prevent re-entrancy for closeConnection

HISTORY

@@ -1,7 +1,8 @@
 
-Version 1.39  2025-12-18
+Version 1.39  2025-12-19
   * ConnectionPool.getKey() use '-' instead of ':'
   * ConnectionManager.java: remove private AtomicInteger freeCount
+  * ConnectionManager.java: prevent re-entrancy for closeConnection
 
 Version 1.38  2025-11-28
   * bugfixed: loadStorageServersFromTracker correctly with rw option

src/main/java/org/csource/fastdfs/pool/Connection.java

@@ -120,6 +120,10 @@ public class Connection {
         return false;
     }
 
+    public boolean isClosed() {
+        return this.sock == null;
+    }
+
     public boolean isNeedActiveTest() {
         return needActiveTest;
     }

src/main/java/org/csource/fastdfs/pool/ConnectionManager.java

@@ -104,6 +104,7 @@ public class ConnectionManager {
         if (connection == null) {
             return;
         }
+
         lock.lock();
         try {
             connection.setLastAccessTime(System.currentTimeMillis());
@@ -115,8 +116,12 @@ public class ConnectionManager {
     }
 
     public void closeConnection(Connection connection) {
+        if (connection == null) {
+            return;
+        }
+
         try {
-            if (connection != null) {
+            if (!connection.isClosed()) {
                 totalCount.decrementAndGet();
                 connection.closeDirectly();
             }