[15] RFR: 8241130: com.sun.jndi.ldap.EventSupport.removeDeadNotifier: java.lang.NullPointerException

[Chris Yin]

Hello

Please review following changes to fix corner issue in com.sun.jndi.ldap.EventSupport, thanks

Bug: https://bugs.openjdk.java.net/browse/JDK-8241130
Webrev: http://cr.openjdk.java.net/~xyin/8241130/webrev.00/


This is a follow up item which related to 8202117. When testing the second revision fix for 8202117 (http://mail.openjdk.java.net/pipermail/core-libs-dev/2020-March/065270.html <http://mail.openjdk.java.net/pipermail/core-libs-dev/2020-March/065270.html>), intermittent failure with java.lang.NullPointerException been observed(Thanks Daniel for additional testing), that exposed another issue in com.sun.jndi.ldap.EventSupport. 

“com.sun.jndi.ldap.NamingEventNotifier" is a background thread which been created when addNamingListener with ldap context, per code logic, it will call EventSupport.removeDeadNotifier when encounter NamingException (maybe wrapped a SocketException) in some case, if user closed source ldap context first (EventSupport.cleanup been triggered), the call to EventSupport.removeDeadNotifier will throw NullPointerException since var “notifiers” already been set to null in previous EventSupport.cleanup. Maybe in real world, it’s hard to get all criteria been satisfied to reproduce, but it’s still a potential multithreading issue and caught by test with repeat run.

Combined this change and 8202117 second revision change, run test com/sun/jndi/ldap/RemoveNamingListenerTest.java on 4 platforms for total 2000 times, no failure been observed, also tier1, tier2, tier3 tests passed.

Thanks,
Chris