From 00d90317d8e7e1586eb1e30ff9643ccf0b20b469 Mon Sep 17 00:00:00 2001
From: Wei-Chiu Chuang <weichiu@apache.org>
Date: Sat, 3 Jul 2021 00:45:21 +0800
Subject: [PATCH] PHOENIX-6510 Double-Checked Locking field must be volatile

added volatile keyword to the variable to be doubly checked.
Do not use double check pattern in PhoenixConnection.
---
 .../phoenix/jdbc/PhoenixConnection.java       | 29 ++++---------------
 .../apache/phoenix/log/TableLogWriter.java    |  2 +-
 .../org/apache/phoenix/schema/PNameImpl.java  |  2 +-
 3 files changed, 8 insertions(+), 25 deletions(-)

diff --git a/phoenix-core/src/main/java/org/apache/phoenix/jdbc/PhoenixConnection.java b/phoenix-core/src/main/java/org/apache/phoenix/jdbc/PhoenixConnection.java
index da704420d37..105f45b6999 100644
--- a/phoenix-core/src/main/java/org/apache/phoenix/jdbc/PhoenixConnection.java
+++ b/phoenix-core/src/main/java/org/apache/phoenix/jdbc/PhoenixConnection.java
@@ -177,8 +177,8 @@ public class PhoenixConnection implements Connection, MetaDataMutated, SQLClosea
     private Double logSamplingRate;
     private String sourceOfOperation;
 
-    private Object queueCreationLock = new Object(); // lock for the lazy init path of childConnections structure
-    private ConcurrentLinkedQueue<PhoenixConnection> childConnections = null;
+    private final ConcurrentLinkedQueue<PhoenixConnection> childConnections =
+        new ConcurrentLinkedQueue<>();
 
     //For now just the copy constructor paths will have this as true as I don't want to change the
     //public interfaces.
@@ -467,18 +467,10 @@ public boolean isInternalConnection() {
     }
 
     /**
-     * This method, and *only* this method is thread safe
+     * Add connection to the internal childConnections queue
      * @param connection
      */
     public void addChildConnection(PhoenixConnection connection) {
-        //double check for performance
-        if(childConnections == null) {
-            synchronized (queueCreationLock) {
-                if (childConnections == null) {
-                    childConnections = new ConcurrentLinkedQueue<>();
-                }
-            }
-        }
         childConnections.add(connection);
     }
 
@@ -488,9 +480,7 @@ public void addChildConnection(PhoenixConnection connection) {
      * @param connection
      */
     public void removeChildConnection(PhoenixConnection connection) {
-        if (childConnections != null) {
-            childConnections.remove(connection);
-        }
+        childConnections.remove(connection);
     }
 
     /**
@@ -500,10 +490,7 @@ public void removeChildConnection(PhoenixConnection connection) {
      */
     @VisibleForTesting
     public int getChildConnectionsCount() {
-        if (childConnections != null) {
-            return childConnections.size();
-        }
-        return 0;
+        return childConnections.size();
     }
 
     public Sampler<?> getSampler() {
@@ -721,11 +708,7 @@ public void close() throws SQLException {
                     traceScope.close();
                 }
                 closeStatements();
-                synchronized (queueCreationLock) {
-                    if (childConnections != null) {
-                        SQLCloseables.closeAllQuietly(childConnections);
-                    }
-                }
+                SQLCloseables.closeAllQuietly(childConnections);
             } finally {
                 services.removeConnection(this);
             }
diff --git a/phoenix-core/src/main/java/org/apache/phoenix/log/TableLogWriter.java b/phoenix-core/src/main/java/org/apache/phoenix/log/TableLogWriter.java
index 966bed42a89..dc610b556bc 100644
--- a/phoenix-core/src/main/java/org/apache/phoenix/log/TableLogWriter.java
+++ b/phoenix-core/src/main/java/org/apache/phoenix/log/TableLogWriter.java
@@ -41,7 +41,7 @@
  */
 public class TableLogWriter implements LogWriter {
     private static final Logger LOGGER = LoggerFactory.getLogger(LogWriter.class);
-    private Connection connection;
+    private volatile Connection connection;
     private boolean isClosed;
     private PreparedStatement upsertStatement;
     private Configuration config;
diff --git a/phoenix-core/src/main/java/org/apache/phoenix/schema/PNameImpl.java b/phoenix-core/src/main/java/org/apache/phoenix/schema/PNameImpl.java
index dd1f6eca986..bccf7bf5422 100644
--- a/phoenix-core/src/main/java/org/apache/phoenix/schema/PNameImpl.java
+++ b/phoenix-core/src/main/java/org/apache/phoenix/schema/PNameImpl.java
@@ -33,7 +33,7 @@ private static class PNameImplData {
         /**  */
         public byte[] bytesName;
         /**  */
-        public ImmutableBytesPtr ptr;
+        public volatile ImmutableBytesPtr ptr;
 
         /**
          *