Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260

Ingo Molnar
2016-03-29T08:47:10Z

* 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