It will always be inexact. All dynamic analyses of this type are, because they only observe what the program does as it executes and do not enforce any restrictions.

If you want a more guaranteed form of race freedom, you need to constrain what programs can do, either with dynamic restrictions on mutable state sharing (like Erlang or the parallel extensions to JavaScript do) or with a type system strong enough to reason about sharing of data (like Haskell or Rust).