From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758944AbcIMPVc (ORCPT ); Tue, 13 Sep 2016 11:21:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50046 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753117AbcIMPVb (ORCPT ); Tue, 13 Sep 2016 11:21:31 -0400 Date: Tue, 13 Sep 2016 17:20:42 +0200 From: Oleg Nesterov To: Nikolay Borisov Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org Subject: Re: BUG_ON in rcu_sync_func triggered Message-ID: <20160913152042.GA30160@redhat.com> References: <57D69CEC.5010103@kyup.com> <20160912130124.GA7984@redhat.com> <57D7B6F5.4040106@kyup.com> <20160913131852.GA4112@redhat.com> <20160913134304.GA26160@redhat.com> <57D80EB8.9080405@kyup.com> <57D80F52.6090804@kyup.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <57D80F52.6090804@kyup.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 13 Sep 2016 15:21:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/13, Nikolay Borisov wrote: > > On 09/13/2016 05:35 PM, Nikolay Borisov wrote: > > > > On 09/13/2016 04:43 PM, Oleg Nesterov wrote: > >> On 09/13, Oleg Nesterov wrote: > >>> > >>> OK... perhaps the unbalanced up_write... I'll try to look at freeze/thaw code, > >> > >> Heh, yes, it looks racy or I am totally confused. > >> > >>> could test the debugging patch below meanwhile? > >> > >> Yes please. I'll send you another patch (hopefully fix) later, but it > >> would be nice if you can test this patch to get more info. > > > > I've already started testing with this patch on 4.4.20 this time I think it would be better to stay with the same kernel version to debug the problem... > Actually forget that, here is a warning that this triggered: > > [ 844.290454] WARNING: CPU: 2 PID: 1900 at kernel/rcu/sync.c:160 rcu_sync_func+0xc8/0x150() > ... > [ 844.754708] XXX: ffff88047527da78 gp=2 cnt=0 cb=1 Hmm. Thanks. Please show us all the warnings you get. Oleg.