();
 107         if (initialSize < 0)
 108             initialSize = Runtime.getRuntime().availableProcessors();
 109         // default to thread factory that creates daemon threads
 110         ThreadFactory threadFactory = getDefaultThreadPoolThreadFactory();
 111         if (threadFactory == null)
 112             threadFactory = defaultThreadFactory();
 113         // create thread pool
 114         ExecutorService executor = Executors.newCachedThreadPool(threadFactory);
 115         return new ThreadPool(executor, false, initialSize);
 116     }
 117 
 118     // create using given parameters
 119     static ThreadPool create(int nThreads, ThreadFactory factory) {
 120         if (nThreads <= 0)
 121             throw new IllegalArgumentException("'nThreads' must be > 0");
 122         ExecutorService executor = Executors.newFixedThreadPool(nThreads, factory);
 123         return new ThreadPool(executor, true, nThreads);
 124     }
 125 
 126     // wrap a user-supplied executor
 127     public static ThreadPool wrap(ExecutorService executor, int initialSize) {
 128         if (executor == null)
 129             throw new NullPointerException("'executor' is null");
 130         // attempt to check if cached thread pool
 131         if (executor instanceof ThreadPoolExecutor) {
 132             int max = ((ThreadPoolExecutor)executor).getMaximumPoolSize();
 133             if (max == Integer.MAX_VALUE) {
 134                 if (initialSize < 0) {
 135                     initialSize = Runtime.getRuntime().availableProcessors();
 136                 } else {
 137                    // not a cached thread pool so ignore initial size
 138                     initialSize = 0;
 139                 }
 140             }
 141         } else {
 142             // some other type of thread pool
 143             if (initialSize < 0)
 144                 initialSize = 0;
 145         }
 146         return new ThreadPool(executor, false, initialSize);
 147     }
 148 
 149     private static int getDefaultThreadPoolInitialSize() {
 150         String propValue = AccessController.doPrivileged(new
 151             GetPropertyAction(DEFAULT_THREAD_POOL_INITIAL_SIZE));
 152         if (propValue != null) {
 153             try {
 154                 return Integer.parseInt(propValue);
 155             } catch (NumberFormatException x) {
 156                 throw new Error("Value of property '" + DEFAULT_THREAD_POOL_INITIAL_SIZE +
 157                     "' is invalid: " + x);
 158             }
 159         }
 160         return -1;
 161     }
 162 
 163     private static ThreadFactory getDefaultThreadPoolThreadFactory() {
 164         String propValue = AccessController.doPrivileged(new
 165             GetPropertyAction(DEFAULT_THREAD_POOL_THREAD_FACTORY));
 166         if (propValue != null) {
 167             try {
 168                 @SuppressWarnings("deprecation")
 169                 Object tmp = Class
 170                     .forName(propValue, true, ClassLoader.getSystemClassLoader()).newInstance();
 171                 return (ThreadFactory)tmp;
 172             } catch (ClassNotFoundException | InstantiationException | IllegalAccessException x) {
 173                 throw new Error(x);
 174             }
 175         }
 176         return null;
 177     }
 178 }