linux-kernel - Re: [PATCH v12 8/9] cpumask: Add initialiser CPUMASK

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Message-ID: <aMg5EzmxG3hG7aJK@yury>
Date: Mon, 15 Sep 2025 12:04:43 -0400
From: Yury Norov <yury.norov@...il.com>
To: Gabriele Monaco <gmonaco@...hat.com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH v12 8/9] cpumask: Add initialiser CPUMASK_NULL to use
 cleanup helpers

On Mon, Sep 15, 2025 at 04:59:29PM +0200, Gabriele Monaco wrote:
> The cleanup helper __free(free_cpumask_var) works only if the function
> returns after alloc_cpumask_var, this can complicate the code in case
> there are multiple cpumasks using the cleanup helper.
> 
> Define a cpumask initialiser that is NULL if the cpumask is a pointer
> and {} if it's on stack. This allows users of the cleanup helper to use
> it freely on initialised cpumasks as the actual free will be called only
> if the mask is not NULL (and of course if it's a pointer).
> 
> This solution was first used in [1], dropped as eventually a single mask
> was sufficient.
> 
> [1] - https://lore.kernel.org/lkml/20240120025053.684838-8-yury.norov@gmail.com

So why don't you pick the original patch instead?
 
> Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
> ---
>  include/linux/cpumask.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index ff8f41ab7ce6..5fb9c3fe4256 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -1005,6 +1005,7 @@ static __always_inline unsigned int cpumask_size(void)
>  
>  #define this_cpu_cpumask_var_ptr(x)	this_cpu_read(x)
>  #define __cpumask_var_read_mostly	__read_mostly
> +#define CPUMASK_NULL			NULL
>  
>  bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node);
>  
> @@ -1051,6 +1052,7 @@ static __always_inline bool cpumask_available(cpumask_var_t mask)
>  
>  #define this_cpu_cpumask_var_ptr(x) this_cpu_ptr(x)
>  #define __cpumask_var_read_mostly
> +#define CPUMASK_NULL {}
>  
>  static __always_inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
>  {
> -- 
> 2.51.0