From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759977AbaGYI1j (ORCPT ); Fri, 25 Jul 2014 04:27:39 -0400 Received: from numascale.com ([213.162.240.84]:33770 "EHLO numascale.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759958AbaGYI1f (ORCPT ); Fri, 25 Jul 2014 04:27:35 -0400 X-Greylist: delayed 2231 seconds by postgrey-1.27 at vger.kernel.org; Fri, 25 Jul 2014 04:27:34 EDT Message-ID: <53D20C2E.3070902@numascale.com> Date: Fri, 25 Jul 2014 15:50:06 +0800 From: Daniel J Blueman Organization: Numascale AS User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Oleg Nesterov , Thomas Gleixner , Peter Zijlstra , Hillf Danton CC: Borislav Petkov , Ingo Molnar , Igor Mammedov , Steffen Persvold , LKML Subject: [3.14] core onlining/hotplug regression Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OutGoing-Spam-Status: No, score=-2.9 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - cpanel21.proisp.no X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - numascale.com X-Get-Message-Sender-Via: cpanel21.proisp.no: authenticated_id: daniel@numascale.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas et al, On a larger x86 system with 1728 cores, 3.15(.6) asserts on smpboot_thread_fn's td->cpu != smp_processor_id() consistently after ~1500 cores are online. Reverting the only directly related changes I could find [1,2] doesn't help. Debugging indicates there is a race where the created thread is quickly migrated to core 0 when this occurs, since smp_processor_id returns 0 in these cases. Thomas introduced a thread parked state to fix related issues a year back. Linux 3.14(.13) boots just nice. Full boot output is at: https://resources.numascale.com/linux-315-thread-mig.txt Any theories so far? I'll start bisecting when I have full access to the system again in a week and I'll do some more debugging with intermittent access before then. Thanks, Daniel -- [1] commit 81c98869faa5f3a9457c93efef908ef476326b31 Author: Nishanth Aravamudan Date: Thu Apr 3 14:46:25 2014 -0700 kthread: ensure locality of task_struct allocations -- [2] commit 89f898c1e195fa6235c869bb457e500b7b3ac49d Author: Igor Mammedov Date: Thu Jun 5 15:42:43 2014 +0200 x86: Fix list/memory corruption on CPU hotplug -- Daniel J Blueman Principal Software Engineer, Numascale