Re: [PATCH] memcg: Don't call schedule_work when no spinning is allowed

[David Stevens]

On Tue, Sep 1, 2026 at 1:18 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Mon 31-08-26 18:04:57, David Stevens wrote:
> > On Mon, Aug 31, 2026 at 5:10 PM Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
> > >
> > > On Mon, Aug 31, 2026 at 04:43:39PM -0700, David Stevens wrote:
> > > > Memcg charging can be done from any context, but calling schedule_work()
> > > > isn't safe from an NMI. If memory.high is breached from a context where
> > > > spinning isn't allowed, use irq_work to schedule the reclaim work.
> > > >
> > > > Fixes: 3ac4638a734a ("memcg: make memcg_rstat_updated nmi safe")
> > > > Signed-off-by: David Stevens <stevensd@xxxxxxxxxx>
> > >
> > > Did you hit this issue or just code inspection? I assume this is the
> > > done_restock code path.
> >
> > I just found this via code inspection. I spent a little bit trying to
> > trigger it for real, but the only way I managed was by writing a hacky
> > driver absuing alloc_pages_nolock().
>
> Then this is not really a fix but rather a new feature.

I spent a bit longer looking, and this can be hit via bpf_arena_alloc_pages().

-David