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Date: Tue, 29 Mar 2016 10:47:02 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>,
        Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Sedat Dilek <sedat.dilek@gmail.com>, "Theodore Ts'o" <tytso@mit.edu>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at
 kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Sun, Mar 27, 2016 at 05:03:44AM -0700, Linus Torvalds wrote:
> > Anyway, I don't think that DEBUG_LOCKS_WARN_ON() in
> > 
> >   kernel/locking/lockdep.c:2017 __lock_acquire
> > 
> > would be an ext4 issue, it looks more like an internal lockdep issue.
> > 
> > Adding in the lockdep people, who will set me right.
> 
> You are right; this is lockdep running into a hash collision; which is a new 
> DEBUG_LOCKDEP test. See 9e4e7554e755 ("locking/lockdep: Detect chain_key 
> collisions").

I've Cc:-ed Alfredo Alvarez Fernandez who added that test.

Thanks,

	Ingo