From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932806Ab0BEJek (ORCPT ); Fri, 5 Feb 2010 04:34:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45285 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932408Ab0BEJej (ORCPT ); Fri, 5 Feb 2010 04:34:39 -0500 Message-ID: <4B6BE6BC.4070506@redhat.com> Date: Fri, 05 Feb 2010 17:37:00 +0800 From: Cong Wang User-Agent: Thunderbird 2.0.0.23 (X11/20091001) MIME-Version: 1.0 To: "Eric W. Biederman" CC: linux-kernel@vger.kernel.org, Tejun Heo , Greg Kroah-Hartman , Peter Zijlstra , Miles Lane , Heiko Carstens , Benjamin Herrenschmidt , Larry Finger , akpm@linux-foundation.org Subject: Re: [Patch v2] sysfs: add lockdep class support to s_active References: <20100205064622.4141.72867.sendpatchset@localhost.localdomain> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Eric W. Biederman wrote: > Amerigo Wang writes: > >> Recently we met a lockdep warning from sysfs during s2ram or cpu hotplug. >> As reported by several people, it is something like: > > The interesting case is the cpu hotplug is actually a problem. It isn't > useful to get a complaint about the non-problems code paths triggered > by pm. However my earlier review spotted a real deadlock case. Where > in one of the sysfs attributes we iterate over the list of online cpus > and that appeared to an attribute that removing a cpu would remove > from sysfs... > You are referring this one: http://marc.info/?l=linux-kernel&m=126474021428905&w=2 ? Hmm, yeah, I missed that the lock it is holding is not s_active, thus so not be the case we are trying to fix here. Thanks for pointing this out.