1 /*
   2  * Copyright (c) 2016, 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 jdk.internal.ref;
  27 
  28 import jdk.internal.misc.InnocuousThread;
  29 import jdk.internal.vm.annotation.ReservedStackAccess;
  30 
  31 import java.lang.ref.Cleaner;
  32 import java.security.AccessController;
  33 import java.security.PrivilegedAction;
  34 import java.util.concurrent.ThreadFactory;
  35 
  36 /**
  37  * CleanerFactory provides a Cleaner for use within system modules.
  38  * The cleaner is created on the first reference to the CleanerFactory.
  39  */
  40 public final class CleanerFactory {
  41 
  42     /* The common Cleaner. Lazily initialized */
  43     private static class Common {
  44         static final Cleaner INSTANCE = Cleaner.create(new ThreadFactory() {
  45             @Override
  46             public Thread newThread(Runnable r) {
  47                 return AccessController.doPrivileged(new PrivilegedAction<>() {
  48                     @Override
  49                     public Thread run() {
  50                         Thread t = InnocuousThread.newSystemThread("Common-Cleaner", r);
  51                         t.setPriority(Thread.MAX_PRIORITY - 2);
  52                         return t;
  53                     }
  54                 });
  55             }
  56         });
  57     }
  58 
  59     /* The NIO DirectByteBuffer ExtendedCleaner. Lazily initialized */
  60     private static class DBB {
  61         static final ExtendedCleaner INSTANCE = ExtendedCleaner.create(new ThreadFactory() {
  62             @Override
  63             public Thread newThread(Runnable r) {
  64                 return AccessController.doPrivileged(new PrivilegedAction<>() {
  65                     @Override
  66                     public Thread run() {
  67                         Thread t = InnocuousThread.newSystemThread("DirectByteBuffer-Cleaner", r);
  68                         t.setPriority(Thread.MAX_PRIORITY - 2);
  69                         return t;
  70                     }
  71                 });
  72             }
  73         });
  74     }
  75 
  76     /**
  77      * Cleaner for use within system modules.
  78      * <p>
  79      * This Cleaner will run on a thread whose context class loader
  80      * is {@code null}. The system cleaning action to perform in
  81      * this Cleaner should handle a {@code null} context class loader.
  82      *
  83      * @return a Cleaner for use within system modules
  84      */
  85     public static Cleaner cleaner() {
  86         return Common.INSTANCE;
  87     }
  88 
  89     /**
  90      * ExtendedCleaner for DirectByteBuffer use.
  91      * <p>
  92      * This Cleaner will mostly run on a background thread whose
  93      * context class loader is {@code null}. But since this is
  94      * {@link ExtendedCleaner} it allows other threads to help executing
  95      * cleaning actions. Cleaning actions to be performed in this ExtendedCleaner
  96      * should handle a {@code null} context class loader and any application
  97      * thread. When they are executed by an application thread they are
  98      * executed in the context of {@link ReservedStackAccess} annotation.
  99      *
 100      * @return an ExtendedCleaner for use in DirectByteBuffer
 101      */
 102     public static ExtendedCleaner dbbCleaner() {
 103         return DBB.INSTANCE;
 104     }
 105 }