linux-kernel - Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock

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Date:	Sun, 27 Mar 2016 21:40:07 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Sedat Dilek <sedat.dilek@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at
 kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260

On Sun, Mar 27, 2016 at 8:23 PM, Theodore Ts'o <tytso@....edu> wrote:
> On Sun, Mar 27, 2016 at 05:03:44AM -0700, Linus Torvalds wrote:
>>
>> Unless you're using overlayfs or per-file encryption, I'm not seeing
>> that any of that should make any difference (but it's entirely
>> possible I'm missing something).
>>
>> Was it entirely repeatable before? Maybe it just happened to happen
>> without that update, and then happened to _not_ happen after you
>> rebooted with that 'dev' branch pulled in?
>>
>> 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.
>
> That's my guess.  I've been doing a lot of regression testing with
> lockdep enabled, and I haven't seen the problem which Sedat has
> reported.
>
> At the moment I'm testing my ext4 bug fixes on top of 243d5067858310
> (Merge branch 'overlayfs-linus'....) dating from March 22nd, and the
> lockdep merges came much earlier than that, on March 15th, just two
> days after v4.5 was released, and I'm not noticing any lockdep issues
> with ext4 while running all of my regression tests.
>

So far I can say, that I am *not* seeing this with ext4.git#dev on top
of v4.6-rc1.

Not sure how I can force/reproduce the lockdep call-trace.

Any idea on how to check/test lockdep issues like this?
LTP? (Latest tarball: ltp-full-20160126.tar.xz?
xfstests?
xfstests-bld?
Does the linux-sources ship some test-suite?

- Sedat -