Re: [PATCH v3 04/16] lockdep: check that no locks held at freeze time

[Pavel Machek]

On Mon 2013-05-06 16:50:09, Colin Cross wrote:
> From: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
> 
> 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.
> 
> [akpm@xxxxxxxxxxxxxxxxxxxx: export debug_check_no_locks_held]
> Signed-off-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
> Cc: Ben Chan <benchan@xxxxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Rafael J. Wysocki <rjw@xxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> [ccross@xxxxxxxxxxx: don't warn if try_to_freeze_unsafe is called]
> Signed-off-by: Colin Cross <ccross@xxxxxxxxxxx>

Acked-by: Pavel Machek <pavel@xxxxxx>

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