# Waiting on lock \<0x754d0045\> (a org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader)

**URL:** <https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880>\
**Category:** Hibernate ORM\
**Created:** [November 9, 2022, 3:41pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880 "2022-11-09T15:41:22Z")\
**Posts on this page:** 13\
**Page:** 1

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**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 9, 2022, 3:41pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/1 "2022-11-09T15:41:23Z")

</div>

Hi, we are using Hibernate 3.5.5.85 as ORM tool on our [Lucee application server](https://www.lucee.org/). Occasionally, during the day, Hibernate brings our application practically to a halt. That always happens when the website is receiving a lot of traffic. Then requests keep getting blocked and, withing minutes, there is a pile-up of requests.

Invariably, the cause is something like _“Waiting on lock \<0x754d0045\> (a org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader)”._ Here is an excerpt from a typical stacktrace:

> dvnt.stdmtr.orm.leveltestuserstatusforoverview\_cfc$cf.udfCall(/nl/devnt/stdmtr/orm/LevelTestUserStatusForOverview.cfc)  
> lucee.runtime.functions.orm.EntityLoad.call(EntityLoad.java)  
> org.lucee.extension.orm.hibernate.HibernateORMSession.loadAsArray(HibernateORMSession.java) (hide)  
> org.lucee.extension.orm.hibernate.HibernateORMSession.load(HibernateORMSession.java)  
> org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java)  
> org.hibernate.internal.SessionImpl.list(SessionImpl.java)  
> org.hibernate.metamodel.internal.MetamodelImpl.getImplementors(MetamodelImpl.java)  
> org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java)  
> java.lang.Class.forName(Unknown Source)  
> java.lang.Class.forName0(Native Method)  
> Waiting on lock \<0x754d0045\> (a org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader)

Could you please give me any tips on how to solve this?

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<div class="post-metadata">

**Author:** ![beikov](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/beikov/32/258_2.png) [@beikov](https://discourse.hibernate.org/u/beikov)\
**Post date:** [November 9, 2022, 6:07pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/2 "2022-11-09T18:07:55Z")

</div>

I don’t know what Hibernate version this application server is exactly using, but it seems to be a very old one. There is nothing we can do to help you here. You will have to ask the community of that app server.

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 10, 2022, 5:19am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/3 "2022-11-10T05:19:07Z")

</div>

Thanks, Beikov.  
I read off the wrong version. Correct is: 5.4.29.15-BETA. Sorry about that.

In any case, the question is about _“Waiting on lock \<0x754d0045\> (a org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader)”._  
That is a Hibernate classloader, which is why I came here. I am hoping someone will know something about it.

Thread dumps show dozens of request threads being blocked by the AggregatedClassLoader:

> Blockquote  
> ‘“XNIO-1 task-13” Id=10898 BLOCKED on org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader@4ce3a236 owned by “XNIO-1 task-7” Id=10651  
> java.lang.Thread.State: BLOCKED’

The “waiting on lock” suggests that the classloader is single-threaded. Is there, for example, a solution that enables multithreaded classloading?.

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<div class="post-metadata">

**Author:** ![beikov](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/beikov/32/258_2.png) [@beikov](https://discourse.hibernate.org/u/beikov)\
**Post date:** [November 10, 2022, 11:05am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/4 "2022-11-10T11:05:49Z")

</div>

Class loaders usually need some sort of locking because they may only load a class once. This shouldn’t be an issue though, because at some point you loaded all classes of you app and no new loading will happen. I don’t know what this application server is doing, but either way, I don’t see an issue with Hibernate here.

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 10, 2022, 12:46pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/5 "2022-11-10T12:46:39Z")

</div>

Thanks, @beikov .  
Your answer provides clarity on the Hibernate side.  
I am continuing this in the Lucee community.

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 11, 2022, 7:26am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/6 "2022-11-11T07:26:17Z")

</div>

I am returning with new information. Lucee is an application server built in Java. It is based on the weakly-type language of the same name (Lucee).

Hence the following question: could the Hibernate setting _hibernate.query.conventional\_java\_constants=false_ help solve the problem? I got this idea from [Vlad Mihalcea](https://vladmihalcea.com/the-performance-penalty-of-class-forname-when-parsing-jpql-and-criteria-queries/).

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<div class="post-metadata">

**Author:** ![beikov](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/beikov/32/258_2.png) [@beikov](https://discourse.hibernate.org/u/beikov)\
**Post date:** [November 14, 2022, 9:29am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/7 "2022-11-14T09:29:35Z")

</div>

> Hence the following question: could the Hibernate setting _hibernate.query.conventional\_java\_constants=false_ help solve the problem?

Did you try it out? You didn’t share stack traces for these lock scenarios, so it’s hard for me to understand what is calling into the class loader, but this flag could indeed help to avoid some class loader interaction. Either way, the class loader is only hit when queries are freshly compiled which shouldn’t happen anymore once your application is warmed up. After that, the compiled query is served from a cache. Are you using some sort of dynamic querying?

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 14, 2022, 2:11pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/8 "2022-11-14T14:11:29Z")

</div>

Hi @beikov, thank you very much for your answer.

To answer your questions:

- We’re currently testing the flag, and have yet to run it in production where the necessary load is.
- No, we’re not using dynamic queries here.

In any case, your remark and question,

> “the class loader is only hit when queries are freshly compiled which shouldn’t happen anymore once your application is warmed up. After that, the compiled query is served from a cache. Are you using some sort of dynamic querying?”

are insightful. They give us a lot to go on.

Thank you for your help.

---

<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 16, 2022, 10:36am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/9 "2022-11-16T10:36:05Z")

</div>

An update. We have tried the flag in our production environment. We tried it in the form of a Java Virtual Machine property,

> -DHibernate.query.conventional\_java\_constants=false

Alas, that didn’t have any effect on the problem.

---

<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 24, 2022, 9:30am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/10 "2022-11-24T09:30:32Z")

</div>

There is new information. Thread dumps show the following phenomenon time and time again: one entityload request to Hibernate may block every other subsequent entityLoad request. As a result users may be kept waiting for up to 2 minutes! Their request then gets timed out anyway.

You will find below an example of the stacktrace of a request that blocks every other entityLoad request.

In other words, such access to Hibernate is apparently single-threaded. That is a shortcoming in Hibernate, wouldn’t you say?

See, for example, “[the critical 3%: Performance Pitfalls - Hibernate Criteria API](http://dimovelev.blogspot.com/2015/02/performance-pitfalls-hibernate-criteria.html)” and “[ClassNotFoundException: is it slowing down your JVM? ~ Java EE Support Patterns](http://javaeesupportpatterns.blogspot.com/2014/03/classnotfoundexception-is-it-slowing.html)”.

Our Hibernate version is 5.4.29.

> “XNIO-1 task-31” Id=28567 RUNNABLE  
> java.lang.Thread.State: RUNNABLE  
> at org.apache.felix.framework.BundleWiringImpl$BundleClassLoader.loadClass(BundleWiringImpl.java:1967)  
> at java.base@11.0.15/java.lang.ClassLoader.loadClass(Unknown Source)  
> at org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader.findClass(AggregatedClassLoader.java:202)  
> at java.base@11.0.15/java.lang.ClassLoader.loadClass(Unknown Source)  
> - locked org.hibernate.boot.registry.classloading.internal.AggregatedClassLoader@18367cd  
> at java.base@11.0.15/java.lang.ClassLoader.loadClass(Unknown Source)  
> at java.base@11.0.15/java.lang.Class.forName0(Native Method)  
> at java.base@11.0.15/java.lang.Class.forName(Unknown Source)  
> at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.classForName(ClassLoaderServiceImpl.java:130)  
> at org.hibernate.metamodel.internal.MetamodelImpl.getImplementors(MetamodelImpl.java:661)  
> at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1851)  
> at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:370)  
> at org.lucee.extension.orm.hibernate.HibernateORMSession.load(HibernateORMSession.java:851)  
> at org.lucee.extension.orm.hibernate.HibernateORMSession.loadAsArray(HibernateORMSession.java:676)  
> at org.lucee.extension.orm.hibernate.HibernateORMSession.loadAsArray(HibernateORMSession.java:653)  
> at lucee.runtime.functions.orm.EntityLoad.call(EntityLoad.java:67)  
> at lucee.runtime.functions.orm.EntityLoad.call(EntityLoad.java:39)  
> at dvnt.stdmtr.service.userdata\_cfc$cf.udfCall2(/nl/dvnt/stdmtr/service/UserData.cfc:949)  
> at dvnt.stdmtr.service.userdata\_cfc$cf.udfCall(/nl/dvnt/stdmtr/service/UserData.cfc)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:698)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:585)  
> at lucee.runtime.ComponentImpl.callWithNamedValues(ComponentImpl.java:1951)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:866)  
> at lucee.runtime.PageContextImpl.getFunctionWithNamedValues(PageContextImpl.java:1784)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall4(/nl/dvnt/stdmtr/service/Exercises.cfc:3679)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall(/nl/dvnt/stdmtr/service/Exercises.cfc)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.type.scope.UndefinedImpl.callWithNamedValues(UndefinedImpl.java:804)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:866)  
> at lucee.runtime.PageContextImpl.getFunctionWithNamedValues(PageContextImpl.java:1784)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall5(/nl/dvnt/stdmtr/service/Exercises.cfc:3780)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall(/nl/dvnt/stdmtr/service/Exercises.cfc)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.type.scope.UndefinedImpl.callWithNamedValues(UndefinedImpl.java:804)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:866)  
> at lucee.runtime.PageContextImpl.getFunctionWithNamedValues(PageContextImpl.java:1784)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall2(/nl/dvnt/stdmtr/service/Exercises.cfc:597)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall(/nl/dvnt/stdmtr/service/Exercises.cfc)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.type.scope.UndefinedImpl.callWithNamedValues(UndefinedImpl.java:804)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:866)  
> at lucee.runtime.PageContextImpl.getFunctionWithNamedValues(PageContextImpl.java:1784)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall1(/nl/dvnt/stdmtr/service/Exercises.cfc:505)  
> at dvnt.stdmtr.service.exercises\_cfc$cf.udfCall(/nl/dvnt/stdmtr/service/Exercises.cfc)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:698)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:585)  
> at lucee.runtime.ComponentImpl.callWithNamedValues(ComponentImpl.java:1951)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:866)  
> at lucee.runtime.PageContextImpl.getFunctionWithNamedValues(PageContextImpl.java:1784)  
> at nl.dvnt.stdmtr.facades.exercisesfacade\_cfc$cf.udfCall(/nl/dvnt/stdmtr/facades/ExercisesFacade.cfc:48)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.callWithNamedValues(UDFImpl.java:213)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:698)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:585)  
> at lucee.runtime.ComponentImpl.callWithNamedValues(ComponentImpl.java:1951)  
> at lucee.runtime.util.VariableUtilImpl.callFunctionWithNamedValues(VariableUtilImpl.java:900)  
> at lucee.runtime.functions.dynamicEvaluation.Invoke.call(Invoke.java:49)  
> at application\_cfc$cf.udfCall(/Application.cfc:87)  
> at lucee.runtime.type.UDFImpl.implementation(UDFImpl.java:112)  
> at lucee.runtime.type.UDFImpl.\_call(UDFImpl.java:350)  
> at lucee.runtime.type.UDFImpl.call(UDFImpl.java:223)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:697)  
> at lucee.runtime.ComponentImpl.\_call(ComponentImpl.java:585)  
> at lucee.runtime.ComponentImpl.call(ComponentImpl.java:1932)  
> at lucee.runtime.listener.ModernAppListener.call(ModernAppListener.java:444)  
> at lucee.runtime.listener.ModernAppListener.\_onRequest(ModernAppListener.java:200)  
> at lucee.runtime.listener.MixedAppListener.onRequest(MixedAppListener.java:44)  
> at lucee.runtime.PageContextImpl.execute(PageContextImpl.java:2482)  
> at lucee.runtime.PageContextImpl.\_execute(PageContextImpl.java:2468)  
> at lucee.runtime.PageContextImpl.executeCFML(PageContextImpl.java:2439)  
> at lucee.runtime.engine.Request.exe(Request.java:45)  
> at lucee.runtime.engine.CFMLEngineImpl.\_service(CFMLEngineImpl.java:1198)  
> at lucee.runtime.engine.CFMLEngineImpl.serviceCFML(CFMLEngineImpl.java:1144)  
> at lucee.loader.engine.CFMLEngineWrapper.serviceCFML(CFMLEngineWrapper.java:97)  
> at lucee.loader.servlet.CFMLServlet.service(CFMLServlet.java:51)  
> at app//javax.servlet.http.HttpServlet.service(HttpServlet.java:590)  
> at app//io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)  
> at app//io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:129)  
> at app//org.cfmlprojects.regexpathinfofilter.RegexPathInfoFilter.doFilter(RegexPathInfoFilter.java:47)  
> at app//io.undertow.servlet.core.ManagedFilter.doFilter(ManagedFilter.java:61)  
> at app//io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java:131)  
> at jdk.internal.reflect.GeneratedMethodAccessor53.invoke(Unknown Source)  
> at java.base@11.0.15/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
> at java.base@11.0.15/java.lang.reflect.Method.invoke(Unknown Source)  
> at com.intergral.fusionreactor.j2ee.filterchain.WrappedFilterChain.doFilter(WrappedFilterChain.java:134)  
> at com.intergral.fusionreactor.j2ee.filter.FusionReactorRequestHandler.doNext(FusionReactorRequestHandler.java:772)  
> at com.intergral.fusionreactor.j2ee.filter.FusionReactorRequestHandler.doHttpServletRequest(FusionReactorRequestHandler.java:344)  
> at com.intergral.fusionreactor.j2ee.filter.FusionReactorRequestHandler.doFusionRequest(FusionReactorRequestHandler.java:207)  
> at com.intergral.fusionreactor.j2ee.filter.FusionReactorRequestHandler.handle(FusionReactorRequestHandler.java:809)  
> at com.intergral.fusionreactor.j2ee.filter.FusionReactorCoreFilter.doFilter(FusionReactorCoreFilter.java:36)  
> at jdk.internal.reflect.GeneratedMethodAccessor51.invoke(Unknown Source)  
> at java.base@11.0.15/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
> at java.base@11.0.15/java.lang.reflect.Method.invoke(Unknown Source)  
> at com.intergral.fusionreactor.j2ee.filterchain.WrappedFilterChain.doFilter(WrappedFilterChain.java:71)  
> at jdk.internal.reflect.GeneratedMethodAccessor48.invoke(Unknown Source)  
> at java.base@11.0.15/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
> at java.base@11.0.15/java.lang.reflect.Method.invoke(Unknown Source)  
> at app//com.intergral.fusionreactor.agent.filter.FusionReactorStaticFilter.doFilter(FusionReactorStaticFilter.java:54)  
> at app//com.intergral.fusionreactor.agent.pointcuts.NewFilterChainPointCut$1.invoke(NewFilterChainPointCut.java:42)  
> at app//io.undertow.servlet.handlers.FilterHandler$FilterChainImpl.doFilter(FilterHandler.java)  
> at app//io.undertow.servlet.handlers.FilterHandler.handleRequest(FilterHandler.java:84)  
> at app//io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)  
> at app//io.undertow.servlet.handlers.ServletChain$1.handleRequest(ServletChain.java:68)  
> at app//io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)  
> at app//io.undertow.servlet.handlers.RedirectDirHandler.handleRequest(RedirectDirHandler.java:68)  
> at app//io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:117)  
> at app//io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)  
> at app//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)  
> at app//io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)  
> at app//io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)  
> at app//io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)  
> at app//io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)  
> at app//io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)  
> at app//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)  
> at app//io.undertow.servlet.handlers.SendErrorPageHandler.handleRequest(SendErrorPageHandler.java:52)  
> at app//io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:275)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:79)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:134)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:131)  
> at app//io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)  
> at app//io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)  
> at app//io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:255)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:79)  
> at app//io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:100)  
> at app//io.undertow.server.Connectors.executeRootHandler(Connectors.java:387)  
> at app//io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:852)  
> at app//org.jboss.threads.ContextClassLoaderSavingRunnable.run(ContextClassLoaderSavingRunnable.java:35)  
> at app//org.jboss.threads.EnhancedQueueExecutor.safeRun(EnhancedQueueExecutor.java:2019)  
> at app//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.doRunTask(EnhancedQueueExecutor.java:1558)  
> at app//org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1433)  
> at app//org.xnio.XnioWorker$WorkerThreadFactory$1$1.run(XnioWorker.java:1280)  
> at java.base@11.0.15/java.lang.Thread.run(Unknown Source)  
> Locked ownable synchronizers:  
> - java.util.concurrent.locks.ReentrantReadWriteLock$FairSync \<0x541bbaa\>

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 24, 2022, 9:36am UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/11 "2022-11-24T09:36:49Z")

</div>

See also [Are Lucee's custom class loaders single-threaded or multithreaded? - #12 by BK\_BK - dev - Lucee Dev](https://dev.lucee.org/t/are-lucees-custom-class-loaders-single-threaded-or-multithreaded/11123/12)

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<div class="post-metadata">

**Author:** ![beikov](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/beikov/32/258_2.png) [@beikov](https://discourse.hibernate.org/u/beikov)\
**Post date:** [November 24, 2022, 2:08pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/12 "2022-11-24T14:08:06Z")

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Look, I understand that this isn’t ideal, and we fixed that in Hibernate 6, but you usually don’t run into this unless you are creating a ton of “unique” queries that trash the query plan cache. So IMO you should size the query plan cache accordingly.

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<div class="post-metadata">

**Author:** ![BK\_BK](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.hibernate.org/bk_bk/32/2106_2.png) [@BK\_BK](https://discourse.hibernate.org/u/BK_BK)\
**Post date:** [November 24, 2022, 3:15pm UTC](https://discourse.hibernate.org/t/waiting-on-lock-0x754d0045-a-org-hibernate-boot-registry-classloading-internal-aggregatedclassloader/6880/13 "2022-11-24T15:15:02Z")

</div>

Thanks for the information, @beikov .  
I am thrilled to hear that this issue has been fixed in Hibernate 6.  
We are now going to check whether we can upgrade our application to Hibernate 6.