Re: [PATCH bpf-next v1 2/5] cgroup: bpf: add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs

[Tejun Heo]

On Fri, May 20, 2022 at 03:06:07PM +0530, Kumar Kartikeya Dwivedi wrote:
> With static noinline, the compiler will optimize away the function. With global
> noinline, it can still optimize away the call site, but will keep the function
> definition, so attach works. Therefore __weak is needed to ensure call is still
> emitted. With GCC __attribute__((noipa)) might have been more appropritate, but
> LLVM doesn't support it, so __weak is the next best thing supported by both with
> the same side effect.

Ah, okay, so it's to prevent compiler from optimizing away call to a noop
function by telling it that we don't know what the function might eventually
be. Thanks for the explanation. Yosry, can you please add a comment
explaining what's going on?

Thanks.

-- 
tejun