From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: PROBLEM: BUG when using memory.kmem.limit_in_bytes Date: Fri, 22 Jan 2016 10:51:04 -0500 Message-ID: <20160122155104.GG32380@htj.duckdns.org> References: <20160122135042.GF26192@esperanza> <20160122144854.GA14432@cmpxchg.org> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=IRh2oYQjVZ4i/TmFnbeu4td4k9ZP2nGs18UDX39FYY8=; b=bJWZ9xJpvg1KXR2izN3bj90ULraqTbJkHP/8zoBCaJf04Er3CRk2HRhrTe5GLVCiTM XiQhyjlim2cdGf016C8PKfdIBmPz7hGCnW68TuLyj63AiFSVmtW7n1cCWmCfOAbugFio iU2glLxCnTP6ustBlehWJwDSjlCq4mSh7akj6F/CjWpYyRBXXDAJqE3fCr0hpwhm0ZOG ErnGXRDei9HKvhvpNE00hvyIw5CyeLSZPMOKK/jEB4f5O6sl6TdMDi0ZrI+Yq25JJA+R JYV6ERofCMkuNH8tP6AgHhDcIMoJfwIrT3OyfSSYmOV7RokuX/0SPQyiAP3ZxCRKtWZ1 xDsw== Content-Disposition: inline In-Reply-To: <20160122144854.GA14432@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Johannes Weiner Cc: Vladimir Davydov , Brian Christiansen , Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org 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 Thanks. -- tejun -- 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