Re: [RFC PATCH 03/21] list: Annotate lockless list primitives with data_race()

[Jann Horn]

On Tue, Mar 24, 2020 at 5:51 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Tue, Mar 24, 2020 at 03:36:25PM +0000, Will Deacon wrote:
> > diff --git a/include/linux/list.h b/include/linux/list.h
> > index 4fed5a0f9b77..4d9f5f9ed1a8 100644
> > --- a/include/linux/list.h
> > +++ b/include/linux/list.h
> > @@ -279,7 +279,7 @@ static inline int list_is_last(const struct list_head *list,
> >   */
> >  static inline int list_empty(const struct list_head *head)
> >  {
> > -     return READ_ONCE(head->next) == head;
> > +     return data_race(READ_ONCE(head->next) == head);
> >  }
>
> list_empty() isn't lockless safe, that's what we have
> list_empty_careful() for.

That thing looks like it could also use some READ_ONCE() sprinkled in...