Can the callback for SDL_AddEventWatch be called concurrently?

I am now wondering if the callback passed to SDL_AddEventWatch may be called concurrently from multiple threads. If so, we have to care about thread safety when treating my user data. The documentation does not seem to mention about this, so I’m asking a question here.

// I’m writing a Rust wrapper for SDL_AddEventWatch / SDL_DelEventWatch here, where safety is important