From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753026AbcFTIeb (ORCPT ); Mon, 20 Jun 2016 04:34:31 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:37044 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752942AbcFTIeY (ORCPT ); Mon, 20 Jun 2016 04:34:24 -0400 Date: Mon, 20 Jun 2016 10:34:17 +0200 From: Peter Zijlstra To: AMIT NAGAL Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, ajeet.y@samsung.com, pankaj.m@samsung.com Subject: Re: tg_load_down NULL pointer dereference Message-ID: <20160620083417.GE30154@twins.programming.kicks-ass.net> References: <594315041.16511466403240766.JavaMail.weblogic@ep2mlwas08d> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <594315041.16511466403240766.JavaMail.weblogic@ep2mlwas08d> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 20, 2016 at 06:14:01AM +0000, AMIT NAGAL wrote: > Hi > I am using Linux kernel version 3.10.28 (ARM platform) . > I am getting NULL pointer dereference in tg_load_down() . > At the time of error , tg->parent->cfs_rq value is 0 and tg->se value is 0x00000400 . ( refer to backtrace in 5) ). Were you destroying cgroups at the time? If so, there were some problems with cgroup teardown recently, see patches: 6fe1f348b3dd ("sched/cgroup: Fix cgroup entity load tracking tear-down") 2f5177f0fd7e ("sched/cgroup: Fix/cleanup cgroup teardown/init") Which depend on: aa226ff4a1ce ("cgroup: make sure a parent css isn't offlined before its children") 8bb5ef79bc0f ("cgroup: make sure a parent css isn't freed before its children") I've no idea if any of that is relevant to your ancient kernel, let alone applies, that's your problem for using ancient wares. If you can reproduce with a current kernel (4.6+) then I might look more.