### Eclipse Workspace Patch 1.0
#P org.eclipse.jdt.core
Index: model/org/eclipse/jdt/core/package.html
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/core/package.html,v
retrieving revision 1.3
diff -u -r1.3 package.html
--- model/org/eclipse/jdt/core/package.html	1 Jul 2002 11:20:31 -0000	1.3
+++ model/org/eclipse/jdt/core/package.html	26 Aug 2008 14:25:42 -0000
@@ -13,7 +13,15 @@
 Package Specification</h2>
 
 <p><br>This package contains the Java model classes, which implement Java
-specific behaviour for resources and further decompose java resources into
+specific behaviour for resources and further decompose Java resources into
 model elements.
+</p><p>
+Note that a lot of Java model operations require a Java project's classpath resolution.
+For example IJavaProject#getResolvedClasspath(boolean) or JavaCore#setClasspathContainer()
+will require to resolve the classpath of one or more projects. Client should be aware that
+this resolution may require to take project modification rule 
+(see IResourceRuleFactory#modifyRule(IResource)).
+</p>
+
 </body>
 </html>
Index: model/org/eclipse/jdt/internal/core/DeltaProcessor.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/DeltaProcessor.java,v
retrieving revision 1.325
diff -u -r1.325 DeltaProcessor.java
--- model/org/eclipse/jdt/internal/core/DeltaProcessor.java	27 Jun 2008 16:03:50 -0000	1.325
+++ model/org/eclipse/jdt/internal/core/DeltaProcessor.java	26 Aug 2008 14:25:42 -0000
@@ -1963,6 +1963,11 @@
 				return;
 
 			case IResourceChangeEvent.PRE_BUILD :
+				// force initialization of roots before builders run to avoid deadlock in another thread
+				// (note this is no-op if already initialized)
+				// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=241751
+				this.state.initializeRoots(false/*not initiAfterLoad*/);
+				
 				boolean isAffected = isAffectedBy(delta);
 				boolean needCycleValidation = isAffected && validateClasspaths(delta);
 
Index: model/org/eclipse/jdt/internal/core/ProjectReferenceChange.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jdt.core/model/org/eclipse/jdt/internal/core/ProjectReferenceChange.java,v
retrieving revision 1.7
diff -u -r1.7 ProjectReferenceChange.java
--- model/org/eclipse/jdt/internal/core/ProjectReferenceChange.java	27 Jun 2008 16:03:51 -0000	1.7
+++ model/org/eclipse/jdt/internal/core/ProjectReferenceChange.java	26 Aug 2008 14:25:42 -0000
@@ -41,69 +41,72 @@
 	 * Update projects references so that the build order is consistent with the classpath
 	 */
 	public void updateProjectReferencesIfNecessary() throws JavaModelException {
-
-		final String[] oldRequired = this.oldResolvedClasspath == null ? CharOperation.NO_STRINGS : this.project.projectPrerequisites(this.oldResolvedClasspath);
+		
+		String[] oldRequired = this.oldResolvedClasspath == null ? CharOperation.NO_STRINGS : this.project.projectPrerequisites(this.oldResolvedClasspath);
 		IClasspathEntry[] newResolvedClasspath = this.project.getResolvedClasspath();
-		final String[] newRequired = this.project.projectPrerequisites(newResolvedClasspath);
+		String[] newRequired = this.project.projectPrerequisites(newResolvedClasspath);
 		final IProject projectResource = this.project.getProject();
-		IWorkspaceRunnable runnable = new IWorkspaceRunnable() {
-			public void run(IProgressMonitor monitor) throws CoreException {
-				IProjectDescription description = projectResource.getDescription();
-
-				IProject[] projectReferences = description.getDynamicReferences();
-
-				HashSet oldReferences = new HashSet(projectReferences.length);
-				for (int i = 0; i < projectReferences.length; i++){
-					String projectName = projectReferences[i].getName();
-					oldReferences.add(projectName);
-				}
-				HashSet newReferences = (HashSet)oldReferences.clone();
-
-				for (int i = 0; i < oldRequired.length; i++){
-					String projectName = oldRequired[i];
-					newReferences.remove(projectName);
-				}
-				for (int i = 0; i < newRequired.length; i++){
-					String projectName = newRequired[i];
-					newReferences.add(projectName);
-				}
-
-				Iterator iter;
-				int newSize = newReferences.size();
-
-				checkIdentity: {
-					if (oldReferences.size() == newSize){
-						iter = newReferences.iterator();
-						while (iter.hasNext()){
-							if (!oldReferences.contains(iter.next())){
-								break checkIdentity;
-							}
+		
+		try {
+			IProject[] projectReferences = projectResource.getDescription().getDynamicReferences();
+			
+			HashSet oldReferences = new HashSet(projectReferences.length);
+			for (int i = 0; i < projectReferences.length; i++){
+				String projectName = projectReferences[i].getName();
+				oldReferences.add(projectName);
+			}
+			HashSet newReferences = (HashSet)oldReferences.clone();
+	
+			for (int i = 0; i < oldRequired.length; i++){
+				String projectName = oldRequired[i];
+				newReferences.remove(projectName);
+			}
+			for (int i = 0; i < newRequired.length; i++){
+				String projectName = newRequired[i];
+				newReferences.add(projectName);
+			}
+	
+			Iterator iter;
+			int newSize = newReferences.size();
+			
+			checkIdentity: {
+				if (oldReferences.size() == newSize){
+					iter = newReferences.iterator();
+					while (iter.hasNext()){
+						if (!oldReferences.contains(iter.next())){
+							break checkIdentity;
 						}
-						return;
 					}
+					return;
 				}
-				String[] requiredProjectNames = new String[newSize];
-				int index = 0;
-				iter = newReferences.iterator();
-				while (iter.hasNext()){
-					requiredProjectNames[index++] = (String)iter.next();
-				}
-				Util.sort(requiredProjectNames); // ensure that if changed, the order is consistent
-
-				IProject[] requiredProjectArray = new IProject[newSize];
-				IWorkspaceRoot wksRoot = projectResource.getWorkspace().getRoot();
-				for (int i = 0; i < newSize; i++){
-					requiredProjectArray[i] = wksRoot.getProject(requiredProjectNames[i]);
-				}
-				description.setDynamicReferences(requiredProjectArray);
-				projectResource.setDescription(description, IResource.AVOID_NATURE_CONFIG, null);
 			}
-		};
-		try {
-			// ensure that a sheduling rule is used so that the project description is not modified by another thread while we update it
+			String[] requiredProjectNames = new String[newSize];
+			int index = 0;
+			iter = newReferences.iterator();
+			while (iter.hasNext()){
+				requiredProjectNames[index++] = (String)iter.next();
+			}
+			Util.sort(requiredProjectNames); // ensure that if changed, the order is consistent
+			
+			final IProject[] requiredProjectArray = new IProject[newSize];
+			IWorkspaceRoot wksRoot = projectResource.getWorkspace().getRoot();
+			for (int i = 0; i < newSize; i++){
+				requiredProjectArray[i] = wksRoot.getProject(requiredProjectNames[i]);
+			}
+				
+			// ensure that a scheduling rule is used so that the project description is not modified by another thread while we update it
 			// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=214981
+			// also ensure that if no change (checkIdentify block returned above) we don't reach here
+			// see https://bugs.eclipse.org/bugs/show_bug.cgi?id=241751
 			IWorkspace workspace = projectResource.getWorkspace();
-			ISchedulingRule rule = workspace.getRuleFactory().modifyRule(projectResource); // sheduling rule for modifying the project
+			ISchedulingRule rule = workspace.getRuleFactory().modifyRule(projectResource); // scheduling rule for modifying the project
+			IWorkspaceRunnable runnable = new IWorkspaceRunnable() {
+				public void run(IProgressMonitor monitor) throws CoreException {
+					IProjectDescription description = projectResource.getDescription();
+					description.setDynamicReferences(requiredProjectArray);
+					projectResource.setDescription(description, IResource.AVOID_NATURE_CONFIG, null);
+				}
+			};
 			workspace.run(runnable, rule, IWorkspace.AVOID_UPDATE, null);
 		} catch(CoreException e){
 			if (!ExternalJavaProject.EXTERNAL_PROJECT_NAME.equals(this.project.getElementName()))