linux-kernel - Re: [PATCH v3 5/9] memcg: use css_get/put when charging/uncharging kmem

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Date:	Fri, 14 Jun 2013 09:17:40 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Michal Hocko <mhocko@...e.cz>
CC:	Tejun Heo <tj@...nel.org>, Glauber Costa <glommer@...nvz.org>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	cgroups <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH v3 5/9] memcg: use css_get/put when charging/uncharging
 kmem

>>  static void memcg_kmem_mark_dead(struct mem_cgroup *memcg)
>>  {
>> +	/*
>> +	 * We need to call css_get() first, because memcg_uncharge_kmem()
>> +	 * will call css_put() if it sees the memcg is dead.
>> +	 */
>> +	smb_wmb();
>>  	if (test_bit(KMEM_ACCOUNTED_ACTIVE, &memcg->kmem_account_flags))
>>  		set_bit(KMEM_ACCOUNTED_DEAD, &memcg->kmem_account_flags);
> 
> I do not feel strongly about that but maybe open coding this in
> mem_cgroup_css_offline would be even better. There is only single caller
> and there is smaller chance somebody will use the function incorrectly
> later on.
> 
> So I leave the decision on you because this doesn't matter much.
> 

Yeah, it should go away soon. I'll post a patch after this patchset gets
merged into -mm tree and then we can discuss there.

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