Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753233Ab3IJQX5 (ORCPT ); Tue, 10 Sep 2013 12:23:57 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:65331 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753119Ab3IJQXy (ORCPT ); Tue, 10 Sep 2013 12:23:54 -0400 Message-ID: <522F4797.1050509@linaro.org> Date: Tue, 10 Sep 2013 09:23:51 -0700 From: John Stultz User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: Ingo Molnar CC: Gerlando Falauto , "linux-kernel@vger.kernel.org" , Thomas Gleixner , Richard Cochran , Prarit Bhargava , "Brunck, Holger" , "Longchamp, Valentin" , "Bigler, Stefan" , Peter Zijlstra Subject: Re: kernel deadlock References: <521F6D06.1040107@keymile.com> <521FDD12.7050000@linaro.org> <52212511.9050206@keymile.com> <5221264F.4070402@linaro.org> <5225F8EF.3040701@keymile.com> <52261BBB.60904@linaro.org> <5226EB35.6080604@keymile.com> <522E2FBB.4070406@linaro.org> <20130910072908.GA32257@gmail.com> In-Reply-To: <20130910072908.GA32257@gmail.com> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1504 Lines: 33 On 09/10/2013 12:29 AM, Ingo Molnar wrote: > * John Stultz wrote: > >> Now, I'm still in the dark as to why HRTICK exposes this, but seems like >> the following patch should resolve the issue (and quiets the lockdep >> warnings in my testing). Let me know how it works for you! >> >> Ingo: This makes me think we really should have some lockdep smarts >> added to seqlock/seqcount structures. Is there something already >> discovered thats preventing this, or has this just not yet been tried? > There's no fundamental reason to not do it, it's a very good idea! > >> From 09885df9734aa678ccb61dbef356fea4faeff16c Mon Sep 17 00:00:00 2001 >> From: John Stultz >> Date: Mon, 9 Sep 2013 13:07:18 -0700 >> Subject: [PATCH] timekeepeing: Fix HRTICK related deadlock from ntp lock changes > Cool fix! I think I've seen this deadlock in various incarnations but was > never able to track it down. Do you have a guesstimate about roughly when > it was introduced? Is it an ancient bug? 3.10, I believe. So no not ancient, but we've seen and resolved similar issues in the past (the old printk while holding xtime_lock deadlock). Hopefully the lockdep enablement helps sort these out for good. thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/