From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752688Ab2DBOdI (ORCPT ); Mon, 2 Apr 2012 10:33:08 -0400 Received: from e23smtp01.au.ibm.com ([202.81.31.143]:33958 "EHLO e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751291Ab2DBOdG (ORCPT ); Mon, 2 Apr 2012 10:33:06 -0400 Message-ID: <4F79B891.8020704@linux.vnet.ibm.com> Date: Mon, 02 Apr 2012 20:02:49 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-Version: 1.0 To: Jeff Moyer CC: Sasha Levin , Nick Bowler , linux-kernel@vger.kernel.org, Kay Sievers Subject: Re: the maxcpus= boot parameter broke somewhere along the line References: <20120306164835.GA26094@elliptictech.com> <4F578198.8060708@linux.vnet.ibm.com> <4F59E802.6070301@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-cbid: 12040204-1618-0000-0000-000001361C89 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/02/2012 07:35 PM, Jeff Moyer wrote: > "Srivatsa S. Bhat" writes: > >> Looking at the mention of udev above, and considering the commit you bisected >> to, I think it would be good to see whether someone is writing 1 to >> /sys/device/system/cpu/cpu*/online and hence the cpus are getting hot-added >> towards the end of boot. Maybe that sounds stupid, but worth a try :) >> >> So can you try the debug patch below? It applies on latest linux-3.3-rc6+ > > Sorry it took me so long to get back to you. You're patch did, in fact, > trigger: > > udev: starting version 147 > CPU 3 online initated from userspace > SMP alternatives: switching to SMP code > WARNING! power/level is deprecated; use power/control instead > Booting Node 0 Processor 3 APIC 0x3 > NMI watchdog: enabled, takes one hw-pmu counter. > CPU 1 online initated from userspace > Booting Node 0 Processor 1 APIC 0x2 > NMI watchdog: enabled, takes one hw-pmu counter. > CPU 2 online initated from userspace > Booting Node 0 Processor 2 APIC 0x1 > NMI watchdog: enabled, takes one hw-pmu counter. > CPU 1 online initated from userspace > CPU 3 online initated from userspace > CPU 2 online initated from userspace > Aha! Just like I thought! So there is no kernel bug with respect to the maxcpus= boot parameter :-) Regards, Srivatsa S. Bhat > Checking through udev rules, I found this in > /lib/udev/rules.d/40-redhat.rules (this is a RHEL 6 install, btw): > > ACTION=="add", KERNEL=="cpu[0-9]*", RUN+="/bin/bash -c 'echo 1 > /sys/devices/system/cpu/%k/online'" > > So, what do you suppose is the right way to fix this? > > Cheers, > Jeff > > Kay, you can read up on the rest of the thread here: > https://lkml.org/lkml/2012/3/6/242 >