linux-kernel - Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message

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Date:   Mon, 02 Oct 2017 23:46:14 +0800
From:   "Yang Shi" <yang.s@...baba-inc.com>
To:     Michal Hocko <mhocko@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom
 message



On 10/2/17 4:20 AM, Michal Hocko wrote:
> On Thu 28-09-17 13:36:57, Tetsuo Handa wrote:
>> On 2017/09/28 6:46, Yang Shi wrote:
>>> Changelog v7 —> v8:
>>> * Adopted Michal’s suggestion to dump unreclaim slab info when unreclaimable slabs amount > total user memory. Not only in oom panic path.
>>
>> Holding slab_mutex inside dump_unreclaimable_slab() was refrained since V2
>> because there are
>>
>> 	mutex_lock(&slab_mutex);
>> 	kmalloc(GFP_KERNEL);
>> 	mutex_unlock(&slab_mutex);
>>
>> users. If we call dump_unreclaimable_slab() for non OOM panic path, aren't we
>> introducing a risk of crash (i.e. kernel panic) for regular OOM path?
> 
> yes we are
>   
>> We can try mutex_trylock() from dump_unreclaimable_slab() at best.
>> But it is still remaining unsafe, isn't it?
> 
> using the trylock sounds like a reasonable compromise.

OK, it sounds we reach agreement on trylock. Will solve those comments 
in v9.

Thanks,
Yang

>