From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755229AbbIHPbm (ORCPT ); Tue, 8 Sep 2015 11:31:42 -0400 Received: from mail-yk0-f182.google.com ([209.85.160.182]:33710 "EHLO mail-yk0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755152AbbIHPbh (ORCPT ); Tue, 8 Sep 2015 11:31:37 -0400 Date: Tue, 8 Sep 2015 11:31:32 -0400 From: Tejun Heo To: Jens Axboe Cc: Josh Boyer , Jeff Moyer , msnitzer@redhat.com, Li Zefan , Johannes Weiner , cgroups@vger.kernel.org, "Linux-Kernel@Vger. Kernel. Org" , "Richard W.M. Jones" Subject: Re: [PATCH block/for-linus] block: blkg_destroy_all() should clear q->root_blkg and ->root_rl.blkg Message-ID: <20150908153132.GD13749@mtj.duckdns.org> 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> <20150905154840.GA19460@redhat.com> <20150905183801.GA8231@mtj.duckdns.org> <20150905194736.GB8231@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150905194736.GB8231@mtj.duckdns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 05, 2015 at 03:47:36PM -0400, Tejun Heo wrote: > While making the root blkg unconditional, ec13b1d6f0a0 ("blkcg: always > create the blkcg_gq for the root blkcg") removed the part which clears > q->root_blkg and ->root_rl.blkg during q exit. This leaves the two > pointers dangling after blkg_destroy_all(). blk-throttle exit path > performs blkg traversals and dereferences ->root_blkg and can lead to > the following oops. Jens, can you please route this one w/ Richard's tested-by added? Thanks! -- tejun