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Date:   Wed, 2 Sep 2020 13:32:04 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Pavel Tatashin <pasha.tatashin@soleen.com>,
        Roman Gushchin <guro@fb.com>,
        Bharata B Rao <bharata@linux.ibm.com>,
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        David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller
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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.
-- 
Michal Hocko
SUSE Labs