1 /* |
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2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package sun.misc; |
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27 |
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28 import java.security.AccessControlContext; |
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29 import java.security.AccessController; |
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30 import java.security.ProtectionDomain; |
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31 import java.security.PrivilegedAction; |
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32 import java.util.concurrent.atomic.AtomicInteger; |
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33 |
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34 /** |
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35 * A thread that has no permissions, is not a member of any user-defined |
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36 * ThreadGroup and supports the ability to erase ThreadLocals. |
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37 */ |
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38 public final class InnocuousThread extends Thread { |
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39 private static final jdk.internal.misc.Unsafe UNSAFE; |
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40 private static final long THREAD_LOCALS; |
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41 private static final long INHERITABLE_THREAD_LOCALS; |
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42 private static final ThreadGroup INNOCUOUSTHREADGROUP; |
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43 private static final AccessControlContext ACC; |
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44 private static final long INHERITEDACCESSCONTROLCONTEXT; |
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45 private static final long CONTEXTCLASSLOADER; |
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46 |
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47 private static final AtomicInteger threadNumber = new AtomicInteger(1); |
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48 |
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49 public InnocuousThread(Runnable target) { |
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50 this(INNOCUOUSTHREADGROUP, target, |
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51 "InnocuousThread-" + threadNumber.getAndIncrement()); |
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52 } |
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53 |
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54 public InnocuousThread(Runnable target, String name) { |
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55 this(INNOCUOUSTHREADGROUP, target, name); |
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56 } |
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57 |
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58 public InnocuousThread(ThreadGroup group, Runnable target, String name) { |
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59 super(group, target, name, 0L, false); |
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60 UNSAFE.putOrderedObject(this, INHERITEDACCESSCONTROLCONTEXT, ACC); |
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61 UNSAFE.putOrderedObject(this, CONTEXTCLASSLOADER, ClassLoader.getSystemClassLoader()); |
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62 } |
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63 |
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64 @Override |
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65 public void setUncaughtExceptionHandler(UncaughtExceptionHandler x) { |
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66 // silently fail |
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67 } |
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68 |
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69 @Override |
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70 public void setContextClassLoader(ClassLoader cl) { |
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71 // Allow clearing of the TCCL to remove the reference to the system classloader. |
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72 if (cl == null) |
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73 super.setContextClassLoader(null); |
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74 else |
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75 throw new SecurityException("setContextClassLoader"); |
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76 } |
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77 |
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78 /** |
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79 * Drops all thread locals (and inherited thread locals). |
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80 */ |
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81 public final void eraseThreadLocals() { |
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82 UNSAFE.putObject(this, THREAD_LOCALS, null); |
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83 UNSAFE.putObject(this, INHERITABLE_THREAD_LOCALS, null); |
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84 } |
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85 |
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86 // ensure run method is run only once |
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87 private volatile boolean hasRun; |
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88 |
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89 @Override |
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90 public void run() { |
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91 if (Thread.currentThread() == this && !hasRun) { |
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92 hasRun = true; |
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93 super.run(); |
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94 } |
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95 } |
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96 |
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97 // Use Unsafe to access Thread group and ThreadGroup parent fields |
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98 static { |
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99 try { |
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100 ACC = new AccessControlContext(new ProtectionDomain[] { |
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101 new ProtectionDomain(null, null) |
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102 }); |
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103 |
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104 // Find and use topmost ThreadGroup as parent of new group |
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105 UNSAFE = jdk.internal.misc.Unsafe.getUnsafe(); |
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106 Class<?> tk = Thread.class; |
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107 Class<?> gk = ThreadGroup.class; |
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108 |
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109 THREAD_LOCALS = UNSAFE.objectFieldOffset |
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110 (tk.getDeclaredField("threadLocals")); |
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111 INHERITABLE_THREAD_LOCALS = UNSAFE.objectFieldOffset |
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112 (tk.getDeclaredField("inheritableThreadLocals")); |
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113 INHERITEDACCESSCONTROLCONTEXT = UNSAFE.objectFieldOffset |
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114 (tk.getDeclaredField("inheritedAccessControlContext")); |
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115 CONTEXTCLASSLOADER = UNSAFE.objectFieldOffset |
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116 (tk.getDeclaredField("contextClassLoader")); |
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117 |
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118 long tg = UNSAFE.objectFieldOffset(tk.getDeclaredField("group")); |
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119 long gp = UNSAFE.objectFieldOffset(gk.getDeclaredField("parent")); |
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120 ThreadGroup group = (ThreadGroup) |
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121 UNSAFE.getObject(Thread.currentThread(), tg); |
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122 |
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123 while (group != null) { |
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124 ThreadGroup parent = (ThreadGroup)UNSAFE.getObject(group, gp); |
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125 if (parent == null) |
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126 break; |
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127 group = parent; |
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128 } |
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129 final ThreadGroup root = group; |
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130 INNOCUOUSTHREADGROUP = AccessController.doPrivileged( |
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131 (PrivilegedAction<ThreadGroup>) () -> |
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132 { return new ThreadGroup(root, "InnocuousThreadGroup"); }); |
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133 } catch (Exception e) { |
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134 throw new Error(e); |
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135 } |
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136 } |
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137 } |
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