251 lines
8.2 KiB
Java
251 lines
8.2 KiB
Java
/*
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* Copyright (c) 1999, 2020, 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 com.sun.tools.jdi;
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import com.sun.jdi.*;
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import java.lang.ref.WeakReference;
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import java.util.*;
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class VMState {
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private final VirtualMachineImpl vm;
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// Listeners
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private final List<WeakReference<VMListener>> listeners = new ArrayList<WeakReference<VMListener>>(); // synchronized (this)
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private boolean notifyingListeners = false; // synchronized (this)
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/*
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* Certain information can be cached only when the entire VM is
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* suspended and there are no pending resumes. The field below
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* is used to track whether there are pending resumes.
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*/
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private final Set<Integer> pendingResumeCommands = Collections.synchronizedSet(new HashSet<>());
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// This is cached only while the VM is suspended
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private static class Cache {
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List<ThreadGroupReference> groups = null; // cached Top Level ThreadGroups
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List<ThreadReference> threads = null; // cached Threads
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}
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private Cache cache = null; // synchronized (this)
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private static final Cache markerCache = new Cache();
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private void disableCache() {
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synchronized (this) {
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cache = null;
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}
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}
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private void enableCache() {
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synchronized (this) {
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cache = markerCache;
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}
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}
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private Cache getCache() {
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synchronized (this) {
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if (cache == markerCache) {
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cache = new Cache();
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}
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return cache;
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}
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}
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VMState(VirtualMachineImpl vm) {
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this.vm = vm;
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}
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/**
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* Is the VM currently suspended, for the purpose of caching?
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* Must be called synchronized on vm.state()
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*/
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boolean isSuspended() {
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return cache != null;
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}
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/*
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* A JDWP command has been completed (reply has been received).
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* Update data that tracks pending resume commands.
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*/
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void notifyCommandComplete(int id) {
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pendingResumeCommands.remove(id);
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}
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synchronized void freeze() {
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if (cache == null && (pendingResumeCommands.isEmpty())) {
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/*
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* No pending resumes to worry about. The VM is suspended
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* and additional state can be cached. Notify all
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* interested listeners.
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*/
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processVMAction(new VMAction(vm, VMAction.VM_SUSPENDED));
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enableCache();
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}
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}
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synchronized PacketStream thawCommand(CommandSender sender) {
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PacketStream stream = sender.send();
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pendingResumeCommands.add(stream.id());
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thaw();
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return stream;
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}
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/**
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* All threads are resuming
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*/
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void thaw() {
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thaw(null);
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}
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/**
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* Tell listeners to invalidate suspend-sensitive caches.
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* If resumingThread != null, then only that thread is being
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* resumed.
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*/
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synchronized void thaw(ThreadReference resumingThread) {
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if (cache != null) {
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if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
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vm.printTrace("Clearing VM suspended cache");
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}
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disableCache();
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}
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processVMAction(new VMAction(vm, resumingThread, VMAction.VM_NOT_SUSPENDED));
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}
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private synchronized void processVMAction(VMAction action) {
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if (!notifyingListeners) {
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// Prevent recursion
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notifyingListeners = true;
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Iterator<WeakReference<VMListener>> iter = listeners.iterator();
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while (iter.hasNext()) {
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WeakReference<VMListener> ref = iter.next();
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VMListener listener = ref.get();
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if (listener != null) {
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boolean keep = true;
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switch (action.id()) {
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case VMAction.VM_SUSPENDED:
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keep = listener.vmSuspended(action);
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break;
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case VMAction.VM_NOT_SUSPENDED:
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keep = listener.vmNotSuspended(action);
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break;
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}
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if (!keep) {
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iter.remove();
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}
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} else {
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// Listener is unreachable; clean up
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iter.remove();
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}
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}
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notifyingListeners = false;
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}
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}
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synchronized void addListener(VMListener listener) {
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listeners.add(new WeakReference<VMListener>(listener));
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}
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synchronized boolean hasListener(VMListener listener) {
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Iterator<WeakReference<VMListener>> iter = listeners.iterator();
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while (iter.hasNext()) {
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WeakReference<VMListener> ref = iter.next();
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if (listener.equals(ref.get())) {
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return true;
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}
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}
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return false;
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}
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synchronized void removeListener(VMListener listener) {
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Iterator<WeakReference<VMListener>> iter = listeners.iterator();
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while (iter.hasNext()) {
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WeakReference<VMListener> ref = iter.next();
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if (listener.equals(ref.get())) {
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iter.remove();
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break;
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}
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}
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}
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List<ThreadReference> allThreads() {
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List<ThreadReference> threads = null;
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try {
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Cache local = getCache();
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if (local != null) {
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// may be stale when returned, but not provably so
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threads = local.threads;
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}
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if (threads == null) {
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threads = Arrays.asList((ThreadReference[])JDWP.VirtualMachine.AllThreads.
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process(vm).threads);
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if (local != null) {
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local.threads = threads;
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if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
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vm.printTrace("Caching all threads (count = " +
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threads.size() + ") while VM suspended");
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}
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}
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}
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} catch (JDWPException exc) {
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throw exc.toJDIException();
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}
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return threads;
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}
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List<ThreadGroupReference> topLevelThreadGroups() {
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List<ThreadGroupReference> groups = null;
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try {
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Cache local = getCache();
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if (local != null) {
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groups = local.groups;
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}
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if (groups == null) {
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groups = Arrays.asList(
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(ThreadGroupReference[])JDWP.VirtualMachine.TopLevelThreadGroups.
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process(vm).groups);
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if (local != null) {
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local.groups = groups;
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if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
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vm.printTrace(
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"Caching top level thread groups (count = " +
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groups.size() + ") while VM suspended");
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}
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}
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}
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} catch (JDWPException exc) {
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throw exc.toJDIException();
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}
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return groups;
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}
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}
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