diff --git a/python/pdo/common/block_store_manager.py b/python/pdo/common/block_store_manager.py
index c705edb9..8865fa66 100644
--- a/python/pdo/common/block_store_manager.py
+++ b/python/pdo/common/block_store_manager.py
@@ -33,14 +33,20 @@
 
 # XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 # XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+import threading
+__block_manager_lock__ = threading.Lock()
 __local_block_manager__ = None
 
 def local_block_manager() :
     global __local_block_manager__
+
+    __block_manager_lock__.acquire()
     if __local_block_manager__ is None :
         block_store_file = pconfig.shared_configuration(['StorageService','BlockStore'], "./blockstore.mdb")
 
         __local_block_manager__ = BlockStoreManager(block_store_file, True)
+    __block_manager_lock__.release()
+
     return __local_block_manager__
 
 # XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
diff --git a/python/pdo/common/key_value.py b/python/pdo/common/key_value.py
index 6d4787cf..b556a14e 100644
--- a/python/pdo/common/key_value.py
+++ b/python/pdo/common/key_value.py
@@ -25,12 +25,19 @@
 import logging
 logger = logging.getLogger(__name__)
 
+# XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+# XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+import threading
+__block_store_lock__ = threading.Lock()
 __block_store_initialized__ = False
 
 # -----------------------------------------------------------------
 # -----------------------------------------------------------------
 def KeyValueInitialize(block_store_file = None) :
     global __block_store_initialized__
+
+    __block_store_lock__.acquire()
+
     if __block_store_initialized__ :
         raise Exception("duplicate block store initialization")
 
@@ -41,6 +48,8 @@ def KeyValueInitialize(block_store_file = None) :
     kvs.block_store_open(block_store_file)
     __block_store_initialized__ = True
 
+    __block_store_lock__.release()
+
 # -----------------------------------------------------------------
 # -----------------------------------------------------------------
 def KeyValueTerminate() :