Re: [PATCH v2 00/28] The new cgroup slab memory controller

[Pavel Tatashin]

On Wed, Sep 2, 2020 at 7:32 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Wed 02-09-20 11:53:00, Vlastimil Babka wrote:
> > >> > > Thread #2: ccs killer kthread
> > >> > >    css_killed_work_fn
> > >> > >      cgroup_mutex  <- Grab this Mutex
> > >> > >      mem_cgroup_css_offline
> > >> > >        memcg_offline_kmem.part
> > >> > >           memcg_deactivate_kmem_caches
> > >> > >             get_online_mems
> > >> > >               mem_hotplug_lock <- waits for Thread#1 to get read access
>
> And one more thing. THis has been brought up several times already.
> Maybe I have forgoten but why do we take hotplug locks in this path in
> the first place? Memory hotplug notifier takes slab_mutex so this
> shouldn't be really needed.

Good point, it seems this lock can be completely removed from
memcg_deactivate_kmem_caches

Pasha

> --
> Michal Hocko
> SUSE Labs