Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751601AbdI1T54 (ORCPT ); Thu, 28 Sep 2017 15:57:56 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:16889 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751088AbdI1T5z (ORCPT ); Thu, 28 Sep 2017 15:57:55 -0400 To: yang.s@alibaba-inc.com, mhocko@kernel.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message From: Tetsuo Handa References: <1506548776-67535-1-git-send-email-yang.s@alibaba-inc.com> <7e8684c2-c9e8-f76a-d7fb-7d5bf7682321@alibaba-inc.com> In-Reply-To: <7e8684c2-c9e8-f76a-d7fb-7d5bf7682321@alibaba-inc.com> Message-Id: <201709290457.CAC30283.VFtMFOFOJLQHOS@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Fri, 29 Sep 2017 04:57:53 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1237 Lines: 35 Yang Shi wrote: > On 9/27/17 9:36 PM, 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? > > I don't see the difference between regular oom path and oom path other > than calling panic() at last. > > And, the slab dump may be called by panic path too, it is for both > regular and panic path. Calling a function that might cause kerneloops immediately before calling panic() would be tolerable, for the kernel will panic after all. But calling a function that might cause kerneloops when there is no plan to call panic() is a bug. > > Thanks, > Yang > > > > > We can try mutex_trylock() from dump_unreclaimable_slab() at best. > > But it is still remaining unsafe, isn't it? > > >