Refs #23079. Enable thread support for directors and release lock in server run().

Signed-off-by: Miguel Company <miguelcompany@eprosima.com>

Author: MiguelCompany

src/main/java/com/eprosima/fastcdr/idl/templates/TypesSwigInterface.stg

@@ -20,7 +20,15 @@ import "FastCdrCommon.stg"
 main(ctx, definitions) ::= <<
 $fileHeader(ctx=ctx, file=[ctx.filename, ".i"], description=["This header file contains the SWIG interface of the described types in the IDL file."])$
 
-%module(directors="1",moduleimport="if __import__('os').name == 'nt': import win32api; win32api.LoadLibrary('$ctx.filename$.dll')\nif __package__ or '.' in __name__:\n    from . import _$ctx.filename$Wrapper\nelse:\n    import _$ctx.filename$Wrapper") $ctx.filename$
+%module($if(ctx.thereIsInterface)$threads="1",$endif$directors="1",moduleimport="if __import__('os').name == 'nt': import win32api; win32api.LoadLibrary('$ctx.filename$.dll')\nif __package__ or '.' in __name__:\n    from . import _$ctx.filename$Wrapper\nelse:\n    import _$ctx.filename$Wrapper") $ctx.filename$
+
+$if(ctx.thereIsInterface)$
+// We have enabled threads because the RPC server directors will call the target language environment
+// from the C++ server threads, but we don't want the calls from the target language to release their
+// locks (e.g. Python GIL) when calling the C++ methods.
+// See a very nice explanation at https://github.com/swig/swig/issues/927#issuecomment-289279243
+%feature("nothreadallow");
+$endif$
 
 // If using windows in debug, it would try to use python_d, which would not be found.
 %begin %{
@@ -376,6 +384,16 @@ $export_list$
 %shared_ptr($interface.scopedname$);
 $if(!interface.annotatedAsNested)$
 %shared_ptr($interface.scopedname$Server);
+%extend $interface.scopedname$Server
+{
+    void run()
+    {
+        Py_BEGIN_ALLOW_THREADS
+        self->run();
+        Py_END_ALLOW_THREADS
+    }
+}
+
 %shared_ptr($interface.scopedname$Server_IServerImplementation);
 %shared_ptr($interface.scopedname$ServerImplementation);
 %feature("director") $interface.scopedname$ServerImplementation;