On Tue, Mar 30, 2021 at 11:00:36AM +0200, Arnd Bergmann arnd@kernel.org wrote:
Would it be possible to enclose most or all of kernel/cgroup/cgroup.c in an #ifdef CGROUP_SUBSYS_COUNT block?
Even without any controllers, there can still be named hierarchies (v1) or the default hierarchy (v2) (for instance) for process tracking purposes. So only parts of kernel/cgroup/cgroup.c could be ifdef'd.
Beware that CGROUP_SUBSYS_COUNT is not known at preprocessing stage (you could have a macro alternative though).
I didn't try that myself, but this might be a way to guarantee that there cannot be any callers (it would cause a link error).
Such a guarantee would be nicer, I agree. I tried a bit but anandoned it when I saw macros proliferate (which I found less readable than your current variant). But YMMV.
Michal