191 lines
6.7 KiB
Java
191 lines
6.7 KiB
Java
/*
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* Copyright (c) 1999, 2018, 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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import jdk.internal.misc.VM;
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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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* @see java.io.Console
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* @see ApplicationShutdownHooks
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* @see java.io.DeleteOnExitHook
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*/
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class Shutdown {
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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) ApplicationShutdownHooks that invokes all registered application
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// shutdown hooks and waits until they finish
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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 = -1;
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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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/**
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* Add a new system shutdown hook. Checks the shutdown state and
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* the hook itself, 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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* @throws 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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if (slot < 0 || slot >= MAX_SYSTEM_HOOKS) {
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throw new IllegalArgumentException("Invalid slot: " + slot);
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}
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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 (currentRunningHook >= 0)
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throw new IllegalStateException("Shutdown in progress");
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} else {
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if (VM.isShutdown() || 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 system shutdown hooks.
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*
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* The system shutdown hooks are run in the thread synchronized on
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* Shutdown.class. Other threads calling Runtime::exit, Runtime::halt
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* or JNI DestroyJavaVM will block indefinitely.
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*
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* ApplicationShutdownHooks is registered as one single hook that starts
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* all application shutdown hooks and waits until they finish.
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*/
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private static void runHooks() {
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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 (VM.isShutdown()) return;
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}
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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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// set shutdown state
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VM.shutdown();
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}
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/* Notify the VM that it's time to halt. */
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static native void beforeHalt();
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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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/* 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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synchronized (lock) {
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if (status != 0 && VM.isShutdown()) {
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/* Halt immediately on nonzero status */
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halt(status);
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}
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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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beforeHalt();
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runHooks();
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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 (Shutdown.class) {
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runHooks();
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}
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}
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}
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