From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759667AbaGYJhQ (ORCPT ); Fri, 25 Jul 2014 05:37:16 -0400 Received: from numascale.com ([213.162.240.84]:45472 "EHLO numascale.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750699AbaGYJhO (ORCPT ); Fri, 25 Jul 2014 05:37:14 -0400 Message-ID: <53D22533.9030401@numascale.com> Date: Fri, 25 Jul 2014 17:36:51 +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: Thomas Gleixner CC: Oleg Nesterov , Peter Zijlstra , Hillf Danton , Borislav Petkov , Ingo Molnar , Igor Mammedov , Steffen Persvold , LKML Subject: Re: [3.14] core onlining/hotplug regression References: <53D20C2E.3070902@numascale.com> In-Reply-To: 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 On 07/25/2014 05:05 PM, Thomas Gleixner wrote: > On Fri, 25 Jul 2014, Daniel J Blueman wrote: >> 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. > > Weird. Commits [1,2] are definitely not the culprits. > >> Full boot output is at: >> https://resources.numascale.com/linux-315-thread-mig.txt > > Not really helpful, as we don't see what causes it. We just see the > wreckage. > >> 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. > > One thing you could try is enabling tracing. > > "ftrace=function ftrace_dump_on_oops" > > It'll take a looooong time to spill out the traces, but that should > give us the root cause precisely. Good trick. I'll get this early next week and we'll see what's up. Thanks, Daniel -- Daniel J Blueman Principal Software Engineer, Numascale