[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 03:49, David Howells <dhowells at redhat.com> wrote:
>
> Anyway, I'll find a different way to do this, not involving checking the prev
> pointer.  What I don't want to do is hard code "prev == LIST_POISON2" into my
> stuff.  Anything like that really needs to be in list.h.

So i think the proper model is:

(a) normal and good list users should never *use* this kind of "is
this entry on a list or not".

Dammit, you should *KNOW* that already from core logic. Not with a
flag, not with a function to ask, but from how things work. The whole
"am I on a list or not" should not be a list issue, it should be
obvious.

(b) if the code in question really doesn't know what the ^%&%^ it did,
and has lost sight of what it has done to a list entry, and really
wants some kind of "did I remove this entry already" logic, I would
encourage such uses to either re-consider, or just use the
"__list_del_clearprev()" function when removing entries.

Because I really don't want the core list handling to cater to code
that doesn't know what the hell it has done.

                Linus