Bugzilla 205603 & 221899.

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/launch/StackFramesVMNode.java

@@ -71,7 +71,11 @@ public class StackFramesVMNode extends AbstractDMVMNode
 
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(IStack.class, null, update)) return;
+    	
+        if ( getServicesTracker().getService(IStack.class) == null ) {
+                handleFailedUpdate(update);
+                return;
+        }
         
         final IExecutionDMContext execDmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IExecutionDMContext.class);
         if (execDmc == null) {
@@ -88,7 +92,10 @@ public class StackFramesVMNode extends AbstractDMVMNode
                         // Failed to retrieve frames.  If we are stepping, we 
                         // might still be able to retrieve just the top stack 
                         // frame, which would still be useful in Debug View.
-                        if (!checkService(IRunControl.class, null, update)) return;                        
+                        if ( getServicesTracker().getService(IRunControl.class) == null ) {
+                        	handleFailedUpdate(update);
+                        	return;
+                        }
                         if (getServicesTracker().getService(IRunControl.class).isStepping(execDmc)) {
                             getElementsTopStackFrameOnly(update);
                         } else {
@@ -121,8 +128,11 @@ public class StackFramesVMNode extends AbstractDMVMNode
         try {
             getSession().getExecutor().execute(new DsfRunnable() {
                 public void run() {
-                    if (!checkService(IStack.class, null, update)) return;
+                	if ( getServicesTracker().getService(IStack.class) == null ) {
-
+                		handleFailedUpdate(update);
+                		return;
+                	}
+                
                     getServicesTracker().getService(IStack.class).getTopFrame(
                         execDmc, 
                         new DataRequestMonitor<IFrameDMContext>(getExecutor(), null) { 
@@ -173,7 +183,16 @@ public class StackFramesVMNode extends AbstractDMVMNode
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
             final IFrameDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IFrameDMContext.class);
-            if (!checkDmc(dmc, update) || !checkService(IStack.class, null, update)) continue;
+            
+            if ( dmc == null ) {
+            	handleFailedUpdate(update);
+            	continue;
+            }
+            if ( getServicesTracker().getService(IStack.class) == null ) {
+            	handleFailedUpdate(update);
+            	continue;
+            }
+        
             
             getDMVMProvider().getModelData(
                 this, update, 

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/modules/ModulesVMNode.java

@@ -42,7 +42,11 @@ public class ModulesVMNode extends AbstractDMVMNode
     
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(IModules.class, null, update)) return;
+    	
+        if ( getServicesTracker().getService(IModules.class) == null ) {
+            handleFailedUpdate(update);
+            return;
+    	}
         
         final ISymbolDMContext symDmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), ISymbolDMContext.class) ;
         
@@ -83,7 +87,16 @@ public class ModulesVMNode extends AbstractDMVMNode
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
             final IModuleDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IModuleDMContext.class);
-            if (!checkDmc(dmc, update) || !checkService(IModules.class, null, update)) continue;
+            // If either update or service are not valid, fail the update and exit.
+            if ( dmc == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
+            if ( getServicesTracker().getService(IModules.class) == null ) {
+                handleFailedUpdate(update);
+                continue;
+        	}
+            
             // Use  different image for loaded and unloaded symbols when event to report loading of symbols is implemented.
             update.setImageDescriptor(DsfDebugUIPlugin.getImageDescriptor(IDsfDebugUIConstants.IMG_OBJS_SHARED_LIBRARY_SYMBOLS_LOADED), 0);
       

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/register/RegisterBitFieldVMNode.java

@@ -29,6 +29,7 @@ import org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.numberformat.I
 import org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.register.RegisterBitFieldCellModifier.BitFieldEditorStyle;
 import org.eclipse.dd.dsf.debug.internal.ui.DsfDebugUIPlugin;
 import org.eclipse.dd.dsf.debug.service.IFormattedValues;
+import org.eclipse.dd.dsf.debug.service.IMemory;
 import org.eclipse.dd.dsf.debug.service.IRegisters;
 import org.eclipse.dd.dsf.debug.service.IRunControl;
 import org.eclipse.dd.dsf.debug.service.IFormattedValues.FormattedValueDMContext;
@@ -69,9 +70,8 @@ import org.eclipse.swt.widgets.Composite;
 
 @SuppressWarnings("restriction")
 public class RegisterBitFieldVMNode extends AbstractExpressionVMNode 
-    implements IElementEditor, IElementLabelProvider 
+    implements IElementEditor, IElementLabelProvider
 {
-
     protected class BitFieldVMC extends DMVMContext
         implements IFormattedValueVMContext
     {
@@ -271,7 +271,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         );
     }
     
-    
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementLabelProvider#update(org.eclipse.debug.internal.ui.viewers.model.provisional.ILabelUpdate[])
+     */
     public void update(final ILabelUpdate[] updates) {
         try {
             getSession().getExecutor().execute(new DsfRunnable() {
@@ -285,17 +288,25 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         }
     }
 
-    
+    /*
+     * Updates the requested label based on the specified column.
+     */
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
             
-            if (!checkService(IRegisters.class, null, update)) continue;
+        	final IRegisters regService = getServicesTracker().getService(IRegisters.class);
+            
+            if ( regService == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
             
             final IBitFieldDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IRegisters.IBitFieldDMContext.class);
             
             getDMVMProvider().getModelData(
-                this, update, 
+                this, 
-				getServicesTracker().getService(IRegisters.class),
+                update, 
+				regService,
                 dmc, 
                 new DataRequestMonitor<IBitFieldDMData>(getSession().getExecutor(), null) { 
                     @Override
@@ -422,6 +433,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         }
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#updateElementsInSessionThread(org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate)
+     */
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
         final IRegisterDMContext regDmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IRegisterDMContext.class);
@@ -431,9 +446,15 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
             return;
         }          
         
-        if (!checkService(IRegisters.class, null, update)) return;
+        IRegisters regService = getServicesTracker().getService(IRegisters.class);
         
-        getServicesTracker().getService(IRegisters.class).getBitFields(
+        if ( regService == null ) {
+        	handleFailedUpdate(update);
+            return;
+        }
+        
+        
+        regService.getBitFields(
             regDmc,
             new DataRequestMonitor<IBitFieldDMContext[]>(getSession().getExecutor(), null) {
                 @Override
@@ -449,11 +470,19 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
             });            
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#createVMContext(org.eclipse.dd.dsf.datamodel.IDMContext)
+     */
     @Override
     protected IDMVMContext createVMContext(IDMContext dmc) {
         return new BitFieldVMC(dmc);
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#getDeltaFlags(java.lang.Object)
+     */
     public int getDeltaFlags(Object e) {
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
@@ -463,6 +492,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
             return IModelDelta.STATE;
         }
 
+        if (e instanceof IMemory.IMemoryChangedEvent) {
+            return IModelDelta.CONTENT;
+        }
+        
         if (e instanceof PropertyChangeEvent && 
             ((PropertyChangeEvent)e).getProperty() == IDebugVMConstants.CURRENT_FORMAT_STORAGE) 
         {
@@ -472,6 +505,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         return IModelDelta.NO_CHANGE;
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#buildDelta(java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, int, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDelta(Object e, VMDelta parentDelta, int nodeOffset, RequestMonitor rm) {
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             // Create a delta that the whole register group has changed.
@@ -479,14 +516,17 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         } 
 
         if (e instanceof IRegisters.IBitFieldChangedDMEvent) {
-            
             /*
              *  Create a delta indicating the bit field has changed.
              */
             parentDelta.addNode( createVMContext(((IRegisters.IBitFieldChangedDMEvent)e).getDMContext()), IModelDelta.STATE );
         } 
 
-        if (e instanceof PropertyChangeEvent && 
+        if (e instanceof IMemory.IMemoryChangedEvent) {
+        	parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
+        }
+        
+        if (e instanceof PropertyChangeEvent &&
             ((PropertyChangeEvent)e).getProperty() == IDebugVMConstants.CURRENT_FORMAT_STORAGE) 
         {
             parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
@@ -495,6 +535,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         rm.done();
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellEditor(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.String, java.lang.Object, org.eclipse.swt.widgets.Composite)
+     */
     public CellEditor getCellEditor(IPresentationContext context, String columnId, Object element, Composite parent) {
         
         if (IDebugVMConstants.COLUMN_ID__VALUE.equals(columnId)) {
@@ -541,6 +585,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         return null;
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellModifier(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.Object)
+     */
     public ICellModifier getCellModifier(IPresentationContext context, Object element) {
         
         /*
@@ -628,6 +676,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         return null;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#testElementForExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression, org.eclipse.dd.dsf.concurrent.DataRequestMonitor)
+     */
     @Override
     protected void testElementForExpression(Object element, IExpression expression, final DataRequestMonitor<Boolean> rm) {
         if (!(element instanceof IDMVMContext)) {
@@ -670,6 +722,10 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         }
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#associateExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression)
+     */
     @Override
     protected void associateExpression(Object element, IExpression expression) {
         if (element instanceof BitFieldVMC) {
@@ -677,33 +733,56 @@ public class RegisterBitFieldVMNode extends AbstractExpressionVMNode
         }
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#getDeltaFlagsForExpression(org.eclipse.debug.core.model.IExpression, java.lang.Object)
+     */
     public int getDeltaFlagsForExpression(IExpression expression, Object event) {
         if (event instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
         }
 
         if (event instanceof PropertyChangeEvent && 
-            ((PropertyChangeEvent)event).getProperty() == IDebugVMConstants.CURRENT_FORMAT_STORAGE) 
+            ((PropertyChangeEvent)event).getProperty() == IDebugVMConstants.CURRENT_FORMAT_STORAGE) {
-        {
             return IModelDelta.CONTENT;            
         }
 
+        if (event instanceof IMemory.IMemoryChangedEvent) {
+            return IModelDelta.CONTENT;
+        }
+        
         return IModelDelta.NO_CHANGE;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpression(org.eclipse.debug.core.model.IExpression, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.jface.viewers.TreePath, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpression(final IExpression expression, final int elementIdx, final Object event, final VMDelta parentDelta, final TreePath path, final RequestMonitor rm) 
     {
         if (event instanceof ISuspendedDMEvent) {
             // Mark the parent delta indicating that elements were added and/or removed.
             parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
-        } else if (event instanceof IRegisters.IRegisterChangedDMEvent) {
+        }
+        else if (event instanceof IRegisters.IRegisterChangedDMEvent) {
             parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
         } 
+        else if (event instanceof IMemory.IMemoryChangedEvent) {
+        	parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
+        }
         rm.done();
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpressionElement(java.lang.Object, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpressionElement(Object element, int elementIdx, Object event, VMDelta parentDelta, final RequestMonitor rm) 
     {
+    	if (event instanceof IMemory.IMemoryChangedEvent) {
+    		parentDelta.addNode(element, IModelDelta.STATE);
+        }
+    	
         if (event instanceof IBitFieldChangedDMEvent) {
             parentDelta.addNode(element, IModelDelta.STATE);
         } 

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/register/RegisterGroupVMNode.java

@@ -58,7 +58,6 @@ import org.eclipse.swt.widgets.Composite;
 public class RegisterGroupVMNode extends AbstractExpressionVMNode
     implements IElementEditor, IElementLabelProvider
 {
-
     protected class RegisterGroupVMC extends DMVMContext
     {
         private IExpression fExpression;
@@ -134,10 +133,21 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         return fSyncRegisterDataAccess;
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#updateElementsInSessionThread(org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate)
+     */
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(IRegisters.class, null, update)) return;
+    	
-        getServicesTracker().getService(IRegisters.class).getRegisterGroups(
+        IRegisters regService = getServicesTracker().getService(IRegisters.class);
+        
+        if ( regService == null ) {
+        	handleFailedUpdate(update);
+            return;
+        }
+        
+        regService.getRegisterGroups(
             createCompositeDMVMContext(update),
             new DataRequestMonitor<IRegisterGroupDMContext[]>(getSession().getExecutor(), null) { 
                 @Override
@@ -151,12 +161,19 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
                 }}); 
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#createVMContext(org.eclipse.dd.dsf.datamodel.IDMContext)
+     */
     @Override
     protected IDMVMContext createVMContext(IDMContext dmc) {
         return new RegisterGroupVMC(dmc);
     }
 
-    
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementLabelProvider#update(org.eclipse.debug.internal.ui.viewers.model.provisional.ILabelUpdate[])
+     */
     public void update(final ILabelUpdate[] updates) {
         try {
             getSession().getExecutor().execute(new DsfRunnable() {
@@ -170,15 +187,28 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         }
     }
 
-    
+    /*
+     *  Updates the labels with the required information for each visible column.
+     */
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
+        	
             final IRegisterGroupDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IRegisterGroupDMContext.class);
-            if (!checkDmc(dmc, update) || !checkService(IRegisters.class, null, update)) continue;
+            if ( dmc == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
+            
+            IRegisters regService = getServicesTracker().getService(IRegisters.class);
+            if ( regService == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
             
             getDMVMProvider().getModelData(
-                this, update, 
+                this, 
-                getServicesTracker().getService(IRegisters.class, null),
+                update, 
+                regService,
                 dmc, 
                 new DataRequestMonitor<IRegisterGroupDMData>(getSession().getExecutor(), null) { 
                     @Override
@@ -214,6 +244,9 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         }
     }
 
+    /*
+     * Based on the specified visible column, provide the appropriate value/label.
+     */
     protected void fillColumnLabel(IRegisterGroupDMContext dmContext, IRegisterGroupDMData dmData,
                                    String columnId, int idx, ILabelUpdate update) 
     {
@@ -247,7 +280,11 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
             update.setImageDescriptor(DebugPluginImages.getImageDescriptor(IDebugUIConstants.IMG_OBJS_REGISTER_GROUP), idx);
         }
     }
-    
+   
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#getDeltaFlags(java.lang.Object)
+     */
     public int getDeltaFlags(Object e) {
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
@@ -261,6 +298,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         return IModelDelta.NO_CHANGE;
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#buildDelta(java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, int, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDelta(Object e, VMDelta parentDelta, int nodeOffset, RequestMonitor rm) {
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             // Create a delta that indicates all groups have changed
@@ -277,6 +318,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         rm.done();
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#canParseExpression(org.eclipse.debug.core.model.IExpression)
+     */
     public boolean canParseExpression(IExpression expression) {
         return parseExpressionForGroupName(expression.getExpressionText()) != null;
     }
@@ -298,6 +343,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         return null;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#getDeltaFlagsForExpression(org.eclipse.debug.core.model.IExpression, java.lang.Object)
+     */
     public int getDeltaFlagsForExpression(IExpression expression, Object event) {
         if (event instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
@@ -306,6 +355,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         return IModelDelta.NO_CHANGE;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpression(org.eclipse.debug.core.model.IExpression, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.jface.viewers.TreePath, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpression(IExpression expression, int elementIdx, Object event, VMDelta parentDelta, 
         TreePath path, RequestMonitor rm) 
     {
@@ -316,6 +369,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         rm.done();
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpressionElement(java.lang.Object, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpressionElement(Object element, int elementIdx, Object event, VMDelta parentDelta, final RequestMonitor rm) 
     {
         if (event instanceof IRegisters.IGroupsChangedDMEvent) {
@@ -327,6 +384,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         rm.done();
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#testElementForExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression, org.eclipse.dd.dsf.concurrent.DataRequestMonitor)
+     */
     @Override
     protected void testElementForExpression(Object element, IExpression expression, final DataRequestMonitor<Boolean> rm) {
         if (!(element instanceof IDMVMContext)) {
@@ -368,6 +429,10 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         }
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#associateExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression)
+     */
     @Override
     protected void associateExpression(Object element, IExpression expression) {
         if (element instanceof RegisterGroupVMC) {
@@ -375,15 +440,22 @@ public class RegisterGroupVMNode extends AbstractExpressionVMNode
         }
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellEditor(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.String, java.lang.Object, org.eclipse.swt.widgets.Composite)
+     */
     public CellEditor getCellEditor(IPresentationContext context, String columnId, Object element, Composite parent) {
         if (IDebugVMConstants.COLUMN_ID__EXPRESSION.equals(columnId)) {
             return new TextCellEditor(parent);
         } 
         return null;
     }
-    
+
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellModifier(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.Object)
+     */
     public ICellModifier getCellModifier(IPresentationContext context, Object element) {
         return fWatchExpressionCellModifier;
     }
-
+}
-}

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/register/RegisterVMNode.java

@@ -28,6 +28,7 @@ import org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.numberformat.I
 import org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.numberformat.IFormattedValueVMContext;
 import org.eclipse.dd.dsf.debug.internal.ui.DsfDebugUIPlugin;
 import org.eclipse.dd.dsf.debug.service.IFormattedValues;
+import org.eclipse.dd.dsf.debug.service.IMemory;
 import org.eclipse.dd.dsf.debug.service.IRegisters;
 import org.eclipse.dd.dsf.debug.service.IRunControl;
 import org.eclipse.dd.dsf.debug.service.IFormattedValues.FormattedValueDMContext;
@@ -159,9 +160,13 @@ public class RegisterVMNode extends AbstractExpressionVMNode
      */
     private void updateFormattedRegisterValue(final ILabelUpdate update, final int labelIndex, final IRegisterDMContext dmc)
     {
-        if (!checkService(IRegisters.class, null, update)) return;
-        
         final IRegisters regService = getServicesTracker().getService(IRegisters.class);
+        
+        if ( regService == null ) {
+        	handleFailedUpdate(update);
+            return;
+        }
+        
         /*
          *  First select the format to be used. This involves checking so see that the preference
          *  page format is supported by the register service. If the format is not supported then 
@@ -259,7 +264,11 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             }
         );
     }
-
+    
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementLabelProvider#update(org.eclipse.debug.internal.ui.viewers.model.provisional.ILabelUpdate[])
+     */
     
     public void update(final ILabelUpdate[] updates) {
         try {
@@ -274,15 +283,29 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         }
     }
 
-    
+    /*
+     *  Updates the labels which are controlled by the column being requested.
+     */
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
+        	
             final IRegisterDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IRegisters.IRegisterDMContext.class);
-            if (!checkDmc(dmc, update) || !checkService(IRegisters.class, null, update)) continue;
+            if ( dmc == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
+            
+            IRegisters regService = getServicesTracker().getService(IRegisters.class);
+            if ( regService == null ) {
+            	handleFailedUpdate(update);
+                continue;
+            }
+            
             
             getDMVMProvider().getModelData(
-                this, update, 
+                this, 
-        		getServicesTracker().getService(IRegisters.class),
+                update, 
+                regService,
         		dmc,             
         		new DataRequestMonitor<IRegisterDMData>(getSession().getExecutor(), null) { 
                 @Override
@@ -409,10 +432,21 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         }
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#updateElementsInSessionThread(org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate)
+     */
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(IRegisters.class, null, update)) return;
+        
-        getServicesTracker().getService(IRegisters.class).getRegisters(
+        IRegisters regService = getServicesTracker().getService(IRegisters.class);
+        
+        if ( regService == null ) {
+        	handleFailedUpdate(update);
+            return;
+        }
+        
+        regService.getRegisters(
             createCompositeDMVMContext(update),
             new DataRequestMonitor<IRegisterDMContext[]>(getSession().getExecutor(), null) { 
                 @Override
@@ -427,21 +461,20 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             });            
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.datamodel.AbstractDMVMNode#createVMContext(org.eclipse.dd.dsf.datamodel.IDMContext)
+     */
     @Override
     protected IDMVMContext createVMContext(IDMContext dmc) {
         return new RegisterVMC(dmc);
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#getDeltaFlags(java.lang.Object)
+     */
     public int getDeltaFlags(Object e) {
-        /* In theory we want each node to act independently in terms of events. It might be
-         * the case that we would only have elements of this type at the root level.  It is
-         * the case that the current layout model always starts with the GROUPS followed by
-         * REGISTERS followed by BITFIELDS. But if we do this when a run-control event  has
-         * occured we generate a DELTA for every element,  which can create  a massive list
-         * of entries all of which say update the entire view. So for now we will just have
-         * the GROUP LAYOUT node do this.  Later we need to revisit the logic and make sure
-         * there is a way for the nodes to operate independently and efficiently.
-         */
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
         }
@@ -450,10 +483,14 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             return IModelDelta.CONTENT;
         }
         
+        if (e instanceof IMemory.IMemoryChangedEvent) {
+            return IModelDelta.CONTENT;
+        }
+        
         if (e instanceof IRegisters.IRegisterChangedDMEvent) {
             /*
-             *  Logically one would think that STATE should be specified here. But we specifiy CONTENT
+             *  Logically one would think that STATE should be specified here.  But we specify  CONTENT
-             *  as well so that if there are subregisters ( BIT FIELDS ) they will be forced to update
+             *  as well so that if there are sub-registers ( BIT FIELDS ) they will be forced to update
              *  and show new values when the total register changes.
              */
             return IModelDelta.CONTENT;
@@ -467,6 +504,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         return IModelDelta.NO_CHANGE;
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.ui.viewmodel.IVMNode#buildDelta(java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, int, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDelta(Object e, VMDelta parentDelta, int nodeOffset, RequestMonitor rm) {
         if (e instanceof IRunControl.ISuspendedDMEvent) {
             // Create a delta that the whole register group has changed.
@@ -477,6 +518,11 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);;
         } 
         
+        if (e instanceof IMemory.IMemoryChangedEvent) {
+            // Mark the parent delta indicating that elements were added and/or removed.
+            parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
+        }
+
         if (e instanceof IRegisters.IRegisterChangedDMEvent) {
             parentDelta.addNode( createVMContext(((IRegisterChangedDMEvent)e).getDMContext()), IModelDelta.CONTENT | IModelDelta.STATE );
         } 
@@ -539,6 +585,11 @@ public class RegisterVMNode extends AbstractExpressionVMNode
     	
         return null;
     }
+    
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#testElementForExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression, org.eclipse.dd.dsf.concurrent.DataRequestMonitor)
+     */
     @Override
     protected void testElementForExpression(Object element, IExpression expression, final DataRequestMonitor<Boolean> rm) {
         if (!(element instanceof IDMVMContext)) {
@@ -580,6 +631,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         }
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.AbstractExpressionVMNode#associateExpression(java.lang.Object, org.eclipse.debug.core.model.IExpression)
+     */
     @Override
     protected void associateExpression(Object element, IExpression expression) {
         if (element instanceof RegisterVMC) {
@@ -587,6 +642,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         }
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#getDeltaFlagsForExpression(org.eclipse.debug.core.model.IExpression, java.lang.Object)
+     */
     public int getDeltaFlagsForExpression(IExpression expression, Object event) {
         if (event instanceof IRunControl.ISuspendedDMEvent) {
             return IModelDelta.CONTENT;
@@ -597,9 +656,17 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             return IModelDelta.CONTENT;            
         }
 
+        if (event instanceof IMemory.IMemoryChangedEvent) {
+        	return IModelDelta.CONTENT;
+        }
+        
         return IModelDelta.NO_CHANGE;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpression(org.eclipse.debug.core.model.IExpression, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.jface.viewers.TreePath, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpression(IExpression expression, int elementIdx, Object event, VMDelta parentDelta, 
         TreePath path, RequestMonitor rm) 
     {
@@ -607,9 +674,18 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             // Mark the parent delta indicating that elements were added and/or removed.
             parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
         } 
+        
+        if (event instanceof IMemory.IMemoryChangedEvent) {
+        	parentDelta.setFlags(parentDelta.getFlags() | IModelDelta.CONTENT);
+        }
+        
         rm.done();
     }
 
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.dd.dsf.debug.internal.provisional.ui.viewmodel.expression.IExpressionVMNode#buildDeltaForExpressionElement(java.lang.Object, int, java.lang.Object, org.eclipse.dd.dsf.ui.viewmodel.VMDelta, org.eclipse.dd.dsf.concurrent.RequestMonitor)
+     */
     public void buildDeltaForExpressionElement(Object element, int elementIdx, Object event, VMDelta parentDelta, final RequestMonitor rm) 
     {
         if (event instanceof IRegisters.IRegisterChangedDMEvent) {
@@ -620,6 +696,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
             parentDelta.addNode(element, IModelDelta.STATE);
         } 
         
+        if (event instanceof IMemory.IMemoryChangedEvent) {
+            parentDelta.addNode(element, IModelDelta.CONTENT);
+        }
+        
         if (event instanceof PropertyChangeEvent && 
             ((PropertyChangeEvent)event).getProperty() == IDebugVMConstants.CURRENT_FORMAT_STORAGE) 
         {
@@ -629,7 +709,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
         rm.done();
     }
 
-    
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellEditor(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.String, java.lang.Object, org.eclipse.swt.widgets.Composite)
+     */
     public CellEditor getCellEditor(IPresentationContext context, String columnId, Object element, Composite parent) {
         if (IDebugVMConstants.COLUMN_ID__EXPRESSION.equals(columnId)) {
             return new TextCellEditor(parent);
@@ -648,6 +731,10 @@ public class RegisterVMNode extends AbstractExpressionVMNode
       return null;
     }
     
+    /*
+     * (non-Javadoc)
+     * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IElementEditor#getCellModifier(org.eclipse.debug.internal.ui.viewers.model.provisional.IPresentationContext, java.lang.Object)
+     */
     public ICellModifier getCellModifier(IPresentationContext context, Object element) {
         return new RegisterCellModifier( 
             getDMVMProvider(), fFormattedPrefStore, fSyncRegisterDataAccess );

plugins/org.eclipse.dd.dsf.debug.ui/src/org/eclipse/dd/dsf/debug/internal/provisional/ui/viewmodel/variable/VariableVMNode.java

@@ -68,10 +68,10 @@ import org.eclipse.swt.widgets.Composite;
 
 @SuppressWarnings({"restriction", "nls"})
 public class VariableVMNode extends AbstractExpressionVMNode 
-    implements IElementEditor, IElementLabelProvider 
+    implements IElementEditor, IElementLabelProvider
 {
     
-    private final static int MAX_STRING_VALUE_LENGTH = 40;
+    //private final static int MAX_STRING_VALUE_LENGTH = 40;
     
     public int getDeltaFlags(Object e) {
         /*
@@ -408,11 +408,9 @@ public class VariableVMNode extends AbstractExpressionVMNode
                                 update.setFontData(JFaceResources.getFontDescriptor(IInternalDebugUIConstants.VARIABLE_TEXT_FONT).getFontData()[0], labelIndex);
                                 
                                 // Color based on change history
-                                FormattedValueDMData oldData = (FormattedValueDMData) getDMVMProvider().getArchivedModelData(
+                                FormattedValueDMData oldData = (FormattedValueDMData) getDMVMProvider().getArchivedModelData(VariableVMNode.this, update, valueDmc);
-                                    VariableVMNode.this, update, valueDmc);
 
-                        		IExpressionDMData oldDMData = (IExpressionDMData) getDMVMProvider().getArchivedModelData(
+                        		IExpressionDMData oldDMData = (IExpressionDMData) getDMVMProvider().getArchivedModelData(VariableVMNode.this, update, dmc); 
-                                    VariableVMNode.this, update, dmc); 
                                 /* Commented out, to be replaced.  See bug 225612.
                                 String oldStringValue = oldDMData == null ? null : oldDMData.getStringValue();*/
                                 
@@ -421,9 +419,7 @@ public class VariableVMNode extends AbstractExpressionVMNode
                         			/* Commented out, to be replaced.  See bug 225612.
                         			|| (oldStringValue != null && !oldStringValue.equals(stringValue))) {*/
                                     update.setBackground(
-                                        DebugUIPlugin.getPreferenceColor(
+                                        DebugUIPlugin.getPreferenceColor(IInternalDebugUIConstants.PREF_CHANGED_VALUE_BACKGROUND).getRGB(), labelIndex);
-                                            IInternalDebugUIConstants.PREF_CHANGED_VALUE_BACKGROUND).getRGB(),
-                                        labelIndex);
                                 }
 
                                 update.done();

plugins/org.eclipse.dd.dsf.ui/src/org/eclipse/dd/dsf/ui/viewmodel/datamodel/AbstractDMVMNode.java

@@ -182,8 +182,25 @@ abstract public class AbstractDMVMNode extends AbstractVMNode implements IVMNode
      * appropriate error message is set in the update.
      * @param dmc Data Model Context (DMC) to check.
      * @param update Update to handle in case the DMC is null.
-     * @return true if the DMC is NOT null, indicating that it's OK to proceed.  
+     * @return true if the DMC is NOT null, indicating that it's OK to proceed. 
+     * 
+     *  This method has been deprecated. Users should simply perform this functionality in-line
+     *  
+     *  Example :
+     *  
+     *      IExampleDmc dmc = final TimerDMContext dmc = findDmcInPath(...)
+     *      if ( dmc == null ) {
+     *          handleFailedUpdate(update);
+     *          //
+     *          // Perform whatever cleanup or completion is needed because of a lack of 
+     *          // a valid data model context.
+     *          //
+     *          ........
+     *          return;
+     *      }
      */
+    
+    @Deprecated
     protected boolean checkDmc(IDMContext dmc, IViewerUpdate update) {
         if (dmc == null) {
             update.setStatus(new Status(IStatus.ERROR, DsfUIPlugin.PLUGIN_ID, IDsfStatusConstants.INVALID_STATE, 
@@ -200,7 +217,21 @@ abstract public class AbstractDMVMNode extends AbstractVMNode implements IVMNode
      * @param serviceClass Service class to find.
      * @param filter Service filter to use in addition to the service class name.
      * @param update Update object to fill in.
-     * @return true if service IS found, indicating that it's OK to proceed.  
+     * @return true if service IS found, indicating that it's OK to proceed. 
+     * 
+     *  This method has been deprecated. Users should simply perform this functionality in-line
+     *  
+     *  Example :
+     *  
+     *      IExampleService service = getServicesTracker().getService(IExampleService.class,null);
+     *      if ( service == null ) {
+     *          handleFailedUpdate(update);
+     *          //
+     *          // Perform whatever cleanup or completion is needed because of a lack of the service.
+     *          //
+     *          ........
+     *          return;
+     *      }
      */
     @Deprecated
     protected boolean checkService(Class<? extends IDsfService> serviceClass, String filter, IViewerUpdate update) {

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/AsyncDataViewer.java

@@ -0,0 +1,272 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.dd.dsf.concurrent.ConfinedToDsfExecutor;
+import org.eclipse.dd.dsf.concurrent.ThreadSafe;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.DsfExecutor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.Query;
+import org.eclipse.dd.dsf.ui.concurrent.DisplayDsfExecutor;
+import org.eclipse.jface.viewers.ILazyContentProvider;
+import org.eclipse.jface.viewers.TableViewer;
+import org.eclipse.jface.viewers.Viewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.graphics.Font;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Table;
+
+/**
+ * Data viewer based on a table, which reads data using asynchronous methods.
+ * <p>
+ * This viewer implements the {@link ILazyContentProvider} interface 
+ * which is used by the JFace TableViewer class to populate a Table.  This 
+ * interface contains separate asynchronous methods for requesting the count 
+ * and values for individual indexes, which neatly correspond to the methods
+ * in {@link IDataGenerator}.  As an added optimization, this viewer 
+ * implementation checks for the range of visible items in the view upon each 
+ * request, and it cancels old requests which scroll out of view but have not
+ * been completed yet.  However, it is up to the data generator implementation 
+ * to check the canceled state of the requests and ignore them.
+ * </p>
+ */
+@ConfinedToDsfExecutor("fDisplayExecutor")
+public class AsyncDataViewer 
+    implements ILazyContentProvider, IDataGenerator.Listener
+{
+    // Executor to use instead of Display.asyncExec().
+    @ThreadSafe
+    final private DsfExecutor fDisplayExecutor;
+    
+    // The viewer and generator that this content provider using.
+    final private TableViewer fViewer;
+    final private IDataGenerator fDataGenerator;
+
+    // Fields used in request cancellation logic.
+    private List<ValueDataRequestMonitor> fItemDataRequestMonitors = new LinkedList<ValueDataRequestMonitor>();
+    private Set<Integer> fIndexesToCancel = new HashSet<Integer>();
+    private int fCancelCallsPending = 0;
+    
+    public AsyncDataViewer(TableViewer viewer, IDataGenerator generator) {
+        fViewer = viewer;
+        fDisplayExecutor = DisplayDsfExecutor.getDisplayDsfExecutor(fViewer.getTable().getDisplay());
+        fDataGenerator = generator;
+        fDataGenerator.addListener(this);
+    }    
+    
+    public void dispose() {
+        fDataGenerator.removeListener(this);
+    }
+
+    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
+        // Set the initial count to the viewer after the input is set.
+        queryItemCount();
+    }
+
+    public void updateElement(final int index) {
+        // Calculate the visible index range.
+        final int topIdx = fViewer.getTable().getTopIndex();
+        final int botIdx = topIdx + getVisibleItemCount(topIdx);
+
+        // Request the item for the given index.
+        queryValue(index);
+
+        // Invoke a cancel task with a delay.  The delay allows multiple cancel 
+        // calls to be combined together improving performance of the viewer.
+        fCancelCallsPending++;
+        fDisplayExecutor.schedule(
+            new Runnable() { public void run() {
+                cancelStaleRequests(topIdx, botIdx);
+            }}, 
+            1, TimeUnit.MILLISECONDS);
+    }
+        
+    private int getVisibleItemCount(int top) {
+        Table table = fViewer.getTable();
+        int itemCount = table.getItemCount();
+        return Math.min((table.getBounds().height / table.getItemHeight()) + 2, itemCount - top);
+    }   
+    
+    @ThreadSafe
+    public void countChanged() {
+        queryItemCount();
+    }
+    
+    @ThreadSafe
+    public void valuesChanged(final Set<Integer> indexes) {
+        // Mark the changed items in table viewer as dirty, this will 
+        // trigger update requests for these indexes if they are 
+        // visible in the viewer.
+        final TableViewer tableViewer = fViewer;
+        fDisplayExecutor.execute( new Runnable() { 
+            public void run() {
+                if (!fViewer.getTable().isDisposed()) {
+                    for (Integer index : indexes) {
+                        tableViewer.clear(index);
+                    }
+                }
+            }});
+    }
+    
+
+    private void queryItemCount() {
+        // Request count from data provider.  When the count is returned, we 
+        // have to re-dispatch into the display thread to avoid calling
+        // the table widget on the DSF dispatch thread.
+        fIndexesToCancel.clear();
+        fDataGenerator.getCount( 
+            // Use the display executor to construct the request monitor, this 
+            // will cause the handleCompleted() method to be automatically
+            // called on the display thread.
+            new DataRequestMonitor<Integer>(fDisplayExecutor, null) {
+                @Override
+                protected void handleCompleted() {
+                    if (!fViewer.getTable().isDisposed()) {
+                        fViewer.setItemCount(getData());
+                        fViewer.getTable().clearAll();
+                    }
+                }
+            }); 
+        
+    }
+
+    
+    // Dedicated class for data item requests.  This class holds the index
+    // argument so it can be examined when canceling stale requests.
+    private class ValueDataRequestMonitor extends DataRequestMonitor<String> {
+        
+        /** Index is used when canceling stale requests. */
+        int fIndex;
+        
+        ValueDataRequestMonitor(int index) {
+            super(fDisplayExecutor, null);
+            fIndex = index; 
+        }
+
+        @Override
+        protected void handleCompleted() {
+            fItemDataRequestMonitors.remove(this);
+
+            // Check if the request completed successfully, otherwise ignore it.
+            if (isSuccess()) {
+                if (!fViewer.getTable().isDisposed()) {
+                    fViewer.replace(getData(), fIndex);
+                }
+            }
+        }
+    }
+
+    private void queryValue(final int index) {
+        ValueDataRequestMonitor rm = new ValueDataRequestMonitor(index);
+        fItemDataRequestMonitors.add(rm);
+        fDataGenerator.getValue(index, rm); 
+    }
+    
+    private void cancelStaleRequests(int topIdx, int botIdx) {
+        // Decrement the count of outstanding cancel calls.
+        fCancelCallsPending--;
+
+        // Must check again, in case disposed while re-dispatching.
+        if (fDataGenerator == null || fViewer.getTable().isDisposed()) return;
+
+        // Go through the outstanding requests and cancel any that 
+        // are not visible anymore.
+        for (Iterator<ValueDataRequestMonitor> itr = fItemDataRequestMonitors.iterator(); itr.hasNext();) {
+            ValueDataRequestMonitor item = itr.next();
+            if (item.fIndex < topIdx || item.fIndex > botIdx) {
+                // Set the item to canceled status, so that the data provider 
+                // will ignore it.
+                item.cancel();
+                
+                // Add the item index to list of indexes that were canceled, 
+                // which will be sent to the table widget. 
+                fIndexesToCancel.add(item.fIndex);
+                
+                // Remove the item from the outstanding cancel requests.
+                itr.remove(); 
+            }
+        }
+        if (!fIndexesToCancel.isEmpty() && fCancelCallsPending == 0) {
+            Set<Integer> canceledIdxs = fIndexesToCancel;
+            fIndexesToCancel = new HashSet<Integer>();
+            
+            // Clear the indexes of the canceled request, so that the 
+            // viewer knows to request them again when needed.  
+            // Note: clearing using TableViewer.clear(int) seems very
+            // inefficient, it's better to use Table.clear(int[]).
+            int[] canceledIdxsArray = new int[canceledIdxs.size()];
+            int i = 0;
+            for (Integer index : canceledIdxs) {
+                canceledIdxsArray[i++] = index;
+            }
+            fViewer.getTable().clear(canceledIdxsArray);
+        }
+    }
+    
+    
+    public static void main(String[] args) {
+        // Create the shell to hold the viewer.
+        Display display = new Display();
+        Shell shell = new Shell(display, SWT.SHELL_TRIM);
+        shell.setLayout(new GridLayout());
+        GridData data = new GridData(GridData.FILL_BOTH);
+        shell.setLayoutData(data);
+        Font font = new Font(display, "Courier", 10, SWT.NORMAL);
+
+        // Create the table viewer.
+        TableViewer tableViewer = new TableViewer(shell, SWT.BORDER | SWT.VIRTUAL);
+        tableViewer.getControl().setLayoutData(data);
+
+        // Create the data generator.
+        final IDataGenerator generator = new DataGeneratorWithExecutor();
+        
+        // Create the content provider which will populate the viewer.
+        AsyncDataViewer contentProvider = new AsyncDataViewer(tableViewer, generator);
+        tableViewer.setContentProvider(contentProvider);
+        tableViewer.setInput(new Object());
+
+        // Open the shell and service the display dispatch loop until user
+        // closes the shell.
+        shell.open();
+        while (!shell.isDisposed()) {
+            if (!display.readAndDispatch())
+                display.sleep();
+        }
+        
+        // The IDataGenerator.shutdown() method is asynchronous, this requires
+        // using a query again in order to wait for its completion.
+        Query<Object> shutdownQuery = new Query<Object>() {
+            @Override
+            protected void execute(DataRequestMonitor<Object> rm) {
+                generator.shutdown(rm);
+            }
+        };
+        ImmediateExecutor.getInstance().execute(shutdownQuery);
+        try {
+            shutdownQuery.get();
+        } catch (Exception e) {} 
+        
+        // Shut down the display.
+        font.dispose();    
+        display.dispose();
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/DataGeneratorWithExecutor.java

@@ -0,0 +1,336 @@
+/*******************************************************************************
+ * Copyright (c) 2006 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer;
+
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+
+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.DefaultDsfExecutor;
+import org.eclipse.dd.dsf.concurrent.DsfExecutor;
+import org.eclipse.dd.dsf.concurrent.DsfRunnable;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.examples.dsf.DsfExamplesPlugin;
+
+/**
+ * DSF Executor-based implementation of the data generator.
+ * <p>
+ * This generator uses a queue of client requests and processes these
+ * requests periodically using a DSF executor.  The main feature of this
+ * generator is that it uses the executor as its only synchronization object.
+ * This means that all the fields with the exception of the executor can only
+ * be accessed while running in the executor thread.
+ * </p>
+ */
+//TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+//indicating allowed thread access to this class/method/member
+public class DataGeneratorWithExecutor implements IDataGenerator {
+
+    // Request objects are used to serialize the interface calls into objects
+    // which can then be pushed into a queue.
+    // TODO Ecercise 4 - Add an annotationindicating allowed concurrency access
+    // Hint: Request and its subclasses have all their fields declared as final.
+    abstract class Request {
+        final RequestMonitor fRequestMonitor;
+        
+        Request(RequestMonitor rm) {
+            fRequestMonitor = rm;
+        }
+    }
+    
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    class CountRequest extends Request {
+        CountRequest(DataRequestMonitor<Integer> rm) { 
+            super(rm); 
+        }
+    } 
+
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    class ItemRequest extends Request {
+        final int fIndex;
+        ItemRequest(int index, DataRequestMonitor<String> rm) { 
+            super(rm);
+            fIndex = index; 
+        }
+    } 
+
+    // The executor used to access all internal data of the generator.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    // Hint: If a member does not have an annotation, the programmer can assume
+    // that the concurrency rule that applies to the class also applies to this
+    // member.
+    private DsfExecutor fExecutor;
+    
+    // Main request queue of the data generator.  The getValue(), getCount(), 
+    // and shutdown() methods write into the queue, while the serviceQueue()
+    // method reads from it.
+    // The executor used to access all internal data of the generator.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private List<Request> fQueue = new LinkedList<Request>();
+
+    // List of listeners is not synchronized, it also has to be accessed
+    // using the executor.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private List<Listener> fListeners = new LinkedList<Listener>();
+
+    // Current number of elements in this generator.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private int fCount = MIN_COUNT;
+    
+    // Counter used to determine when to reset the element count.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private int fCountResetTrigger = 0;
+    
+    // Elements which were modified since the last reset.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private Set<Integer> fChangedIndexes = new HashSet<Integer>();
+    
+    // Flag used to ensure that requests are processed sequentially.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private boolean fServiceQueueInProgress = false;
+ 
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public DataGeneratorWithExecutor() {
+        // Create the executor
+        fExecutor = new DefaultDsfExecutor("Supplier Executor");
+        
+        // Schedule a runnable to make the random changes.
+        fExecutor.scheduleAtFixedRate(
+            new DsfRunnable() {
+                public void run() {
+                    randomChanges();
+                }
+            },
+            RANDOM_CHANGE_INTERVAL, 
+            RANDOM_CHANGE_INTERVAL, 
+            TimeUnit.MILLISECONDS);
+    }
+     
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public void shutdown(final RequestMonitor rm) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    // Empty the queue of requests and fail them.
+                    for (Request request : fQueue) {
+                        request.fRequestMonitor.setStatus(
+                            new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+                        request.fRequestMonitor.done();
+                    }
+                    fQueue.clear();
+                    
+                    // Kill executor.
+                    fExecutor.shutdown();
+                    rm.done();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    }
+
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public void getCount(final DataRequestMonitor<Integer> rm) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fQueue.add(new CountRequest(rm));
+                    serviceQueue();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    }
+    
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public void getValue(final int index, final DataRequestMonitor<String> rm) { 
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fQueue.add(new ItemRequest(index, rm));
+                    serviceQueue();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    } 
+
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public void addListener(final Listener listener) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fListeners.add(listener);
+                }
+            });
+        } catch (RejectedExecutionException e) {}
+    }
+
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    public void removeListener(final Listener listener) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fListeners.remove(listener);
+                }
+            });
+        } catch (RejectedExecutionException e) {}
+    }
+
+    // Main processing function of this generator.
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void serviceQueue() {
+        
+        // TODO Exercise 3 - Add logic to discard cancelled requests from queue.
+        // Hint: Since serviceQueue() is called using the executor, and the 
+        // fQueue list can only be modified when running in the executor 
+        // thread.  This method can safely iterate and modify fQueue without 
+        // risk of race conditions or concurrent modification exceptions.
+        
+        // If a queue servicing is already scheduled, do nothing.
+        if (fServiceQueueInProgress) {
+            return;
+        }
+        
+        if (fQueue.size() != 0) {
+            // If there are requests to service, remove one from the queue and 
+            // schedule a runnable to process the request after a processing
+            // delay.
+            fServiceQueueInProgress = true;
+            final Request request = fQueue.remove(0);
+            fExecutor.schedule(
+                new DsfRunnable() {
+                    public void run() {
+                        if (request instanceof CountRequest) {
+                            processCountRequest((CountRequest)request);
+                        } else if (request instanceof ItemRequest) {
+                            processItemRequest((ItemRequest)request);
+                        } 
+                        
+                        // Reset the processing flag and process next
+                        // request.
+                        fServiceQueueInProgress = false;
+                        serviceQueue();
+                    }
+                }, 
+                PROCESSING_DELAY, TimeUnit.MILLISECONDS);
+        }
+    }
+    
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void processCountRequest(CountRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<Integer> rm = (DataRequestMonitor<Integer>)request.fRequestMonitor;
+        
+        rm.setData(fCount);
+        rm.done();
+    }
+
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void processItemRequest(ItemRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<String> rm = (DataRequestMonitor<String>)request.fRequestMonitor; 
+
+        if (fChangedIndexes.contains(request.fIndex)) {
+            rm.setData("Changed: " + request.fIndex);
+        } else {
+            rm.setData(Integer.toString(request.fIndex)); 
+        }
+        rm.done();
+    } 
+ 
+    /**
+     * This method simulates changes in the supplier's data set.
+     */
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void randomChanges() {
+        // Once every number of changes, reset the count, the rest of the 
+        // times just change certain values.
+        if (++fCountResetTrigger % RANDOM_COUNT_CHANGE_INTERVALS == 0){
+            randomCountReset();
+        } else {
+            randomDataChange();
+        }
+    }
+     
+    /**
+     * Calculates new size for provider's data set.
+     */
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void randomCountReset() {
+        // Calculate the new count.
+        Random random = new java.util.Random();
+        fCount = MIN_COUNT + Math.abs(random.nextInt()) % (MAX_COUNT - MIN_COUNT);
+
+        // Reset the changed values.
+        fChangedIndexes.clear();
+        
+        // Notify listeners  
+        for (Listener listener : fListeners) {
+            listener.countChanged();
+        }
+    }
+     
+    /**
+     * Invalidates a random range of indexes.
+     */
+    // TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+    // indicating allowed thread access to this class/method/member
+    private void randomDataChange() {
+        // Calculate the indexes to change.
+        Random random = new java.util.Random();
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i = 0; i < fCount * RANDOM_CHANGE_SET_PERCENTAGE / 100; i++) {
+            set.add( new Integer(Math.abs(random.nextInt()) % fCount) );
+        }                    
+
+        // Add the indexes to an overall set of changed indexes.
+        fChangedIndexes.addAll(set);
+        
+        // Notify listeners  
+        for (Listener listener : fListeners) {
+            listener.valuesChanged(set);
+        }
+    }    
+}
+

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/DataGeneratorWithThread.java

@@ -0,0 +1,238 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.ListenerList;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.examples.dsf.DsfExamplesPlugin;
+
+/**
+ * Thread-based implementation of the data generator.
+ * <p>
+ * This generator is based around a queue of client requests and a thread which 
+ * reads the requests from the queue and processes them. The distinguishing 
+ * feature of this generator is that it uses a a blocking queue as the main 
+ * synchronization object.  However, fListeners, fShutdown,  and fChangedIndexes 
+ * fields also need to be thread-safe and so they implement their own 
+ * synchronization.
+ * </p>
+ */
+public class DataGeneratorWithThread extends Thread implements IDataGenerator {
+
+    // Request objects are used to serialize the interface calls into objects
+    // which can then be pushed into a queue.
+    abstract class Request {
+        final RequestMonitor fRequestMonitor;
+        
+        Request(RequestMonitor rm) {
+            fRequestMonitor = rm;
+        }
+    }
+    
+    class CountRequest extends Request {
+        CountRequest(DataRequestMonitor<Integer> rm) { 
+            super(rm); 
+        }
+    } 
+
+    class ItemRequest extends Request {
+        final int fIndex;
+        ItemRequest(int index, DataRequestMonitor<String> rm) { 
+            super(rm);
+            fIndex = index; 
+        }
+    } 
+
+    class ShutdownRequest extends Request {
+        ShutdownRequest(RequestMonitor rm) { 
+            super(rm);
+        }
+    }
+
+    // Main request queue of the data generator.  The getValue(), getCount(), 
+    // and shutdown() methods write into the queue, while the run() method 
+    // reads from it.
+    private final BlockingQueue<Request> fQueue = new LinkedBlockingQueue<Request>();
+
+    // ListenerList class provides thread safety.
+    private ListenerList fListeners = new ListenerList();
+    
+    // Current number of elements in this generator.
+    private int fCount = MIN_COUNT;
+    
+    // Counter used to determine when to reset the element count.
+    private int fCountResetTrigger = 0;
+    
+    // Elements which were modified since the last reset.
+    private Set<Integer> fChangedIndexes = Collections.synchronizedSet(new HashSet<Integer>());
+    
+    // Used to determine when to make changes in data.
+    private long fLastChangeTime = System.currentTimeMillis();
+
+    // Flag indicating when the generator has been shut down.
+    private AtomicBoolean fShutdown = new AtomicBoolean(false);
+ 
+    public DataGeneratorWithThread() {
+        // Immediately kick off the request processing thread.
+        start();
+    }
+     
+    public void shutdown(RequestMonitor rm) {
+        // Mark the generator as shut down.  After the fShutdown flag is set,
+        // all new requests should be shut down.
+        if (!fShutdown.getAndSet(true)) {
+            fQueue.add(new ShutdownRequest(rm));
+        } else {
+            // 
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    }
+
+    public void getCount(DataRequestMonitor<Integer> rm) {
+        if (!fShutdown.get()) {
+            fQueue.add(new CountRequest(rm));
+        } else {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    }
+    
+    public void getValue(int index, DataRequestMonitor<String> rm) { 
+        if (!fShutdown.get()) {
+            fQueue.add(new ItemRequest(index, rm));
+        } else {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    } 
+
+    public void addListener(Listener listener) {
+        fListeners.add(listener);
+    }
+
+    public void removeListener(Listener listener) {
+        fListeners.remove(listener);
+    }
+    
+    @Override
+    public void run() {
+        try {
+            while(true) {
+                // Get the next request from the queue.  The time-out 
+                // ensures that that the random changes get processed. 
+                final Request request = fQueue.poll(100, TimeUnit.MILLISECONDS);
+                
+                // If a request was dequeued, process it.
+                if (request != null) {
+                    // Simulate a processing delay.
+                    Thread.sleep(PROCESSING_DELAY);
+                    
+                    if (request instanceof CountRequest) {
+                        processCountRequest((CountRequest)request);
+                    } else if (request instanceof ItemRequest) {
+                        processItemRequest((ItemRequest)request);
+                    } else if (request instanceof ShutdownRequest) {
+                        // If shutting down, just break out of the while(true) 
+                        // loop and thread will exit.
+                        request.fRequestMonitor.done();
+                        break;
+                    }
+                }
+                
+                // Simulate data changes.
+                randomChanges();
+            }
+        }
+        catch (InterruptedException x) {}
+    } 
+
+    private void processCountRequest(CountRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<Integer> rm = (DataRequestMonitor<Integer>)request.fRequestMonitor;
+        
+        rm.setData(fCount);
+        rm.done();
+    }
+
+    private void processItemRequest(ItemRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<String> rm = (DataRequestMonitor<String>)request.fRequestMonitor; 
+
+        if (fChangedIndexes.contains(request.fIndex)) {
+            rm.setData("Changed: " + request.fIndex);
+        } else {
+            rm.setData(Integer.toString(request.fIndex));
+        }
+        rm.done();
+    } 
+ 
+    
+    private void randomChanges() {
+        // Check if enough time is elapsed.
+        if (System.currentTimeMillis() > fLastChangeTime + RANDOM_CHANGE_INTERVAL) {
+            fLastChangeTime = System.currentTimeMillis();
+            
+            // Once every number of changes, reset the count, the rest of the 
+            // times just change certain values.
+            if (++fCountResetTrigger % RANDOM_COUNT_CHANGE_INTERVALS == 0){
+                randomCountReset();
+            } else {
+                randomDataChange();
+            }
+        }
+    }
+     
+    private void randomCountReset() {
+        // Calculate the new count.
+        Random random = new java.util.Random();
+        fCount = MIN_COUNT + Math.abs(random.nextInt()) % (MAX_COUNT - MIN_COUNT);
+
+        // Reset the changed values.
+        fChangedIndexes.clear();
+        
+        // Notify listeners  
+        for (Object listener : fListeners.getListeners()) {
+            ((Listener)listener).countChanged();
+        }
+    }
+     
+    private void randomDataChange() {
+        // Calculate the indexes to change.
+        Random random = new java.util.Random();
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i = 0; i < fCount * RANDOM_CHANGE_SET_PERCENTAGE / 100; i++) {
+            set.add( new Integer(Math.abs(random.nextInt()) % fCount) );
+        }                
+
+        // Add the indexes to an overall set of changed indexes.
+        fChangedIndexes.addAll(set);
+        
+        // Notify listeners  
+        for (Object listener : fListeners.getListeners()) {
+            ((Listener)listener).valuesChanged(set);
+        }
+    }    
+}
+
+

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/IDataGenerator.java

@@ -0,0 +1,59 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer;
+
+import java.util.Set;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+
+/**
+ * Data generator is simple source of data used to populate the example table 
+ * view.  It contains two asynchronous methods for retrieving the data 
+ * parameters: the count and the value for a given index.  It also allows the 
+ * view to receive events indicating when the data supplied by the generator 
+ * is changed. 
+ */
+// TODO Exercise 4 - Add an annotation (ThreadSafe/ConfinedToDsfExecutor) 
+// indicating allowed thread access to this class/method/member
+public interface IDataGenerator {
+
+    // Constants which control the data generator behavior.
+    // Changing the count range can stress the scalability of the system, while
+    // changing of the process delay and random change interval can stress 
+    // its performance.
+    final static int MIN_COUNT = 100;
+    final static int MAX_COUNT = 200;
+    final static int PROCESSING_DELAY = 10;
+    final static int RANDOM_CHANGE_INTERVAL = 10000;
+    final static int RANDOM_COUNT_CHANGE_INTERVALS = 3;
+    final static int RANDOM_CHANGE_SET_PERCENTAGE = 10;
+
+    
+    // Listener interface that the view needs to implement to react
+    // to the changes in data.
+    public interface Listener {
+        void countChanged();
+        void valuesChanged(Set<Integer> indexes);
+    }
+
+    // Data access methods.
+    void getCount(DataRequestMonitor<Integer> rm);
+    void getValue(int index, DataRequestMonitor<String> rm); 
+    
+    // Method used to shutdown the data generator including any threads that 
+    // it may use.  
+    void shutdown(RequestMonitor rm);
+
+    // Methods for registering change listeners.
+    void addListener(Listener listener);
+    void removeListener(Listener listener);
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/SyncDataViewer.java

@@ -0,0 +1,183 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer;
+
+import java.util.Set;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.Query;
+import org.eclipse.jface.viewers.IStructuredContentProvider;
+import org.eclipse.jface.viewers.TableViewer;
+import org.eclipse.jface.viewers.Viewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.graphics.Font;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+
+/**
+ * Data viewer based on a table, which reads data using synchronous methods.
+ * <p>
+ * This viewer implements the {@link IStructuredContentProvider} interface 
+ * which is used by the JFace TableViewer class to populate a Table.  This 
+ * interface contains one principal methods for reading data {@link #getElements(Object)}, 
+ * which synchronously returns an array of elements.  In order to implement this 
+ * method using the asynchronous data generator, this provider uses the 
+ * {@link Query} object. 
+ * </p>
+ */
+public class SyncDataViewer 
+    implements IStructuredContentProvider, IDataGenerator.Listener 
+{
+    // The viewer and generator that this content provider using.
+    final private TableViewer fViewer;
+    final private IDataGenerator fDataGenerator;
+    
+    public SyncDataViewer(TableViewer viewer, IDataGenerator generator) {
+        fViewer = viewer;
+        fDataGenerator = generator;
+        fDataGenerator.addListener(this);
+    }
+    
+    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
+        // Not used
+    }
+
+    
+    public Object[] getElements(Object inputElement) {
+        
+        // Create the query object for reading data count. 
+        Query<Integer> countQuery = new Query<Integer>() {
+            @Override
+            protected void execute(DataRequestMonitor<Integer> rm) {
+                fDataGenerator.getCount(rm);
+            }
+        };
+        
+        // Submit the query to be executed.  A query implements a runnable
+        // interface and it has to be executed in order to do its work.
+        ImmediateExecutor.getInstance().execute(countQuery);
+        int count = 0;
+        
+        // Block until the query completes, which will happen when the request
+        // monitor of the execute() method is marked done.
+        try {
+            count = countQuery.get();
+        } catch (Exception e) { 
+            // InterruptedException and ExecutionException can be thrown here.
+            // ExecutionException containing a CoreException will be thrown 
+            // if an error status is set to the Query's request monitor.
+            return new Object[0]; 
+        } 
+
+        // Create the array that will be filled with elements.
+        // For each index in the array execute a query to get the element at
+        // that index.
+        final Object[] elements = new Object[count];
+
+        for (int i = 0; i < count; i++) {
+            final int index = i;
+            Query<String> valueQuery = new Query<String>() {
+                @Override
+                protected void execute(DataRequestMonitor<String> rm) {
+                    fDataGenerator.getValue(index, rm);
+                }
+            };
+            ImmediateExecutor.getInstance().execute(valueQuery);
+            try {
+                elements[i] = valueQuery.get();
+            } catch (Exception e) { 
+                elements[i] = "error";
+            } 
+        }
+        return elements;
+    }
+
+    public void dispose() {
+        fDataGenerator.removeListener(this);
+    }
+
+    public void countChanged() {
+        // For any event from the generator, refresh the whole viewer.
+        refreshViewer();
+    }
+    
+    public void valuesChanged(Set<Integer> indexes) {
+        // For any event from the generator, refresh the whole viewer.
+        refreshViewer();
+    }
+    
+    private void refreshViewer() {
+        // TODO Exercise 5 - Add a call to getElements() to force a deadlock.
+        
+        // This method may be called on any thread, switch to the display 
+        // thread before calling the viewer.
+        Display display = fViewer.getControl().getDisplay(); 
+        display.asyncExec( new Runnable() {
+            public void run() {
+                if (!fViewer.getControl().isDisposed()) {
+                    fViewer.refresh();
+                }
+            }
+        });
+    }
+    
+    public static void main(String[] args) {
+        // Create the shell to hold the viewer.
+        Display display = new Display();
+        Shell shell = new Shell(display, SWT.SHELL_TRIM);
+        shell.setLayout(new GridLayout());
+        GridData data = new GridData(GridData.FILL_BOTH);
+        shell.setLayoutData(data);
+        Font font = new Font(display, "Courier", 10, SWT.NORMAL);
+
+        // Create the table viewer.
+        TableViewer tableViewer = new TableViewer(shell, SWT.BORDER);
+        tableViewer.getControl().setLayoutData(data);
+
+        // Create the data generator.
+        // TODO Exercise 5 - Use the DataGeneratorWithExecutor() instead.
+        final IDataGenerator generator = new DataGeneratorWithThread();
+        
+        // Create the content provider which will populate the viewer.
+        SyncDataViewer contentProvider = new SyncDataViewer(tableViewer, generator);
+        tableViewer.setContentProvider(contentProvider);
+        tableViewer.setInput(new Object());
+
+        // Open the shell and service the display dispatch loop until user
+        // closes the shell.
+        shell.open();
+        while (!shell.isDisposed()) {
+            if (!display.readAndDispatch())
+                display.sleep();
+        }
+        
+        // The IDataGenerator.shutdown() method is asynchronous, this requires
+        // using a query again in order to wait for its completion.
+        Query<Object> shutdownQuery = new Query<Object>() {
+            @Override
+            protected void execute(DataRequestMonitor<Object> rm) {
+                generator.shutdown(rm);
+            }
+        };
+        ImmediateExecutor.getInstance().execute(shutdownQuery);
+        try {
+            shutdownQuery.get();
+        } catch (Exception e) {}
+        
+        // Shut down the display.
+        font.dispose();    
+        display.dispose();
+    }
+    
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/answers/AsyncDataViewer.java

@@ -0,0 +1,272 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer.answers;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.dd.dsf.concurrent.ConfinedToDsfExecutor;
+import org.eclipse.dd.dsf.concurrent.ThreadSafe;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.DsfExecutor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.Query;
+import org.eclipse.dd.dsf.ui.concurrent.DisplayDsfExecutor;
+import org.eclipse.jface.viewers.ILazyContentProvider;
+import org.eclipse.jface.viewers.TableViewer;
+import org.eclipse.jface.viewers.Viewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.graphics.Font;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Table;
+
+/**
+ * Data viewer based on a table, which reads data using asynchronous methods.
+ * <p>
+ * This viewer implements the {@link ILazyContentProvider} interface 
+ * which is used by the JFace TableViewer class to populate a Table.  This 
+ * interface contains separate asynchronous methods for requesting the count 
+ * and values for individual indexes, which neatly correspond to the methods
+ * in {@link IDataGenerator}.  As an added optimization, this viewer 
+ * implementation checks for the range of visible items in the view upon each 
+ * request, and it cancels old requests which scroll out of view but have not
+ * been completed yet.  However, it is up to the data generator implementation 
+ * to check the canceled state of the requests and ignore them.
+ * </p>
+ */
+@ConfinedToDsfExecutor("fDisplayExecutor")
+public class AsyncDataViewer 
+    implements ILazyContentProvider, IDataGenerator.Listener
+{
+    // Executor to use instead of Display.asyncExec().
+    @ThreadSafe
+    final private DsfExecutor fDisplayExecutor;
+    
+    // The viewer and generator that this content provider using.
+    final private TableViewer fViewer;
+    final private IDataGenerator fDataGenerator;
+
+    // Fields used in request cancellation logic.
+    private List<ValueDataRequestMonitor> fItemDataRequestMonitors = new LinkedList<ValueDataRequestMonitor>();
+    private Set<Integer> fIndexesToCancel = new HashSet<Integer>();
+    private int fCancelCallsPending = 0;
+    
+    public AsyncDataViewer(TableViewer viewer, IDataGenerator generator) {
+        fViewer = viewer;
+        fDisplayExecutor = DisplayDsfExecutor.getDisplayDsfExecutor(fViewer.getTable().getDisplay());
+        fDataGenerator = generator;
+        fDataGenerator.addListener(this);
+    }    
+    
+    public void dispose() {
+        fDataGenerator.removeListener(this);
+    }
+
+    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
+        // Set the initial count to the viewer after the input is set.
+        queryItemCount();
+    }
+
+    public void updateElement(final int index) {
+        // Calculate the visible index range.
+        final int topIdx = fViewer.getTable().getTopIndex();
+        final int botIdx = topIdx + getVisibleItemCount(topIdx);
+
+        // Request the item for the given index.
+        queryValue(index);
+
+        // Invoke a cancel task with a delay.  The delay allows multiple cancel 
+        // calls to be combined together improving performance of the viewer.
+        fCancelCallsPending++;
+        fDisplayExecutor.schedule(
+            new Runnable() { public void run() {
+                cancelStaleRequests(topIdx, botIdx);
+            }}, 
+            1, TimeUnit.MILLISECONDS);
+    }
+        
+    private int getVisibleItemCount(int top) {
+        Table table = fViewer.getTable();
+        int itemCount = table.getItemCount();
+        return Math.min((table.getBounds().height / table.getItemHeight()) + 2, itemCount - top);
+    }   
+    
+    @ThreadSafe
+    public void countChanged() {
+        queryItemCount();
+    }
+    
+    @ThreadSafe
+    public void valuesChanged(final Set<Integer> indexes) {
+        // Mark the changed items in table viewer as dirty, this will 
+        // trigger update requests for these indexes if they are 
+        // visible in the viewer.
+        final TableViewer tableViewer = fViewer;
+        fDisplayExecutor.execute( new Runnable() { 
+            public void run() {
+                if (!fViewer.getTable().isDisposed()) {
+                    for (Integer index : indexes) {
+                        tableViewer.clear(index);
+                    }
+                }
+            }});
+    }
+    
+
+    private void queryItemCount() {
+        // Request count from data provider.  When the count is returned, we 
+        // have to re-dispatch into the display thread to avoid calling
+        // the table widget on the DSF dispatch thread.
+        fIndexesToCancel.clear();
+        fDataGenerator.getCount( 
+            // Use the display executor to construct the request monitor, this 
+            // will cause the handleCompleted() method to be automatically
+            // called on the display thread.
+            new DataRequestMonitor<Integer>(fDisplayExecutor, null) {
+                @Override
+                protected void handleCompleted() {
+                    if (!fViewer.getTable().isDisposed()) {
+                        fViewer.setItemCount(getData());
+                        fViewer.getTable().clearAll();
+                    }
+                }
+            }); 
+        
+    }
+
+    
+    // Dedicated class for data item requests.  This class holds the index
+    // argument so it can be examined when canceling stale requests.
+    private class ValueDataRequestMonitor extends DataRequestMonitor<String> {
+        
+        /** Index is used when canceling stale requests. */
+        int fIndex;
+        
+        ValueDataRequestMonitor(int index) {
+            super(fDisplayExecutor, null);
+            fIndex = index; 
+        }
+
+        @Override
+        protected void handleCompleted() {
+            fItemDataRequestMonitors.remove(this);
+
+            // Check if the request completed successfully, otherwise ignore it.
+            if (isSuccess()) {
+                if (!fViewer.getTable().isDisposed()) {
+                    fViewer.replace(getData(), fIndex);
+                }
+            }
+        }
+    }
+
+    private void queryValue(final int index) {
+        ValueDataRequestMonitor rm = new ValueDataRequestMonitor(index);
+        fItemDataRequestMonitors.add(rm);
+        fDataGenerator.getValue(index, rm); 
+    }
+    
+    private void cancelStaleRequests(int topIdx, int botIdx) {
+        // Decrement the count of outstanding cancel calls.
+        fCancelCallsPending--;
+
+        // Must check again, in case disposed while re-dispatching.
+        if (fDataGenerator == null || fViewer.getTable().isDisposed()) return;
+
+        // Go through the outstanding requests and cancel any that 
+        // are not visible anymore.
+        for (Iterator<ValueDataRequestMonitor> itr = fItemDataRequestMonitors.iterator(); itr.hasNext();) {
+            ValueDataRequestMonitor item = itr.next();
+            if (item.fIndex < topIdx || item.fIndex > botIdx) {
+                // Set the item to canceled status, so that the data provider 
+                // will ignore it.
+                item.cancel();
+                
+                // Add the item index to list of indexes that were canceled, 
+                // which will be sent to the table widget. 
+                fIndexesToCancel.add(item.fIndex);
+                
+                // Remove the item from the outstanding cancel requests.
+                itr.remove(); 
+            }
+        }
+        if (!fIndexesToCancel.isEmpty() && fCancelCallsPending == 0) {
+            Set<Integer> canceledIdxs = fIndexesToCancel;
+            fIndexesToCancel = new HashSet<Integer>();
+            
+            // Clear the indexes of the canceled request, so that the 
+            // viewer knows to request them again when needed.  
+            // Note: clearing using TableViewer.clear(int) seems very
+            // inefficient, it's better to use Table.clear(int[]).
+            int[] canceledIdxsArray = new int[canceledIdxs.size()];
+            int i = 0;
+            for (Integer index : canceledIdxs) {
+                canceledIdxsArray[i++] = index;
+            }
+            fViewer.getTable().clear(canceledIdxsArray);
+        }
+    }
+    
+    
+    public static void main(String[] args) {
+        // Create the shell to hold the viewer.
+        Display display = new Display();
+        Shell shell = new Shell(display, SWT.SHELL_TRIM);
+        shell.setLayout(new GridLayout());
+        GridData data = new GridData(GridData.FILL_BOTH);
+        shell.setLayoutData(data);
+        Font font = new Font(display, "Courier", 10, SWT.NORMAL);
+
+        // Create the table viewer.
+        TableViewer tableViewer = new TableViewer(shell, SWT.BORDER | SWT.VIRTUAL);
+        tableViewer.getControl().setLayoutData(data);
+
+        // Create the data generator.
+        final IDataGenerator generator = new DataGeneratorWithExecutor();
+        
+        // Create the content provider which will populate the viewer.
+        AsyncDataViewer contentProvider = new AsyncDataViewer(tableViewer, generator);
+        tableViewer.setContentProvider(contentProvider);
+        tableViewer.setInput(new Object());
+
+        // Open the shell and service the display dispatch loop until user
+        // closes the shell.
+        shell.open();
+        while (!shell.isDisposed()) {
+            if (!display.readAndDispatch())
+                display.sleep();
+        }
+        
+        // The IDataGenerator.shutdown() method is asynchronous, this requires
+        // using a query again in order to wait for its completion.
+        Query<Object> shutdownQuery = new Query<Object>() {
+            @Override
+            protected void execute(DataRequestMonitor<Object> rm) {
+                generator.shutdown(rm);
+            }
+        };
+        ImmediateExecutor.getInstance().execute(shutdownQuery);
+        try {
+            shutdownQuery.get();
+        } catch (Exception e) {} 
+        
+        // Shut down the display.
+        font.dispose();    
+        display.dispose();
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/answers/DataGeneratorWithExecutor.java

@@ -0,0 +1,311 @@
+/*******************************************************************************
+ * Copyright (c) 2006 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer.answers;
+
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.dd.dsf.concurrent.ConfinedToDsfExecutor;
+import org.eclipse.dd.dsf.concurrent.Immutable;
+import org.eclipse.dd.dsf.concurrent.ThreadSafe;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.DefaultDsfExecutor;
+import org.eclipse.dd.dsf.concurrent.DsfExecutor;
+import org.eclipse.dd.dsf.concurrent.DsfRunnable;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.examples.dsf.DsfExamplesPlugin;
+
+/**
+ * DSF Executor-based implementation of the data generator.
+ * <p>
+ * This generator uses a queue of client requests and processes these
+ * requests periodically using a DSF executor.  The main feature of this
+ * generator is that it uses the executor as its only synchronization object.
+ * This means that all the fields with the exception of the executor can only
+ * be accessed while running in the executor thread.
+ * </p>
+ */
+@ThreadSafe
+public class DataGeneratorWithExecutor implements IDataGenerator {
+
+    // Request objects are used to serialize the interface calls into objects
+    // which can then be pushed into a queue.
+    @Immutable
+    abstract class Request {
+        final RequestMonitor fRequestMonitor;
+        
+        Request(RequestMonitor rm) {
+            fRequestMonitor = rm;
+        }
+    }
+    
+    @Immutable
+    class CountRequest extends Request {
+        CountRequest(DataRequestMonitor<Integer> rm) { 
+            super(rm); 
+        }
+    } 
+
+    @Immutable
+    class ItemRequest extends Request {
+        final int fIndex;
+        ItemRequest(int index, DataRequestMonitor<String> rm) { 
+            super(rm);
+            fIndex = index; 
+        }
+    } 
+
+    // The executor used to access all internal data of the generator.
+    private DsfExecutor fExecutor;
+    
+    // Main request queue of the data generator.  The getValue(), getCount(), 
+    // and shutdown() methods write into the queue, while the serviceQueue()
+    // method reads from it.
+    // The executor used to access all internal data of the generator.
+    @ConfinedToDsfExecutor("fExecutor")
+    private List<Request> fQueue = new LinkedList<Request>();
+
+    // List of listeners is not synchronized, it also has to be accessed
+    // using the executor.
+    @ConfinedToDsfExecutor("fExecutor")
+    private List<Listener> fListeners = new LinkedList<Listener>();
+
+    // Current number of elements in this generator.
+    @ConfinedToDsfExecutor("fExecutor")
+    private int fCount = MIN_COUNT;
+    
+    // Counter used to determine when to reset the element count.
+    @ConfinedToDsfExecutor("fExecutor")
+    private int fCountResetTrigger = 0;
+    
+    // Elements which were modified since the last reset.
+    @ConfinedToDsfExecutor("fExecutor")
+    private Set<Integer> fChangedIndexes = new HashSet<Integer>();
+    
+    // Flag used to ensure that requests are processed sequentially.
+    @ConfinedToDsfExecutor("fExecutor")
+    private boolean fServiceQueueInProgress = false;
+ 
+    public DataGeneratorWithExecutor() {
+        // Create the executor
+        fExecutor = new DefaultDsfExecutor("Supplier Executor");
+        
+        // Schedule a runnable to make the random changes.
+        fExecutor.scheduleAtFixedRate(
+            new DsfRunnable() {
+                public void run() {
+                    randomChanges();
+                }
+            },
+            RANDOM_CHANGE_INTERVAL, 
+            RANDOM_CHANGE_INTERVAL, 
+            TimeUnit.MILLISECONDS);
+    }
+     
+    public void shutdown(final RequestMonitor rm) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    // Empty the queue of requests and fail them.
+                    for (Request request : fQueue) {
+                        request.fRequestMonitor.setStatus(
+                            new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+                        request.fRequestMonitor.done();
+                    }
+                    fQueue.clear();
+                    
+                    // Kill executor.
+                    fExecutor.shutdown();
+                    rm.done();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    }
+
+    public void getCount(final DataRequestMonitor<Integer> rm) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fQueue.add(new CountRequest(rm));
+                    serviceQueue();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    }
+    
+    public void getValue(final int index, final DataRequestMonitor<String> rm) { 
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fQueue.add(new ItemRequest(index, rm));
+                    serviceQueue();
+                }
+            });
+        } catch (RejectedExecutionException e) {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }
+    } 
+
+    public void addListener(final Listener listener) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fListeners.add(listener);
+                }
+            });
+        } catch (RejectedExecutionException e) {}
+    }
+
+    public void removeListener(final Listener listener) {
+        try {
+            fExecutor.execute( new DsfRunnable() {
+                public void run() {
+                    fListeners.remove(listener);
+                }
+            });
+        } catch (RejectedExecutionException e) {}
+    }
+
+    // Main processing function of this generator.
+    @ConfinedToDsfExecutor("fExecutor")
+    private void serviceQueue() {
+        
+        for (Iterator<Request> requestItr = fQueue.iterator(); requestItr.hasNext();) {
+            Request request = requestItr.next();
+            if (request.fRequestMonitor.isCanceled()) {
+                request.fRequestMonitor.setStatus(
+                    new Status(IStatus.CANCEL, DsfExamplesPlugin.PLUGIN_ID, "Request canceled"));
+                request.fRequestMonitor.done();
+                requestItr.remove();
+            }
+        }
+        
+        // If a queue servicing is already scheduled, do nothing.
+        if (fServiceQueueInProgress) {
+            return;
+        }
+        
+        if (fQueue.size() != 0) {
+            // If there are requests to service, remove one from the queue and 
+            // schedule a runnable to process the request after a processing
+            // delay.
+            fServiceQueueInProgress = true;
+            final Request request = fQueue.remove(0);
+            fExecutor.schedule(
+                new DsfRunnable() {
+                    public void run() {
+                        if (request instanceof CountRequest) {
+                            processCountRequest((CountRequest)request);
+                        } else if (request instanceof ItemRequest) {
+                            processItemRequest((ItemRequest)request);
+                        } 
+                        
+                        // Reset the processing flag and process next
+                        // request.
+                        fServiceQueueInProgress = false;
+                        serviceQueue();
+                    }
+                }, 
+                PROCESSING_DELAY, TimeUnit.MILLISECONDS);
+        }
+    }
+    
+    @ConfinedToDsfExecutor("fExecutor")
+    private void processCountRequest(CountRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<Integer> rm = (DataRequestMonitor<Integer>)request.fRequestMonitor;
+        
+        rm.setData(fCount);
+        rm.done();
+    }
+
+    @ConfinedToDsfExecutor("fExecutor")
+    private void processItemRequest(ItemRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<String> rm = (DataRequestMonitor<String>)request.fRequestMonitor; 
+
+        if (fChangedIndexes.contains(request.fIndex)) {
+            rm.setData("Changed: " + request.fIndex);
+        } else {
+            rm.setData(Integer.toString(request.fIndex)); 
+        }
+        rm.done();
+    } 
+ 
+    /**
+     * This method simulates changes in the supplier's data set.
+     */
+    @ConfinedToDsfExecutor("fExecutor")
+    private void randomChanges() {
+        // Once every number of changes, reset the count, the rest of the 
+        // times just change certain values.
+        if (++fCountResetTrigger % RANDOM_COUNT_CHANGE_INTERVALS == 0){
+            randomCountReset();
+        } else {
+            randomDataChange();
+        }
+    }
+     
+    /**
+     * Calculates new size for provider's data set.
+     */
+    @ConfinedToDsfExecutor("fExecutor")
+    private void randomCountReset() {
+        // Calculate the new count.
+        Random random = new java.util.Random();
+        fCount = MIN_COUNT + Math.abs(random.nextInt()) % (MAX_COUNT - MIN_COUNT);
+
+        // Reset the changed values.
+        fChangedIndexes.clear();
+        
+        // Notify listeners  
+        for (Listener listener : fListeners) {
+            listener.countChanged();
+        }
+    }
+     
+    /**
+     * Invalidates a random range of indexes.
+     */
+    @ConfinedToDsfExecutor("fExecutor")
+    private void randomDataChange() {
+        // Calculate the indexes to change.
+        Random random = new java.util.Random();
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i = 0; i < fCount * RANDOM_CHANGE_SET_PERCENTAGE / 100; i++) {
+            set.add( new Integer(Math.abs(random.nextInt()) % fCount) );
+        }                    
+
+        // Add the indexes to an overall set of changed indexes.
+        fChangedIndexes.addAll(set);
+        
+        // Notify listeners  
+        for (Listener listener : fListeners) {
+            listener.valuesChanged(set);
+        }
+    }    
+}
+

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/answers/DataGeneratorWithThread.java

@@ -0,0 +1,238 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer.answers;
+
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.ListenerList;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.examples.dsf.DsfExamplesPlugin;
+
+/**
+ * Thread-based implementation of the data generator.
+ * <p>
+ * This generator is based around a queue of client requests and a thread which 
+ * reads the requests from the queue and processes them. The distinguishing 
+ * feature of this generator is that it uses a a blocking queue as the main 
+ * synchronization object.  However, fListeners, fShutdown,  and fChangedIndexes 
+ * fields also need to be thread-safe and so they implement their own 
+ * synchronization.
+ * </p>
+ */
+public class DataGeneratorWithThread extends Thread implements IDataGenerator {
+
+    // Request objects are used to serialize the interface calls into objects
+    // which can then be pushed into a queue.
+    abstract class Request {
+        final RequestMonitor fRequestMonitor;
+        
+        Request(RequestMonitor rm) {
+            fRequestMonitor = rm;
+        }
+    }
+    
+    class CountRequest extends Request {
+        CountRequest(DataRequestMonitor<Integer> rm) { 
+            super(rm); 
+        }
+    } 
+
+    class ItemRequest extends Request {
+        final int fIndex;
+        ItemRequest(int index, DataRequestMonitor<String> rm) { 
+            super(rm);
+            fIndex = index; 
+        }
+    } 
+
+    class ShutdownRequest extends Request {
+        ShutdownRequest(RequestMonitor rm) { 
+            super(rm);
+        }
+    }
+
+    // Main request queue of the data generator.  The getValue(), getCount(), 
+    // and shutdown() methods write into the queue, while the run() method 
+    // reads from it.
+    private final BlockingQueue<Request> fQueue = new LinkedBlockingQueue<Request>();
+
+    // ListenerList class provides thread safety.
+    private ListenerList fListeners = new ListenerList();
+    
+    // Current number of elements in this generator.
+    private int fCount = MIN_COUNT;
+    
+    // Counter used to determine when to reset the element count.
+    private int fCountResetTrigger = 0;
+    
+    // Elements which were modified since the last reset.
+    private Set<Integer> fChangedIndexes = Collections.synchronizedSet(new HashSet<Integer>());
+    
+    // Used to determine when to make changes in data.
+    private long fLastChangeTime = System.currentTimeMillis();
+
+    // Flag indicating when the generator has been shut down.
+    private AtomicBoolean fShutdown = new AtomicBoolean(false);
+ 
+    public DataGeneratorWithThread() {
+        // Immediately kick off the request processing thread.
+        start();
+    }
+     
+    public void shutdown(RequestMonitor rm) {
+        // Mark the generator as shut down.  After the fShutdown flag is set,
+        // all new requests should be shut down.
+        if (!fShutdown.getAndSet(true)) {
+            fQueue.add(new ShutdownRequest(rm));
+        } else {
+            // 
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    }
+
+    public void getCount(DataRequestMonitor<Integer> rm) {
+        if (!fShutdown.get()) {
+            fQueue.add(new CountRequest(rm));
+        } else {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    }
+    
+    public void getValue(int index, DataRequestMonitor<String> rm) { 
+        if (!fShutdown.get()) {
+            fQueue.add(new ItemRequest(index, rm));
+        } else {
+            rm.setStatus(new Status(IStatus.ERROR, DsfExamplesPlugin.PLUGIN_ID, "Supplier shut down"));
+            rm.done();
+        }        
+    } 
+
+    public void addListener(Listener listener) {
+        fListeners.add(listener);
+    }
+
+    public void removeListener(Listener listener) {
+        fListeners.remove(listener);
+    }
+    
+    @Override
+    public void run() {
+        try {
+            while(true) {
+                // Get the next request from the queue.  The time-out 
+                // ensures that that the random changes get processed. 
+                final Request request = fQueue.poll(100, TimeUnit.MILLISECONDS);
+                
+                // If a request was dequeued, process it.
+                if (request != null) {
+                    // Simulate a processing delay.
+                    Thread.sleep(PROCESSING_DELAY);
+                    
+                    if (request instanceof CountRequest) {
+                        processCountRequest((CountRequest)request);
+                    } else if (request instanceof ItemRequest) {
+                        processItemRequest((ItemRequest)request);
+                    } else if (request instanceof ShutdownRequest) {
+                        // If shutting down, just break out of the while(true) 
+                        // loop and thread will exit.
+                        request.fRequestMonitor.done();
+                        break;
+                    }
+                }
+                
+                // Simulate data changes.
+                randomChanges();
+            }
+        }
+        catch (InterruptedException x) {}
+    } 
+
+    private void processCountRequest(CountRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<Integer> rm = (DataRequestMonitor<Integer>)request.fRequestMonitor;
+        
+        rm.setData(fCount);
+        rm.done();
+    }
+
+    private void processItemRequest(ItemRequest request) {
+        @SuppressWarnings("unchecked") // Suppress warning about lost type info.
+        DataRequestMonitor<String> rm = (DataRequestMonitor<String>)request.fRequestMonitor; 
+
+        if (fChangedIndexes.contains(request.fIndex)) {
+            rm.setData("Changed: " + request.fIndex);
+        } else {
+            rm.setData(Integer.toString(request.fIndex));
+        }
+        rm.done();
+    } 
+ 
+    
+    private void randomChanges() {
+        // Check if enough time is elapsed.
+        if (System.currentTimeMillis() > fLastChangeTime + RANDOM_CHANGE_INTERVAL) {
+            fLastChangeTime = System.currentTimeMillis();
+            
+            // Once every number of changes, reset the count, the rest of the 
+            // times just change certain values.
+            if (++fCountResetTrigger % RANDOM_COUNT_CHANGE_INTERVALS == 0){
+                randomCountReset();
+            } else {
+                randomDataChange();
+            }
+        }
+    }
+     
+    private void randomCountReset() {
+        // Calculate the new count.
+        Random random = new java.util.Random();
+        fCount = MIN_COUNT + Math.abs(random.nextInt()) % (MAX_COUNT - MIN_COUNT);
+
+        // Reset the changed values.
+        fChangedIndexes.clear();
+        
+        // Notify listeners  
+        for (Object listener : fListeners.getListeners()) {
+            ((Listener)listener).countChanged();
+        }
+    }
+     
+    private void randomDataChange() {
+        // Calculate the indexes to change.
+        Random random = new java.util.Random();
+        Set<Integer> set = new HashSet<Integer>();
+        for (int i = 0; i < fCount * RANDOM_CHANGE_SET_PERCENTAGE / 100; i++) {
+            set.add( new Integer(Math.abs(random.nextInt()) % fCount) );
+        }                
+
+        // Add the indexes to an overall set of changed indexes.
+        fChangedIndexes.addAll(set);
+        
+        // Notify listeners  
+        for (Object listener : fListeners.getListeners()) {
+            ((Listener)listener).valuesChanged(set);
+        }
+    }    
+}
+
+

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/answers/IDataGenerator.java

@@ -0,0 +1,59 @@
+/*******************************************************************************
+ * Copyright (c) 2006, 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer.answers;
+
+import java.util.Set;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ThreadSafe;
+
+/**
+ * Data generator is simple source of data used to populate the example table 
+ * view.  It contains two asynchronous methods for retrieving the data 
+ * parameters: the count and the value for a given index.  It also allows the 
+ * view to receive events indicating when the data supplied by the generator 
+ * is changed. 
+ */
+@ThreadSafe
+public interface IDataGenerator {
+
+    // Constants which control the data generator behavior.
+    // Changing the count range can stress the scalability of the system, while
+    // changing of the process delay and random change interval can stress 
+    // its performance.
+    final static int MIN_COUNT = 100;
+    final static int MAX_COUNT = 200;
+    final static int PROCESSING_DELAY = 10;
+    final static int RANDOM_CHANGE_INTERVAL = 10000;
+    final static int RANDOM_COUNT_CHANGE_INTERVALS = 3;
+    final static int RANDOM_CHANGE_SET_PERCENTAGE = 10;
+
+    
+    // Listener interface that the view needs to implement to react
+    // to the changes in data.
+    public interface Listener {
+        void countChanged();
+        void valuesChanged(Set<Integer> indexes);
+    }
+
+    // Data access methods.
+    void getCount(DataRequestMonitor<Integer> rm);
+    void getValue(int index, DataRequestMonitor<String> rm); 
+    
+    // Method used to shutdown the data generator including any threads that 
+    // it may use.  
+    void shutdown(RequestMonitor rm);
+
+    // Methods for registering change listeners.
+    void addListener(Listener listener);
+    void removeListener(Listener listener);
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/dataviewer/answers/SyncDataViewer.java

@@ -0,0 +1,182 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.dataviewer.answers;
+
+import java.util.Set;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.Query;
+import org.eclipse.jface.viewers.IStructuredContentProvider;
+import org.eclipse.jface.viewers.TableViewer;
+import org.eclipse.jface.viewers.Viewer;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.graphics.Font;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+
+/**
+ * Data viewer based on a table, which reads data using synchronous methods.
+ * <p>
+ * This viewer implements the {@link IStructuredContentProvider} interface 
+ * which is used by the JFace TableViewer class to populate a Table.  This 
+ * interface contains one principal methods for reading data {@link #getElements(Object)}, 
+ * which synchronously returns an array of elements.  In order to implement this 
+ * method using the asynchronous data generator, this provider uses the 
+ * {@link Query} object. 
+ * </p>
+ */
+public class SyncDataViewer 
+    implements IStructuredContentProvider, IDataGenerator.Listener 
+{
+    // The viewer and generator that this content provider using.
+    final private TableViewer fViewer;
+    final private IDataGenerator fDataGenerator;
+    
+    public SyncDataViewer(TableViewer viewer, IDataGenerator generator) {
+        fViewer = viewer;
+        fDataGenerator = generator;
+        fDataGenerator.addListener(this);
+    }
+    
+    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
+        // Not used
+    }
+
+    
+    public Object[] getElements(Object inputElement) {
+        
+        // Create the query object for reading data count. 
+        Query<Integer> countQuery = new Query<Integer>() {
+            @Override
+            protected void execute(DataRequestMonitor<Integer> rm) {
+                fDataGenerator.getCount(rm);
+            }
+        };
+        
+        // Submit the query to be executed.  A query implements a runnable
+        // interface and it has to be executed in order to do its work.
+        ImmediateExecutor.getInstance().execute(countQuery);
+        int count = 0;
+        
+        // Block until the query completes, which will happen when the request
+        // monitor of the execute() method is marked done.
+        try {
+            count = countQuery.get();
+        } catch (Exception e) { 
+            // InterruptedException and ExecutionException can be thrown here.
+            // ExecutionException containing a CoreException will be thrown 
+            // if an error status is set to the Query's request monitor.
+            return new Object[0]; 
+        } 
+
+        // Create the array that will be filled with elements.
+        // For each index in the array execute a query to get the element at
+        // that index.
+        final Object[] elements = new Object[count];
+
+        for (int i = 0; i < count; i++) {
+            final int index = i;
+            Query<String> valueQuery = new Query<String>() {
+                @Override
+                protected void execute(DataRequestMonitor<String> rm) {
+                    fDataGenerator.getValue(index, rm);
+                }
+            };
+            ImmediateExecutor.getInstance().execute(valueQuery);
+            try {
+                elements[i] = valueQuery.get();
+            } catch (Exception e) { 
+                elements[i] = "error";
+            } 
+        }
+        return elements;
+    }
+
+    public void dispose() {
+        fDataGenerator.removeListener(this);
+    }
+
+    public void countChanged() {
+        // For any event from the generator, refresh the whole viewer.
+        refreshViewer();
+    }
+    
+    public void valuesChanged(Set<Integer> indexes) {
+        // For any event from the generator, refresh the whole viewer.
+        refreshViewer();
+    }
+    
+    private void refreshViewer() {
+        getElements(null);
+        
+        // This method may be called on any thread, switch to the display 
+        // thread before calling the viewer.
+        Display display = fViewer.getControl().getDisplay(); 
+        display.asyncExec( new Runnable() {
+            public void run() {
+                if (!fViewer.getControl().isDisposed()) {
+                    fViewer.refresh();
+                }
+            }
+        });
+    }
+    
+    public static void main(String[] args) {
+        // Create the shell to hold the viewer.
+        Display display = new Display();
+        Shell shell = new Shell(display, SWT.SHELL_TRIM);
+        shell.setLayout(new GridLayout());
+        GridData data = new GridData(GridData.FILL_BOTH);
+        shell.setLayoutData(data);
+        Font font = new Font(display, "Courier", 10, SWT.NORMAL);
+
+        // Create the table viewer.
+        TableViewer tableViewer = new TableViewer(shell, SWT.BORDER);
+        tableViewer.getControl().setLayoutData(data);
+
+        // Create the data generator.
+        final IDataGenerator generator = new DataGeneratorWithExecutor();     
+        
+        // Create the content provider which will populate the viewer.
+        SyncDataViewer contentProvider = new SyncDataViewer(tableViewer, generator);
+        tableViewer.setContentProvider(contentProvider);
+        tableViewer.setInput(new Object());
+
+        // Open the shell and service the display dispatch loop until user
+        // closes the shell.
+        shell.open();
+        while (!shell.isDisposed()) {
+            if (!display.readAndDispatch())
+                display.sleep();
+        }
+        
+        // The IDataGenerator.shutdown() method is asynchronous, this requires
+        // using a query again in order to wait for its completion.
+        Query<Object> shutdownQuery = new Query<Object>() {
+            @Override
+            protected void execute(DataRequestMonitor<Object> rm) {
+                generator.shutdown(rm);
+            }
+        };
+        ImmediateExecutor.getInstance().execute(shutdownQuery);
+        try {
+            shutdownQuery.get();
+        } catch (Exception e) {}
+        
+        // Shut down the display.
+        font.dispose();    
+        display.dispose();
+    }
+    
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/Async2Plus2.java

@@ -0,0 +1,40 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor;
+
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+
+/**
+ * Example of using a DataRequestMonitor to retrieve a result from an 
+ * asynchronous method.
+ */
+public class Async2Plus2 {
+    
+    public static void main(String[] args) {
+        Executor executor = ImmediateExecutor.getInstance();
+        DataRequestMonitor<Integer> rm = 
+            new DataRequestMonitor<Integer>(executor, null) {
+                @Override
+                protected void handleCompleted() {
+                    System.out.println("2 + 2 = " + getData());
+                }
+            };
+        asyncAdd(2, 2, rm);
+    }
+
+    static void asyncAdd(int value1, int value2, DataRequestMonitor<Integer> rm) {
+        rm.setData(value1 + value2);
+        rm.done();
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/AsyncHelloWorld.java

@@ -0,0 +1,46 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor;
+
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+
+/**
+ * "Hello world" example which uses an asynchronous method to print out
+ * the result.  
+ * <p>
+ * The main method uses an immediate executor, which executes runnables
+ * as soon as they are submitted, in creating its request monitor. 
+ * 
+ */
+public class AsyncHelloWorld {
+
+    public static void main(String[] args) {
+        Executor executor = ImmediateExecutor.getInstance();
+        RequestMonitor rm = new RequestMonitor(executor, null);
+        asyncHelloWorld(rm);
+    }
+
+    static void asyncHelloWorld(RequestMonitor rm) {
+        System.out.println("Hello world");
+        // TODO Exercise 1: - Call the second async. "Hello world 2" method.
+        // Hint: Calling an asynchronous method requires passing to it a 
+        // request monitor.  A new request monitor can be constructed with 
+        // a parent RequestMonitor as an argument argument.  The parent gets 
+        // completed automatically when the lower level request monitor is 
+        // completed.
+        rm.done();
+    }
+    
+    // TODO: Exercise 1 - Add a second async. "Hello world 2" method.   
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/AsyncQuicksort.java

@@ -0,0 +1,111 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor;
+
+import java.util.Arrays;
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.CountingRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+
+/**
+ * Example of using a CountingRequestMonitor to wait for multiple 
+ * asynchronous calls to complete.  
+ */
+public class AsyncQuicksort {
+
+    static Executor fgExecutor = ImmediateExecutor.getInstance();
+
+    public static void main(String[] args) {
+        final int[] array = {5, 7, 8, 3, 2, 1, 9, 5, 4};
+
+        System.out.println("To sort: " + Arrays.toString(array));
+        asyncQuicksort(
+            array, 0, array.length - 1, 
+            new RequestMonitor(fgExecutor, null) {
+                @Override
+                protected void handleCompleted() {
+                    System.out.println("Sorted: " + Arrays.toString(array));
+                }
+            });
+    }
+
+    static void asyncQuicksort(final int[] array, final int left, 
+        final int right, final RequestMonitor rm) 
+    {
+        if (right > left) {
+            int pivot = left;
+            // TODO: Exercise 2 - Convert the call to partition into an
+            // asynchronous call to asyncPartition().
+            // Hint: The rest of the code below should be executed inside
+            // the DataRequestMonitor.handleCompleted() overriding method.
+            int newPivot = partition(array, left, right, pivot);
+            printArray(array, left, right, newPivot);
+
+            CountingRequestMonitor countingRm = new CountingRequestMonitor(fgExecutor, rm);
+            asyncQuicksort(array, left, newPivot - 1, countingRm);
+            asyncQuicksort(array, newPivot + 1, right, countingRm);
+            countingRm.setDoneCount(2);
+        } else {
+            rm.done();
+        }
+    }
+
+    // TODO Exercise 2 - Convert partition to an asynchronous method.
+    // Hint: a DataRequestMonitor<Integer> should be used to carry the 
+    // return value to the caller.
+    static int partition(int[] array, int left, int right, int pivot)
+    {
+        int pivotValue = array[pivot];
+        array[pivot] = array[right]; 
+        array[right] = pivotValue; 
+        int store = left;
+        for (int i  = left; i < right; i++) {
+            if (array[i] <= pivotValue) {
+                int tmp = array[store];
+                array[store] = array[i];
+                array[i] = tmp;
+                store++;
+            }
+        }
+        array[right] = array[store];
+        array[store] = pivotValue;
+
+        // TODO: Request Monitors Exercise 2 - Return the data to caller using 
+        // a request monitor.
+        return store;
+    }
+
+    static void printArray(int[] array, int left, int right, int pivot) {
+        StringBuffer buffer = new StringBuffer();
+        for (int i = 0; i < array.length; i++ ) {
+            if (i == left) {
+                buffer.append('>');
+            } else if (i == pivot) {
+                buffer.append('-');
+            } else {
+                buffer.append(' ');
+            }
+            buffer.append(array[i]);
+
+            if (i == right) {
+                buffer.append('<');
+            } else if (i == pivot) {
+                buffer.append('-');
+            } else {
+                buffer.append(' ');
+            }
+        }
+
+        System.out.println(buffer);
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/answers/Async2Plus2.java

@@ -0,0 +1,40 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor.answers;
+
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+
+/**
+ * Example of using a DataRequestMonitor to retrieve a result from an 
+ * asynchronous method.
+ */
+public class Async2Plus2 {
+    
+    public static void main(String[] args) {
+        Executor executor = ImmediateExecutor.getInstance();
+        DataRequestMonitor<Integer> rm = 
+            new DataRequestMonitor<Integer>(executor, null) {
+                @Override
+                protected void handleCompleted() {
+                    System.out.println("2 + 2 = " + getData());
+                }
+            };
+        asyncAdd(2, 2, rm);
+    }
+
+    static void asyncAdd(int value1, int value2, DataRequestMonitor<Integer> rm) {
+        rm.setData(value1 + value2);
+        rm.done();
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/answers/AsyncHelloWorld.java

@@ -0,0 +1,44 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor.answers;
+
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+
+/**
+ * "Hello world" example which uses an asynchronous method to print out
+ * the result.  
+ * <p>
+ * The main method uses an immediate executor, which executes runnables
+ * as soon as they are submitted, in creating its request monitor. 
+ * 
+ */
+public class AsyncHelloWorld {
+
+    public static void main(String[] args) {
+        Executor executor = ImmediateExecutor.getInstance();
+        RequestMonitor rm = new RequestMonitor(executor, null);
+        asyncHelloWorld(rm);
+    }
+
+    static void asyncHelloWorld(RequestMonitor rm) {
+        System.out.println("Hello world");
+        RequestMonitor rm2 = new RequestMonitor(ImmediateExecutor.getInstance(), rm);
+        asyncHelloWorld2(rm2);
+    }
+    
+    static void asyncHelloWorld2(RequestMonitor rm) {
+        System.out.println("Hello world 2");
+        rm.done();
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/requestmonitor/answers/AsyncQuicksort.java

@@ -0,0 +1,113 @@
+/*******************************************************************************
+ * Copyright (c) 2008 Wind River Systems and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Wind River Systems - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.dd.examples.dsf.requestmonitor.answers;
+
+import java.util.Arrays;
+import java.util.concurrent.Executor;
+
+import org.eclipse.dd.dsf.concurrent.CountingRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.DataRequestMonitor;
+import org.eclipse.dd.dsf.concurrent.ImmediateExecutor;
+import org.eclipse.dd.dsf.concurrent.RequestMonitor;
+
+/**
+ * Example of using a CountingRequestMonitor to wait for multiple 
+ * asynchronous calls to complete.  
+ */
+public class AsyncQuicksort {
+
+    static Executor fgExecutor = ImmediateExecutor.getInstance();
+
+    public static void main(String[] args) {
+        final int[] array = {5, 7, 8, 3, 2, 1, 9, 5, 4};
+
+        System.out.println("To sort: " + Arrays.toString(array));
+        asyncQuicksort(
+            array, 0, array.length - 1, 
+            new RequestMonitor(fgExecutor, null) {
+                @Override
+                protected void handleCompleted() {
+                    System.out.println("Sorted: " + Arrays.toString(array));
+                }
+            });
+    }
+
+    static void asyncQuicksort(final int[] array, final int left, 
+        final int right, final RequestMonitor rm) 
+    {
+        if (right > left) {
+            int pivot = left;
+            asyncPartition(
+                array, left, right, pivot, 
+                new DataRequestMonitor<Integer>(fgExecutor, rm) {
+                    @Override
+                    protected void handleCompleted() {
+                        int newPivot = getData();
+                        printArray(array, left, right, newPivot);
+                       
+                        CountingRequestMonitor countingRm = new CountingRequestMonitor(fgExecutor, rm);
+                        asyncQuicksort(array, left, newPivot - 1, countingRm);
+                        asyncQuicksort(array, newPivot + 1, right, countingRm);
+                        countingRm.setDoneCount(2);
+                    }
+            });
+        } else {
+            rm.done();
+        }
+    }
+
+    static void asyncPartition(int[] array, int left, int right, int pivot, DataRequestMonitor<Integer> rm)
+    {
+        int pivotValue = array[pivot];
+        array[pivot] = array[right]; 
+        array[right] = pivotValue; 
+        int store = left;
+        for (int i  = left; i < right; i++) {
+            if (array[i] <= pivotValue) {
+                int tmp = array[store];
+                array[store] = array[i];
+                array[i] = tmp;
+                store++;
+            }
+        }
+        array[right] = array[store];
+        array[store] = pivotValue;
+
+        // Java 5 automatically converts the int type of the store variable
+        // to an Integer object.
+        rm.setData(store);
+        rm.done();
+    }
+
+    static void printArray(int[] array, int left, int right, int pivot) {
+        StringBuffer buffer = new StringBuffer();
+        for (int i = 0; i < array.length; i++ ) {
+            if (i == left) {
+                buffer.append('>');
+            } else if (i == pivot) {
+                buffer.append('-');
+            } else {
+                buffer.append(' ');
+            }
+            buffer.append(array[i]);
+
+            if (i == right) {
+                buffer.append('<');
+            } else if (i == pivot) {
+                buffer.append('-');
+            } else {
+                buffer.append(' ');
+            }
+        }
+
+        System.out.println(buffer);
+    }
+}

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/timers/AlarmsVMNode.java

@@ -44,8 +44,14 @@ class AlarmsVMNode extends AbstractDMVMNode
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
         // Check that the services are available
-        if (!checkService(AlarmService.class, null, update)) return;
+        if ( getServicesTracker().getService(AlarmService.class) == null ) {
-        if (!checkService(TimerService.class, null, update)) return;
+            handleFailedUpdate(update);
+            return;
+        }
+        if ( getServicesTracker().getService(TimerService.class) == null ) {
+            handleFailedUpdate(update);
+            return;
+        }
 
         // Find the trigger and timer contexts.  If not found, fail.
         TriggerDMContext alarmDmc = findDmcInPath(

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/timers/TimersVMNode.java

@@ -84,12 +84,14 @@ class TimersVMNode extends AbstractDMVMNode
     
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(AlarmService.class, null, update)) return;
+    	if ( getServicesTracker().getService(TimerService.class) == null ) {
+            handleFailedUpdate(update);
+            return;
+    	}
 
         // Retrieve the timer DMContexts, create the corresponding VMCs array, and 
         // set them as result.
-        TimerDMContext[] timers = 
+        TimerDMContext[] timers = getServicesTracker().getService(TimerService.class).getTimers();
-            getServicesTracker().getService(TimerService.class).getTimers();
         fillUpdateWithVMCs(update, timers);
         update.done();
     }
@@ -118,14 +120,17 @@ class TimersVMNode extends AbstractDMVMNode
             update.getViewerInput(), update.getElementPath(), TimerDMContext.class);
         
         // If either update or service are not valid, fail the update and exit.
-        if (!checkDmc(dmc, update) || 
+        if ( dmc == null ) {
-            !checkService(TimerService.class, null, update)) 
+        	handleFailedUpdate(update);
-        {
+            return;
-           return;
         }
         
-        TimerService timerService = 
+        TimerService timerService = getServicesTracker().getService(TimerService.class, null);
-            getServicesTracker().getService(TimerService.class, null);
+        if ( timerService == null ) {
+            handleFailedUpdate(update);
+            return;
+    	}
+        
         int value = timerService.getTimerValue(dmc);
         
         if (value == -1) {

plugins/org.eclipse.dd.examples.dsf/src/org/eclipse/dd/examples/dsf/timers/TriggersVMNode.java

@@ -85,10 +85,12 @@ class TriggersVMNode extends AbstractDMVMNode
     
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-        if (!checkService(AlarmService.class, null, update)) return;
+        if ( getServicesTracker().getService(AlarmService.class) == null ) {
+            handleFailedUpdate(update);
+            return;
+    	}
 
-        TriggerDMContext[] triggers = 
+        TriggerDMContext[] triggers = getServicesTracker().getService(AlarmService.class).getTriggers();
-            getServicesTracker().getService(AlarmService.class).getTriggers();
         fillUpdateWithVMCs(update, triggers);
         update.done();
     }
@@ -119,16 +121,19 @@ class TriggersVMNode extends AbstractDMVMNode
         TriggerDMContext triggerCtx = findDmcInPath( 
             update.getViewerInput(), update.getElementPath(), TriggerDMContext.class);
         
-        // If either update or service are not valid, fail the update and exit.
+        // If either update or service are not valid, fail the update and return.
-        if (!checkDmc(triggerCtx, update) || 
+        if ( triggerCtx == null ) {
-            !checkService(AlarmService.class, null, update)) 
+        	handleFailedUpdate(update);
-        {
             return;
         }
         
+        AlarmService alarmService = getServicesTracker().getService(AlarmService.class, null); 
+        if ( alarmService == null ) {
+            handleFailedUpdate(update);
+            return;
+    	}
+        
         // Calculate and set the update properties.
-        AlarmService alarmService = 
-            getServicesTracker().getService(AlarmService.class, null); 
         int value = alarmService.getTriggerValue(triggerCtx);
         
         if (value == -1) {

plugins/org.eclipse.dd.gdb.ui/src/org/eclipse/dd/gdb/internal/ui/viewmodel/launch/ContainerVMNode.java

@@ -54,9 +54,14 @@ public class ContainerVMNode extends AbstractDMVMNode
 
 	@Override
 	protected void updateElementsInSessionThread(IChildrenUpdate update) {
-      if (!checkService(AbstractMIControl.class, null, update)) return;
       
-      MIControlDMContext containerCtx = getServicesTracker().getService(AbstractMIControl.class).getControlDMContext();
+      AbstractMIControl controlService = getServicesTracker().getService(AbstractMIControl.class);
+      if ( controlService == null ) {
+              handleFailedUpdate(update);
+              return;
+      }
+      
+      MIControlDMContext containerCtx = controlService.getControlDMContext();
       update.setChild(createVMContext(containerCtx), 0); 
       update.done();
 	}
@@ -77,9 +82,12 @@ public class ContainerVMNode extends AbstractDMVMNode
 	
 	protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
-            if (!checkService(GDBRunControl.class, null, update)) continue;
+        	final GDBRunControl runControl = getServicesTracker().getService(GDBRunControl.class);
-            final GDBRunControl runControl = getServicesTracker().getService(GDBRunControl.class);
+            if ( runControl == null ) {
-
+                handleFailedUpdate(update);
+                continue;
+            }
+            
             final GDBControlDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), GDBControlDMContext.class);
 
             String imageKey = null;

plugins/org.eclipse.dd.gdb.ui/src/org/eclipse/dd/gdb/internal/ui/viewmodel/launch/ThreadVMNode.java

@@ -61,26 +61,30 @@ public class ThreadVMNode extends AbstractDMVMNode
 
     @Override
     protected void updateElementsInSessionThread(final IChildrenUpdate update) {
-    	 if (!checkService(IRunControl.class, null, update)) return;
+    	IRunControl runControl = getServicesTracker().getService(IRunControl.class);
-         final IContainerDMContext contDmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IContainerDMContext.class);
+    	if ( runControl == null ) {
+    		handleFailedUpdate(update);
+    		return;
+    	}
 
-         if (contDmc == null) {
+    	final IContainerDMContext contDmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IContainerDMContext.class);
-             handleFailedUpdate(update);
+    	if (contDmc == null) {
-             return;
+    		handleFailedUpdate(update);
-         } 
+    		return;
-  
+    	} 
-         getServicesTracker().getService(IRunControl.class).getExecutionContexts(contDmc, 
+
-    			 new DataRequestMonitor<IExecutionDMContext[]>(getSession().getExecutor(), null){
+    	runControl.getExecutionContexts(contDmc, 
-    	                @Override
+    			new DataRequestMonitor<IExecutionDMContext[]>(getSession().getExecutor(), null){
-						public void handleCompleted() {
+    				@Override
-    	                    if (!isSuccess()) {
+    				public void handleCompleted() {
-    	                        handleFailedUpdate(update);
+    					if (!isSuccess()) {
-    	                        return;
+    						handleFailedUpdate(update);
-    	                    }
+    						return;
-    	                    fillUpdateWithVMCs(update, getData());
+    					}
-                            update.done();
+    					fillUpdateWithVMCs(update, getData());
-    	                }
+    					update.done();
-    			 });
+    				}
+    			});
     }
 
 
@@ -195,8 +199,11 @@ public class ThreadVMNode extends AbstractDMVMNode
     
     protected void updateLabelInSessionThread(ILabelUpdate[] updates) {
         for (final ILabelUpdate update : updates) {
-            if (!checkService(GDBRunControl.class, null, update)) continue;
+        	final GDBRunControl runControl = getServicesTracker().getService(GDBRunControl.class);
-            final GDBRunControl runControl = getServicesTracker().getService(GDBRunControl.class);
+            if ( runControl == null ) {
+                    handleFailedUpdate(update);
+                    continue;
+            }
             
             final IMIExecutionDMContext dmc = findDmcInPath(update.getViewerInput(), update.getElementPath(), IMIExecutionDMContext.class);
 
@@ -220,7 +227,11 @@ public class ThreadVMNode extends AbstractDMVMNode
 
                     // We're in a new dispatch cycle, and we have to check whether the 
                     // service reference is still valid.
-                    if (!checkService(GDBRunControl.class, null, update)) return;
+                    final GDBRunControl runControl = getServicesTracker().getService(GDBRunControl.class);
+                    if ( runControl == null ) {
+                        handleFailedUpdate(update);
+                        return;
+                    }
 
                     final StateChangeReason reason = getData().getStateChangeReason();