Comment by gpderetta

CPS can trivially deadlock for all meaningful definitions of deadlock.

Would you consider this a mutex?

   async_mutex mux;

   co_await mux.lock();
   /* critical section */
   co_await mux.unlock();
   

What about: my_mutex mux;

   {
      std::lock_guard _{mux};
      /* critical section */
   }

where the code runs in a user space fiber.

Would you consider boost synchronized a mutex?

Don't confuse the semantics with the implementation details (yes async/await leaks implementation details).