1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * Copyright (c) 1999, 2005, Oracle and/or its affiliates. All rights reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. Oracle designates this 9 * particular file as subject to the "Classpath" exception as provided 10 * by Oracle in the LICENSE file that accompanied this code. 11 * 12 * This code is distributed in the hope that it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * version 2 for more details (a copy is included in the LICENSE file that 16 * accompanied this code). 17 * 18 * You should have received a copy of the GNU General Public License version 19 * 2 along with this work; if not, write to the Free Software Foundation, 20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 21 * 22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 23 * or visit www.oracle.com if you need additional information or have any 24 * questions. 25 */ 26 27 package java.lang; 28 29 30 /** 31 * Package-private utility class containing data structures and logic 32 * governing the virtual-machine shutdown sequence. 33 * 34 * @author Mark Reinhold 35 * @since 1.3 36 * @hide 37 */ 38 // Android-changed: Make class public. 39 public class Shutdown { 40 41 /* Shutdown state */ 42 private static final int RUNNING = 0; 43 private static final int HOOKS = 1; 44 private static final int FINALIZERS = 2; 45 private static int state = RUNNING; 46 47 /* Should we run all finalizers upon exit? */ 48 private static boolean runFinalizersOnExit = false; 49 50 // The system shutdown hooks are registered with a predefined slot. 51 // The list of shutdown hooks is as follows: 52 // (0) Console restore hook 53 // (1) Application hooks 54 // (2) DeleteOnExit hook 55 private static final int MAX_SYSTEM_HOOKS = 10; 56 private static final Runnable[] hooks = new Runnable[MAX_SYSTEM_HOOKS]; 57 58 // the index of the currently running shutdown hook to the hooks array 59 private static int currentRunningHook = 0; 60 61 /* The preceding static fields are protected by this lock */ 62 private static class Lock { }; 63 private static Object lock = new Lock(); 64 65 /* Lock object for the native halt method */ 66 private static Object haltLock = new Lock(); 67 68 /* Invoked by Runtime.runFinalizersOnExit */ setRunFinalizersOnExit(boolean run)69 static void setRunFinalizersOnExit(boolean run) { 70 synchronized (lock) { 71 runFinalizersOnExit = run; 72 } 73 } 74 75 76 /** 77 * Add a new shutdown hook. Checks the shutdown state and the hook itself, 78 * but does not do any security checks. 79 * 80 * The registerShutdownInProgress parameter should be false except 81 * registering the DeleteOnExitHook since the first file may 82 * be added to the delete on exit list by the application shutdown 83 * hooks. 84 * 85 * @param slot the slot in the shutdown hook array, whose element 86 * will be invoked in order during shutdown 87 * @param registerShutdownInProgress true to allow the hook 88 * to be registered even if the shutdown is in progress. 89 * @param hook the hook to be registered 90 * 91 * @throws IllegalStateException 92 * if registerShutdownInProgress is false and shutdown is in progress; or 93 * if registerShutdownInProgress is true and the shutdown process 94 * already passes the given slot 95 */ 96 // Android changed s/@params/@param add(int slot, boolean registerShutdownInProgress, Runnable hook)97 public static void add(int slot, boolean registerShutdownInProgress, Runnable hook) { 98 synchronized (lock) { 99 if (hooks[slot] != null) 100 throw new InternalError("Shutdown hook at slot " + slot + " already registered"); 101 102 if (!registerShutdownInProgress) { 103 if (state > RUNNING) 104 throw new IllegalStateException("Shutdown in progress"); 105 } else { 106 if (state > HOOKS || (state == HOOKS && slot <= currentRunningHook)) 107 throw new IllegalStateException("Shutdown in progress"); 108 } 109 110 hooks[slot] = hook; 111 } 112 } 113 114 /* Run all registered shutdown hooks 115 */ runHooks()116 private static void runHooks() { 117 for (int i=0; i < MAX_SYSTEM_HOOKS; i++) { 118 try { 119 Runnable hook; 120 synchronized (lock) { 121 // acquire the lock to make sure the hook registered during 122 // shutdown is visible here. 123 currentRunningHook = i; 124 hook = hooks[i]; 125 } 126 if (hook != null) hook.run(); 127 } catch(Throwable t) { 128 if (t instanceof ThreadDeath) { 129 ThreadDeath td = (ThreadDeath)t; 130 throw td; 131 } 132 } 133 } 134 } 135 136 /* The halt method is synchronized on the halt lock 137 * to avoid corruption of the delete-on-shutdown file list. 138 * It invokes the true native halt method. 139 */ halt(int status)140 static void halt(int status) { 141 synchronized (haltLock) { 142 halt0(status); 143 } 144 } 145 halt0(int status)146 static native void halt0(int status); 147 148 /* Wormhole for invoking java.lang.ref.Finalizer.runAllFinalizers */ runAllFinalizers()149 private static native void runAllFinalizers(); 150 151 152 /* The actual shutdown sequence is defined here. 153 * 154 * If it weren't for runFinalizersOnExit, this would be simple -- we'd just 155 * run the hooks and then halt. Instead we need to keep track of whether 156 * we're running hooks or finalizers. In the latter case a finalizer could 157 * invoke exit(1) to cause immediate termination, while in the former case 158 * any further invocations of exit(n), for any n, simply stall. Note that 159 * if on-exit finalizers are enabled they're run iff the shutdown is 160 * initiated by an exit(0); they're never run on exit(n) for n != 0 or in 161 * response to SIGINT, SIGTERM, etc. 162 */ sequence()163 private static void sequence() { 164 synchronized (lock) { 165 /* Guard against the possibility of a daemon thread invoking exit 166 * after DestroyJavaVM initiates the shutdown sequence 167 */ 168 if (state != HOOKS) return; 169 } 170 runHooks(); 171 boolean rfoe; 172 synchronized (lock) { 173 state = FINALIZERS; 174 rfoe = runFinalizersOnExit; 175 } 176 if (rfoe) runAllFinalizers(); 177 } 178 179 180 /* Invoked by Runtime.exit, which does all the security checks. 181 * Also invoked by handlers for system-provided termination events, 182 * which should pass a nonzero status code. 183 */ exit(int status)184 static void exit(int status) { 185 boolean runMoreFinalizers = false; 186 synchronized (lock) { 187 if (status != 0) runFinalizersOnExit = false; 188 switch (state) { 189 case RUNNING: /* Initiate shutdown */ 190 state = HOOKS; 191 break; 192 case HOOKS: /* Stall and halt */ 193 break; 194 case FINALIZERS: 195 if (status != 0) { 196 /* Halt immediately on nonzero status */ 197 halt(status); 198 } else { 199 /* Compatibility with old behavior: 200 * Run more finalizers and then halt 201 */ 202 runMoreFinalizers = runFinalizersOnExit; 203 } 204 break; 205 } 206 } 207 if (runMoreFinalizers) { 208 runAllFinalizers(); 209 halt(status); 210 } 211 synchronized (Shutdown.class) { 212 /* Synchronize on the class object, causing any other thread 213 * that attempts to initiate shutdown to stall indefinitely 214 */ 215 sequence(); 216 halt(status); 217 } 218 } 219 220 221 /* Invoked by the JNI DestroyJavaVM procedure when the last non-daemon 222 * thread has finished. Unlike the exit method, this method does not 223 * actually halt the VM. 224 */ shutdown()225 static void shutdown() { 226 synchronized (lock) { 227 switch (state) { 228 case RUNNING: /* Initiate shutdown */ 229 state = HOOKS; 230 break; 231 case HOOKS: /* Stall and then return */ 232 case FINALIZERS: 233 break; 234 } 235 } 236 synchronized (Shutdown.class) { 237 sequence(); 238 } 239 } 240 241 } 242