ConcurrentModificationException on startup ------------------------------------------ Key: WFLY-10253 URL: https://issues.jboss.org/browse/WFLY-10253 Project: WildFly Issue Type: Bug Components: JPA / Hibernate Affects Versions: 10.1.0.Final Reporter: Martin Herschke Assignee: Dmitrii Tikhomirov standalone wildfly startup: This exception appears sporadically and is caused by different modules and projects. Multiple threads are used to deploy modules ({{MSC service thread 1-7}}), but a static method {{lookupProvider}} is called. The provider list is a normal ArrayList that causes the exception. {code} 16:36:23,604 ERROR [org.jboss.msc.service.fail] (MSC service thread 1-7) MSC000001: Failed to start service jboss.deployment.subunit."<our_ear>"."<our_module>".FIRST_MODULE_USE: org.jboss.msc.service.StartException in service jboss.deployment.subunit."<our_ear>"."<our_module>".FIRST_MODULE_USE: WFLYSRV0153: Failed to process phase FIRST_MODULE_USE of subdeployment "<our_module>" of deployment "<our_ear>" at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:154) at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1948) at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1881) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Caused by: java.util.ConcurrentModificationException at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) at java.util.ArrayList$Itr.next(ArrayList.java:851) at org.jboss.as.jpa.processor.PersistenceUnitServiceHandler.lookupProvider(PersistenceUnitServiceHandler.java:940) at org.jboss.as.jpa.processor.PersistenceUnitServiceHandler.nextPhaseDependsOnPersistenceUnit(PersistenceUnitServiceHandler.java:1052) at org.jboss.as.jpa.processor.PersistenceUnitServiceHandler.deploy(PersistenceUnitServiceHandler.java:136) at org.jboss.as.jpa.processor.PersistenceBeginInstallProcessor.deploy(PersistenceBeginInstallProcessor.java:52) at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:147) ... 5 more {code}