/*
* Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package com.sun.tools.jdi;
import com.sun.jdi.*;
import java.lang.ref.WeakReference;
import java.util.*;
class VMState {
private final VirtualMachineImpl vm;
// Listeners
private final List<WeakReference> listeners = new ArrayList<WeakReference>(); // synchronized (this)
private boolean notifyingListeners = false; // synchronized (this)
/*
* Certain information can be cached only when the entire VM is
* suspended and there are no pending resumes. The fields below
* are used to track whether there are pending resumes. (There
* is an assumption that JDWP command ids are increasing over time.)
*/
private int lastCompletedCommandId = 0; // synchronized (this)
private int lastResumeCommandId = 0; // synchronized (this)
// This is cached only while the VM is suspended
private static class Cache {
List<ThreadGroupReference> groups = null; // cached Top Level ThreadGroups
List<ThreadReference> threads = null; // cached Threads
}
private Cache cache = null; // synchronized (this)
private static final Cache markerCache = new Cache();
private void disableCache() {
synchronized (this) {
cache = null;
}
}
private void enableCache() {
synchronized (this) {
cache = markerCache;
}
}
private Cache getCache() {
synchronized (this) {
if (cache == markerCache) {
cache = new Cache();
}
return cache;
}
}
VMState(VirtualMachineImpl vm) {
this.vm = vm;
}
/**
* Is the VM currently suspended, for the purpose of caching?
* Must be called synchronized on vm.state()
*/
boolean isSuspended() {
return cache != null;
}
/*
* A JDWP command has been completed (reply has been received).
* Update data that tracks pending resume commands.
*/
synchronized void notifyCommandComplete(int id) {
lastCompletedCommandId = id;
}
synchronized void freeze() {
if (cache == null && (lastCompletedCommandId >= lastResumeCommandId)) {
/*
* No pending resumes to worry about. The VM is suspended
* and additional state can be cached. Notify all
* interested listeners.
*/
processVMAction(new VMAction(vm, VMAction.VM_SUSPENDED));
enableCache();
}
}
synchronized PacketStream thawCommand(CommandSender sender) {
PacketStream stream = sender.send();
lastResumeCommandId = stream.id();
thaw();
return stream;
}
/**
* All threads are resuming
*/
void thaw() {
thaw(null);
}
/**
* Tell listeners to invalidate suspend-sensitive caches.
* If resumingThread != null, then only that thread is being
* resumed.
*/
synchronized void thaw(ThreadReference resumingThread) {
if (cache != null) {
if ((vm.traceFlags & vm.TRACE_OBJREFS) != 0) {
vm.printTrace("Clearing VM suspended cache");
}
disableCache();
}
processVMAction(new VMAction(vm, resumingThread, VMAction.VM_NOT_SUSPENDED));
}
private synchronized void processVMAction(VMAction action) {
if (!notifyingListeners) {
// Prevent recursion
notifyingListeners = true;
Iterator iter = listeners.iterator();
while (iter.hasNext()) {
WeakReference ref = (WeakReference)iter.next();
VMListener listener = (VMListener)ref.get();
if (listener != null) {
boolean keep = true;
switch (action.id()) {
case VMAction.VM_SUSPENDED:
keep = listener.vmSuspended(action);
break;
case VMAction.VM_NOT_SUSPENDED:
keep = listener.vmNotSuspended(action);
break;
}
if (!keep) {
iter.remove();
}
} else {
// Listener is unreachable; clean up
iter.remove();
}
}
notifyingListeners = false;
}
}
synchronized void addListener(VMListener listener) {
listeners.add(new WeakReference<VMListener>(listener));
}
synchronized boolean hasListener(VMListener listener) {
return listeners.contains(listener);
}
synchronized void removeListener(VMListener listener) {
Iterator iter = listeners.iterator();
while (iter.hasNext()) {
WeakReference ref = (WeakReference)iter.next();
if (listener.equals(ref.get())) {
iter.remove();
break;
}
}
}
List<ThreadReference> allThreads() {
List<ThreadReference> threads = null;
try {
Cache local = getCache();
if (local != null) {
// may be stale when returned, but not provably so
threads = local.threads;
}
if (threads == null) {
threads = Arrays.asList((ThreadReference[])JDWP.VirtualMachine.AllThreads.
process(vm).threads);
if (local != null) {
local.threads = threads;
if ((vm.traceFlags & vm.TRACE_OBJREFS) != 0) {
vm.printTrace("Caching all threads (count = " +
threads.size() + ") while VM suspended");
}
}
}
} catch (JDWPException exc) {
throw exc.toJDIException();
}
return threads;
}
List<ThreadGroupReference> topLevelThreadGroups() {
List<ThreadGroupReference> groups = null;
try {
Cache local = getCache();
if (local != null) {
groups = local.groups;
}
if (groups == null) {
groups = Arrays.asList(
(ThreadGroupReference[])JDWP.VirtualMachine.TopLevelThreadGroups.
process(vm).groups);
if (local != null) {
local.groups = groups;
if ((vm.traceFlags & vm.TRACE_OBJREFS) != 0) {
vm.printTrace(
"Caching top level thread groups (count = " +
groups.size() + ") while VM suspended");
}
}
}
} catch (JDWPException exc) {
throw exc.toJDIException();
}
return groups;
}
}