From: Glauber Costa <glommer@parallels.com>
To: Michal Hocko <mhocko@suse.cz>
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
Tejun Heo <tj@kernel.org>,
kamezawa.hiroyu@jp.fujitsu.com,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 4/4] memcg: replace cgroup_lock with memcg specific memcg_lock
Date: Tue, 4 Dec 2012 11:49:14 +0400 [thread overview]
Message-ID: <50BDAAFA.2010708@parallels.com> (raw)
In-Reply-To: <20121203173002.GH17093@dhcp22.suse.cz>
On 12/03/2012 09:30 PM, Michal Hocko wrote:
> On Mon 03-12-12 18:15:32, Michal Hocko wrote:
> [...]
>>> @@ -3915,7 +3926,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
>>> */
>>> if ((!parent_memcg || !parent_memcg->use_hierarchy) &&
>>> (val == 1 || val == 0)) {
>>> - if (list_empty(&cont->children))
>>> + if (!memcg_has_children(memcg))
>>> memcg->use_hierarchy = val;
>>> else
>>> retval = -EBUSY;
>>
>> Nothing prevents from a race when a task is on the way to be attached to
>> the group. This means that we might miss some charges up the way to the
>> parent.
>>
>> mem_cgroup_hierarchy_write
>> cgroup_attach_task
>> ss->can_attach() = mem_cgroup_can_attach
>> mutex_lock(&memcg_lock)
>> memcg->attach_in_progress++
>> mutex_unlock(&memcg_lock)
>> __mem_cgroup_can_attach
>> mem_cgroup_precharge_mc (*)
>> mutex_lock(memcg_lock)
>> memcg_has_children(memcg)==false
>
> Dohh, retard alert. I obviously mixed tasks and children cgroups here.
> Why I thought we also do check for no tasks in the group? Ahh, because
> we should, at least here otherwise parent could see more uncharges than
> charges.
> But that deserves a separate patch. Sorry, for the confusion.
That is okay, here is a beer for you: http://bit.ly/R3rkML
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next prev parent reply other threads:[~2012-12-04 7:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-30 13:31 [PATCH 0/4] replace cgroup_lock with local lock in memcg Glauber Costa
2012-11-30 13:31 ` [PATCH 1/4] cgroup: warn about broken hierarchies only after css_online Glauber Costa
2012-11-30 15:11 ` Tejun Heo
2012-11-30 15:13 ` Glauber Costa
2012-11-30 15:45 ` Tejun Heo
2012-11-30 15:49 ` Michal Hocko
2012-11-30 15:57 ` Glauber Costa
2012-11-30 13:31 ` [PATCH 2/4] memcg: prevent changes to move_charge_at_immigrate during task attach Glauber Costa
2012-11-30 15:19 ` Tejun Heo
2012-11-30 15:29 ` Glauber Costa
2012-12-04 9:29 ` Michal Hocko
2012-11-30 13:31 ` [PATCH 3/4] memcg: split part of memcg creation to css_online Glauber Costa
2012-12-03 17:32 ` Michal Hocko
2012-12-04 8:05 ` Glauber Costa
2012-12-04 8:17 ` Michal Hocko
2012-12-04 8:32 ` Glauber Costa
2012-12-04 8:52 ` Michal Hocko
2012-11-30 13:31 ` [PATCH 4/4] memcg: replace cgroup_lock with memcg specific memcg_lock Glauber Costa
2012-12-03 17:15 ` Michal Hocko
2012-12-03 17:30 ` Michal Hocko
2012-12-04 7:49 ` Glauber Costa [this message]
2012-12-04 7:58 ` Glauber Costa
2012-12-04 8:23 ` Michal Hocko
2012-12-04 8:31 ` Glauber Costa
2012-12-04 8:45 ` Michal Hocko
2012-12-04 14:52 ` Tejun Heo
2012-12-04 15:14 ` Michal Hocko
2012-12-04 15:22 ` Tejun Heo
2012-12-05 14:35 ` Michal Hocko
2012-12-05 14:41 ` Tejun Heo
2012-11-30 15:52 ` [PATCH 0/4] replace cgroup_lock with local lock in memcg Tejun Heo
2012-11-30 15:59 ` Glauber Costa
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