On Tue, 14 Sept 2021 at 17:41, Linus Torvalds
[off-list ref] wrote:

On Tue, Sep 14, 2021 at 5:10 AM Ard Biesheuvel [off-list ref] wrote:

quoted

The CPU field will be moved back into thread_info even when
THREAD_INFO_IN_TASK is enabled, so add it back to arm64's definition of
struct thread_info.

The series looks sane to me, but it strikes me that it's inconsistent
- here for arm64, you make it unconditional, but for the other
architectures you end up putting it inside a #ifdef CONFIG_SMP.

Was there some reason for this odd behavior?

Yes. CONFIG_SMP is a 'def_bool y' on arm64.