1 /*
2 * Copyright (c) 1999, 2011, 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 com.sun.tools.jdi;
27
28 import com.sun.jdi.*;
29
30 import java.lang.ref.WeakReference;
31 import java.util.*;
32
33 class VMState {
34 private final VirtualMachineImpl vm;
35
36 // Listeners
37 private final List<WeakReference<VMListener>> listeners = new ArrayList<WeakReference<VMListener>>(); // synchronized (this)
38 private boolean notifyingListeners = false; // synchronized (this)
39
40 /*
41 * Certain information can be cached only when the entire VM is
42 * suspended and there are no pending resumes. The fields below
43 * are used to track whether there are pending resumes. (There
44 * is an assumption that JDWP command ids are increasing over time.)
45 */
46 private int lastCompletedCommandId = 0; // synchronized (this)
47 private int lastResumeCommandId = 0; // synchronized (this)
48
49 // This is cached only while the VM is suspended
50 private static class Cache {
51 List<ThreadGroupReference> groups = null; // cached Top Level ThreadGroups
52 List<ThreadReference> threads = null; // cached Threads
53 }
54
55 private Cache cache = null; // synchronized (this)
56 private static final Cache markerCache = new Cache();
57
58 private void disableCache() {
59 synchronized (this) {
60 cache = null;
61 }
62 }
63
64 private void enableCache() {
65 synchronized (this) {
66 cache = markerCache;
67 }
68 }
69
70 private Cache getCache() {
71 synchronized (this) {
72 if (cache == markerCache) {
73 cache = new Cache();
74 }
75 return cache;
76 }
77 }
78
79 VMState(VirtualMachineImpl vm) {
80 this.vm = vm;
81 }
82
83 /**
84 * Is the VM currently suspended, for the purpose of caching?
85 * Must be called synchronized on vm.state()
86 */
87 boolean isSuspended() {
88 return cache != null;
89 }
90
91 /*
92 * A JDWP command has been completed (reply has been received).
93 * Update data that tracks pending resume commands.
94 */
95 synchronized void notifyCommandComplete(int id) {
96 lastCompletedCommandId = id;
97 }
98
99 synchronized void freeze() {
100 if (cache == null && (lastCompletedCommandId >= lastResumeCommandId)) {
101 /*
102 * No pending resumes to worry about. The VM is suspended
103 * and additional state can be cached. Notify all
104 * interested listeners.
105 */
106 processVMAction(new VMAction(vm, VMAction.VM_SUSPENDED));
107 enableCache();
108 }
109 }
110
111 synchronized PacketStream thawCommand(CommandSender sender) {
112 PacketStream stream = sender.send();
113 lastResumeCommandId = stream.id();
114 thaw();
115 return stream;
116 }
117
118 /**
119 * All threads are resuming
120 */
121 void thaw() {
122 thaw(null);
123 }
124
125 /**
126 * Tell listeners to invalidate suspend-sensitive caches.
127 * If resumingThread != null, then only that thread is being
128 * resumed.
129 */
130 synchronized void thaw(ThreadReference resumingThread) {
131 if (cache != null) {
132 if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
133 vm.printTrace("Clearing VM suspended cache");
134 }
135 disableCache();
136 }
137 processVMAction(new VMAction(vm, resumingThread, VMAction.VM_NOT_SUSPENDED));
138 }
139
140 private synchronized void processVMAction(VMAction action) {
141 if (!notifyingListeners) {
142 // Prevent recursion
143 notifyingListeners = true;
144
145 Iterator<WeakReference<VMListener>> iter = listeners.iterator();
146 while (iter.hasNext()) {
147 WeakReference<VMListener> ref = iter.next();
148 VMListener listener = ref.get();
149 if (listener != null) {
150 boolean keep = true;
151 switch (action.id()) {
152 case VMAction.VM_SUSPENDED:
153 keep = listener.vmSuspended(action);
154 break;
155 case VMAction.VM_NOT_SUSPENDED:
156 keep = listener.vmNotSuspended(action);
157 break;
158 }
159 if (!keep) {
160 iter.remove();
161 }
162 } else {
163 // Listener is unreachable; clean up
164 iter.remove();
165 }
166 }
167
168 notifyingListeners = false;
169 }
170 }
171
172 synchronized void addListener(VMListener listener) {
173 listeners.add(new WeakReference<VMListener>(listener));
174 }
175
176 synchronized boolean hasListener(VMListener listener) {
177 return listeners.contains(listener);
178 }
179
180 synchronized void removeListener(VMListener listener) {
181 Iterator<WeakReference<VMListener>> iter = listeners.iterator();
182 while (iter.hasNext()) {
183 WeakReference<VMListener> ref = iter.next();
184 if (listener.equals(ref.get())) {
185 iter.remove();
186 break;
187 }
188 }
189 }
190
191 List<ThreadReference> allThreads() {
192 List<ThreadReference> threads = null;
193 try {
194 Cache local = getCache();
195
196 if (local != null) {
197 // may be stale when returned, but not provably so
198 threads = local.threads;
199 }
200 if (threads == null) {
201 threads = Arrays.asList((ThreadReference[])JDWP.VirtualMachine.AllThreads.
202 process(vm).threads);
203 if (local != null) {
204 local.threads = threads;
205 if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
206 vm.printTrace("Caching all threads (count = " +
207 threads.size() + ") while VM suspended");
208 }
209 }
210 }
211 } catch (JDWPException exc) {
212 throw exc.toJDIException();
213 }
214 return threads;
215 }
216
217
218 List<ThreadGroupReference> topLevelThreadGroups() {
219 List<ThreadGroupReference> groups = null;
220 try {
221 Cache local = getCache();
222
223 if (local != null) {
224 groups = local.groups;
225 }
226 if (groups == null) {
227 groups = Arrays.asList(
228 (ThreadGroupReference[])JDWP.VirtualMachine.TopLevelThreadGroups.
229 process(vm).groups);
230 if (local != null) {
231 local.groups = groups;
232 if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
233 vm.printTrace(
234 "Caching top level thread groups (count = " +
235 groups.size() + ") while VM suspended");
236 }
237 }
238 }
239 } catch (JDWPException exc) {
240 throw exc.toJDIException();
241 }
242 return groups;
243 }
244
245 }