On startup of JBoss 5.1.0-GA sometimes (seen it several times) it comes to a Thread deadlock between the main thread and an other Thread.

We use XA datasources and we have configured in the file conf/jbossts-properties.xml the Arjuna Transaction Manager Recovery Module.

<properties depends="arjuna" name="jta">
<property name="com.arjuna.ats.jta.recovery.XAResourceRecoveryJDBC" value="com.arjuna.ats.internal.jbossatx.jta.AppServerJDBCXARecovery;jndiname=nxcore/resource/DS"/>

This RecoveryModule is triggered during startup in a Thread which causes together with the "main" Thread a deadlock
in the method toClass() of the class org.jboss.aop.asintegration.jboss5.ToClassInvoker.

1.) The "main" Thread has already locked the org.jboss.classloader.spi.base.BaseClassLoader and waits to lock the "tmplock" Object in class ToClassInvoker.

2.) The other Thread ("Thread-20") has already locked the "tmplock" Object and waits to lock the BaseClassLoader for the call
of the synchronized method loadClass() (myloader.loadClass()).

Source can be seen here:
http://grepcode.com/file/repository.jboss.com/maven2/org.jboss.aop/jboss-aop-asintegration-mc/2.1.1.GA/org/jboss/aop/asintegration/jboss5/ToClassInvoker.java#ToClassInvoker

IMHO a locking of the BaseClassLoader "synchronized (myloader)" before the locking of the "tmplock" Object should prevent this deadlock situation.

"main":
at org.jboss.aop.asintegration.jboss5.ToClassInvoker.toClass(ToClassInvoker.java:72)

• waiting to lock <0xffffffff64f63d00> (a java.lang.Object)
  at org.jboss.aop.classpool.jbosscl.JBossClDelegatingClassPool.toClass(JBossClDelegatingClassPool.java:81)
  at javassist.CtClass.toClass(CtClass.java:1094)
  at org.jboss.aop.instrument.TransformerCommon$ToClassAction$2.toClass(TransformerCommon.java:331)
  at org.jboss.aop.instrument.TransformerCommon.compileOrLoadClass(TransformerCommon.java:103)
  at org.jboss.aop.instrument.TransformerCommon.compileOrLoadClass(TransformerCommon.java:65)
  at org.jboss.aop.instrument.MethodJoinPointGenerator$BaseClassGenerator.generate(MethodJoinPointGenerator.java:239)
  at org.jboss.aop.instrument.MethodJoinPointGenerator.createJoinpointBaseClass(MethodJoinPointGenerator.java:172)
  at org.jboss.aop.instrument.GeneratedAdvisorMethodExecutionTransformer.createJoinpointClass(GeneratedAdvisorMethodExecutionTransformer.java:95)
  at org.jboss.aop.instrument.GeneratedAdvisorMethodExecutionTransformer.addJoinpoint(GeneratedAdvisorMethodExecutionTransformer.java:83)
  at org.jboss.aop.instrument.GeneratedAdvisorMethodExecutionTransformer.addMethodInfoFieldToGenAdvisor(GeneratedAdvisorMethodExecutionTransformer.java:58)
  at org.jboss.aop.instrument.GeneratedAdvisorMethodExecutionTransformer.transformMethod(GeneratedAdvisorMethodExecutionTransformer.java:304)
  at org.jboss.aop.instrument.MethodExecutionTransformer.instrument(MethodExecutionTransformer.java:146)
  at org.jboss.aop.instrument.Instrumentor.transform(Instrumentor.java:744)
  at org.jboss.aop.instrument.GeneratedAdvisorInstrumentor.transform(GeneratedAdvisorInstrumentor.java:119)
  at org.jboss.aop.SuperClassesFirstWeavingStrategy.instrumentClass(SuperClassesFirstWeavingStrategy.java:202)
  at org.jboss.aop.SuperClassesFirstWeavingStrategy.translate(SuperClassesFirstWeavingStrategy.java:69)
  at org.jboss.aop.AspectManager.translate(AspectManager.java:1071)
  at org.jboss.aop.AspectManager.transform(AspectManager.java:1015)
  at org.jboss.aop.standalone.AOPTransformer.aspectTransform(AOPTransformer.java:87)
  at org.jboss.aop.standalone.AOPTransformer.transform(AOPTransformer.java:75)
  at sun.instrument.TransformerManager.transform(TransformerManager.java:169)
  at sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:365)
  at java.lang.ClassLoader.defineClass1(Native Method)
  at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
  at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:63)
  at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:572)
  at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:532)
  at java.security.AccessController.doPrivileged(Native Method)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:530)
• locked <0xffffffff60aba990> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:507)
  at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:134)
  at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131)
  at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:452)
  at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:251)
  at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:150)
  at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:265)
  at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:1119)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:798)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:441)
• locked <0xffffffff60aba990> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
  at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316)
• locked <0xffffffff60aba990> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at java.lang.ClassLoader.defineClass1(Native Method)
  at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
  at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:63)
  at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:572)
  at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:532)
  at java.security.AccessController.doPrivileged(Native Method)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:530)
• locked <0xffffffff60aba990> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassLocally(BaseClassLoader.java:507)
  at org.jboss.classloader.spi.base.BaseDelegateLoader.loadClass(BaseDelegateLoader.java:134)
  at org.jboss.classloader.spi.filter.FilteredDelegateLoader.loadClass(FilteredDelegateLoader.java:131)
  at org.jboss.classloader.spi.base.ClassLoadingTask$ThreadTask.run(ClassLoadingTask.java:452)
  at org.jboss.classloader.spi.base.ClassLoaderManager.nextTask(ClassLoaderManager.java:251)
  at org.jboss.classloader.spi.base.ClassLoaderManager.process(ClassLoaderManager.java:150)
  at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:265)
  at org.jboss.classloader.spi.base.BaseClassLoaderDomain.loadClass(BaseClassLoaderDomain.java:1119)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClassFromDomain(BaseClassLoader.java:798)
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:441)
• locked <0xffffffff65eda3b0> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
  at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316)
• locked <0xffffffff65eda3b0> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at org.jboss.resource.deployers.builder.ConnectionManagerBuilder.getCode(ConnectionManagerBuilder.java:245)
  at org.jboss.resource.deployers.builder.AbstractBuilder.buildService(AbstractBuilder.java:54)
  at org.jboss.resource.deployers.builder.AbstractBuilder.build(AbstractBuilder.java:65)
  at org.jboss.resource.deployers.ManagedConnectionFactoryDeployer.deploy(ManagedConnectionFactoryDeployer.java:177)
  at org.jboss.resource.deployers.ManagedConnectionFactoryDeployer.deploy(ManagedConnectionFactoryDeployer.java:52)
  at org.jboss.deployers.spi.deployer.helpers.AbstractSimpleRealDeployer.internalDeploy(AbstractSimpleRealDeployer.java:62)
  at org.jboss.deployers.spi.deployer.helpers.AbstractRealDeployer.deploy(AbstractRealDeployer.java:50)
  at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:171)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.doDeploy(DeployersImpl.java:1439)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1157)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:1098)
  at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
  at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
  at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:781)
  at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:702)
  at org.jboss.system.server.profileservice.repository.MainDeployerAdapter.process(MainDeployerAdapter.java:117)
  at org.jboss.system.server.profileservice.repository.ProfileDeployAction.install(ProfileDeployAction.java:70)
  at org.jboss.system.server.profileservice.repository.AbstractProfileAction.install(AbstractProfileAction.java:53)
  at org.jboss.system.server.profileservice.repository.AbstractProfileService.install(AbstractProfileService.java:361)
  at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
  at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
  at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
  at org.jboss.system.server.profileservice.repository.AbstractProfileService.activateProfile(AbstractProfileService.java:306)
  at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(ProfileServiceBootstrap.java:271)
  at org.jboss.bootstrap.AbstractServerImpl.start(AbstractServerImpl.java:461)
  at org.jboss.Main.boot(Main.java:221)
  at org.jboss.Main$1.run(Main.java:556)
  at java.lang.Thread.run(Thread.java:619)
  "Thread-20":
  at org.jboss.classloader.spi.base.BaseClassLoader.loadClass(BaseClassLoader.java:437)
• waiting to lock <0xffffffff60aba990> (a org.jboss.classloader.spi.base.BaseClassLoader)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
  at org.jboss.aop.asintegration.jboss5.ToClassInvoker.toClass(ToClassInvoker.java:88)
• locked <0xffffffff64f63d00> (a java.lang.Object)
  at org.jboss.aop.classpool.jbosscl.JBossClDelegatingClassPool.toClass(JBossClDelegatingClassPool.java:81)
  at javassist.CtClass.toClass(CtClass.java:1094)
  at org.jboss.aop.instrument.TransformerCommon$ToClassAction$2.toClass(TransformerCommon.java:331)
  at org.jboss.aop.instrument.TransformerCommon.toClass(TransformerCommon.java:139)
  at org.jboss.aop.instrument.JoinPointGenerator.toClass(JoinPointGenerator.java:315)
  at org.jboss.aop.instrument.JoinPointGenerator.generateJoinpointClass(JoinPointGenerator.java:380)
  at org.jboss.aop.instrument.JoinPointGenerator.doGenerateJoinPointClass(JoinPointGenerator.java:284)
  at org.jboss.aop.instrument.JoinPointGenerator.access$300(JoinPointGenerator.java:76)
  at org.jboss.aop.instrument.JoinPointGenerator$GenerateJoinPointClassAction$2.generateJoinPointClass(JoinPointGenerator.java:1729)
  at org.jboss.aop.instrument.JoinPointGenerator.generateJoinPointClass(JoinPointGenerator.java:249)
• locked <0xfffffffe7d0d0538> (a org.jboss.aop.instrument.MethodJoinPointGenerator)
  at org.jboss.aop.GeneratedClassAdvisor.generateJoinPointClass(GeneratedClassAdvisor.java:1044)
  at org.jboss.jmx.connector.invoker.AuthenticationInterceptor$AuthenticationInterceptorAdvisor.invoke_N_5788773513025575775(AuthenticationInterceptor$AuthenticationInterceptorAdvisor.java)
  at org.jboss.jmx.connector.invoker.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java)
  at org.jboss.mx.server.Invocation.invoke(Invocation.java:90)
  at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
  at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668)
  at org.jboss.invocation.jrmp.server.JRMPProxyFactory.invoke(JRMPProxyFactory.java:180)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:157)
  at org.jboss.mx.server.Invocation.dispatch(Invocation.java:96)
  at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
  at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
  at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668)
  at org.jboss.invocation.local.LocalInvoker$MBeanServerAction.invoke(LocalInvoker.java:169)
  at org.jboss.invocation.local.LocalInvoker.invoke(LocalInvoker.java:118)
  at org.jboss.invocation.InvokerInterceptor.invokeLocal(InvokerInterceptor.java:209)
  at org.jboss.invocation.InvokerInterceptor.invoke(InvokerInterceptor.java:195)
  at org.jboss.jmx.connector.invoker.client.InvokerAdaptorClientInterceptor.invoke(InvokerAdaptorClientInterceptor.java:66)
  at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:68)
  at org.jboss.proxy.ClientMethodInterceptor.invoke(ClientMethodInterceptor.java:74)
  at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:101)
  at $Proxy247.invoke(Unknown Source)
  at com.arjuna.ats.internal.jbossatx.jta.AppServerJDBCXARecovery.createDataSource(AppServerJDBCXARecovery.java:189)
  at com.arjuna.ats.internal.jbossatx.jta.AppServerJDBCXARecovery.hasMoreResources(AppServerJDBCXARecovery.java:144)
  at com.arjuna.ats.internal.jta.recovery.arjunacore.XARecoveryModule.resourceInitiatedRecovery(XARecoveryModule.java:659)
  at com.arjuna.ats.internal.jta.recovery.arjunacore.XARecoveryModule.periodicWorkSecondPass(XARecoveryModule.java:200)
  at com.arjuna.ats.internal.arjuna.recovery.PeriodicRecovery.doWorkInternal(PeriodicRecovery.java:799)
  at com.arjuna.ats.internal.arjuna.recovery.PeriodicRecovery.run(PeriodicRecovery.java:412)

Found 1 deadlock.