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 
  30 import java.security.AccessController;
  31 import java.security.PrivilegedAction;
  32 import java.util.concurrent.ThreadFactory;
  33 
  34 /**
  35  * CleanerFactory provides a Cleaner for use within system modules.
  36  * The cleaner is created on the first reference to the CleanerFactory.
  37  */
  38 public final class CleanerFactory {
  39 
  40     /* The common Cleaner. */
  41     private final static ExtendedCleaner commonCleaner = ExtendedCleaner.create(
  42         new ThreadFactory() {
  43             @Override
  44             public Thread newThread(Runnable r) {
  45                 return AccessController.doPrivileged(new PrivilegedAction<>() {
  46                     @Override
  47                     public Thread run() {
  48                         Thread t = InnocuousThread.newSystemThread("Common-Cleaner", r);
  49                         t.setPriority(Thread.MAX_PRIORITY - 2);
  50                         return t;
  51                     }
  52                 });
  53             }
  54         }
  55     );
  56 
  57     /**
  58      * ExtendedCleaner for use within system modules.
  59      * <p>
  60      * This Cleaner's cleaning loop will run on a thread whose context
  61      * class loader is {@code null}. The system cleaning action to perform in
  62      * this Cleaner should handle a {@code null} context class loader.
  63      * <p>
  64      * This Cleaner is an {@link ExtendedCleaner} which supports helping
  65      * the cleaner thread from arbitrary application threads. The system cleaning
  66      * action to perform in this Cleaner should also handle being executed by
  67      * arbitrary application thread.
  68      *
  69      * @return an ExtendedCleaner for use within system modules
  70      */
  71     public static ExtendedCleaner cleaner() {
  72         return commonCleaner;
  73     }
  74 }