From: Balbir Singh <bsingharora@gmail.com>
To: Vladimir Davydov <vdavydov@tarantool.org>
Cc: mpe@ellerman.id.au, hannes@cmpxchg.org, mhocko@kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org,
Tejun Heo <tj@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RESEND] [PATCH v1 1/3] Add basic infrastructure for memcg hotplug support
Date: Tue, 22 Nov 2016 11:17:53 +1100 [thread overview]
Message-ID: <2395f702-8246-4ce6-ca23-7d71ce872507@gmail.com> (raw)
In-Reply-To: <20161121083616.GC18431@esperanza>
>>
>> The iterator internally takes rcu_read_lock() to avoid any side-effects
>> of cgroups added/removed. I suspect you are also suggesting using get_online_mems()
>> around each call to for_each_online_node
>>
>> My understanding so far is
>>
>> 1. invalidate_reclaim_iterators should be safe (no bad side-effects)
>> 2. mem_cgroup_free - should be safe as well
>> 3. mem_cgroup_alloc - needs protection
>> 4. mem_cgroup_init - needs protection
>> 5. mem_cgroup_remove_from_tress - should be safe
>
> I'm not into the memory hotplug code, but my understanding is that if
> memcg offline happens to race with node unplug, it's possible that
>
> - mem_cgroup_free() doesn't free the node's data, because it sees the
> node as already offline
> - memcg hotplug code doesn't free the node's data either, because it
> sees the cgroup as offline
>
> May be, we should surround all the loops over online nodes with
> get/put_online_mems() to be sure that nothing wrong can happen.
> They are slow path, anyway.
>
Makes sense, agreed
Balbir
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next prev parent reply other threads:[~2016-11-22 0:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-15 23:44 [RESEND][v1 0/3] Support memory cgroup hotplug Balbir Singh
2016-11-15 23:44 ` [RESEND] [PATCH v1 1/3] Add basic infrastructure for memcg hotplug support Balbir Singh
2016-11-16 9:01 ` Vladimir Davydov
2016-11-17 0:28 ` Balbir Singh
2016-11-21 8:36 ` Vladimir Davydov
2016-11-22 0:17 ` Balbir Singh [this message]
2016-11-15 23:45 ` [RESEND] [PATCH v1 2/3] Move from all possible nodes to online nodes Balbir Singh
2016-11-15 23:45 ` [RESEND] [PATCH v1 3/3] powerpc: fix node_possible_map limitations Balbir Singh
2016-11-16 16:40 ` Reza Arbab
2016-11-16 16:45 ` [PATCH] powerpc/mm: allow memory hotplug into an offline node Reza Arbab
2017-02-01 1:05 ` Michael Ellerman
2016-11-21 14:03 ` [RESEND][v1 0/3] Support memory cgroup hotplug Michal Hocko
2016-11-22 0:16 ` Balbir Singh
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