From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: lockdep warning with 2.6.29-rc6-mm1 (mmotm 24-feb-2009) Date: Fri, 6 Mar 2009 21:08:08 +0530 Message-ID: <20090306153808.GA863@balbir.in.ibm.com> References: <20090304125709.GA6251@balbir.in.ibm.com> <1236173267.5330.7487.camel@laptop> <20090304174115.GE25962@elte.hu> <20090305070045.GC11916@wotan.suse.de> Reply-To: balbir@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Cc: Ingo Molnar , Peter Zijlstra , Andrew Morton , "linux-kernel@vger.kernel.org" , Eric Paris , linux-fsdevel To: Nick Piggin Return-path: Received: from e28smtp05.in.ibm.com ([59.145.155.5]:48163 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756177AbZCFPiX (ORCPT ); Fri, 6 Mar 2009 10:38:23 -0500 Content-Disposition: inline In-Reply-To: <20090305070045.GC11916@wotan.suse.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: * Nick Piggin [2009-03-05 08:00:45]: > On Wed, Mar 04, 2009 at 06:41:15PM +0100, Ingo Molnar wrote: > > > > * Peter Zijlstra wrote: > > > > > On Wed, 2009-03-04 at 18:27 +0530, Balbir Singh wrote: > > > > I see the following on my machine. My understanding is that the > > > > lockdep warning is complaining about a potential deadlock while > > > > reclaiming, where we could end up waiting on holding inotify_mutex, > > > > and we could end up calling reclaim with inotify_mutex held. > > > > > > > > The race seems rare, since one path shows a new inode being created > > > > and the other one being deleted. It seems like a false positive unless > > > > the inode's in question turn out to be potentially the same. > > > > > > Its not a false positive until you can guarantee the inodes will _never_ > > > be the same. > > > > > > This thing has been reported numerous times, Ingo even posted > > > a potential fix for it, Nick poked the inotify people to speak > > > up, but they have so far been silent on the issue :-( > > > > that particular fix is upstream, via: > > > > 3023a3e: inotify: fix GFP_KERNEL related deadlock > > > > so does this reproduce with latest .29-rc7-ish kernels too - or > > do we have some other problem in this area too? > > Well as I said, I think it is just a bandaid to shut up lockdep, > because I think inotify always is guaranteed to have a ref on > the inode at this point so it should not be subject to reclaim. I got dropped from the cc and thus could not respond earlier. The problem can be seen even in 2.6.29-rc7-mm1. -- Balbir