[ARTEMIS-1408] FindBugs: Synchronization on java.util.concurrent objects in MQTTSessionState.java - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Minor
Resolution: Fixed
Affects Version/s: 2.4.0
Fix Version/s: 2.5.0
Component/s: Broker, MQTT
Labels:
None

External issue URL:
https://scan7.coverity.com/reports.htm#v14452/p14213/g14452g/fileInstanceId=34202107&defectInstanceId=7508433&mergedDefectId=1419085
External issue ID:
1419085, 1419151

Description

82   boolean addSubscription(MqttTopicSubscription subscription, WildcardConfiguration wildcardConfiguration) {
   	
CID 1419151 (#1 of 1): JLM: Synchronization on java.util.concurrent objects (FB.JLM_JSR166_UTILCONCURRENT_MONITORENTER)
1. defect: Synchronization performed on java.util.concurrent.ConcurrentHashMap.
 83      synchronized (subscriptions) {
 84         addressMessageMap.putIfAbsent(MQTTUtil.convertMQTTAddressFilterToCore(subscription.topicName(), wildcardConfiguration), new ConcurrentHashMap<Long, Integer>());
 85
 86         MqttTopicSubscription existingSubscription = subscriptions.get(subscription.topicName());
 87         if (existingSubscription != null) {
 88            if (subscription.qualityOfService().value() > existingSubscription.qualityOfService().value()) {
 89               subscriptions.put(subscription.topicName(), subscription);
 90               return true;
 91            }
 92         } else {
 93            subscriptions.put(subscription.topicName(), subscription);
 94            return true;
 95         }
 96      }
 97      return false;
 98   }
 99

100   void removeSubscription(String address) {
   	
CID 1419085 (#1 of 1): JLM: Synchronization on java.util.concurrent objects (FB.JLM_JSR166_UTILCONCURRENT_MONITORENTER)
1. defect: Synchronization performed on java.util.concurrent.ConcurrentHashMap.
101      synchronized (subscriptions) {
102         subscriptions.remove(address);
103         addressMessageMap.remove(address);
104      }
105   }

JLM: Synchronization performed on util.concurrent instance (JLM_JSR166_UTILCONCURRENT_MONITORENTER)

This method performs synchronization an object that is an instance of a class from the java.util.concurrent package (or its subclasses). Instances of these classes have their own concurrency control mechanisms that are orthogonal to the synchronization provided by the Java keyword synchronized. For example, synchronizing on an AtomicBoolean will not prevent other threads from modifying the AtomicBoolean.

Such code may be correct, but should be carefully reviewed and documented, and may confuse people who have to maintain the code at a later date.

http://findbugs.sourceforge.net/bugDescriptions.html#JLM_JSR166_UTILCONCURRENT_MONITORENTER