In other words, for Rust you'll need unsafe to exploit race conditions for performance optimisations.
It is possible (and in rare cases, desirable) to have data races while still having a perfectly safe program.
Even if your program is not conforming to whatever standard, it may be very well be useful and working in most compilers out there.
As an example, Linux is not conforming C, including triggering UB. But at least two major compilers support the intended semantics even if they are forbidden by the standard.
Linux, as Linus has said, isn't written in ISO C it's written (or was) in GNU C. The two had something of a symbiotic relationship for a long time. Which is why porting it to LLVM was such a tremendous effort.
Which is to say, Linux conforms to the memory model of the compilers it compiles on (or vice versa). Not ISO C's memory model. So I'm not sure how your example is relevant.
If your software is designed with that in mind, then a data race is not a bug.
Data races are undefined behavior on all major programming languages (C, C++, Rust, Java, Go, Swift, ...) and all major compilers compile code under the assumption that they do not happen.
If your program has a data-race, neither the language specification nor the compiler make any guarantees about the behavior of such programs.
Needles to say, this is neither safe, nor desirable, nor doing so produces perfectly safe programs.
The idea that data-races are safe because the load and store memory instructions that the CPU has are atomic is completely flawed, because it ignores the fact that the CPU does not execute the program you wrote, but the machine code that the compiler generates, and the compiler can and will reorganize non-atomic loads and stores under the assumption that they don't need to be atomic.
If your program has a data-race, the compiler provides no guarantees. It does not guarantee that the binary will reach the location where the data race happens. It does not even guarantee that the binary produced will be an executable binary, or that it will produce a binary at all (e.g. it does not guarantee that compilation terminates successfully).
* Data races using normal memory access function are impossible in safe code, and undefined behaviour in unsafe code. So unsafe code attempting this is incorrect.
* Data races using atomic types are possible in safe code. Some of the setup code might be unsafe internally while presenting a safe API (e.g. creating shared memory and giving you an `&[AtomicU8]` to that memory).
* Other race conditions (mostly non-deterministic order of lock acquisition) are also possible in safe code. The typical example of this is that writing to the console from multiple threads uses locks on individual write calls, which prevents torn writes but the order of those write outputs in non deterministic.