From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id 92EDD6B0005 for ; Fri, 22 Jan 2016 11:33:35 -0500 (EST) Received: by mail-pa0-f50.google.com with SMTP id cy9so44103480pac.0 for ; Fri, 22 Jan 2016 08:33:35 -0800 (PST) Received: from mx2.parallels.com (mx2.parallels.com. [199.115.105.18]) by mx.google.com with ESMTPS id t72si10510085pfi.38.2016.01.22.08.33.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Jan 2016 08:33:34 -0800 (PST) Date: Fri, 22 Jan 2016 19:33:24 +0300 From: Vladimir Davydov Subject: Re: PROBLEM: BUG when using memory.kmem.limit_in_bytes Message-ID: <20160122163324.GH26192@esperanza> References: <20160122135042.GF26192@esperanza> <20160122144854.GA14432@cmpxchg.org> <20160122155104.GG32380@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160122155104.GG32380@htj.duckdns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Johannes Weiner , Brian Christiansen , Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org On Fri, Jan 22, 2016 at 10:51:04AM -0500, Tejun Heo wrote: > On Fri, Jan 22, 2016 at 09:48:54AM -0500, Johannes Weiner wrote: > > On Fri, Jan 22, 2016 at 04:50:42PM +0300, Vladimir Davydov wrote: > > > From first glance, it looks like the bug was triggered, because > > > mem_cgroup_css_offline was run for a child cgroup earlier than for its > > > parent. This couldn't happen for sure before the cgroup was switched to > > > percpu_ref, because cgroup_destroy_wq has always had max_active == 1. > > > Now, however, it looks like this is perfectly possible for > > > css_killed_ref_fn is called from an rcu callback - see kill_css -> > > > percpu_ref_kill_and_confirm. This breaks kmemcg assumptions. > > > > > > I'll take a look what can be done about that. > > > > It's an acknowledged problem in the cgroup core then, and not an issue > > with kmemcg. Tejun sent a fix to correct the offlining order here: > > > > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1056544.html > > Patche descriptions updated and applied to cgroup/for-4.5-fixes. > > http://lkml.kernel.org/g/20160122154503.GD32380@htj.duckdns.org > http://lkml.kernel.org/g/20160122154552.GE32380@htj.duckdns.org I couldn't reproduce the issue with the two patches applied. Looks like they fix it. Thanks, Vladimir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org