Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753278AbaAWCPg (ORCPT ); Wed, 22 Jan 2014 21:15:36 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:25763 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752201AbaAWCPf (ORCPT ); Wed, 22 Jan 2014 21:15:35 -0500 Message-ID: <52E07B31.8070104@oracle.com> Date: Wed, 22 Jan 2014 21:15:13 -0500 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: David Rientjes CC: khlebnikov@openvz.org, Andrew Morton , "linux-mm@kvack.org" , LKML Subject: Re: mm: BUG: Bad rss-counter state References: <52E06B6F.90808@oracle.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/22/2014 08:39 PM, David Rientjes wrote: > On Wed, 22 Jan 2014, Sasha Levin wrote: > >> Hi all, >> >> While fuzzing with trinity running inside a KVM tools guest using latest -next >> kernel, >> I've stumbled on a "mm: BUG: Bad rss-counter state" error which was pretty >> non-obvious >> in the mix of the kernel spew (why?). >> > > It's not a fatal condition and there's only a few possible stack traces > that could be emitted during the exit() path. I don't see how we could > make it more visible other than its log-level which is already KERN_ALERT. Would it make sense to add a VM_BUG_ON() to make it more obvious when we have CONFIG_VM_DEBUG enabled? Many of the VM_BUG_ON test cases are non-fatal either, and it would make it easier spotting this issue. >> I've added a small BUG() after the printk() in check_mm(), and here's the full >> output: >> > > Worst place to add it :) At line 562 of kernel/fork.c in linux-next > you're going to hit BUG() when there may be other counters that are also > bad and they don't get printed. I gave the condition before curly braces :) if (unlikely(x)) { printk(KERN_ALERT "BUG: Bad rss-counter state " "mm:%p idx:%d val:%ld\n", mm, i, x); BUG(); } >> [ 318.334905] BUG: Bad rss-counter state mm:ffff8801e6dec000 idx:0 val:1 > > So our mm has a non-zero MM_FILEPAGES count, but there's nothing that was > cited that would tell us what that is so there's not much to go on, unless > someone already recognizes this as another issue. Is this reproducible on > 3.13 or only on linux-next? Yup, I see it in v3.13 too, which is odd. Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/