Re: [GIT PULL] RCU regression fix for v6.4

[Linus Torvalds]

On Fri, 16 Jun 2023 at 09:34, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> Yes, it would be nice to abstract this somehow in order to hide it in
> SRCU, but I still don't see a good way of doing this.

Ehh - like we actually do spinlocks in general, perhaps?

Spinlocks always exist. On UP - with no spinlock debugging - it turns
into a zero-sized data structure, and the spin lock/unlock operations
are no-ops.

Why don't you just do the exact same thing with the "struct
srcu_usage". For Tiny SRCU, just make it an empty struct, with an
empty initializer.

IOW, don't "abstract it out". Abstract it IN. Make tiny-rcu still have
it, just as a no-op.

Anyway, I've pulled your fix, but maybe the above would have been the
cleaner solution?

          Linus