[ http://issues.apache.org/jira/browse/TAPESTRY-806?page=comments#action_12370295 ]
Nick Westgate commented on TAPESTRY-806: ---------------------------------------- Yay! The squeeky wheel gets oiled! :-) I've checked the source and inspected the patch. There are exactly 7 defects in the source. This patch addresses all of them. > (T3 only) Multithreading problems possibly due to double-checked locking > ------------------------------------------------------------------------ > > Key: TAPESTRY-806 > URL: http://issues.apache.org/jira/browse/TAPESTRY-806 > Project: Tapestry > Type: Bug > Components: Framework > Versions: 3.0.3 > Environment: Unspecified, except for "8-CPU server" > Reporter: Nick Westgate > Assignee: Jesse Kuhnert > Attachments: TapestryDoubleCheckedLockingIssue.patch > > Flawed synchronization code using "double-checked locking" is used in these > methods: > (1) > org.apache.tapestry.enhance.DefaultComponentClassEnhancer.getEnhancedClass() > (2) org.apache.tapestry.enhance.javassist.EnhancedClassFactory.getObjectType() > Suggested fix for (1) is: > public Class getEnhancedClass(IComponentSpecification specification, > String className) > { > synchronized (specification) > { > Class result = getCachedClass(specification); > if (result == null) > { > result = getCachedClass(specification); > if (result == null) > { > result = constructComponentClass(specification, className); > storeCachedClass(specification, result); > } > } > } > return result; > } > Original bug report, from Michael Prescott ( [EMAIL PROTECTED] ) in users > list is: > We're coming across an unusual exception that occurs when our > application is under load. Below is an example stack trace, although > the problem can occur while enhancing any of a number of things, so it > doesn't seem specific to one part of our application. The root > exception is always the same, however: > > javassist.CannotCompileException: duplicate method: <init> > > Since it seemed to be related to concurrency, we were reading through > the Tapestry classes along this stack, and found what looks like a > threading problem in DefaultComponentClassEnhancer.java: > > public Class getEnhancedClass(IComponentSpecification specification, > String className) > { > Class result = getCachedClass(specification); > > if (result == null) > { > synchronized (this) > { > result = getCachedClass(specification); > if (result == null) > { > result = constructComponentClass(specification, > className); > storeCachedClass(specification, result); > } > } > } > > return result; > } > > This is double-checked locking, which isn't safe given instruction > reordering and thread-specific copies of variables, and all that > multi-CPU magic. This problem is occurring on an 8-CPU server, which > I'm guessing is enough processors to expose the subtle ways in which > double-checked locking can fail. > > Does this ring any bells for anyone? I realize this is a somewhat > nebulous query. > > Michael > > org.apache.tapestry.ApplicationRuntimeException: A code generation error > occured while enhancing class org.apache.tapestry.link.GenericLink. > at > org.apache.tapestry.enhance.DefaultComponentClassEnhancer.constructCompo > nentClass(DefaultComponentClassEnhancer.java:151) > at > org.apache.tapestry.enhance.DefaultComponentClassEnhancer.getEnhancedCla > ss(DefaultComponentClassEnhancer.java:97) > at > org.apache.tapestry.pageload.PageLoader.instantiateComponent(PageLoader. > java:603) > at > org.apache.tapestry.pageload.PageLoader.createImplicitComponent(PageLoad > er.java:569) > at > org.apache.tapestry.BaseComponentTemplateLoader.createImplicitComponent( > BaseComponentTemplateLoader.java:295) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:237) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:172) > at > org.apache.tapestry.BaseComponent.readTemplate(BaseComponent.java:100) > at > org.apache.tapestry.BaseComponent.finishLoad(BaseComponent.java:135) > at > org.apache.tapestry.pageload.PageLoader.constructComponent(PageLoader.ja > va:519) > at > org.apache.tapestry.pageload.PageLoader.createImplicitComponent(PageLoad > er.java:576) > at > org.apache.tapestry.BaseComponentTemplateLoader.createImplicitComponent( > BaseComponentTemplateLoader.java:295) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:237) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:172) > at > org.apache.tapestry.BaseComponent.readTemplate(BaseComponent.java:100) > at > org.apache.tapestry.BaseComponent.finishLoad(BaseComponent.java:135) > at > org.apache.tapestry.pageload.PageLoader.constructComponent(PageLoader.ja > va:519) > at > org.apache.tapestry.pageload.PageLoader.createImplicitComponent(PageLoad > er.java:576) > at > org.apache.tapestry.BaseComponentTemplateLoader.createImplicitComponent( > BaseComponentTemplateLoader.java:295) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:237) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:172) > at > org.apache.tapestry.BaseComponent.readTemplate(BaseComponent.java:100) > at > org.apache.tapestry.BaseComponent.finishLoad(BaseComponent.java:135) > at > org.apache.tapestry.pageload.PageLoader.constructComponent(PageLoader.ja > va:519) > at > org.apache.tapestry.pageload.PageLoader.createImplicitComponent(PageLoad > er.java:576) > at > org.apache.tapestry.BaseComponentTemplateLoader.createImplicitComponent( > BaseComponentTemplateLoader.java:295) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:237) > at > org.apache.tapestry.BaseComponentTemplateLoader.process(BaseComponentTem > plateLoader.java:172) > at > org.apache.tapestry.BaseComponent.readTemplate(BaseComponent.java:100) > at > org.apache.tapestry.BaseComponent.finishLoad(BaseComponent.java:135) > at > org.apache.tapestry.pageload.PageLoader.constructComponent(PageLoader.ja > va:519) > at > org.apache.tapestry.pageload.PageLoader.loadPage(PageLoader.java:764) > at > org.apache.tapestry.pageload.PageSource.getPage(PageSource.java:152) > at > org.apache.tapestry.engine.RequestCycle.getPage(RequestCycle.java:195) > at > org.apache.tapestry.engine.ActionService.service(ActionService.java:125) > at > org.apache.tapestry.engine.AbstractEngine.service(AbstractEngine.java:88 > 9) > at > org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java > :198) > at > net.exchangesolutions.sn.ui.tapestry.SynchronizedServlet.doService(Synch > ronizedServlet.java:37) > at > org.apache.tapestry.ApplicationServlet.doGet(ApplicationServlet.java:159 > ) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:115) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:92) > at > com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChai > n.java:99) > at > net.exchangesolutions.sncore.servlet.StateFilter.doFilter(StateFilter.ja > va:56) > at > com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain. > java:70) > at > com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.ja > va:163) > at > com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.j > ava:208) > at > com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:396) > at > com.caucho.server.port.TcpConnection.run(TcpConnection.java:363) > at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:490) > at com.caucho.util.ThreadPool.run(ThreadPool.java:423) > at java.lang.Thread.run(Thread.java:595) > Caused by: org.apache.tapestry.enhance.CodeGenerationException > at > org.apache.tapestry.enhance.javassist.ClassFabricator.getByteCode(ClassF > abricator.java:291) > at > org.apache.tapestry.enhance.javassist.EnhancedClass.createEnhancedSubcla > ss(EnhancedClass.java:130) > at > org.apache.tapestry.enhance.ComponentClassFactory.createEnhancedSubclass > (ComponentClassFactory.java:336) > at > org.apache.tapestry.enhance.DefaultComponentClassEnhancer.constructCompo > nentClass(DefaultComponentClassEnhancer.java:143) > ... 50 more > Caused by: javassist.CannotCompileException: duplicate method: <init> > at > javassist.bytecode.ClassFile.testExistingMethod(ClassFile.java:488) > at javassist.bytecode.ClassFile.addMethod(ClassFile.java:472) > at javassist.CtClassType.addConstructor(CtClassType.java:885) > at javassist.CtNewClass.addConstructor(CtNewClass.java:55) > at > javassist.CtNewClass.inheritAllConstructors(CtNewClass.java:96) > at javassist.CtNewClass.toBytecode(CtNewClass.java:63) > at javassist.CtClass.toBytecode(CtClass.java:1021) > at > org.apache.tapestry.enhance.javassist.ClassFabricator.getByteCode(ClassF > abricator.java:279) > ... 53 more > > Michael Prescott > direct: 416.646.7062 > main: 416.646.7000 > fax: 416.646.7050 > Exchange Solutions Inc. > 250 Yonge Street, 18th Floor > Toronto, ON M5B 2L7 > www.exchangesolutions.com -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
