1 /*
   2  * Copyright (c) 2005, 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.rmi.runtime;
  27 
  28 import java.security.AccessController;
  29 import java.security.Permission;
  30 import java.security.PrivilegedAction;
  31 import java.util.concurrent.ScheduledThreadPoolExecutor;
  32 import java.util.concurrent.ThreadFactory;
  33 import java.util.concurrent.TimeUnit;
  34 import java.util.concurrent.atomic.AtomicInteger;
  35 import java.util.logging.Level;
  36 import sun.security.action.GetIntegerAction;
  37 
  38 /**
  39  * RMI runtime implementation utilities.
  40  *
  41  * There is a single instance of this class, which can be obtained
  42  * with a GetInstanceAction.  Getting the instance requires
  43  * RuntimePermission("sun.rmi.runtime.RuntimeUtil.getInstance")
  44  * because the public methods of this class expose security-sensitive
  45  * capabilities.
  46  *
  47  * @author      Peter Jones
  48  **/
  49 public final class RuntimeUtil {
  50 
  51     /** runtime package log */
  52     private static final Log runtimeLog =
  53         Log.getLog("sun.rmi.runtime", null, false);
  54 
  55     /** number of scheduler threads */
  56     private static final int schedulerThreads =         // default 1
  57         AccessController.doPrivileged(
  58             new GetIntegerAction("sun.rmi.runtime.schedulerThreads", 1));
  59 
  60     /** permission required to get instance */
  61     private static final Permission GET_INSTANCE_PERMISSION =
  62         new RuntimePermission("sun.rmi.runtime.RuntimeUtil.getInstance");
  63 
  64     /** the singleton instance of this class */
  65     private static final RuntimeUtil instance = new RuntimeUtil();
  66 
  67     /** thread pool for scheduling delayed tasks */
  68     private final ScheduledThreadPoolExecutor scheduler;
  69 
  70     private RuntimeUtil() {
  71         scheduler = new ScheduledThreadPoolExecutor(
  72             schedulerThreads,
  73             new ThreadFactory() {
  74                 private final AtomicInteger count = new AtomicInteger(0);
  75                 public Thread newThread(Runnable runnable) {
  76                     try {
  77                         return AccessController.doPrivileged(
  78                             new NewThreadAction(runnable,
  79                                 "Scheduler(" + count.getAndIncrement() + ")",
  80                                 true));
  81                     } catch (Throwable t) {
  82                         runtimeLog.log(Level.WARNING,
  83                                        "scheduler thread factory throws", t);
  84                         return null;
  85                     }
  86                 }
  87             });
  88         /*
  89          * We would like to allow the scheduler's threads to terminate
  90          * if possible, but a bug in DelayQueue.poll can cause code
  91          * like this to result in a busy loop:
  92          */
  93         // stpe.setKeepAliveTime(10, TimeUnit.MINUTES);
  94         // stpe.allowCoreThreadTimeOut(true);
  95     }
  96 
  97     /**
  98      * A PrivilegedAction for getting the RuntimeUtil instance.
  99      **/
 100     public static class GetInstanceAction
 101         implements PrivilegedAction<RuntimeUtil>
 102     {
 103         /**
 104          * Creates an action that returns the RuntimeUtil instance.
 105          **/
 106         public GetInstanceAction() {
 107         }
 108 
 109         public RuntimeUtil run() {
 110             return getInstance();
 111         }
 112     }
 113 
 114     private static RuntimeUtil getInstance() {
 115         SecurityManager sm = System.getSecurityManager();
 116         if (sm != null) {
 117             sm.checkPermission(GET_INSTANCE_PERMISSION);
 118         }
 119         return instance;
 120     }
 121 
 122     /**
 123      * Returns the shared thread pool for scheduling delayed tasks.
 124      *
 125      * Note that the returned pool has limited concurrency, so
 126      * submitted tasks should be short-lived and should not block.
 127      **/
 128     public ScheduledThreadPoolExecutor getScheduler() {
 129         return scheduler;
 130     }
 131 }