From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752315Ab2FLLId (ORCPT ); Tue, 12 Jun 2012 07:08:33 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33429 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750987Ab2FLLIc convert rfc822-to-8bit (ORCPT ); Tue, 12 Jun 2012 07:08:32 -0400 Message-ID: <1339499306.31548.75.camel@twins> Subject: Re: Kernel panic - not syncing: Attempted to kill the idle task! From: Peter Zijlstra To: Linus Torvalds Cc: hi3766691@gmail.com, Hillf Danton , LKML , Andrea Arcangeli , Zhouping Liu Date: Tue, 12 Jun 2012 13:08:26 +0200 In-Reply-To: <1339496836.31548.68.camel@twins> References: <1339421268.30462.15.camel@twins> <4FD6BD72.2070808@redhat.com> <1339490988.31548.40.camel@twins> <1339496836.31548.68.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-06-12 at 12:27 +0200, Peter Zijlstra wrote: > On Tue, 2012-06-12 at 13:20 +0300, Linus Torvalds wrote: > > Peter, you are very fundamentally wrong if you think the distance > > array has to be symmetric. That is fundamentally not true for many > > typologies. > > > > The trivial example of a non symmetric case is just a simple > > unidirectional ring. The distance from n to n+1 is just one, but the > > distance from n+1 to n is n-1 hops. > > > > So don't try to say that distances have to be symmetric. That's just > > garbage. > > Sure, I realize this, but the 17,18 thing isn't a ring. It looks like > something that should be symmetric but isn't. Not a unidirectional one that is.. I played around a bit more and found a shape that isn't too odd: 2 / \ 0 5 / / \ 1 --- / --- 3 \ / / 4 6 \ / 7 I would've crossed 0<->6 instead of 1<->3 so the 2/3 connected nodes are spread better, but what do I know. The only really odd thing is the numbering, which is what threw me. But yeah, the possibility of uni-directional rings makes detecting obvious crack tables harder, which is why I haven't got it -- yet.