The flush() method sets _active.flag = True without first checking if it's already set. Unlike add() which guards with if getattr(self._active, "flag", False): return None, flush() unconditionally sets the flag and proceeds. If _flush() triggers a GC warning that routes back through the logging integration to flush() (instead of add()), the nested flush() will execute, and its finally block will set _active.flag = False prematurely, leaving subsequent re-entrant calls unprotected.