The updated webrev is now at http://btrace.kenai.com/webrevs/JDK-6809322/
I am sorry for this chaos with webrev locations but its not that easy to work efficiently without an OpenJDK username :/ -JB- On 10/12/2012 09:47 AM, Jaroslav Bachorik wrote: > On Fri 12 Oct 2012 04:44:31 AM CEST, David Holmes wrote: >> Hi Jaroslav, >> >> >> On 11/10/2012 6:07 PM, Jaroslav Bachorik wrote: >>> Dmitry has put the webrev on the public CR - >>> http://cr.openjdk.java.net/~dsamersoff/sponsorship/jbachorik/JDK-6809322-v2/ >>> >>> >>> Thanks! >>> >>> -JB- >>> >>> On 10/10/2012 04:17 PM, Jaroslav Bachorik wrote: >>>> I am looking for a review and a sponsor. >>>> >>>> The issue is about some javax.management.timer.Timer notifications not >>>> being received by the listeners if the notifications are generated >>>> rapidly. >>>> >>>> The problem is caused by ConcurrentModificationException being thrown - >>>> the exception itself is ignored but the dispatcher logic is skipped. >>>> Therefore the currently processed notification gets lost. >> >> Can you point out where exactly in the code the exception is thrown >> and caught. I'd like to understand the problem better. > > The CME is thrown in Timer.notifyAlarmClock() method in this case - but > may happen in other places as well. > > Actually, in some places the access to the timerTable map is > synchronized while in others it isn't. While switching the Hashtable > for ConcurrentHashMap resolves this particular issue it might be > beneficial to correct the partial synchronization instead. > >> >>>> >>>> The CME is thrown due to the Timer.timerTable being iterated over while >>>> other threads try to remove some of its elements. Fix consists of >>>> replacing the Hashtable used for Timer.timerTable by ConcurrentHashMap >>>> which handles such situations with grace. >> >> Be aware that it may also give surprising results as removal is no >> longer synchronized at all with processing. So it could now appear >> that a notification is processed after a listener has been removed. > > Indeed, the CME is the symptom of the out-of-order processing - the > removal method is synchronized on (Timer.this) while the > notifyAlarmClock() method, processing the notifications, runs > unsynchronized. > > Thanks for pointing this out. I will have something to think about. > > -JB- > >> >> David >> ----- >> >>>> The patch webrev is available @ >>>> https://jbs.oracle.com/bugs/browse/JDK-6809322 >>>> >>>> Thanks, >>>> >>>> -JB- >>>> >>> > >
