From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752705AbbIEPsv (ORCPT ); Sat, 5 Sep 2015 11:48:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbbIEPsm (ORCPT ); Sat, 5 Sep 2015 11:48:42 -0400 Date: Sat, 5 Sep 2015 16:48:40 +0100 From: "Richard W.M. Jones" To: Tejun Heo Cc: Josh Boyer , Jeff Moyer , msnitzer@redhat.com, Li Zefan , Johannes Weiner , cgroups@vger.kernel.org, "Linux-Kernel@Vger. Kernel. Org" Subject: Re: __blkg_lookup oops with 4.2-rcX Message-ID: <20150905154840.GA19460@redhat.com> References: <20150902145307.GG22326@mtj.duckdns.org> <20150902153255.GH22326@mtj.duckdns.org> <20150904104602.GN29283@redhat.com> <20150904171302.GE25329@mtj.duckdns.org> <20150904204244.GQ29283@redhat.com> <20150905153439.GA18461@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150905153439.GA18461@redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 05, 2015 at 04:34:39PM +0100, Richard W.M. Jones wrote: > [ 52.259269] BUG: unable to handle kernel NULL pointer dereference at 00000000000009c8 > [ 52.259269] IP: [] __blkg_lookup+0x40/0xe0 And also: $ addr2line -e /usr/lib/debug/lib/modules/4.3.0-0.rc0.git7.1.rwmj3.fc24.x86_64/vmlinux ffffffff813f8b10 /usr/src/debug/kernel-4.2.fc24/linux-4.3.0-0.rc0.git7.1.rwmj3.fc24.x86_64/block/blk-cgroup.c:158 152 /* 153 * Hint didn't match. Look up from the radix tree. Note that the 154 * hint can only be updated under queue_lock as otherwise @blkg 155 * could have already been removed from blkg_tree. The caller is 156 * responsible for grabbing queue_lock if @update_hint. 157 */ 158 blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id); 159 if (blkg && blkg->q == q) { 160 if (update_hint) { 161 lockdep_assert_held(q->queue_lock); 162 rcu_assign_pointer(blkcg->blkg_hint, blkg); 163 } 164 return blkg; 165 } Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org