author | rriggs |
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parent 5506 | 202f599c92aa |
permissions | -rw-r--r-- |
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/* |
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* Copyright (c) 1999, 2005, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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package java.lang; |
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/** |
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* Package-private utility class containing data structures and logic |
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* governing the virtual-machine shutdown sequence. |
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* |
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* @author Mark Reinhold |
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* @since 1.3 |
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*/ |
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class Shutdown { |
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/* Shutdown state */ |
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private static final int RUNNING = 0; |
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private static final int HOOKS = 1; |
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private static final int FINALIZERS = 2; |
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private static int state = RUNNING; |
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/* Should we run all finalizers upon exit? */ |
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private static boolean runFinalizersOnExit = false; |
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// The system shutdown hooks are registered with a predefined slot. |
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// The list of shutdown hooks is as follows: |
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// (0) Console restore hook |
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// (1) Application hooks |
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// (2) DeleteOnExit hook |
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private static final int MAX_SYSTEM_HOOKS = 10; |
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private static final Runnable[] hooks = new Runnable[MAX_SYSTEM_HOOKS]; |
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// the index of the currently running shutdown hook to the hooks array |
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private static int currentRunningHook = 0; |
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/* The preceding static fields are protected by this lock */ |
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private static class Lock { }; |
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private static Object lock = new Lock(); |
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/* Lock object for the native halt method */ |
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private static Object haltLock = new Lock(); |
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/* Invoked by Runtime.runFinalizersOnExit */ |
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static void setRunFinalizersOnExit(boolean run) { |
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synchronized (lock) { |
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runFinalizersOnExit = run; |
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} |
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} |
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/** |
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* Add a new shutdown hook. Checks the shutdown state and the hook itself, |
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* but does not do any security checks. |
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* |
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* The registerShutdownInProgress parameter should be false except |
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* registering the DeleteOnExitHook since the first file may |
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* be added to the delete on exit list by the application shutdown |
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* hooks. |
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* |
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* @params slot the slot in the shutdown hook array, whose element |
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* will be invoked in order during shutdown |
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* @params registerShutdownInProgress true to allow the hook |
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* to be registered even if the shutdown is in progress. |
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* @params hook the hook to be registered |
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* |
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* @throw IllegalStateException |
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* if registerShutdownInProgress is false and shutdown is in progress; or |
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* if registerShutdownInProgress is true and the shutdown process |
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* already passes the given slot |
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*/ |
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static void add(int slot, boolean registerShutdownInProgress, Runnable hook) { |
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synchronized (lock) { |
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if (hooks[slot] != null) |
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throw new InternalError("Shutdown hook at slot " + slot + " already registered"); |
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if (!registerShutdownInProgress) { |
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if (state > RUNNING) |
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throw new IllegalStateException("Shutdown in progress"); |
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} else { |
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if (state > HOOKS || (state == HOOKS && slot <= currentRunningHook)) |
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throw new IllegalStateException("Shutdown in progress"); |
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} |
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hooks[slot] = hook; |
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} |
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} |
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/* Run all registered shutdown hooks |
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*/ |
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private static void runHooks() { |
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for (int i=0; i < MAX_SYSTEM_HOOKS; i++) { |
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try { |
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Runnable hook; |
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synchronized (lock) { |
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// acquire the lock to make sure the hook registered during |
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// shutdown is visible here. |
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currentRunningHook = i; |
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hook = hooks[i]; |
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} |
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if (hook != null) hook.run(); |
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} catch(Throwable t) { |
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if (t instanceof ThreadDeath) { |
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ThreadDeath td = (ThreadDeath)t; |
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throw td; |
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} |
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} |
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} |
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} |
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/* The halt method is synchronized on the halt lock |
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* to avoid corruption of the delete-on-shutdown file list. |
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* It invokes the true native halt method. |
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*/ |
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static void halt(int status) { |
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synchronized (haltLock) { |
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halt0(status); |
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} |
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} |
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static native void halt0(int status); |
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/* Wormhole for invoking java.lang.ref.Finalizer.runAllFinalizers */ |
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private static native void runAllFinalizers(); |
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/* The actual shutdown sequence is defined here. |
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* |
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* If it weren't for runFinalizersOnExit, this would be simple -- we'd just |
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* run the hooks and then halt. Instead we need to keep track of whether |
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* we're running hooks or finalizers. In the latter case a finalizer could |
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* invoke exit(1) to cause immediate termination, while in the former case |
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* any further invocations of exit(n), for any n, simply stall. Note that |
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* if on-exit finalizers are enabled they're run iff the shutdown is |
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* initiated by an exit(0); they're never run on exit(n) for n != 0 or in |
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* response to SIGINT, SIGTERM, etc. |
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*/ |
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private static void sequence() { |
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synchronized (lock) { |
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/* Guard against the possibility of a daemon thread invoking exit |
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* after DestroyJavaVM initiates the shutdown sequence |
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*/ |
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if (state != HOOKS) return; |
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} |
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runHooks(); |
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boolean rfoe; |
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synchronized (lock) { |
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state = FINALIZERS; |
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rfoe = runFinalizersOnExit; |
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} |
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if (rfoe) runAllFinalizers(); |
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} |
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/* Invoked by Runtime.exit, which does all the security checks. |
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* Also invoked by handlers for system-provided termination events, |
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* which should pass a nonzero status code. |
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*/ |
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static void exit(int status) { |
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boolean runMoreFinalizers = false; |
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synchronized (lock) { |
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if (status != 0) runFinalizersOnExit = false; |
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switch (state) { |
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case RUNNING: /* Initiate shutdown */ |
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state = HOOKS; |
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break; |
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case HOOKS: /* Stall and halt */ |
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break; |
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case FINALIZERS: |
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if (status != 0) { |
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/* Halt immediately on nonzero status */ |
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halt(status); |
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} else { |
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/* Compatibility with old behavior: |
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* Run more finalizers and then halt |
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*/ |
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runMoreFinalizers = runFinalizersOnExit; |
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} |
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break; |
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} |
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} |
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if (runMoreFinalizers) { |
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runAllFinalizers(); |
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halt(status); |
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} |
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synchronized (Shutdown.class) { |
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/* Synchronize on the class object, causing any other thread |
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* that attempts to initiate shutdown to stall indefinitely |
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*/ |
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sequence(); |
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halt(status); |
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} |
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} |
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/* Invoked by the JNI DestroyJavaVM procedure when the last non-daemon |
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* thread has finished. Unlike the exit method, this method does not |
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* actually halt the VM. |
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*/ |
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static void shutdown() { |
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synchronized (lock) { |
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switch (state) { |
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case RUNNING: /* Initiate shutdown */ |
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state = HOOKS; |
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break; |
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case HOOKS: /* Stall and then return */ |
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case FINALIZERS: |
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break; |
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} |
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} |
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synchronized (Shutdown.class) { |
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sequence(); |
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} |
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} |
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} |