Concurrent Refresh Token requests

I’m trying to understand how two concurrent refresh token requests are handled when “Revoke Refresh Token” is enabled and “Refresh Token Max Reuse” is set to 1 (see image below)

In this scenario I expect that the second request will fail because invalidate by the first.
Looking at the TokenManager source code

I can’t understand if is implemented any kind of Lock that can ensure that the second request fail because of the previous succed, in fact if the method validateTokenReuse of both requests is execute at the same moment what can prevent both requests to have successful responses?