linux-kernel - Re: lockdep warning with 2.6.29-rc6-mm1 (mmotm 24-feb-2009)

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Message-ID: <20090304174115.GE25962@elte.hu>
Date:	Wed, 4 Mar 2009 18:41:15 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	balbir@...ux.vnet.ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>, Eric Paris <eparis@...hat.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: lockdep warning with 2.6.29-rc6-mm1 (mmotm 24-feb-2009)


* Peter Zijlstra <peterz@...radead.org> 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?

	Ingo
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