diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CProjectDescriptionManager.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CProjectDescriptionManager.java
index ce6e4b670fb..3d32e38b961 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CProjectDescriptionManager.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/CProjectDescriptionManager.java
@@ -443,7 +443,9 @@ public class CProjectDescriptionManager implements ICProjectDescriptionManager {
 			monitor = new NullProgressMonitor();
 
 		// Should the rule be scheduled, or run immediately
-		boolean scheduleRule =  ResourcesPlugin.getWorkspace().isTreeLocked();
+		// Bug 310007 - Always unsafe to modify resources while data structure lock is held
+		boolean scheduleRule = true;
+//		boolean scheduleRule =  ResourcesPlugin.getWorkspace().isTreeLocked();
 
 		// Check whether current job contains rule 'rule'
 		// If not, we must schedule another job to execute the runnable
diff --git a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/xml/XmlProjectDescriptionStorage.java b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/xml/XmlProjectDescriptionStorage.java
index 1772afea4e6..d8316f7d06f 100644
--- a/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/xml/XmlProjectDescriptionStorage.java
+++ b/core/org.eclipse.cdt.core/model/org/eclipse/cdt/internal/core/settings/model/xml/XmlProjectDescriptionStorage.java
@@ -48,9 +48,9 @@ import org.eclipse.cdt.internal.core.settings.model.CProjectDescriptionManager;
 import org.eclipse.cdt.internal.core.settings.model.CProjectDescriptionStorageManager;
 import org.eclipse.cdt.internal.core.settings.model.ExceptionFactory;
 import org.eclipse.cdt.internal.core.settings.model.ICProjectDescriptionStorageType;
+import org.eclipse.cdt.internal.core.settings.model.ICProjectDescriptionStorageType.CProjectDescriptionStorageTypeProxy;
 import org.eclipse.cdt.internal.core.settings.model.SettingsContext;
 import org.eclipse.cdt.internal.core.settings.model.SettingsModelMessages;
-import org.eclipse.cdt.internal.core.settings.model.ICProjectDescriptionStorageType.CProjectDescriptionStorageTypeProxy;
 import org.eclipse.core.filesystem.EFS;
 import org.eclipse.core.filesystem.IFileInfo;
 import org.eclipse.core.filesystem.IFileStore;
@@ -61,6 +61,7 @@ import org.eclipse.core.resources.IProjectDescription;
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.resources.IWorkspaceRunnable;
 import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.core.runtime.IStatus;
@@ -120,6 +121,8 @@ public class XmlProjectDescriptionStorage extends AbstractCProjectDescriptionSto
 		super(type, project, version);
 	}
 
+	private int desSerialTotalCount;
+	private volatile int desSerialCurrent;
 
 	/**
 	 * The workspace runnable that actually goes about serializing the project description
@@ -127,20 +130,22 @@ public class XmlProjectDescriptionStorage extends AbstractCProjectDescriptionSto
 	private class DesSerializationRunnable implements IWorkspaceRunnable {
 		private final ICProjectDescription fDes;
 		private final ICStorageElement fElement;
+		private final int serializingNumber;
 
 		public DesSerializationRunnable(ICProjectDescription des, ICStorageElement el) {
 			fDes = des;
 			fElement = el;
+			serializingNumber = desSerialTotalCount++;
 		}
 
 		public void run(IProgressMonitor monitor) throws CoreException {
-			try {
-				serializingLock.acquire();
-				projectModificaitonStamp = serialize(fDes.getProject(), ICProjectDescriptionStorageType.STORAGE_FILE_NAME, fElement);
-				((ContributedEnvironment) CCorePlugin.getDefault().getBuildEnvironmentManager().getContributedEnvironment()).serialize(fDes);
-			} finally {
-				serializingLock.release();
-			}
+			// Asserting that the platform job API stands by its committment to run jobs
+			// with conflicting scheduling rules in strict order -- so the project configuration
+			// at the end of a batch of changes is consistent.
+			Assert.isTrue(serializingNumber == desSerialCurrent);
+			desSerialCurrent++;
+			projectModificaitonStamp = serialize(fDes.getProject(), ICProjectDescriptionStorageType.STORAGE_FILE_NAME, fElement);
+			((ContributedEnvironment) CCorePlugin.getDefault().getBuildEnvironmentManager().getContributedEnvironment()).serialize(fDes);
 		}
 
 	}