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

Peter Zijlstra
2016-03-27T20:48:15Z

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").