Re: [PATCH net v3 04/11] list: Move on_list_rcu() to list.h and add on_list() also

[Linus Torvalds]

On Mon, 30 Mar 2026 at 16:50, David Howells <dhowells@xxxxxxxxxx> wrote:
>
> If I don't delete entries in rxrpc_destroy_all_calls(), then rxrpc_put_call()
> only needs list_empty() to guard against the call not having being queued yet.
> I could have a flag for that, but it would be superfluous.

So make *that* code use a creaful "delete with flag".

As far as I know, __list_del_clearprev() works fine for RCU walking
too, and that "prev is NULL" works as a "this is not on a list".

Admittedly I didn't think about it a lot.

So my point is more that this should not be some "generic list"
behavior, and I do *not* want people to think that they can just do
"is_on_list()" kind of crap in general.

This should be a "this user needs that particular behavior, and has
used this particular function to get it".

And yes, this pattern started out as a single performance-critical
networking user, and maybe we could rename and codify this pattern
better since we now have a couple of users (bpf and xdp) and another
apparently appearing. But I think that "rename and codify" should be a
separate thing (and done after ths particular issue is fixed).

              Linus