I am not all that familiar with threading. I have a question:

I am not all that familiar with threading. I have a question:
I have critical session in a thread and I call a function outside the
thread code. Do I have to have critical session there too? For example

...beginning of thread code...
CS.Acquire;
- some code -
i := GetIndex(AParam);
- some code -
CS.Release;
... end of thread...


function GetIndex(AParam: string): integer;
var
i: integer;
begin
// do I need CS.Acquire/Release here too?
//arrayName is global variable and is not being
//updated by any other thread
// other threads are calling this function as well
result := -1;
for i := 0 to High(arrayName) do
if AParam = arrayName[i] then
begin
result := i;
break;
end;
end;

Thanks.