Fixed MT access to Learning/TeachingSynchronizer fields

Signed-off-by: Artem Ananev <[email protected]>

Author: artemananiev

platform-sdk/swirlds-common/src/main/java/com/swirlds/common/merkle/synchronization/LearningSynchronizer.java

@@ -41,12 +41,13 @@
 import edu.umd.cs.findbugs.annotations.NonNull;
 import java.util.ArrayList;
 import java.util.Deque;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -149,8 +150,8 @@ public LearningSynchronizer(
         views = new ConcurrentHashMap<>();
         final int viewId = viewIdGen.getAndIncrement();
         views.put(viewId, nodeTreeView(root));
-        viewsToInitialize = new LinkedList<>();
-        rootsToReceive = new LinkedList<>();
+        viewsToInitialize = new ConcurrentLinkedDeque<>();
+        rootsToReceive = new ConcurrentLinkedQueue<>();
         rootsToReceive.add(root);
 
         this.breakConnection = breakConnection;

platform-sdk/swirlds-common/src/main/java/com/swirlds/common/merkle/synchronization/TeachingSynchronizer.java

@@ -38,11 +38,11 @@
 import edu.umd.cs.findbugs.annotations.NonNull;
 import edu.umd.cs.findbugs.annotations.Nullable;
 import java.net.SocketException;
-import java.util.LinkedList;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
@@ -148,7 +148,7 @@ public TeachingSynchronizer(
         final int viewId = viewIdGen.getAndIncrement();
         final TeacherTreeView<?> view = new TeacherPushMerkleTreeView(configuration, root);
         views.put(viewId, view);
-        subtrees = new LinkedList<>();
+        subtrees = new ConcurrentLinkedQueue<>();
         final TeacherSubtree rootSubtree = new TeacherSubtree(root, viewId, view);
         subtrees.add(rootSubtree);