Re: [PATCH 2/2] lockdep: check that no locks held at freeze time

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Fri, May 03, 2013 at 02:04:10PM -0700, Colin Cross wrote:
> From: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> 
> We shouldn't try_to_freeze if locks are held.  Holding a lock can cause a
> deadlock if the lock is later acquired in the suspend or hibernate path
> (e.g.  by dpm).  Holding a lock can also cause a deadlock in the case of
> cgroup_freezer if a lock is held inside a frozen cgroup that is later
> acquired by a process outside that group.
> 
> History:
> This patch was originally applied as 6aa9707099c and reverted in
> dbf520a9d7d4 because NFS was freezing with locks held.  It was
> deemed better to keep the bad freeze point in NFS to allow laptops
> to suspend consistently.  The previous patch in this series converts
> NFS to call _unsafe versions of the freezable helpers so that
> lockdep doesn't complain about them until a more correct fix
> can be applied.

I don't care about %current change, especially given that it's a debug
interface but that really should be a separate patch, so please split
it out if you want it (and I think we want it).

Thanks.

-- 
tejun
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