1 /*
   2  * Copyright (c) 2015, 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 com.sun.corba.se.impl.transport;
  27 
  28 import sun.misc.Unsafe;
  29 import java.lang.reflect.Field;
  30 import java.security.AccessController;
  31 import java.security.PrivilegedAction;
  32 
  33 /**
  34  * A thread that has it's thread locals, and inheritable thread
  35  * locals erased on construction.
  36  */
  37 public class ManagedLocalsThread extends Thread {
  38     private static final Unsafe UNSAFE;
  39     private static final long THREAD_LOCALS;
  40     private static final long INHERITABLE_THREAD_LOCALS;
  41 
  42     public ManagedLocalsThread () {
  43         super();
  44     }
  45 
  46     public ManagedLocalsThread(String  name) {
  47         super(name);
  48         eraseThreadLocals();
  49     }
  50     public ManagedLocalsThread(Runnable target) {
  51         super(target);
  52         eraseThreadLocals();
  53     }
  54 
  55     public ManagedLocalsThread(Runnable target, String name) {
  56         super(target, name);
  57         eraseThreadLocals();
  58     }
  59 
  60     public ManagedLocalsThread(ThreadGroup group, Runnable target, String name) {
  61         super(group, target, name);
  62         eraseThreadLocals();
  63     }
  64 
  65     public ManagedLocalsThread(ThreadGroup group, String name) {
  66         super(group, name);
  67         eraseThreadLocals();
  68     }
  69 
  70     /**
  71      * Drops all thread locals (and inherited thread locals).
  72      */
  73     public final void eraseThreadLocals() {
  74                 UNSAFE.putObject(this, THREAD_LOCALS, null);
  75                 UNSAFE.putObject(this, INHERITABLE_THREAD_LOCALS, null);
  76     }
  77 
  78     private static Unsafe getUnsafe() {
  79         PrivilegedAction<Unsafe> pa = () -> {
  80             Class<?> unsafeClass = sun.misc.Unsafe.class;
  81             try {
  82                 Field f = unsafeClass.getDeclaredField("theUnsafe");
  83                 f.setAccessible(true);
  84                 return (Unsafe) f.get(null);
  85             } catch (Exception e) {
  86                 throw new Error(e);
  87             }
  88         };
  89         return AccessController.doPrivileged(pa);
  90     }
  91 
  92     private static long getThreadFieldOffset(String fieldName) {
  93         PrivilegedAction<Long> pa = () -> {
  94             Class<?> t = Thread.class;
  95             long fieldOffset;
  96             try {
  97                 fieldOffset = UNSAFE.objectFieldOffset(t
  98                         .getDeclaredField("inheritableThreadLocals"));
  99             } catch (Exception e) {
 100                 throw new Error(e);
 101             }
 102             return fieldOffset;
 103         };
 104         return AccessController.doPrivileged(pa);
 105     }
 106 
 107     static {
 108         UNSAFE = getUnsafe();
 109         try {
 110             THREAD_LOCALS = getThreadFieldOffset("threadLocals");
 111             INHERITABLE_THREAD_LOCALS = getThreadFieldOffset("inheritableThreadLocals");
 112         } catch (Exception e) {
 113             throw new Error(e);
 114         }
 115     }
 116 }