Fixed concurrency issue due to get-after-analyse

When updating we must first get the cnode, then analyse how to do the
update and then compareAndSet the new cnode. If we first analyse and
then get the cnode, the cnode may have changed in the meantime, and the
analysis result may no longer be valid.

broker/src/main/java/io/moquette/broker/subscriptions/CTrie.java

@@ -112,35 +112,30 @@ public void addToTree(Subscription newSubscription) {
     }
 
     private Action insert(Topic topic, final INode inode, Subscription newSubscription) {
-        Token token = topic.headToken();
+        final Token token = topic.headToken();
+        final CNode cnode = inode.mainNode();
         if (!topic.isEmpty()) {
-            INode nextInode = inode.mainNode().childOf(token);
+            INode nextInode = cnode.childOf(token);
             if (nextInode != null) {
                 Topic remainingTopic = topic.exceptHeadToken();
                 return insert(remainingTopic, nextInode, newSubscription);
             }
         }
         if (topic.isEmpty()) {
-            return insertSubscription(inode, newSubscription);
+            return insertSubscription(inode, cnode, newSubscription);
         } else {
-            return createNodeAndInsertSubscription(topic, inode, newSubscription);
+            return createNodeAndInsertSubscription(topic, inode, cnode, newSubscription);
         }
     }
 
-    private Action insertSubscription(INode inode, Subscription newSubscription) {
-        CNode cnode = inode.mainNode();
-        CNode updatedCnode = cnode.copy().addSubscription(newSubscription);
-        if (inode.compareAndSet(cnode, updatedCnode)) {
-            return Action.OK;
-        } else {
-            return Action.REPEAT;
-        }
+    private Action insertSubscription(INode inode, CNode cnode, Subscription newSubscription) {
+        final CNode updatedCnode = cnode.copy().addSubscription(newSubscription);
+        return inode.compareAndSet(cnode, updatedCnode) ? Action.OK : Action.REPEAT;
     }
 
-    private Action createNodeAndInsertSubscription(Topic topic, INode inode, Subscription newSubscription) {
-        INode newInode = createPathRec(topic, newSubscription);
-        CNode cnode = inode.mainNode();
-        CNode updatedCnode = cnode.copy();
+    private Action createNodeAndInsertSubscription(Topic topic, INode inode, CNode cnode, Subscription newSubscription) {
+        final INode newInode = createPathRec(topic, newSubscription);
+        final CNode updatedCnode = cnode.copy();
         updatedCnode.add(newInode);
 
         return inode.compareAndSet(cnode, updatedCnode) ? Action.OK : Action.REPEAT;
@@ -174,14 +169,14 @@ public void removeFromTree(Topic topic, String clientID) {
 
     private Action remove(String clientId, Topic topic, INode inode, INode iParent) {
         Token token = topic.headToken();
+        final CNode cnode = inode.mainNode();
         if (!topic.isEmpty()) {
-            INode nextInode = inode.mainNode().childOf(token);
+            INode nextInode = cnode.childOf(token);
             if (nextInode != null) {
                 Topic remainingTopic = topic.exceptHeadToken();
                 return remove(clientId, remainingTopic, nextInode, inode);
             }
         }
-        final CNode cnode = inode.mainNode();
         if (cnode instanceof TNode) {
             // this inode is a tomb, has no clients and should be cleaned up
             // Because we implemented cleanTomb below, this should be rare, but possible