linux-kernel - Re: [RFC][PATCH] oom: Be less verbose if the oom

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Date:	Thu, 05 Jun 2014 17:46:57 +0200
From:	Richard Weinberger <richard@....at>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	hannes@...xchg.org, mhocko@...e.cz, bsingharora@...il.com,
	kamezawa.hiroyu@...fujitsu.com, akpm@...ux-foundation.org,
	vdavydov@...allels.com, tj@...nel.org, handai.szj@...bao.com,
	rientjes@...gle.com, rusty@...tcorp.com.au,
	kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd
 has listeners

Am 05.06.2014 16:18, schrieb Oleg Nesterov:
> On 06/05, Richard Weinberger wrote:
>>
>> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
>> +{
>> +	int ret = 0;
>> +
>> +	if (!memcg)
>> +		goto out;
>> +
>> +	spin_lock(&memcg_oom_lock);
>> +	ret = !list_empty(&memcg->oom_notify);
>> +	spin_unlock(&memcg_oom_lock);
>> +
>> +out:
>> +	return ret;
>> +}
> 
> Do we really need memcg_oom_lock to check list_empty() ? With or without
> this lock we can race with list_add/del anyway, and I guess we do not care.

Hmm, in mm/memcontrol.c all list_dev/add are under memcg_oom_lock.
What do I miss?

Thanks,
//richard
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