Re: [PATCH v4] mm: Fix possible deadlock in kmemleak

[Catalin Marinas <catalin.marinas@arm.com>]

On Wed, Aug 20, 2025 at 11:01:00AM -0400, Waiman Long wrote:
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 84265983f239..eb4e0af5edba 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -856,13 +856,8 @@ static void delete_object_part(unsigned long ptr, size_t size,
> 
>         raw_spin_lock_irqsave(&kmemleak_lock, flags);
>         object = __find_and_remove_object(ptr, 1, objflags);
> -       if (!object) {
> -#ifdef DEBUG
> -               kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
> -                             ptr, size);
> -#endif
> +       if (!object)
>                 goto unlock;
> -       }
> 
>         /*
>          * Create one or two objects that may result from the memory block
> @@ -882,8 +877,14 @@ static void delete_object_part(unsigned long ptr, size_t size,
> 
>  unlock:
>         raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
> -       if (object)
> +       if (object) {
>                 __delete_object(object);
> +       } else {
> +#ifdef DEBUG
> +               kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
> +                             ptr, size);
> +#endif
> +       }
> 
> Anyway, I am not against using printk_deferred_enter/exit here. It is just
> that they should be used as a last resort if there is no easy way to work
> around it.

This works for me if Gu respins the patch

Thanks.

-- 
Catalin