Re: next-20241001: WARNING: at mm/list_lru.c:77 list_lru_del (mm/list_lru.c:212 mm/list_lru.c:200)

[Naresh Kamboju <naresh.kamboju@linaro.org>]

On Wed, 2 Oct 2024 at 16:58, Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> On Wed, Oct 02, 2024 at 02:25:34PM +0300, Dan Carpenter wrote:
> > On Wed, Oct 02, 2024 at 02:24:20PM +0300, Dan Carpenter wrote:
> > > Let's add Kairui Song to the  CC list.
> > >
> > > One simple thing is that we should add a READ_ONCE() to the comparison.  Naresh,
> > > could you test the attached diff?  I don't know that it will fix it but it's
> > > worth checking the easy stuff first.
> > >
> >
> > Actually that's not right.  Let me write a different patch.
>
> Try this one.
>

Thanks for the patch,

I have applied this patch and testing is in progress.
From last night the tests running in a loop did not find the reported warning.


> regards,
> dan carpenter
>
> diff --git a/mm/list_lru.c b/mm/list_lru.c
> index 79c2d21504a2..2c429578ed31 100644
> --- a/mm/list_lru.c
> +++ b/mm/list_lru.c
> @@ -65,6 +65,7 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
>                        bool irq, bool skip_empty)
>  {
>         struct list_lru_one *l;
> +       long nr_items;
>         rcu_read_lock();
>  again:
>         l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg));
> @@ -73,8 +74,9 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
>                         spin_lock_irq(&l->lock);
>                 else
>                         spin_lock(&l->lock);
> -               if (likely(READ_ONCE(l->nr_items) != LONG_MIN)) {
> -                       WARN_ON(l->nr_items < 0);
> +               nr_items = READ_ONCE(l->nr_items);
> +               if (likely(nr_items != LONG_MIN)) {
> +                       WARN_ON(nr_items < 0);
>                         rcu_read_unlock();
>                         return l;
>                 }

- Naresh