Index: include/lldb/Expression/Expression.h
===================================================================
--- include/lldb/Expression/Expression.h
+++ include/lldb/Expression/Expression.h
@@ -99,6 +99,16 @@
   //------------------------------------------------------------------
   lldb::addr_t StartAddress() { return m_jit_start_addr; }
 
+  //------------------------------------------------------------------
+  /// Called to notify the expression that it is about to be executed.
+  //------------------------------------------------------------------
+  virtual void WillStartExecuting() {}
+
+  //------------------------------------------------------------------
+  /// Called to notify the expression that its execution has finished.
+  //------------------------------------------------------------------
+  virtual void DidFinishExecuting() {}
+
   virtual ExpressionTypeSystemHelper *GetTypeSystemHelper() { return nullptr; }
 
 protected:
Index: include/lldb/Target/ThreadPlanCallFunction.h
===================================================================
--- include/lldb/Target/ThreadPlanCallFunction.h
+++ include/lldb/Target/ThreadPlanCallFunction.h
@@ -117,7 +117,7 @@
                         lldb::addr_t &start_load_addr,
                         lldb::addr_t &function_load_addr);
 
-  void DoTakedown(bool success);
+  virtual void DoTakedown(bool success);
 
   void SetBreakpoints();
 
Index: include/lldb/Target/ThreadPlanCallUserExpression.h
===================================================================
--- include/lldb/Target/ThreadPlanCallUserExpression.h
+++ include/lldb/Target/ThreadPlanCallUserExpression.h
@@ -48,6 +48,7 @@
   }
 
 protected:
+  void DoTakedown(bool success) override;
 private:
   lldb::UserExpressionSP
       m_user_expression_sp; // This is currently just used to ensure the
Index: source/Target/ThreadPlanCallUserExpression.cpp
===================================================================
--- source/Target/ThreadPlanCallUserExpression.cpp
+++ source/Target/ThreadPlanCallUserExpression.cpp
@@ -48,6 +48,7 @@
   // stop when done.
   SetIsMasterPlan(true);
   SetOkayToDiscard(false);
+  m_user_expression_sp->WillStartExecuting();
 }
 
 ThreadPlanCallUserExpression::~ThreadPlanCallUserExpression() {}
@@ -113,3 +114,8 @@
 
   return stop_info_sp;
 }
+
+void ThreadPlanCallUserExpression::DoTakedown(bool success) {
+  ThreadPlanCallFunction::DoTakedown(success);
+  m_user_expression_sp->DidFinishExecuting();
+}