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

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Date:   Thu, 28 Sep 2017 13:36:57 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Yang Shi <yang.s@...baba-inc.com>, mhocko@...nel.org
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 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?

We can try mutex_trylock() from dump_unreclaimable_slab() at best.
But it is still remaining unsafe, isn't it?