From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757888Ab1KKNum (ORCPT ); Fri, 11 Nov 2011 08:50:42 -0500 Received: from marge.uochb.cas.cz ([147.231.129.3]:53287 "EHLO marge.uochb.cas.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757462Ab1KKNul (ORCPT ); Fri, 11 Nov 2011 08:50:41 -0500 Message-ID: <4EBD2825.6050806@atlas.cz> Date: Fri, 11 Nov 2011 14:50:29 +0100 From: Clarinet User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:8.0) Gecko/20111105 Thunderbird/8.0 MIME-Version: 1.0 To: Jonathan Nieder CC: 647095@bugs.debian.org, Ben Hutchings , LKML , x86@kernel.org Subject: Re: CPU hyperthreading turned on after soft power-cycle References: <20111030110543.5872.61279.reportbug@supermicro.uochb.cas.cz> <1319988329.6759.88.camel@deadeye> <4EAE9D3A.7000108@atlas.cz> <4EB92181.5030500@seznam.cz> <20111110015212.GB2399@elie.gateway.2wire.net> In-Reply-To: <20111110015212.GB2399@elie.gateway.2wire.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, > Hi Jiri, > > Jiri Polach wrote: > >> On Ben's advice I am trying to locate the commit that causes the problem to >> appear more precisely using 'git bisect'. However, too many of generated >> revisions are unbootable so I have to use 'bisect skip' frequently. > > Ok, so I've looked over the log at, and > this seems totally weird. Have I described the symptoms correctly below? > (Warning: I am making some guesses, especially at step 5. In case of > doubt, see the bug log just mentioned.) > > 1. Disable SMT in the BIOS. > > 2. Boot a bad kernel. /proc/cpuinfo (correctly) shows one entry > per core. > > 3. "shutdown -h now". Enter BIOS. SMT is still disabled. > Don't save. > > 4. Boot any kernel. /proc/cpuinfo shows two entries per core. > > 5. "shutdown -h now". Boot any kernel. /proc/cpuinfo still shows > two entries per core. > > 6. "shutdown -h now". Enter BIOS. SMT is still disabled. Save. > Now /proc/cpuinfo will (correctly) shows one entry per core. > > Reproducible for Jiri with v3.0.4. Yes, this is exactly how it works. Something happens when kernel shuts down. Not when kernel reboots. > Result of bisecting: v2.6.38-rc1 exhibits the problem. v2.6.37 and > many of the topic branches merged in the 2.6.38 merge window work ok. > Some other topic branches do not boot at all. > > Jiri: if you have gitk installed, then "git bisect visualize" can help > get a sense of what's in the middle of the regression range. > "gitk --bisect --first-parent v2.6.37..v2.6.38-rc1" might be a good way > to find mainline commits to test before finding a topic branch to delve > into. I have been able to narrow the interval manually a little bit from the "top" (the bad side) and I will go on from the bottom now. However, there seems to be a large area where kernels are unbootable for me - they mostly stop when init is called and I do not know why. > x86 people: do the symptoms seem familiar? Any hints for tracking it > down? Please! I have spent more than a month trying to resolve it. I cannot revert back to 2.6.37 kernels and I cannot live with SMT changing on every shutdown - I have too many servers to allow such unusual behavior ... Thank you, Jiri Polach > Thanks and hope that helps, > Jonathan