Re: [PATCH 1/2] locking/lockdep: Cleanup reinit_class()

[Waiman Long]

On 2/14/22 06:25, Peter Zijlstra wrote:
> On Thu, Feb 10, 2022 at 10:55:25PM -0500, Waiman Long wrote:
> > Replace the duplicated WARN_ON_ONCE() tests in reinit_class() with
> > BUILD_BUG_ON().
> >
> > Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> > ---
> >   include/linux/lockdep_types.h | 4 ++++
> >   kernel/locking/lockdep.c      | 6 +++---
> >   2 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
> > index d22430840b53..446d981ae3a2 100644
> > --- a/include/linux/lockdep_types.h
> > +++ b/include/linux/lockdep_types.h
> > @@ -108,6 +108,10 @@ struct lock_class {
> >   	 */
> >   	struct list_head		locks_after, locks_before;
> >   
> > +	/*
> > +	 * All the fields that require re-initialization after being zapped
> > +	 * must be put after "key".
> > +	 */
> >   	const struct lockdep_subclass_key *key;
> >   	unsigned int			subclass;
> >   	unsigned int			dep_gen_id;
> > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > index d4252b5c9863..77bbe557d48b 100644
> > --- a/kernel/locking/lockdep.c
> > +++ b/kernel/locking/lockdep.c
> > @@ -6015,10 +6015,10 @@ static void reinit_class(struct lock_class *class)
> >   	WARN_ON_ONCE(!class->lock_entry.next);
> >   	WARN_ON_ONCE(!list_empty(&class->locks_after));
> >   	WARN_ON_ONCE(!list_empty(&class->locks_before));
> > +	BUILD_BUG_ON(offsetof(struct lock_class, lock_entry) > offset);
> > +	BUILD_BUG_ON(offsetof(struct lock_class, locks_after) > offset);
> > +	BUILD_BUG_ON(offsetof(struct lock_class, locks_before) > offset);
> >   	memset(p + offset, 0, sizeof(*class) - offset);
> > -	WARN_ON_ONCE(!class->lock_entry.next);
> > -	WARN_ON_ONCE(!list_empty(&class->locks_after));
> > -	WARN_ON_ONCE(!list_empty(&class->locks_before));
> >   }
> >   
> >   static inline int within(const void *addr, void *start, unsigned long size)
> > --
> > 2.27.0
> Yeah, except that this doesn't build because it conflicts with a
> previous patch you actually Acked:
>
>   https://lore.kernel.org/all/20211213132618.105737-1-xiujianfeng@xxxxxxxxxx/T/#m0e9474a9204ec29fb2135135ce3134640a3f27b5
Sorry, my bad. I forgot to check tip.

I have just sent out a v2 that will work on tip.

Cheers,
Longman