I'm also having problems with foreground thread pauses when using JBoss Tools. It would appear that the entire Eclipse hangs when for instance moving the Project Explorer with the cursor keys, passing by the "JBoss 6.0 Runtime" classpath element. There is no discernible Task going on in the Progress View, since the SWT thread is stuck.
I tried it in a debugger, and got this:
Thread [main] (Suspended)
WinNTFileSystem.getBooleanAttributes(File) line: not available [native method]
File.exists() line: not available
ClientAllRuntimeClasspathProvider.addSinglePath(IPath, ArrayList<IPath>) line: 181
ClientAllRuntimeClasspathProvider.addPaths(IPath, ArrayList<IPath>) line: 167
ClientAllRuntimeClasspathProvider.get50(IPath, IPath) line: 134
ClientAllRuntimeClasspathProvider.get60(IPath, IPath) line: 150
ClientAllRuntimeClasspathProvider.resolveClasspathContainer(IProject, IRuntime) line: 85
ClientAllRuntimeClasspathProvider(RuntimeClasspathProviderDelegate).resolveClasspathContainerImpl(IProject, IRuntime) line: 133
RuntimeClasspathProviderWrapper.resolveClasspathContainerImpl(IProject, IRuntime) line: 153
RuntimeClasspathContainer.getClasspathEntries() line: 77
JavaProject.resolveClasspath(IClasspathEntry[], IClasspathEntry[], boolean, boolean) line: 2656
JavaProject.resolveClasspath(IClasspathEntry[], boolean, boolean) line: 2574
JavaProject.resolveClasspath(IClasspathEntry[]) line: 2562
JavaProject.findPackageFragmentRoots(IClasspathEntry) line: 1219
ClassPathContainer.getPackageFragmentRoots() line: 120
ClassPathContainer.getChildren() line: 125
PackageExplorerContentProvider.getContainerPackageFragmentRoots(PackageFragmentRootContainer) line: 365
PackageExplorerContentProvider.getChildren(Object) line: 292
PackageExplorerContentProvider(StandardJavaElementContentProvider).hasChildren(Object) line: 241
PackageExplorerPart$PackageExplorerProblemTreeViewer(AbstractTreeViewer).isExpandable(Object) line: 2086
PackageExplorerPart$PackageExplorerProblemTreeViewer(TreeViewer).isExpandable(Object) line: 588
PackageExplorerPart$PackageExplorerProblemTreeViewer(ProblemTreeViewer).isExpandable(Object) line: 246
PackagesFrameSource(TreeViewerFrameSource).getSelectionFrame(int) line: 144
PackagesFrameSource(TreeViewerFrameSource).getFrame(int, int) line: 99
GoIntoAction.getSelectionFrame(int) line: 36
GoIntoAction.update() line: 57
PackageExplorerActionGroup$2.selectionChanged(SelectionChangedEvent) line: 161
Viewer$2.run() line: 162
SafeRunner.run(ISafeRunnable) line: 42
JFaceUtil$1.run(ISafeRunnable) line: 49
SafeRunnable.run(ISafeRunnable) line: 175
PackageExplorerPart$PackageExplorerProblemTreeViewer(Viewer).fireSelectionChanged(SelectionChangedEvent) line: 160
PackageExplorerPart$PackageExplorerProblemTreeViewer(StructuredViewer).updateSelection(ISelection) line: 2162
PackageExplorerPart$PackageExplorerProblemTreeViewer(StructuredViewer).handleSelect(SelectionEvent) line: 1190
StructuredViewer$4.widgetSelected(SelectionEvent) line: 1220
OpenStrategy.fireSelectionEvent(SelectionEvent) line: 228
OpenStrategy.access$4(OpenStrategy, SelectionEvent) line: 222
OpenStrategy$1.handleEvent(Event) line: 389
EventTable.sendEvent(Event) line: 84
Tree(Widget).sendEvent(Event) line: 1053
Display.runDeferredEvents() line: 4066
Display.readAndDispatch() line: 3657
Workbench.runEventLoop(Window$IExceptionHandler, Display) line: 2640
Workbench.runUI() line: 2604
Workbench.access$4(Workbench) line: 2438
Workbench$7.run() line: 671
Realm.runWithDefault(Realm, Runnable) line: 332
Workbench.createAndRunWorkbench(Display, WorkbenchAdvisor) line: 664
PlatformUI.createAndRunWorkbench(Display, WorkbenchAdvisor) line: 149
IDEApplication.start(IApplicationContext) line: 115
EclipseAppHandle.run(Object) line: 196
EclipseAppLauncher.runApplication(Object) line: 110
EclipseAppLauncher.start(Object) line: 79
EclipseStarter.run(Object) line: 369
EclipseStarter.run(String[], Runnable) line: 179
NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method]
NativeMethodAccessorImpl.invoke(Object, Object[]) line: not available
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: not available
Method.invoke(Object, Object...) line: not available
Main.invokeFramework(String[], URL[]) line: 619
Main.basicRun(String[]) line: 574
Main.run(String[]) line: 1407
Main.main(String[]) line: 1383
Looks like some expensive classpath code was unexpectedly called from the UI thread. This is on Helios SR1 with JBoss Tools H28 Beta 2.
Keep up the good work - in general ;-)