1 /*
2 * Copyright (c) 1999, 2018, 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 java.lang;
27
28
29 import jdk.internal.misc.VM;
30
31 /**
32 * Package-private utility class containing data structures and logic
33 * governing the virtual-machine shutdown sequence.
34 *
35 * @author Mark Reinhold
36 * @since 1.3
37 *
38 * @see java.io.Console
39 * @see ApplicationShutdownHooks
40 * @see java.io.DeleteOnExitHook
41 */
42
43 class Shutdown {
44
45 // The system shutdown hooks are registered with a predefined slot.
46 // The list of shutdown hooks is as follows:
47 // (0) Console restore hook
48 // (1) ApplicationShutdownHooks that invokes all registered application
49 // shutdown hooks and waits until they finish
50 // (2) DeleteOnExit hook
51 private static final int MAX_SYSTEM_HOOKS = 10;
52 private static final Runnable[] hooks = new Runnable[MAX_SYSTEM_HOOKS];
53
54 // the index of the currently running shutdown hook to the hooks array
55 private static int currentRunningHook = -1;
56
57 /* The preceding static fields are protected by this lock */
58 private static class Lock { };
59 private static Object lock = new Lock();
60
61 /* Lock object for the native halt method */
62 private static Object haltLock = new Lock();
63
64 /**
65 * Add a new system shutdown hook. Checks the shutdown state and
66 * the hook itself, but does not do any security checks.
67 *
68 * The registerShutdownInProgress parameter should be false except
69 * registering the DeleteOnExitHook since the first file may
70 * be added to the delete on exit list by the application shutdown
71 * hooks.
72 *
73 * @params slot the slot in the shutdown hook array, whose element
74 * will be invoked in order during shutdown
75 * @params registerShutdownInProgress true to allow the hook
76 * to be registered even if the shutdown is in progress.
77 * @params hook the hook to be registered
78 *
79 * @throws IllegalStateException
80 * if registerShutdownInProgress is false and shutdown is in progress; or
81 * if registerShutdownInProgress is true and the shutdown process
82 * already passes the given slot
83 */
84 static void add(int slot, boolean registerShutdownInProgress, Runnable hook) {
85 if (slot < 0 || slot >= MAX_SYSTEM_HOOKS) {
86 throw new IllegalArgumentException("Invalid slot: " + slot);
87 }
88 synchronized (lock) {
89 if (hooks[slot] != null)
90 throw new InternalError("Shutdown hook at slot " + slot + " already registered");
91
92 if (!registerShutdownInProgress) {
93 if (currentRunningHook >= 0)
94 throw new IllegalStateException("Shutdown in progress");
95 } else {
96 if (VM.isShutdown() || slot <= currentRunningHook)
97 throw new IllegalStateException("Shutdown in progress");
98 }
99
100 hooks[slot] = hook;
101 }
102 }
103
104 /* Run all system shutdown hooks.
105 *
106 * The system shutdown hooks are run in the thread synchronized on
107 * Shutdown.class. Other threads calling Runtime::exit, Runtime::halt
108 * or JNI DestroyJavaVM will block indefinitely.
109 *
110 * ApplicationShutdownHooks is registered as one single hook that starts
111 * all application shutdown hooks and waits until they finish.
112 */
113 private static void runHooks() {
114 synchronized (lock) {
115 /* Guard against the possibility of a daemon thread invoking exit
116 * after DestroyJavaVM initiates the shutdown sequence
117 */
118 if (VM.isShutdown()) return;
119 }
120
121 for (int i=0; i < MAX_SYSTEM_HOOKS; i++) {
122 try {
123 Runnable hook;
124 synchronized (lock) {
125 // acquire the lock to make sure the hook registered during
126 // shutdown is visible here.
127 currentRunningHook = i;
128 hook = hooks[i];
129 }
130 if (hook != null) hook.run();
131 } catch (Throwable t) {
132 if (t instanceof ThreadDeath) {
133 ThreadDeath td = (ThreadDeath)t;
134 throw td;
135 }
136 }
137 }
138
139 // set shutdown state
140 VM.shutdown();
141 }
142
143 /* Notify the VM that it's time to halt. */
144 static native void beforeHalt();
145
146 /* The halt method is synchronized on the halt lock
147 * to avoid corruption of the delete-on-shutdown file list.
148 * It invokes the true native halt method.
149 */
150 static void halt(int status) {
151 synchronized (haltLock) {
152 halt0(status);
153 }
154 }
155
156 static native void halt0(int status);
157
158 /* Invoked by Runtime.exit, which does all the security checks.
159 * Also invoked by handlers for system-provided termination events,
160 * which should pass a nonzero status code.
161 */
162 static void exit(int status) {
163 synchronized (lock) {
164 if (status != 0 && VM.isShutdown()) {
165 /* Halt immediately on nonzero status */
166 halt(status);
167 }
168 }
169 synchronized (Shutdown.class) {
170 /* Synchronize on the class object, causing any other thread
171 * that attempts to initiate shutdown to stall indefinitely
172 */
173 beforeHalt();
174 runHooks();
175 halt(status);
176 }
177 }
178
179
180 /* Invoked by the JNI DestroyJavaVM procedure when the last non-daemon
181 * thread has finished. Unlike the exit method, this method does not
182 * actually halt the VM.
183 */
184 static void shutdown() {
185 synchronized (Shutdown.class) {
186 runHooks();
187 }
188 }
189
190 }
191