I've seen this happening only once, still it's quite puzzling. Maybe proper visiblity of the variables is not guaranteed?

java.lang.NullPointerException
at org.infinispan.util.concurrent.locks.LockManagerImpl.lockAndRecord(LockManagerImpl.java:83)
at org.infinispan.container.EntryFactoryImpl.acquireLock(EntryFactoryImpl.java:210)
at org.infinispan.container.EntryFactoryImpl.wrapEntryForWriting(EntryFactoryImpl.java:153)
at org.infinispan.container.EntryFactoryImpl.wrapEntryForWriting(EntryFactoryImpl.java:106)
at org.infinispan.interceptors.LockingInterceptor.visitPutKeyValueCommand(LockingInterceptor.java:197)
at org.infinispan.commands.write.PutKeyValueCommand.acceptVisitor(PutKeyValueCommand.java:76)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.base.CommandInterceptor.handleDefault(CommandInterceptor.java:132)
at org.infinispan.commands.AbstractVisitor.visitPutKeyValueCommand(AbstractVisitor.java:57)
at org.infinispan.commands.write.PutKeyValueCommand.acceptVisitor(PutKeyValueCommand.java:76)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.TxInterceptor.enlistWriteAndInvokeNext(TxInterceptor.java:183)
at org.infinispan.interceptors.TxInterceptor.visitPutKeyValueCommand(TxInterceptor.java:132)
at org.infinispan.commands.write.PutKeyValueCommand.acceptVisitor(PutKeyValueCommand.java:76)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.CacheMgmtInterceptor.visitPutKeyValueCommand(CacheMgmtInterceptor.java:113)
at org.infinispan.commands.write.PutKeyValueCommand.acceptVisitor(PutKeyValueCommand.java:76)
at org.infinispan.interceptors.base.CommandInterceptor.invokeNextInterceptor(CommandInterceptor.java:118)
at org.infinispan.interceptors.InvocationContextInterceptor.handleAll(InvocationContextInterceptor.java:57)
at org.infinispan.interceptors.InvocationContextInterceptor.handleDefault(InvocationContextInterceptor.java:38)
at org.infinispan.commands.AbstractVisitor.visitPutKeyValueCommand(AbstractVisitor.java:57)
at org.infinispan.commands.write.PutKeyValueCommand.acceptVisitor(PutKeyValueCommand.java:76)
at org.infinispan.interceptors.InterceptorChain.invoke(InterceptorChain.java:273)
at org.infinispan.CacheDelegate.put(CacheDelegate.java:429)
at org.infinispan.CacheSupport.put(CacheSupport.java:28)
at com.atlassian.jira.propertyset.PropertySetCache.setObject(PropertySetCache.java:205)
at com.atlassian.jira.propertyset.JiraCachingPropertySet.getString(JiraCachingPropertySet.java:647)
at com.opensymphony.user.User.getFullName(User.java:86)
at com.atlassian.jira.user.util.UserUtilImpl.getDisplayableNameSafely(UserUtilImpl.java:573)
at com.atlassian.jira.plugin.profile.ProfileLinkUserFormat.getInitialParams(ProfileLinkUserFormat.java:47)
at com.atlassian.jira.plugin.profile.ProfileLinkUserFormat.format(ProfileLinkUserFormat.java:32)
at com.atlassian.jira.plugin.profile.DefaultUserFormatManager.formatUser(DefaultUserFormatManager.java:62)