WINE mutex functions speed.

[Vincent Povirk]

This is because every call involving a kernel object handle is done
via RPC to the wineserver process.

The semantics of things like DuplicateHandle, and all of the various
types of waitable kernel objects, need to be reproduced exactly. Even
in the case of a single object used by a single thread, in order to
optimize out the wineserver call you'd have to somehow be sure no one
had duplicated that object into another process. Or you'd have to give
the wineserver enough information to duplicate it while letting you
wait for/manipulate the object without an RPC call.

So, I don't know that it's necessarily a fundamental architecture
problem, but there's a lot you have to think about. And I can't
recommend taking on a project like this to a new Wine developer.