From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752546AbdJ0JeX (ORCPT ); Fri, 27 Oct 2017 05:34:23 -0400 Received: from mx2.suse.de ([195.135.220.15]:58691 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105AbdJ0JeV (ORCPT ); Fri, 27 Oct 2017 05:34:21 -0400 Date: Fri, 27 Oct 2017 11:34:18 +0200 From: Michal Hocko To: syzbot Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, hannes@cmpxchg.org, jack@suse.cz, jglisse@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, shli@fb.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, vbabka@suse.cz, ying.huang@intel.com Subject: Re: possible deadlock in lru_add_drain_all Message-ID: <20171027093418.om5e566srz2ztsrk@dhcp22.suse.cz> References: <089e0825eec8955c1f055c83d476@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <089e0825eec8955c1f055c83d476@google.com> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 27-10-17 02:22:40, syzbot wrote: > Hello, > > syzkaller hit the following crash on > a31cc455c512f3f1dd5f79cac8e29a7c8a617af8 > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached > Raw console output is attached. I do not see such a commit. My linux-next top is next-20171018 [...] > Chain exists of: > cpu_hotplug_lock.rw_sem --> &pipe->mutex/1 --> &sb->s_type->i_mutex_key#9 > > Possible unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&sb->s_type->i_mutex_key#9); > lock(&pipe->mutex/1); > lock(&sb->s_type->i_mutex_key#9); > lock(cpu_hotplug_lock.rw_sem); I am quite confused about this report. Where exactly is the deadlock? I do not see where we would get pipe mutex from inside of the hotplug lock. Is it possible this is just a false possitive due to cross release feature? -- Michal Hocko SUSE Labs