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https://issues.apache.org/jira/browse/ZOOKEEPER-954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13072259#comment-13072259
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Laxman commented on ZOOKEEPER-954:
----------------------------------

Findbugs description for this says
"This method performs synchronization an object that implements 
java.util.concurrent.locks.Lock. Such an object is locked/unlocked using 
acquire()/release() rather than using the synchronized (...) construct."

But in our code[ClientCnxt] we used LinkedBlockingQueue [waitingEvents] which 
does not implement Lock. Also, from code it looks intentional and appropriate 
to synchronize waitingEvents explicitly to ensure no event is dropped from 
processing.

Any other thoughts on this?

> Findbugs/ClientCnxn: Bug type JLM_JSR166_UTILCONCURRENT_MONITORENTER
> --------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-954
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-954
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: java client
>            Reporter: Thomas Koch
>            Priority: Minor
>
> JLM   Synchronization performed on java.util.concurrent.LinkedBlockingQueue 
> in org.apache.zookeeper.ClientCnxn$EventThread.queuePacket(ClientCnxn$Packet)
>       
> Bug type JLM_JSR166_UTILCONCURRENT_MONITORENTER (click for details)
> In class org.apache.zookeeper.ClientCnxn$EventThread
> In method 
> org.apache.zookeeper.ClientCnxn$EventThread.queuePacket(ClientCnxn$Packet)
> Type java.util.concurrent.LinkedBlockingQueue
> Value loaded from field 
> org.apache.zookeeper.ClientCnxn$EventThread.waitingEvents
> At ClientCnxn.java:[line 411]
> JLM   Synchronization performed on java.util.concurrent.LinkedBlockingQueue 
> in org.apache.zookeeper.ClientCnxn$EventThread.run()
>       
> Bug type JLM_JSR166_UTILCONCURRENT_MONITORENTER (click for details)
> In class org.apache.zookeeper.ClientCnxn$EventThread
> In method org.apache.zookeeper.ClientCnxn$EventThread.run()
> Type java.util.concurrent.LinkedBlockingQueue
> Value loaded from field 
> org.apache.zookeeper.ClientCnxn$EventThread.waitingEvents
> At ClientCnxn.java:[line 436]
> The respective code:
> 409          public void queuePacket(Packet packet) {
> 410             if (wasKilled) {
> 411                synchronized (waitingEvents) {
> 412                   if (isRunning) waitingEvents.add(packet);
> 413                   else processEvent(packet);
> 414                }
> 415             } else {
> 416                waitingEvents.add(packet);
> 417             }
> 418          }
> 419   
> 420           public void queueEventOfDeath() {
> 421               waitingEvents.add(eventOfDeath);
> 422           }
> 423   
> 424           @Override
> 425           public void run() {
> 426              try {
> 427                 isRunning = true;
> 428                 while (true) {
> 429                    Object event = waitingEvents.take();
> 430                    if (event == eventOfDeath) {
> 431                       wasKilled = true;
> 432                    } else {
> 433                       processEvent(event);
> 434                    }
> 435                    if (wasKilled)
> 436                       synchronized (waitingEvents) {
> 437                          if (waitingEvents.isEmpty()) {
> 438                             isRunning = false;
> 439                             break;
> 440                          }
> 441                       }
> 442                 }

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