/*
* Copyright (c) 1998, 2014, 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 com.sun.jdi.request.BreakpointRequest;
import java.util.*;
import java.lang.ref.WeakReference;
public class ThreadReferenceImpl extends ObjectReferenceImpl
implements ThreadReference, VMListener {
static final int SUSPEND_STATUS_SUSPENDED = 0x1;
static final int SUSPEND_STATUS_BREAK = 0x2;
private int suspendedZombieCount = 0;
/*
* Some objects can only be created while a thread is suspended and are valid
* only while the thread remains suspended. Examples are StackFrameImpl
* and MonitorInfoImpl. When the thread resumes, these objects have to be
* marked as invalid so that their methods can throw
* InvalidStackFrameException if they are called. To do this, such objects
* register themselves as listeners of the associated thread. When the
* thread is resumed, its listeners are notified and mark themselves
* invalid.
* Also, note that ThreadReferenceImpl itself caches some info that
* is valid only as long as the thread is suspended. When the thread
* is resumed, that cache must be purged.
* Lastly, note that ThreadReferenceImpl and its super, ObjectReferenceImpl
* cache some info that is only valid as long as the entire VM is suspended.
* If _any_ thread is resumed, this cache must be purged. To handle this,
* both ThreadReferenceImpl and ObjectReferenceImpl register themselves as
* VMListeners so that they get notified when all threads are suspended and
* when any thread is resumed.
*/
// This is cached for the life of the thread
private ThreadGroupReference threadGroup;
// This is cached only while this one thread is suspended. Each time
// the thread is resumed, we abandon the current cache object and
// create a new initialized one.
private static class LocalCache {
JDWP.ThreadReference.Status status = null;
List<StackFrame> frames = null;
int framesStart = -1;
int framesLength = 0;
int frameCount = -1;
List<ObjectReference> ownedMonitors = null;
List<MonitorInfo> ownedMonitorsInfo = null;
ObjectReference contendedMonitor = null;
boolean triedCurrentContended = false;
}
/*
* The localCache instance var is set by resetLocalCache to an initialized
* object as shown above. This occurs when the ThreadReference
* object is created, and when the mirrored thread is resumed.
* The fields are then filled in by the relevant methods as they
* are called. A problem can occur if resetLocalCache is called
* (ie, a resume() is executed) at certain points in the execution
* of some of these methods - see 6751643. To avoid this, each
* method that wants to use this cache must make a local copy of
* this variable and use that. This means that each invocation of
* these methods will use a copy of the cache object that was in
* effect at the point that the copy was made; if a racy resume
* occurs, it won't affect the method's local copy. This means that
* the values returned by these calls may not match the state of
* the debuggee at the time the caller gets the values. EG,
* frameCount() is called and comes up with 5 frames. But before
* it returns this, a resume of the debuggee thread is executed in a
* different debugger thread. The thread is resumed and running at
* the time that the value 5 is returned. Or even worse, the thread
* could be suspended again and have a different number of frames, eg, 24,
* but this call will still return 5.
*/
private LocalCache localCache;
private void resetLocalCache() {
localCache = new LocalCache();
}
// This is cached only while all threads in the VM are suspended
// Yes, someone could change the name of a thread while it is suspended.
private static class Cache extends ObjectReferenceImpl.Cache {
String name = null;
}
protected ObjectReferenceImpl.Cache newCache() {
return new Cache();
}
// Listeners - synchronized on vm.state()
private List<WeakReference<ThreadListener>> listeners = new ArrayList<WeakReference<ThreadListener>>();
ThreadReferenceImpl(VirtualMachine aVm, long aRef) {
super(aVm,aRef);
resetLocalCache();
vm.state().addListener(this);
}
protected String description() {
return "ThreadReference " + uniqueID();
}
/*
* VMListener implementation
*/
public boolean vmNotSuspended(VMAction action) {
if (action.resumingThread() == null) {
// all threads are being resumed
synchronized (vm.state()) {
processThreadAction(new ThreadAction(this,
ThreadAction.THREAD_RESUMABLE));
}
}
/*
* Othewise, only one thread is being resumed:
* if it is us,
* we have already done our processThreadAction to notify our
* listeners when we processed the resume.
* if it is not us,
* we don't want to notify our listeners
* because we are not being resumed.
*/
return super.vmNotSuspended(action);
}
/**
* Note that we only cache the name string while the entire VM is suspended
* because the name can change via Thread.setName arbitrarily while this
* thread is running.
*/
public String name() {
String name = null;
try {
Cache local = (Cache)getCache();
if (local != null) {
name = local.name;
}
if (name == null) {
name = JDWP.ThreadReference.Name.process(vm, this)
.threadName;
if (local != null) {
local.name = name;
}
}
} catch (JDWPException exc) {
throw exc.toJDIException();
}
return name;
}
/*
* Sends a command to the back end which is defined to do an
* implicit vm-wide resume.
*/
PacketStream sendResumingCommand(CommandSender sender) {
synchronized (vm.state()) {
processThreadAction(new ThreadAction(this,
ThreadAction.THREAD_RESUMABLE));
return sender.send();
}
}
public void suspend() {
try {
JDWP.ThreadReference.Suspend.process(vm, this);
} catch (JDWPException exc) {
throw exc.toJDIException();
}
// Don't consider the thread suspended yet. On reply, notifySuspend()
// will be called.
}
public void resume() {
/*
* If it's a zombie, we can just update internal state without
* going to back end.
*/
if (suspendedZombieCount > 0) {
suspendedZombieCount--;
return;
}
PacketStream stream;
synchronized (vm.state()) {
processThreadAction(new ThreadAction(this,
ThreadAction.THREAD_RESUMABLE));
stream = JDWP.ThreadReference.Resume.enqueueCommand(vm, this);
}
try {
JDWP.ThreadReference.Resume.waitForReply(vm, stream);
} catch (JDWPException exc) {
throw exc.toJDIException();
}
}
public int suspendCount() {
/*
* If it's a zombie, we maintain the count in the front end.
*/
if (suspendedZombieCount > 0) {
return suspendedZombieCount;
}
try {
return JDWP.ThreadReference.SuspendCount.process(vm, this).suspendCount;
} catch (JDWPException exc) {
throw exc.toJDIException();
}
}
public void stop(ObjectReference throwable) throws InvalidTypeException {
validateMirrorOrNull(throwable);
// Verify that the given object is a Throwable instance
List<ReferenceType> list = vm.classesByName("java.lang.Throwable");
ClassTypeImpl throwableClass = (ClassTypeImpl)list.get(0);
if ((throwable == null) ||
!throwableClass.isAssignableFrom(throwable)) {
throw new InvalidTypeException("Not an instance of Throwable");
}
try {
JDWP.ThreadReference.Stop.process(vm, this,
(ObjectReferenceImpl)throwable);
} catch (JDWPException exc) {
throw exc.toJDIException();
}
}
public void interrupt() {
try {
JDWP.ThreadReference.Interrupt.process(vm, this);
} catch (JDWPException exc) {
throw exc.toJDIException();
}
}
private JDWP.ThreadReference.Status jdwpStatus() {
LocalCache snapshot = localCache;
JDWP.ThreadReference.Status myStatus = snapshot.status;
try {
if (myStatus == null) {
myStatus = JDWP.ThreadReference.Status.process(vm, this);
if ((myStatus.suspendStatus & SUSPEND_STATUS_SUSPENDED) != 0) {
// thread is suspended, we can cache the status.
snapshot.status = myStatus;
}
}
} catch (JDWPException exc) {
throw exc.toJDIException();
}
return myStatus;
}
public int status() {
return jdwpStatus().threadStatus;
}
public boolean isSuspended() {
return ((suspendedZombieCount > 0) ||
((jdwpStatus().suspendStatus & SUSPEND_STATUS_SUSPENDED) != 0));
}
public boolean isAtBreakpoint() {
/*
* TO DO: This fails to take filters into account.
*/
try {
StackFrame frame = frame(0);
Location location = frame.location();
List<BreakpointRequest> requests = vm.eventRequestManager().breakpointRequests();
Iterator<BreakpointRequest> iter = requests.iterator();
while (iter.hasNext()) {
BreakpointRequest request = iter.next();
if (location.equals(request.location())) {
return true;
}
}
return false;
} catch (IndexOutOfBoundsException iobe) {
return false; // no frames on stack => not at breakpoint
} catch (IncompatibleThreadStateException itse) {
// Per the javadoc, not suspended => return false
return false;
}
}
public ThreadGroupReference threadGroup() {
/*
* Thread group can't change, so it's cached once and for all.
*/
if (threadGroup == null) {
try {
threadGroup = JDWP.ThreadReference.ThreadGroup.
process(vm, this).group;
} catch (JDWPException exc) {
throw exc.toJDIException();
}
}
return threadGroup;
}
public int frameCount() throws IncompatibleThreadStateException {
LocalCache snapshot = localCache;
try {
if (snapshot.frameCount == -1) {
snapshot.frameCount = JDWP.ThreadReference.FrameCount
.process(vm, this).frameCount;
}
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.THREAD_NOT_SUSPENDED:
case JDWP.Error.INVALID_THREAD: /* zombie */
throw new IncompatibleThreadStateException();
default:
throw exc.toJDIException();
}
}
return snapshot.frameCount;
}
public List<StackFrame> frames() throws IncompatibleThreadStateException {
return privateFrames(0, -1);
}
public StackFrame frame(int index) throws IncompatibleThreadStateException {
List<StackFrame> list = privateFrames(index, 1);
return list.get(0);
}
/**
* Is the requested subrange within what has been retrieved?
* local is known to be non-null. Should only be called from
* a sync method.
*/
private boolean isSubrange(LocalCache snapshot,
int start, int length) {
if (start < snapshot.framesStart) {
return false;
}
if (length == -1) {
return (snapshot.framesLength == -1);
}
if (snapshot.framesLength == -1) {
if ((start + length) > (snapshot.framesStart +
snapshot.frames.size())) {
throw new IndexOutOfBoundsException();
}
return true;
}
return ((start + length) <= (snapshot.framesStart + snapshot.framesLength));
}
public List<StackFrame> frames(int start, int length)
throws IncompatibleThreadStateException {
if (length < 0) {
throw new IndexOutOfBoundsException(
"length must be greater than or equal to zero");
}
return privateFrames(start, length);
}
/**
* Private version of frames() allows "-1" to specify all
* remaining frames.
*/
synchronized private List<StackFrame> privateFrames(int start, int length)
throws IncompatibleThreadStateException {
// Lock must be held while creating stack frames so if that two threads
// do this at the same time, one won't clobber the subset created by the other.
LocalCache snapshot = localCache;
try {
if (snapshot.frames == null || !isSubrange(snapshot, start, length)) {
JDWP.ThreadReference.Frames.Frame[] jdwpFrames
= JDWP.ThreadReference.Frames.
process(vm, this, start, length).frames;
int count = jdwpFrames.length;
snapshot.frames = new ArrayList<StackFrame>(count);
for (int i = 0; i<count; i++) {
if (jdwpFrames[i].location == null) {
throw new InternalException("Invalid frame location");
}
StackFrame frame = new StackFrameImpl(vm, this,
jdwpFrames[i].frameID,
jdwpFrames[i].location);
// Add to the frame list
snapshot.frames.add(frame);
}
snapshot.framesStart = start;
snapshot.framesLength = length;
return Collections.unmodifiableList(snapshot.frames);
} else {
int fromIndex = start - snapshot.framesStart;
int toIndex;
if (length == -1) {
toIndex = snapshot.frames.size() - fromIndex;
} else {
toIndex = fromIndex + length;
}
return Collections.unmodifiableList(snapshot.frames.subList(fromIndex, toIndex));
}
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.THREAD_NOT_SUSPENDED:
case JDWP.Error.INVALID_THREAD: /* zombie */
throw new IncompatibleThreadStateException();
default:
throw exc.toJDIException();
}
}
}
public List<ObjectReference> ownedMonitors() throws IncompatibleThreadStateException {
LocalCache snapshot = localCache;
try {
if (snapshot.ownedMonitors == null) {
snapshot.ownedMonitors = Arrays.asList(
(ObjectReference[])JDWP.ThreadReference.OwnedMonitors.
process(vm, this).owned);
if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
vm.printTrace(description() +
" temporarily caching owned monitors"+
" (count = " + snapshot.ownedMonitors.size() + ")");
}
}
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.THREAD_NOT_SUSPENDED:
case JDWP.Error.INVALID_THREAD: /* zombie */
throw new IncompatibleThreadStateException();
default:
throw exc.toJDIException();
}
}
return snapshot.ownedMonitors;
}
public ObjectReference currentContendedMonitor()
throws IncompatibleThreadStateException {
LocalCache snapshot = localCache;
try {
if (snapshot.contendedMonitor == null &&
!snapshot.triedCurrentContended) {
snapshot.contendedMonitor = JDWP.ThreadReference.CurrentContendedMonitor.
process(vm, this).monitor;
snapshot.triedCurrentContended = true;
if ((snapshot.contendedMonitor != null) &&
((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0)) {
vm.printTrace(description() +
" temporarily caching contended monitor"+
" (id = " + snapshot.contendedMonitor.uniqueID() + ")");
}
}
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.THREAD_NOT_SUSPENDED:
case JDWP.Error.INVALID_THREAD: /* zombie */
throw new IncompatibleThreadStateException();
default:
throw exc.toJDIException();
}
}
return snapshot.contendedMonitor;
}
public List<MonitorInfo> ownedMonitorsAndFrames() throws IncompatibleThreadStateException {
LocalCache snapshot = localCache;
try {
if (snapshot.ownedMonitorsInfo == null) {
JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor[] minfo;
minfo = JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.process(vm, this).owned;
snapshot.ownedMonitorsInfo = new ArrayList<MonitorInfo>(minfo.length);
for (int i=0; i < minfo.length; i++) {
JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor mi =
minfo[i];
MonitorInfo mon = new MonitorInfoImpl(vm, minfo[i].monitor, this, minfo[i].stack_depth);
snapshot.ownedMonitorsInfo.add(mon);
}
if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
vm.printTrace(description() +
" temporarily caching owned monitors"+
" (count = " + snapshot.ownedMonitorsInfo.size() + ")");
}
}
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.THREAD_NOT_SUSPENDED:
case JDWP.Error.INVALID_THREAD: /* zombie */
throw new IncompatibleThreadStateException();
default:
throw exc.toJDIException();
}
}
return snapshot.ownedMonitorsInfo;
}
public void popFrames(StackFrame frame) throws IncompatibleThreadStateException {
// Note that interface-wise this functionality belongs
// here in ThreadReference, but implementation-wise it
// belongs in StackFrame, so we just forward it.
if (!frame.thread().equals(this)) {
throw new IllegalArgumentException("frame does not belong to this thread");
}
if (!vm.canPopFrames()) {
throw new UnsupportedOperationException(
"target does not support popping frames");
}
((StackFrameImpl)frame).pop();
}
public void forceEarlyReturn(Value returnValue) throws InvalidTypeException,
ClassNotLoadedException,
IncompatibleThreadStateException {
if (!vm.canForceEarlyReturn()) {
throw new UnsupportedOperationException(
"target does not support the forcing of a method to return early");
}
validateMirrorOrNull(returnValue);
StackFrameImpl sf;
try {
sf = (StackFrameImpl)frame(0);
} catch (IndexOutOfBoundsException exc) {
throw new InvalidStackFrameException("No more frames on the stack");
}
sf.validateStackFrame();
MethodImpl meth = (MethodImpl)sf.location().method();
ValueImpl convertedValue = ValueImpl.prepareForAssignment(returnValue,
meth.getReturnValueContainer());
try {
JDWP.ThreadReference.ForceEarlyReturn.process(vm, this, convertedValue);
} catch (JDWPException exc) {
switch (exc.errorCode()) {
case JDWP.Error.OPAQUE_FRAME:
throw new NativeMethodException();
case JDWP.Error.THREAD_NOT_SUSPENDED:
throw new IncompatibleThreadStateException(
"Thread not suspended");
case JDWP.Error.THREAD_NOT_ALIVE:
throw new IncompatibleThreadStateException(
"Thread has not started or has finished");
case JDWP.Error.NO_MORE_FRAMES:
throw new InvalidStackFrameException(
"No more frames on the stack");
default:
throw exc.toJDIException();
}
}
}
public String toString() {
return "instance of " + referenceType().name() +
"(name='" + name() + "', " + "id=" + uniqueID() + ")";
}
byte typeValueKey() {
return JDWP.Tag.THREAD;
}
void addListener(ThreadListener listener) {
synchronized (vm.state()) {
listeners.add(new WeakReference<ThreadListener>(listener));
}
}
void removeListener(ThreadListener listener) {
synchronized (vm.state()) {
Iterator<WeakReference<ThreadListener>> iter = listeners.iterator();
while (iter.hasNext()) {
WeakReference<ThreadListener> ref = iter.next();
if (listener.equals(ref.get())) {
iter.remove();
break;
}
}
}
}
/**
* Propagate the thread state change information
* to registered listeners.
* Must be entered while synchronized on vm.state()
*/
private void processThreadAction(ThreadAction action) {
synchronized (vm.state()) {
Iterator<WeakReference<ThreadListener>> iter = listeners.iterator();
while (iter.hasNext()) {
WeakReference<ThreadListener> ref = iter.next();
ThreadListener listener = ref.get();
if (listener != null) {
switch (action.id()) {
case ThreadAction.THREAD_RESUMABLE:
if (!listener.threadResumable(action)) {
iter.remove();
}
break;
}
} else {
// Listener is unreachable; clean up
iter.remove();
}
}
// Discard our local cache
resetLocalCache();
}
}
}