From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: lockdep warning with 2.6.29-rc6-mm1 (mmotm 24-feb-2009) Date: Thu, 5 Mar 2009 08:00:45 +0100 Message-ID: <20090305070045.GC11916@wotan.suse.de> References: <20090304125709.GA6251@balbir.in.ibm.com> <1236173267.5330.7487.camel@laptop> <20090304174115.GE25962@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , balbir@linux.vnet.ibm.com, Andrew Morton , "linux-kernel@vger.kernel.org" , Eric Paris , linux-fsdevel To: Ingo Molnar Return-path: Received: from ns.suse.de ([195.135.220.2]:35801 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755240AbZCEHAv (ORCPT ); Thu, 5 Mar 2009 02:00:51 -0500 Content-Disposition: inline In-Reply-To: <20090304174115.GE25962@elte.hu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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.