From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f176.google.com ([209.85.216.176]:45430 "EHLO mail-qc0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752243AbaBHUKl (ORCPT ); Sat, 8 Feb 2014 15:10:41 -0500 Date: Sat, 8 Feb 2014 15:10:37 -0500 From: Tejun Heo To: David Rientjes Cc: Fengguang Wu , Filipe David Borba Manana , Chris Mason , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [btrfs] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 Message-ID: <20140208201037.GC10975@htj.dyndns.org> References: <20140207023801.GC11051@localhost> <20140207121038.GA1690@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hello, David, Fengguang, Chris. On Fri, Feb 07, 2014 at 01:13:06PM -0800, David Rientjes wrote: > On Fri, 7 Feb 2014, Fengguang Wu wrote: > > > On Fri, Feb 07, 2014 at 02:13:59AM -0800, David Rientjes wrote: > > > On Fri, 7 Feb 2014, Fengguang Wu wrote: > > > > > > > [ 1.625020] BTRFS: selftest: Running btrfs_split_item tests > > > > [ 1.627004] BTRFS: selftest: Running find delalloc tests > > > > [ 2.289182] tsc: Refined TSC clocksource calibration: 2299.967 MHz > > > > [ 292.084537] kthreadd invoked oom-killer: gfp_mask=0x3000d0, order=1, oom_score_adj=0 > > > > [ 292.086439] kthreadd cpuset= > > > > [ 292.087072] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 > > > > [ 292.087372] IP: [] pr_cont_kernfs_name+0x1b/0x6c > > > > > > This looks like a problem with the cpuset cgroup name, are you sure this > > > isn't related to the removal of cgroup->name? > > > > It looks not related to patch "cgroup: remove cgroup->name", because > > that patch lies in the cgroup tree and not contained in output of "git log BAD_COMMIT". > > > > It's dying on pr_cont_kernfs_name which is some tree that has "kernfs: > implement kernfs_get_parent(), kernfs_name/path() and friends", which is > not in linux-next, and is obviously printing the cpuset cgroup name. > > It doesn't look like it has anything at all to do with btrfs or why they > would care about this failure. Yeah, this is from a patch in cgroup/review-post-kernfs-conversion branch which updates cgroup to use pr_cont_kernfs_name(). I forget that cgrp->kn is NULL for the dummy_root's top cgroup and thus it ends up calling the kernfs functions with NULL kn and thus the oops. I posted an updated patch and the git branch has been updated. http://lkml.kernel.org/g/20140208200640.GB10975@htj.dyndns.org So, nothing to do with btrfs and it looks like somehow the test appratus is mixing up branches? Thanks! -- tejun