From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753928AbYEMTAg (ORCPT ); Tue, 13 May 2008 15:00:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754514AbYEMTA1 (ORCPT ); Tue, 13 May 2008 15:00:27 -0400 Received: from mtagate1.de.ibm.com ([195.212.29.150]:4510 "EHLO mtagate1.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090AbYEMTA1 (ORCPT ); Tue, 13 May 2008 15:00:27 -0400 Date: Tue, 13 May 2008 21:00:24 +0200 From: Heiko Carstens To: Avi Kivity Cc: linux-kernel , Ingo Molnar Subject: Re: [BUG] cpu hotplug vs scheduler Message-ID: <20080513190024.GB6465@osiris.boeblingen.de.ibm.com> References: <4829A6A0.5040208@qumranet.com> <4829B4AC.6090909@qumranet.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4829B4AC.6090909@qumranet.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 13, 2008 at 06:33:00PM +0300, Avi Kivity wrote: > Avi Kivity wrote: >> I'm testing host cpu hotplug with kvm. Basically running 7 guests on >> a 4 core machine, offlining and onlining host cpus at random. >> Eventually I hit this: >> > > [snip oops] > >> This seems to be the assignment to cfs_rq after pick_next_entity(). >> >> I'm running kvm.git, which is currently 2.6.26-rc2 plus a few kvm >> patches. It could be kvm's fault, but it doesn't appear so from the >> traces. >> > > I get the same oops running with the kvm modules unloaded. None of > kvm.git's changes are in core code, so this is definitely a mainline > problem. > > It took about 40 minutes to reproduce; 1200 cpus onlined and 1200 cpus > offlined. FWIW, this happens on s390 as well (without kvm support). But until now I didn't have time to look into it. Didn't report it here yet, since we had plenty of cpu hotplug changes in arch code, so I suspected a bug there. This doesn't seem to be the case. It takes only a few minutes to trigger the bug here.