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

[Daniel Fuchs]

Hi Chris,

Thanks for taking care of this followup fix.

I see at least three other places where `notifiers` is accessed
without a null check. It might be good to fix these three other
places too just in case.
(two addNamingListener methods and 1 removeNamingListener)
All of them are already synchronized so a simple null check should
be enough.

Also you could had the @bug 8241130
to RemoveNamingListenerTest.java, since the test can be used
to verify the fix (if run often enough).

best regards,

-- daniel

On 18/03/2020 08:16, Chris Yin wrote:
> 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), 
> 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