From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756950Ab1KJBwU (ORCPT ); Wed, 9 Nov 2011 20:52:20 -0500 Received: from mail-yw0-f46.google.com ([209.85.213.46]:41727 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753312Ab1KJBwS (ORCPT ); Wed, 9 Nov 2011 20:52:18 -0500 Date: Wed, 9 Nov 2011 19:52:12 -0600 From: Jonathan Nieder To: Jiri Polach Cc: 647095@bugs.debian.org, Ben Hutchings , LKML , x86@kernel.org Subject: Re: CPU hyperthreading turned on after soft power-cycle Message-ID: <20111110015212.GB2399@elie.gateway.2wire.net> References: <20111030110543.5872.61279.reportbug@supermicro.uochb.cas.cz> <1319988329.6759.88.camel@deadeye> <4EAE9D3A.7000108@atlas.cz> <4EB92181.5030500@seznam.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4EB92181.5030500@seznam.cz> User-Agent: Mutt/1.5.21+46 (b01d63af6fea) (2011-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. x86 people: do the symptoms seem familiar? Any hints for tracking it down? Thanks and hope that helps, Jonathan