Re: [RFC PATCH 2/2] dma-buf/dma-resv: Improve the dma-resv lockdep checks

["Christian König" <christian.koenig@amd.com>]

On 11/20/25 12:03, Thomas Hellström wrote:
> Ensure that dma_resv_held() and dma_resv_assert_held() operate
> on individual reservation objects within a WW transaction rather
> than on the reservation WW class.
> 
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

I can't judge the lockdep backend changes, but this patch here makes a lot of sense.

Reviewed-by: Christian König <christian.koenig@amd.com>

That reminds me that Pierre-Eric stumbled over some odd lockdep behavior while working on TTM as well. @Pierre-Eric what that this issue?

Regards,
Christian.

> ---
>  include/linux/dma-resv.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> index c5ab6fd9ebe8..001de3880fde 100644
> --- a/include/linux/dma-resv.h
> +++ b/include/linux/dma-resv.h
> @@ -308,8 +308,11 @@ static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
>  	     fence = dma_resv_iter_first(cursor); fence;	\
>  	     fence = dma_resv_iter_next(cursor))
>  
> -#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
> -#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
> +#define dma_resv_held(obj) (lockdep_is_held(&(obj)->lock.base) && ww_mutex_held(&(obj)->lock))
> +#define dma_resv_assert_held(obj) do {			\
> +		lockdep_assert_held(&(obj)->lock.base); \
> +		ww_mutex_assert_held(&(obj)->lock);	\
> +	} while (0)
>  
>  #ifdef CONFIG_DEBUG_MUTEXES
>  void dma_resv_reset_max_fences(struct dma_resv *obj);