[243794] - [update policy] VM Cache can save updates after they were canceled.

plugins/org.eclipse.dd.dsf.ui/.options

@@ -0,0 +1,5 @@
+org.eclipse.dd.dsf.ui/debug = false
+org.eclipse.dd.dsf.ui/debug/vm/contentProvider = false
+org.eclipse.dd.dsf.ui/debug/vm/delta = false
+org.eclipse.dd.dsf.ui/debug/vm/cache = false
+org.eclipse.dd.dsf.ui/debug/vm/presentationId = 

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/internal/ui/DsfUIPlugin.java

@@ -10,6 +10,7 @@
  *******************************************************************************/
 package org.eclipse.dd.dsf.internal.ui;
 
+import org.eclipse.core.runtime.Platform;
 import org.eclipse.ui.plugin.AbstractUIPlugin;
 import org.osgi.framework.BundleContext;
 
@@ -26,6 +27,8 @@ public class DsfUIPlugin extends AbstractUIPlugin {
 	
     private static BundleContext fgBundleContext; 
 
+    public static boolean DEBUG = false;
+
 	/**
 	 * The constructor
 	 */
@@ -41,6 +44,7 @@ public class DsfUIPlugin extends AbstractUIPlugin {
     public void start(BundleContext context) throws Exception {
         fgBundleContext = context;
 		super.start(context);
+	    DEBUG = "true".equals(Platform.getDebugOption("org.eclipse.dd.dsf.ui/debug"));  //$NON-NLS-1$//$NON-NLS-2$
 	}
 
 	/*
@@ -66,5 +70,16 @@ public class DsfUIPlugin extends AbstractUIPlugin {
     public static BundleContext getBundleContext() {
         return fgBundleContext;
     }
+    
+    /**
+     * If the debug flag is set the specified message is printed to the console
+     * @param message
+     */
+    public static void debug(String message) {
+        if (DEBUG) {
+            System.out.println(message);
+        }
+    }
+
 
 }

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/AbstractVMProvider.java

@@ -15,15 +15,16 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
-import java.util.ListIterator;
 import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.concurrent.RejectedExecutionException;
 
+import org.eclipse.core.runtime.Platform;
 import org.eclipse.dd.dsf.concurrent.CountingRequestMonitor;
 import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
 import org.eclipse.dd.dsf.concurrent.IDsfStatusConstants;
 import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.dsf.internal.ui.DsfUIPlugin;
 import org.eclipse.dd.dsf.ui.concurrent.SimpleDisplayExecutor;
 import org.eclipse.dd.dsf.ui.concurrent.ViewerDataRequestMonitor;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenCountUpdate;
@@ -63,7 +64,23 @@ import org.eclipse.swt.widgets.Display;
 @SuppressWarnings("restriction")
 abstract public class AbstractVMProvider implements IVMProvider, IVMEventListener
 {
-    
+    // debug flags
+    public static String DEBUG_PRESENTATION_ID = null;
+    public static boolean DEBUG_CONTENT_PROVIDER = false;
+    public static boolean DEBUG_DELTA = false;
+
+    static {
+        DEBUG_PRESENTATION_ID = Platform.getDebugOption("org.eclipse.dd.dsf.ui/debug/vm/presentationId"); //$NON-NLS-1$
+        if (!DsfUIPlugin.DEBUG || "".equals(DEBUG_PRESENTATION_ID)) { //$NON-NLS-1$
+            DEBUG_PRESENTATION_ID = null;
+        }
+        DEBUG_CONTENT_PROVIDER = DsfUIPlugin.DEBUG && "true".equals( //$NON-NLS-1$
+         Platform.getDebugOption("org.eclipse.dd.dsf.ui/debug/vm/contentProvider")); //$NON-NLS-1$
+
+        DEBUG_DELTA = DsfUIPlugin.DEBUG && "true".equals( //$NON-NLS-1$
+            Platform.getDebugOption("org.eclipse.dd.dsf.ui/debug/vm/delta")); //$NON-NLS-1$
+    }   
+
     /** Reference to the VM adapter that owns this provider */
     private final AbstractVMAdapter fVMAdapter;
     
@@ -126,12 +143,22 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
      */
     private IRootVMNode fRootNode;
     
-    private class ModelProxyEventQueue {
+    private class EventInfo {
-        private boolean fProcessingEvent = false;
+        EventInfo(Object event, RequestMonitor rm) {
-        private List<Object> fEventQueue = new LinkedList<Object>();
+            fEvent = event;
+            fClientRm = rm;
+        }
+        Object fEvent;
+        RequestMonitor fClientRm;
     }
     
-    private Map<IVMModelProxy, ModelProxyEventQueue> fEventQueues = new HashMap<IVMModelProxy, ModelProxyEventQueue>();
+    private class ModelProxyEventQueue {
+        EventInfo fCurrentEvent = null;
+        RequestMonitor fCurrentRm = null;
+        List<EventInfo> fEventQueue = new LinkedList<EventInfo>();
+    }
+    
+    private Map<IVMModelProxy, ModelProxyEventQueue> fProxyEventQueues = new HashMap<IVMModelProxy, ModelProxyEventQueue>();
     
     /**
      * Constructs the view model provider for given DSF session.  The 
@@ -220,25 +247,47 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
 
     	for (final IVMModelProxy proxyStrategy : activeModelProxies) {
             if (proxyStrategy.isDeltaEvent(event)) {
-                if (!fEventQueues.containsKey(proxyStrategy)) {
+                if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
-                    fEventQueues.put(proxyStrategy, new ModelProxyEventQueue());
+                    DsfUIPlugin.debug("eventReceived(proxyRoot = " + proxyStrategy .getRootElement() + ", event = " + event + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
                 }
-                final ModelProxyEventQueue queue = fEventQueues.get(proxyStrategy);
+                if (!fProxyEventQueues.containsKey(proxyStrategy)) {
-                if (queue.fProcessingEvent) {
+                    fProxyEventQueues.put(proxyStrategy, new ModelProxyEventQueue());
-                    if (!queue.fEventQueue.isEmpty()) {
+                    if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
-                        for (ListIterator<Object> itr = queue.fEventQueue.listIterator(queue.fEventQueue.size() - 1); itr.hasPrevious();) {
+                        DsfUIPlugin.debug("eventQueued(proxyRoot = " + proxyStrategy.getRootElement() + ", event = " + event + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
-                            Object eventToSkip = itr.previous();
+                    }
-                            if (canSkipHandlingEvent(event, eventToSkip)) {
+                }
-                                itr.remove();
+                final ModelProxyEventQueue queue = fProxyEventQueues.get(proxyStrategy);
-                            } else {
+                if (queue.fCurrentEvent != null) {
-                                break;
+                    assert queue.fCurrentRm != null;
+                    // Iterate through the events in the queue and check if 
+                    // they can be skipped.  If they can be skipped, then just 
+                    // mark their RM as done.  Stop iterating through the queue
+                    // if an event that cannot be skipped is encountered.
+                    while (!queue.fEventQueue.isEmpty()) {
+                        EventInfo eventToSkipInfo = queue.fEventQueue.get(queue.fEventQueue.size() - 1);
+                        
+                        if (canSkipHandlingEvent(event, eventToSkipInfo.fEvent)) {
+                            if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                DsfUIPlugin.debug("eventSkipped(proxyRoot = " + proxyStrategy.getRootElement() + ", event = " + eventToSkipInfo + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
                             }
+                            queue.fEventQueue.remove(queue.fEventQueue.size() - 1);
+                            eventToSkipInfo.fClientRm.done();
+                        } else {
+                            break;
                         }
                     }
-                    crm.done();
+                    // If the queue is empty check if the current event
-                    queue.fEventQueue.add(event);
+                    // being processed can be skipped.  If so, cancel its
+                    // processing 
+                    if (queue.fEventQueue.isEmpty() && canSkipHandlingEvent(event, queue.fCurrentEvent.fEvent)) {
+                        if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                            DsfUIPlugin.debug("eventCancelled(proxyRoot = " + proxyStrategy.getRootElement() + ", event = " + queue.fCurrentEvent + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
+                        }
+                        queue.fCurrentRm.cancel();
+                    }
+                    queue.fEventQueue.add(new EventInfo(event, crm));
                 } else {
-                    doHandleEvent(queue, proxyStrategy, event, crm);
+                    doHandleEvent(queue, proxyStrategy, new EventInfo(event, crm));
                 }
             } else {
             	crm.done();
@@ -247,28 +296,30 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
 
         // Clean up model proxies that were removed.
         List<IVMModelProxy> activeProxies = getActiveModelProxies();
-        for (Iterator<IVMModelProxy> itr = fEventQueues.keySet().iterator(); itr.hasNext();) {
+        for (Iterator<IVMModelProxy> itr = fProxyEventQueues.keySet().iterator(); itr.hasNext();) {
             if (!activeProxies.contains(itr.next())) {
                 itr.remove();
             }
         }
     }
 
-    private void doHandleEvent(final ModelProxyEventQueue queue, final IVMModelProxy proxyStrategy, final Object event, final RequestMonitor rm) {
+    private void doHandleEvent(final ModelProxyEventQueue queue, final IVMModelProxy proxyStrategy, final EventInfo eventInfo) {
-        queue.fProcessingEvent = true;
+        assert queue.fCurrentEvent == null && queue.fCurrentRm == null;
-        handleEvent(
+        
-            proxyStrategy, event, 
+        queue.fCurrentEvent = eventInfo;
-            new RequestMonitor(getExecutor(), null) {
+        queue.fCurrentRm = new RequestMonitor(getExecutor(), null) {
-                @Override
+            @Override
-                protected void handleCompleted() {
+            protected void handleCompleted() {
-                    queue.fProcessingEvent = false;
+                queue.fCurrentEvent = null;
-                    if (!queue.fEventQueue.isEmpty()) {
+                queue.fCurrentRm = null;
-                        doHandleEvent(queue, proxyStrategy, queue.fEventQueue.remove(0), rm);
+                if (!queue.fEventQueue.isEmpty()) {
-                    } else {
+                    EventInfo eventInfo = queue.fEventQueue.remove(0);
-                    	rm.done();
+                    doHandleEvent(queue, proxyStrategy, eventInfo);
-                    }
+                } 
-                }
+                eventInfo.fClientRm.done();
-            });
+            }
+        };
+        handleEvent(proxyStrategy, eventInfo.fEvent, queue.fCurrentRm);
     }
 
     /**
@@ -287,6 +338,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
      */
     protected void handleEvent(final IVMModelProxy proxyStrategy, final Object event, RequestMonitor rm) {   
         if (!proxyStrategy.isDisposed()) {
+            if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                DsfUIPlugin.debug("eventProcessing(proxyRoot = " + proxyStrategy.getRootElement() + ", event = " + event + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
+            }
             proxyStrategy.createDelta(
                 event, 
                 new DataRequestMonitor<IModelDelta>(getExecutor(), rm) {
@@ -294,6 +348,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
                     public void handleCompleted() {
                         if (isSuccess()) {
                             proxyStrategy.fireModelChanged(getData());
+                            if (DEBUG_DELTA && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                DsfUIPlugin.debug("eventDeltaFired(proxyRoot = " + proxyStrategy.getRootElement() + ", event = " + event + ")" );  //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
+                            }
                         }
                         super.handleCompleted();
                     }
@@ -439,6 +496,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
         IHasChildrenUpdate[] updateProxies = new IHasChildrenUpdate[updates.length];
         for (int i = 0; i < updates.length; i++) {
             final IHasChildrenUpdate update = updates[i];
+            if (DEBUG_CONTENT_PROVIDER && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                DsfUIPlugin.debug("updateNodeHasChildren(node = " + node + ", update = " + update + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
+            }
             updateProxies[i] = new VMHasChildrenUpdate(
                 update,
                 new ViewerDataRequestMonitor<Boolean>(getExecutor(), updates[i]) {
@@ -451,6 +511,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
                     @Override
                     protected void handleErrorOrWarning() {
                         if (getStatus().getCode() == IDsfStatusConstants.NOT_SUPPORTED) {
+                            if (DEBUG_CONTENT_PROVIDER && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                DsfUIPlugin.debug("not-supported:updateNodeHasChildren(node = " + node + ", update = " + update + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
+                            }
                             updateNode(
                                 node, 
                                 new VMChildrenUpdate(
@@ -484,6 +547,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
      * a cache. 
      */
     public void updateNode(final IVMNode node, final IChildrenCountUpdate update) {
+        if (DEBUG_CONTENT_PROVIDER && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+            DsfUIPlugin.debug("updateNodeChildCount(node = " + node + ", update = " + update + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
+        }
         node.update(new IChildrenCountUpdate[] { 
             new VMChildrenCountUpdate(
                 update,
@@ -497,6 +563,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
                     @Override
                     protected void handleErrorOrWarning() {
                         if (getStatus().getCode() == IDsfStatusConstants.NOT_SUPPORTED) {
+                            if (DEBUG_CONTENT_PROVIDER && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                DsfUIPlugin.debug("not-supported:updateNodeChildCount(node = " + node + ", update = " + update + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
+                            }
                             updateNode(
                                 node, 
                                 new VMChildrenUpdate(
@@ -527,6 +596,9 @@ abstract public class AbstractVMProvider implements IVMProvider, IVMEventListene
      * a cache. 
      */
     public void updateNode(IVMNode node, IChildrenUpdate update) {
+        if (DEBUG_CONTENT_PROVIDER && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+            DsfUIPlugin.debug("updateNodeChildren(node = " + node + ", update = " + update + ")");
+        }
         node.update(new IChildrenUpdate[] { update });
     }
 

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/DefaultVMModelProxyStrategy.java

@@ -17,7 +17,6 @@ import java.util.Map;
 
 import org.eclipse.core.runtime.ISafeRunnable;
 import org.eclipse.core.runtime.ListenerList;
-import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.SafeRunner;
 import org.eclipse.dd.dsf.concurrent.ConfinedToDsfExecutor;
 import org.eclipse.dd.dsf.concurrent.CountingRequestMonitor;
@@ -63,16 +62,6 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
     private ListenerList fListeners = new ListenerList();
 	private IDoubleClickListener fDoubleClickListener;
     
-    /**
-     * Debug flag indicating whether the deltas should be traced in stdout. 
-     */
-    private static boolean DEBUG_DELTAS = false;
-    
-    static {
-        DEBUG_DELTAS = DebugUIPlugin.DEBUG && "true".equals( //$NON-NLS-1$
-         Platform.getDebugOption("org.eclipse.debug.ui/debug/viewers/deltas")); //$NON-NLS-1$
-    }   
-
     /**
      * Creates this model proxy strategy for the given provider. 
      */
@@ -122,9 +111,6 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
     public void fireModelChanged(IModelDelta delta) {
         final IModelDelta root = getRootDelta(delta);
         Object[] listeners = getListeners();
-        if (DEBUG_DELTAS) {
-            DebugUIPlugin.debug("FIRE DELTA: " + delta.toString()); //$NON-NLS-1$
-        }
         for (int i = 0; i < listeners.length; i++) {
             final IModelChangedListener listener = (IModelChangedListener) listeners[i];
             ISafeRunnable safeRunnable = new ISafeRunnable() {
@@ -353,6 +339,8 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
                         // super-class to resort to the default behavior which may add a 
                         // delta for every element in this node.
                         buildChildDeltasForAllContexts(node, event, parentDelta, nodeOffset, rm);
+                    } else {
+                        super.handleCompleted();
                     }
                 }
             });
@@ -388,13 +376,13 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
                 node, 
                 new VMChildrenUpdate(
                     parentDelta, getVMProvider().getPresentationContext(), -1, -1,
-                    new DataRequestMonitor<List<Object>>(getVMProvider().getExecutor(), null) {
+                    new DataRequestMonitor<List<Object>>(getVMProvider().getExecutor(), requestMonitor) {
                         @Override
-                        protected void handleCompleted() {
+                        protected void handleSuccess() {
                             // Check for an empty list of elements.  If it's empty then we 
                             // don't have to call the children nodes, so return here.
                             // No need to propagate error, there's no means or need to display it.
-                            if (!isSuccess() || getData().isEmpty()) {
+                            if (getData().isEmpty()) {
                                 requestMonitor.done();
                                 return;
                             }
@@ -490,13 +478,12 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
                     parentDelta, getVMProvider().getPresentationContext(), -1, -1,
                     new DataRequestMonitor<List<Object>>(getVMProvider().getExecutor(), requestMonitor) {
                         @Override
-                        protected void handleCompleted() {
+                        protected void handleSuccess() {
                             if (fDisposed) return;
                             
                             // Check for an empty list of elements.  If it's empty then we 
                             // don't have to call the children nodes, so return here.
-                            // No need to propagate error, there's no means or need to display it.
+                            if (getData().size() == 0) {
-                            if (!isSuccess() || getData().size() == 0) {
                                 requestMonitor.done();
                                 return;
                             }
@@ -556,7 +543,7 @@ public class DefaultVMModelProxyStrategy implements IVMModelProxy {
             node, delta, calculateOffsets, 
             new DataRequestMonitor<Map<IVMNode, Integer>>(getVMProvider().getExecutor(), requestMonitor) {
                 @Override
-                protected void handleCompleted() {
+                protected void handleSuccess() {
                     final CountingRequestMonitor multiRm = new CountingRequestMonitor(getVMProvider().getExecutor(), requestMonitor);
                     int multiRmCount = 0;
                     

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/VMChildrenCountUpdate.java

@@ -45,6 +45,11 @@ public class VMChildrenCountUpdate extends VMViewerUpdate implements IChildrenCo
         fCountRequestMonitor.setData(count);
     }
     
+    @Override
+    public String toString() {
+        return "VMChildrenCountUpdate: " + getElement(); //$NON-NLS-1$
+    }
+    
     @Override
     public void done() {
         assert isCanceled() || fCountRequestMonitor.getData() != null || !fCountRequestMonitor.isSuccess();

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/VMChildrenUpdate.java

@@ -13,11 +13,7 @@ package org.eclipse.dd.dsf.ui.viewmodel;
 import java.util.ArrayList;
 import java.util.List;
 
-import org.eclipse.core.runtime.IStatus;
-import org.eclipse.core.runtime.Status;
 import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
-import org.eclipse.dd.dsf.concurrent.IDsfStatusConstants;
-import org.eclipse.dd.dsf.internal.ui.DsfUIPlugin;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IModelDelta;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext;
@@ -92,7 +88,7 @@ public class VMChildrenUpdate extends VMViewerUpdate implements IChildrenUpdate
         
     @Override
     public String toString() {
-        return "VMElementsUpdate for elements under parent = " + getElement() + ", in range " + getOffset() + " -> " + (getOffset() + getLength());  //$NON-NLS-1$ //$NON-NLS-2$//$NON-NLS-3$
+        return "VMChildrenUpdate:" + getElement() + " {"+ getOffset() + "->" + (getOffset() + getLength()) + "}";  //$NON-NLS-1$ //$NON-NLS-2$//$NON-NLS-3$ //$NON-NLS-4$
     }
 
     @Override
@@ -105,32 +101,21 @@ public class VMChildrenUpdate extends VMViewerUpdate implements IChildrenUpdate
          * A flexible hierarchy bug/optimization causes query with incorrect
          * IChildrenUpdate[] array length.
          *
-         * We found this while deleting a register node. Example:
+         * The problem manifests itself while deleting a register node. 
-         * 
+         * For example, if the register view displays:
-         *  the register view displays:
          *     PC
          *     EAX
          *     EBX
          *     ECX
          *     EDX
-         * 
+         *  And EBX is deleted, forcing a refresh, the viewer will query 
-         *   we delete EBX and force a context refresh.
+         *  for IChildrenUpdate[5] and IChildrenCountUpdate at the same time.
-         * 
+         *  
-         *   flexible hierarchy queries for IChildrenUpdate[5] and IChildrenCountUpdate at
+         *  To avoid this problem do not generate an error if the list of 
-         * the same time.
+         *  children is smaller than the list of requested indexes.  Also,
-         * 
+         *  do not check if any of the elements are null.
-         *   VMElementsUpdate, used by VMCache to wrap the IChildrenUpdate, generates an
-         * IStatus.ERROR with message "Incomplete elements of updates" when fElements
-         * count (provided by service) does not match the length provided by the original
-         * update query.
-         * 
-         * Workaround, always set the elements array in the request monitor, but still set 
-         * the error status. 
          */        
         rm.setData(fElements);
-        if (rm.isSuccess() && fLength != -1 && fElements.size() != fLength) {
-            rm.setStatus(new Status(IStatus.ERROR, DsfUIPlugin.PLUGIN_ID, IDsfStatusConstants.REQUEST_FAILED, "Incomplete elements of updates", null)); //$NON-NLS-1$
-        }
         super.done();
     }
     

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/VMHasChildrenUpdate.java

@@ -46,6 +46,11 @@ public class VMHasChildrenUpdate extends VMViewerUpdate implements IHasChildrenU
         fHasElemsRequestMonitor.setData(hasChildren);
     }
 
+    @Override
+    public String toString() {
+        return "VMHasChildrenUpdate: " + getElement(); //$NON-NLS-1$
+    }
+    
     @Override
     public void done() {
         assert isCanceled() || fHasElemsRequestMonitor.getData() != null || !fHasElemsRequestMonitor.isSuccess();

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/update/AbstractCachingVMProvider.java

@@ -20,6 +20,7 @@ import java.util.Map;
 import java.util.concurrent.Executor;
 
 import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Platform;
 import org.eclipse.dd.dsf.concurrent.CountingRequestMonitor;
 import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
 import org.eclipse.dd.dsf.concurrent.DsfRunnable;
@@ -27,6 +28,7 @@ import org.eclipse.dd.dsf.concurrent.RequestMonitor;
 import org.eclipse.dd.dsf.datamodel.IDMContext;
 import org.eclipse.dd.dsf.datamodel.IDMData;
 import org.eclipse.dd.dsf.datamodel.IDMService;
+import org.eclipse.dd.dsf.internal.ui.DsfUIPlugin;
 import org.eclipse.dd.dsf.ui.concurrent.ViewerCountingRequestMonitor;
 import org.eclipse.dd.dsf.ui.concurrent.ViewerDataRequestMonitor;
 import org.eclipse.dd.dsf.ui.viewmodel.AbstractVMAdapter;
@@ -53,6 +55,14 @@ import org.eclipse.jface.viewers.TreePath;
 @SuppressWarnings("restriction")
 public class AbstractCachingVMProvider extends AbstractVMProvider implements ICachingVMProvider {
 
+    // debug flags
+    public static boolean DEBUG_CACHE = false;
+
+    static {
+        DEBUG_CACHE = DsfUIPlugin.DEBUG && "true".equals( //$NON-NLS-1$
+         Platform.getDebugOption("org.eclipse.dd.dsf.ui/debug/vm/cache")); //$NON-NLS-1$
+    }   
+
     private static final int MAX_CACHE_SIZE = 1000;
 
     /**
@@ -139,14 +149,60 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
             super(key);
         }
         
+        /**
+         * Counter of flush operations performed on this entry.  It is used
+         * by caching update operations to make sure that an update which
+         * was issued for a given entry is still valid for that entry when
+         * it is completed by the node. 
+         */
+        int fFlushCounter = 0;
+        
+        /**
+         * Indicates that the data in this cache entry is out of date with
+         * the data on the target.
+         */
         Boolean fDirty = false;
+        
+        /** 
+         * Cached {@link IHasChildrenUpdate} result. 
+         */
         Boolean fHasChildren = null;
+
+        /** 
+         * Cached {@link IChildrenCountUpdate} result. 
+         */
         Integer fChildrenCount = null;
+        
+        /**
+         * Flag indicating that all the children of the given element are 
+         * alredy cached.
+         */
         boolean fAllChildrenKnown = false;
+        
+        /**
+         * Map containing children of this element, keyed by child index.
+         */
         Map<Integer,Object> fChildren = null;
+        
+        /**
+         * Map of IDMData objects, keyed by the DM context.
+         */
         Map<IDMContext,Object> fDataOrStatus = new HashMap<IDMContext,Object>(1);
+        
+        /**
+         * Previous known value of the DM data objects.
+         */
         Map<IDMContext,IDMData> fArchiveData = new HashMap<IDMContext,IDMData>(1);;
         
+        void ensureChildrenMap() {
+            if (fChildren == null) {
+                Integer childrenCount = fChildrenCount;
+                childrenCount = childrenCount != null ? childrenCount : 0;
+                int capacity = Math.max((childrenCount.intValue() * 4)/3, 32);
+                fChildren = new HashMap<Integer,Object>(capacity);
+            }
+        }
+        
         @Override
         public String toString() {
             return fKey.toString() + " = " + //$NON-NLS-1$ 
@@ -315,23 +371,38 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
     }
     
     @Override
-    public void updateNode(IVMNode node, IHasChildrenUpdate[] updates) {
+    public void updateNode(final IVMNode node, IHasChildrenUpdate[] updates) {
         LinkedList <IHasChildrenUpdate> missUpdates = new LinkedList<IHasChildrenUpdate>();
         for(final IHasChildrenUpdate update : updates) {
+            // Find or create the cache entry for the element of this update.
             ElementDataKey key = makeEntryKey(node, update);
             final ElementDataEntry entry = getElementDataEntry(key);
+            
             if (entry.fHasChildren != null) {
+                // Cache Hit!  Just return the value.
+                if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                    DsfUIPlugin.debug("cacheHitHasChildren(node = " + node + ", update = " + update + ", " + entry.fHasChildren + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
+                }
                 update.setHasChilren(entry.fHasChildren.booleanValue());
                 update.done();
             } else {
+                // Cache miss!  Save the flush counter of the entry and create a proxy update.
+                final int flushCounter = entry.fFlushCounter;
                 missUpdates.add( 
                     new VMHasChildrenUpdate(
                         update, 
                         new ViewerDataRequestMonitor<Boolean>(getExecutor(), update) {
                             @Override
                             protected void handleCompleted() {
+                                // Update completed.  Write value to cache only if update successed 
+                                // and the cache entry wasn't flushed in the mean time. 
                                 if(isSuccess()) {
-                                    entry.fHasChildren = this.getData();
+                                    if (flushCounter == entry.fFlushCounter) {
+                                        if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                            DsfUIPlugin.debug("cacheSavedHasChildren(node = " + node + ", update = " + update + ", " + getData() + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
+                                        }
+                                        entry.fHasChildren = this.getData();
+                                    }
                                     update.setHasChilren(getData());
                                 } else {
                                     update.setStatus(getStatus());
@@ -342,26 +413,42 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
             }
         }
         
+        // Issue all the update proxies with one call.
         if (!missUpdates.isEmpty()) {
             super.updateNode(node, missUpdates.toArray(new IHasChildrenUpdate[missUpdates.size()]));
         }
     }
     
     @Override
-    public void updateNode(IVMNode node, final IChildrenCountUpdate update) {
+    public void updateNode(final IVMNode node, final IChildrenCountUpdate update) {
+        // Find or create the cache entry for the element of this update.
         ElementDataKey key = makeEntryKey(node, update);
         final ElementDataEntry entry = getElementDataEntry(key);
+        
         if(entry.fChildrenCount != null) {
+            // Cache Hit!  Just return the value.
+            if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                DsfUIPlugin.debug("cacheHitChildrenCount(node = " + node + ", update = " + update + ", " + entry.fChildrenCount + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
+            }
             update.setChildCount(entry.fChildrenCount.intValue());
             update.done();
         } else {
+            // Cache miss!  Save the flush counter of the entry and create a proxy update.
+            final int flushCounter = entry.fFlushCounter;
             IChildrenCountUpdate updateProxy = new VMChildrenCountUpdate(
                 update, 
                 new ViewerDataRequestMonitor<Integer>(getExecutor(), update) {
                     @Override
                     protected void handleCompleted() {
+                        // Update completed.  Write value to cache only if update successed 
+                        // and the cache entry wasn't flushed in the mean time. 
                         if(isSuccess()) {
-                            entry.fChildrenCount = this.getData();
+                            if (flushCounter == entry.fFlushCounter) {
+                                if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                    DsfUIPlugin.debug("cacheSavedChildrenCount(node = " + node + ", update = " + update + ", " + getData() + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$
+                                }
+                                entry.fChildrenCount = this.getData();
+                            }
                             update.setChildCount(getData());
                         } else {
                             update.setStatus(getStatus());
@@ -374,61 +461,70 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
     }
 
     @Override
-    public void updateNode(IVMNode node, final IChildrenUpdate update) {
+    public void updateNode(final IVMNode node, final IChildrenUpdate update) {
-        
+        // Find or create the cache entry for the element of this update.
         ElementDataKey key = makeEntryKey(node, update);
-        
         final ElementDataEntry entry = getElementDataEntry(key);
+        
+        final int flushCounter = entry.fFlushCounter;
         if (entry.fChildren == null || (update.getOffset() < 0 && !entry.fAllChildrenKnown)) {
-            // We need to retrieve all the children if we don't have any children information.
+            // Need to retrieve all the children if there is no children information yet.
-            // Or if the client requested all children (offset = -1, length -1) and we have not
+            // Or if the client requested all children (offset = -1, length -1) and all 
-            // retrieved that before.
+            // the children are not yet known.
             IChildrenUpdate updateProxy = new VMChildrenUpdate(
                 update, update.getOffset(), update.getLength(),
                 new ViewerDataRequestMonitor<List<Object>>(getExecutor(), update){
                     @Override
-                    protected void handleCompleted()
+                    protected void handleSuccess() {
-                    {
+                        // Check if the update retrieved all children by specifying "offset = -1, length = -1"
-                        // Workaround for a bug caused by an optimization in the viewer:
+                        int updateOffset = update.getOffset();
-                        // The viewer may request more children then there are at a given level.  
+                        if (updateOffset < 0) 
-                        // This causes the update to return with an error.
+                        {
-                        // See https://bugs.eclipse.org/bugs/show_bug.cgi?id=202109
+                            updateOffset = 0;
-                        // Instead of checking isSuccess(), check getData() != null.
+                            if (entry.fFlushCounter == flushCounter) {
-                        if(getData() != null && !isCanceled()) {
-                            // Check if the udpate retrieved all children by specifying "offset = -1, length = -1"
-                            int updateOffset = update.getOffset();
-                            if (updateOffset < 0) {
-                                updateOffset = 0;
                                 entry.fAllChildrenKnown = true;
                             }
-                            
+                        }
-                            // Estimate size of children map.
+
-                            Integer childrenCount = entry.fChildrenCount;
+                        if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
-                            childrenCount = childrenCount != null ? childrenCount : 0;
+                            DsfUIPlugin.debug("cacheSavedChildren(node = " + node + ", update = " + update + ", children = {" + updateOffset + "->" + (updateOffset + getData().size()) + "})"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$
-                            int capacity = Math.max((childrenCount.intValue() * 4)/3, 32);
+                        }
-                            // Create a new map, but only if it hasn't been created yet by another update.
+
-                            if (entry.fChildren == null) {
+                        if (flushCounter == entry.fFlushCounter) {
-                                entry.fChildren = new HashMap<Integer,Object>(capacity);
+                            entry.ensureChildrenMap();
-                            }
+                        }
-                            
+                        
-                            // Set the children to map and update.
+                        // Set the children to map and update.
-                            for(int j = 0; j < getData().size(); j++) {
+                        for(int j = 0; j < getData().size(); j++) {
-                                int offset = updateOffset + j;
+                            int offset = updateOffset + j;
-                                Object child = getData().get(j);
+                            Object child = getData().get(j);
-                                if (child != null) {
+                            if (child != null) {
+                                if (flushCounter == entry.fFlushCounter) {
                                     entry.fChildren.put(offset, child);
-                                    update.setChild(child, offset);
                                 }
+                                update.setChild(child, offset);
                             }
                         }
                         update.done();
                     }
+                    
+                    @Override
+                    protected void handleCancel() {
+                        if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                            DsfUIPlugin.debug("cacheCanceledChildren(node = " + node + ", update = " + update + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ 
+                        }
+                        super.handleCancel();
+                    }
                 });
             super.updateNode(node, updateProxy);
         } else if (update.getOffset() < 0 ) {
             // The update requested all children.  Fill in all children assuming that 
             // the children array is complete.
-            
+
+            if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                DsfUIPlugin.debug("cacheHitChildren(node = " + node + ", update = " + update + ", children = " + entry.fChildren.keySet() + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ 
+            }
+
             // The following assert should never fail given the first if statement. 
             assert entry.fAllChildrenKnown;
             
@@ -438,13 +534,15 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
             }
             update.done();
         } else {
-            // Make the list of missing children.  If we've retrieved the 
+            // Update for a partial list of children was requested.
+            // Iterate through the known children and make a list of missing 
+            // indexes.   
             List<Integer> childrenMissingFromCache = new LinkedList<Integer>();
             for (int i = update.getOffset(); i < update.getOffset() + update.getLength(); i++) {
                 childrenMissingFromCache.add(i);
             }
 
-            // Fill in the known children from cache.
+            // Write known children from cache into the update.
             for(Integer position = update.getOffset(); position < update.getOffset() + update.getLength(); position++) {
                 Object child = entry.fChildren.get(position);
                 if (child != null) {
@@ -453,13 +551,15 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
                 }
             }
             
+            if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                DsfUIPlugin.debug("cachePartialHitChildren(node = " + node + ", update = " + update + ", missing = " + childrenMissingFromCache + ")"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ 
+            }
+            
             if (childrenMissingFromCache.size() > 0) {
-                // perform a partial update; we only have some of the children of the update request
+                // Some children were not found in the cache, create separate 
-
+                // proxy updates for the continuous ranges of missing children.
                 List<IChildrenUpdate> partialUpdates = new ArrayList<IChildrenUpdate>(2);
-
                 final CountingRequestMonitor multiRm = new ViewerCountingRequestMonitor(getExecutor(), update);
-                
                 while(childrenMissingFromCache.size() > 0)
                 {
                     final int offset = childrenMissingFromCache.get(0);
@@ -475,10 +575,22 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
                         update, offset, length,
                         new DataRequestMonitor<List<Object>>(getExecutor(), multiRm) {
                             @Override
-                            protected void handleCompleted() {
+                            protected void handleSuccess() {
-                                if (getData() != null) {
+                                // Only save the children to the cahce if the entry wasn't flushed.
-                                    for (int i = 0; i < getData().size(); i++) {
+                                if (flushCounter == entry.fFlushCounter) {
+                                    if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+                                        DsfUIPlugin.debug("cachePartialSaveChildren(node = " + node + ", update = " + update + ", saved = {" + offset + "->" + (offset + getData().size()) + "})"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$ //$NON-NLS-4$ //$NON-NLS-5$ 
+                                    }
+                                    entry.ensureChildrenMap();
+                                }
+                                
+                                for (int i = 0; i < getData().size(); i++) {
+                                    if (getData().get(i) != null) {
                                         update.setChild(getData().get(i), offset + i);
+                                        if (flushCounter == entry.fFlushCounter) {
+                                            // Only save the children to the cahce if the entry wasn't flushed.
+                                            entry.fChildren.put(offset + i, getData().get(i));
+                                        }
                                     }
                                 }
                                 multiRm.done();
@@ -491,7 +603,7 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
                 }
                 multiRm.setDoneCount(partialUpdates.size());
             } else {
-                // we have all of the children in cache; return from cache
+                // All children were found in cache.  Compelte the update.
                 update.done();
             }
         }
@@ -506,6 +618,9 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
      * @param archive
      */
     private void flush(FlushMarkerKey flushKey) {
+        if (DEBUG_CACHE && (DEBUG_PRESENTATION_ID == null || getPresentationContext().getId().equals(DEBUG_PRESENTATION_ID))) {
+            DsfUIPlugin.debug("cacheFlushing(" + flushKey + ")"); //$NON-NLS-1$ //$NON-NLS-2$  
+        }
         // For each entry that has the given context as a parent, perform the flush.
         // Iterate through the cache entries backwards.  This means that we will be
         // iterating in order of most-recently-used to least-recently-used.
@@ -528,6 +643,7 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
                 // now.
                 if (entryFlushKey.includes(flushKey)) {
                     break;
+
                 }
             }
             else if (entry instanceof ElementDataEntry) {
@@ -561,9 +677,11 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
                             entry.remove();
                         }
                     }
+                    elementDataEntry.fFlushCounter++;                    
                     elementDataEntry.fHasChildren = null;
                     elementDataEntry.fChildrenCount = null;
                     elementDataEntry.fChildren = null;
+                    elementDataEntry.fAllChildrenKnown = false;
                     elementDataEntry.fDirty = false;
                 } else if ((updateFlags & IVMUpdatePolicy.DIRTY) != 0) {
                     elementDataEntry.fDirty = true;
@@ -754,7 +872,9 @@ public class AbstractCachingVMProvider extends AbstractVMProvider implements ICa
 	                						entry.fDataOrStatus.put(dmc, getData());
 	                						rm.setData(getData());
 	                					} else {
-	                						entry.fDataOrStatus.put(dmc, getStatus());
+	                					    if (!isCanceled()) {
+	                					        entry.fDataOrStatus.put(dmc, getStatus());
+	                					    }
 	                						rm.setStatus(getStatus());
 	                					}
 	                					rm.done();

plugins/org.eclipse.dd.dsf/src/org/eclipse/dd/dsf/concurrent/RequestMonitor.java

@@ -136,7 +136,10 @@ public class RequestMonitor {
      * Sets the status of the result of the request.  If status is OK, this 
      * method does not need to be called. 
      */
-    public synchronized void setStatus(IStatus status) { fStatus = status; }
+    public synchronized void setStatus(IStatus status) { 
+        assert isCanceled() || status.getSeverity() != IStatus.CANCEL; 
+        fStatus = status; 
+    }
     
     /** Returns the status of the completed method. */
     public synchronized IStatus getStatus() {