From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751981AbaKWRXm (ORCPT ); Sun, 23 Nov 2014 12:23:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751504AbaKWRXl (ORCPT ); Sun, 23 Nov 2014 12:23:41 -0500 Date: Sun, 23 Nov 2014 18:22:56 +0100 From: Oleg Nesterov To: Borislav Petkov Cc: lkml , Rik van Riel , Peter Zijlstra , Steven Rostedt , x86-ml Subject: Re: task_stat splat Message-ID: <20141123172256.GA9625@redhat.com> References: <20141123111220.GA6436@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141123111220.GA6436@pd.tnic> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/23, Borislav Petkov wrote: > > where we end up with a zero PMD. RIP is corrupted too so we're somewhere > off in the fields. PMD = 0 is fine I guess, addr == 0 is not mapped. > Comment over thread_group_cputime() talks about dead tasks accounting This comment simply means that we also need to read the accumulated counters in tsk->signal. > which might be relevant as we're seeing not mapped page hierarchy so > something must have gone away recently but we try to look at it. This is called under ->siglock, we can't race with exit/etc. But this doesn't matter, it is not that we (say) get t == NULL or something like this. RIP == 0, and this looks "impossible", I do not see indirect function calls in this paths. > [42460.389625] Call Trace: > [42460.389635] [] ? task_sched_runtime+0x99/0xc0 > [42460.389643] [] thread_group_cputime+0x17c/0x2d0 Could you identify somehow the line which matches task_sched_runtime+0x99 ? Probably do_task_delta_exec()... Oleg.