--- a/List.st	Wed Aug 01 12:00:55 2018 +0200
+++ b/List.st	Wed Aug 01 13:26:08 2018 +0200
@@ -112,6 +112,29 @@
 
 list
     ^ self
+!
+
+synchronizationSemaphore
+    "return a synchronization semaphore for myself"
+    
+    optionalAccessLock notNil ifTrue:[
+        ^ optionalAccessLock
+    ].
+    ^ super synchronizationSemaphore.
+
+    "Created: / 01-08-2018 / 13:22:45 / Claus Gittinger"
+!
+
+synchronizationSemaphore:aSemaphore
+    "set the synchronization semaphore for myself"
+
+    optionalAccessLock notNil ifTrue:[
+        Logger warning:'trying to change the snchronization semaphore'.
+        ^ self
+    ].    
+    optionalAccessLock := aSemaphore
+
+    "Created: / 01-08-2018 / 13:25:58 / Claus Gittinger"
 ! !
 
 !List methodsFor:'adding & removing'!
@@ -684,5 +707,9 @@
 
 version
     ^ '$Header$'
+!
+
+version_CVS
+    ^ '$Header$'
 ! !