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I was using a fairly recent dev build of AspectJ on WebSphere 5.0, using my contributed ClassLoader plugin for load-time weaving (*) and I hit a case where the server deadlocked. On connecting to the server in debug mode, one thread was hanging with this stack trace, trying to load java.sql.ResultSet: Class.forName0(String, boolean, ClassLoader) line: not available [native method] Class.forName(String, boolean, ClassLoader) line: 220 ReflectionBasedReferenceTypeDelegateFactory.createDelegate(ReferenceType, World, ClassLoader) line: 40 LTWWorld.resolveReflectionTypeDelegate(ReferenceType, ClassLoader) line: 126 LTWWorld.resolveIfBootstrapDelegate(ReferenceType) line: 108 LTWWorld.resolveDelegate(ReferenceType) line: 85 LTWWorld(World).resolveToReferenceType(UnresolvedType) line: 343 LTWWorld(World).resolve(UnresolvedType, boolean) line: 259 LTWWorld(World).resolve(UnresolvedType) line: 179 UnresolvedType.resolve(World) line: 652 BcelMethod(ResolvedMemberImpl).resolve(World) line: 480 JoinPointSignatureIterator.addSignaturesUpToFirstDefiningMember() line: 109 JoinPointSignatureIterator.<init>(Member, World) line: 51 BcelMethod(MemberImpl).getJoinPointSignatures(World) line: 909 SignaturePattern.matches(Member, World, boolean) line: 286 KindedPointcut.matchInternal(Shadow) line: 103 KindedPointcut(Pointcut).match(Shadow) line: 144 AndPointcut.matchInternal(Shadow) line: 53 AndPointcut(Pointcut).match(Shadow) line: 144 AndPointcut.matchInternal(Shadow) line: 51 AndPointcut(Pointcut).match(Shadow) line: 144 AndPointcut.matchInternal(Shadow) line: 51 AndPointcut(Pointcut).match(Shadow) line: 144 AndPointcut.matchInternal(Shadow) line: 51 AndPointcut(Pointcut).match(Shadow) line: 144 AndPointcut.matchInternal(Shadow) line: 51 AndPointcut(Pointcut).match(Shadow) line: 144 OrPointcut.matchInternal(Shadow) line: 50 OrPointcut(Pointcut).match(Shadow) line: 144 OrPointcut.matchInternal(Shadow) line: 50 OrPointcut(Pointcut).match(Shadow) line: 144 BcelAdvice(ShadowMunger).match(Shadow, World) line: 64 BcelAdvice(Advice).match(Shadow, World) line: 109 BcelAdvice.match(Shadow, World) line: 105 BcelClassWeaver.match(BcelShadow, List) line: 2210 BcelClassWeaver.match(LazyMethodGen) line: 1752 BcelClassWeaver.weave() line: 479 BcelClassWeaver.weave(BcelWorld, LazyClassGen, List, List, List) line: 109 BcelWeaver.weave(UnwovenClassFile, BcelObjectType, boolean) line: 1574 BcelWeaver.weaveWithoutDump(UnwovenClassFile, BcelObjectType) line: 1525 BcelWeaver.weaveAndNotify(UnwovenClassFile, BcelObjectType, IWeaveRequestor) line: 1305 BcelWeaver.weave(IClassFileProvider) line: 1127 ClassLoaderWeavingAdaptor(WeavingAdaptor).getWovenBytes(String, byte[]) line: 279 ClassLoaderWeavingAdaptor(WeavingAdaptor).weaveClass(String, byte[]) line: 212 Aj.preProcess(String, byte[], ClassLoader) line: 65 WasWeavingPlugin.preDefineApplicationClass(String, byte[]) line: 40 CompoundClassLoader.findClass(String, boolean) line: 355 CompoundClassLoader.loadClass(String, boolean) line: 261 CompoundClassLoader(ClassLoader).loadClass(String) line: 448 Class.forName1(String) line: not available [native method] Class.forName(String) line: 142 <... application code> StrictServletInstance.doInit() line: 82 StrictServletInstance(StrictLifecycleServlet)._init(ServletConfig) line: 147 PreInitializedServletState.init(StrictLifecycleServlet, ServletConfig) line: 270 StrictServletInstance(StrictLifecycleServlet).init(ServletConfig) line: 113 ServletInstance.init() line: 189 ServletInstance(GenericServlet).init(ServletConfig) line: 258 WebAppServletManager.addServlet(String, Servlet, Properties) line: 870 WebAppServletManager.loadServlet(String, Servlet) line: 224 WebAppServletManager.loadAutoLoadServlets() line: 542 WebApp.loadServletManager() line: 1270 WebApp.init(WebApp, WebAppExtension, WebAppContext, WebAppInitializationCollaborator[], WebAppInvocationCollaborator[]) line: 277 WebGroup.loadWebApp() line: 396 WebGroup.init(WebContainer, WebAppHost, DeployedModule, WebAppInitializationCollaborator[], WebAppInvocationCollaborator[]) line: 216 WebContainer.addWebApplication(DeployedModule) line: 984 WebContainerImpl.install(DeployedObject) line: 136 WebContainerImpl.start(DeployedObjectEvent) line: 356 ApplicationMgrImpl.start(DeployedObjectEvent) line: 415 DeployedApplicationImpl.fireDeployedObjectStart(DeployedObjectEvent) line: 787 DeployedModuleImpl.start() line: 351 DeployedApplicationImpl.start() line: 575 ApplicationMgrImpl.startApplication(DeployedApplicationImpl) line: 268 ApplicationMgrImpl.start() line: 246 ApplicationServerImpl(ContainerImpl).startComponents() line: 543 ApplicationServerImpl(ContainerImpl).start() line: 418 ApplicationServerImpl.start() line: 117 ServerImpl(ContainerImpl).startComponents() line: 543 ServerImpl(ContainerImpl).start() line: 418 ServerImpl.start() line: 183 WsServer.start(String[]) line: 128 WsServer.main(String[]) line: 225 Method.invoke(Object, Object[]) line: not available [native method] WSLauncher.main(String[]) line: 94 I don't have regular access to the server to better debug the problem, but wanted to report the issue quickly before 1.5.2 goes out. I believe some other thread has a lock on the bootstrap ClassLoader but that this thread has a lock on something else (perhaps the application ClassLoader). (*) I added recursion protection to my WAS weaving plugin using a similar technique to Matthew's for the JRockIt one. I submit this as a patch.
Fairly recently I changed LTWWorld to use the bootloader i.e. null rather than the application loader i.e. the one with which the world was created to resolve types. I was made aware of a problem in WAS after moving to LTWWorld and this changed seemed to fix it. I suggest you take a build after 21st June.
Thanks: we will test the updated version and close this out once verified. Loading the reflection type on the application loader is clearly a bug: it's important that the type in question be actually resolvable using the reflection loader and not some other loader! I hadn't seen change 1.4 that changed the loader from null (which I had submitted in the patch) to the app loader - but it's good that the working code has restored the use of the bootstrap loader.
Heard nothing for 1 month.
