Re: [PATCH] lockdep: constify usage of struct lock_class_key where possible

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Apr 28, 2026 at 11:05:25PM +0200, Heiner Kallweit wrote:
> Constify usage of struct lock_class_key where possible. This requires
> to constify also usage of struct lockdep_subclass_key in two places.
> 
> Especially relevant is constification of lockdep_map.key, as it makes
> clear that the key isn't changed during lifetime of struct lockdep_map.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  include/linux/lockdep.h       | 18 ++++++++++--------
>  include/linux/lockdep_types.h |  2 +-
>  kernel/locking/lockdep.c      | 12 ++++++------
>  3 files changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 621566345..3fa2b62f2 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -125,25 +125,27 @@ extern void lockdep_unregister_key(struct lock_class_key *key);
>   * to lockdep:
>   */
>  
> -extern void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
> -	struct lock_class_key *key, int subclass, u8 inner, u8 outer, u8 lock_type);
> +void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
> +			   const struct lock_class_key *key, int subclass,
> +			   u8 inner, u8 outer, u8 lock_type);

> @@ -252,9 +254,9 @@ static inline int lock_is_held(const struct lockdep_map *lock)
>  #define lockdep_is_held(lock)		lock_is_held(&(lock)->dep_map)
>  #define lockdep_is_held_type(lock, r)	lock_is_held_type(&(lock)->dep_map, (r))
>  
> -extern void lock_set_class(struct lockdep_map *lock, const char *name,
> -			   struct lock_class_key *key, unsigned int subclass,
> -			   unsigned long ip);
> +void lock_set_class(struct lockdep_map *lock, const char *name,
> +		    const struct lock_class_key *key, unsigned int subclass,
> +		    unsigned long ip);
>  

It is also silently removing extern, why?