linux-kernel - Re: [PATCH] silence unused pgdat warning from alloc_bootmem

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Message-Id: <20061122132414.1db3c22f.akpm@osdl.org>
Date:	Wed, 22 Nov 2006 13:24:14 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Andy Whitcroft <apw@...dowen.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] silence unused pgdat warning from alloc_bootmem_node
 and friends

On Wed, 22 Nov 2006 14:38:51 +0000
Andy Whitcroft <apw@...dowen.org> wrote:

> silence unused pgdat warning from alloc_bootmem_node and friends
> 
> x86 NUMA systems only define bootmem for node 0.  alloc_bootmem_node()
> and friends therefore ignore the passed pgdat and use NODE_DATA(0)
> in all cases.  This leads to the following warnings as we are not
> using the passed parameter:
> 
>   .../mm/page_alloc.c: In function 'zone_wait_table_init':
>   .../mm/page_alloc.c:2259: warning: unused variable 'pgdat'
> 
> One option would be to define all variables used with these macros
> __attribute__ ((unused)), but this would leave us exposed should
> these become genuinely unused.
> 
> The key here is that we _are_ using the value, we ignore it but that
> is a deliberate action.  This patch adds a nested local variable
> within the alloc_bootmem_node helper to which the pgdat parameter is
> assigned making it 'used'.  The nested local is marked __attribute__
> ((unused)) to silence this same warning for it.
> 
> Against 2.6.19-rc5-mm2.
> 
> Signed-off-by: Andy Whitcroft <apw@...dowen.org>
> ---
> diff --git a/include/asm-i386/mmzone.h b/include/asm-i386/mmzone.h
> index 61b0733..3503ad6 100644
> --- a/include/asm-i386/mmzone.h
> +++ b/include/asm-i386/mmzone.h
> @@ -120,13 +120,26 @@ static inline int pfn_valid(int pfn)
>  	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE, __pa(MAX_DMA_ADDRESS))
>  #define alloc_bootmem_low_pages(x) \
>  	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE, 0)
> -#define alloc_bootmem_node(ignore, x) \
> -	__alloc_bootmem_node(NODE_DATA(0), (x), SMP_CACHE_BYTES, __pa(MAX_DMA_ADDRESS))
> -#define alloc_bootmem_pages_node(ignore, x) \
> -	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE, __pa(MAX_DMA_ADDRESS))
> -#define alloc_bootmem_low_pages_node(ignore, x) \
> -	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE, 0)
> -
> +#define alloc_bootmem_node(pgdat, x)					\
> +({									\
> +	struct pglist_data  __attribute__ ((unused))			\
> +				*__alloc_bootmem_node__pgdat = (pgdat);	\
> +	__alloc_bootmem_node(NODE_DATA(0), (x), SMP_CACHE_BYTES,	\
> +						__pa(MAX_DMA_ADDRESS));	\
> +})
> +#define alloc_bootmem_pages_node(pgdat, x)				\
> +({									\
> +	struct pglist_data  __attribute__ ((unused))			\
> +				*__alloc_bootmem_node__pgdat = (pgdat);	\
> +	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE,		\
> +						__pa(MAX_DMA_ADDRESS))	\
> +})
> +#define alloc_bootmem_low_pages_node(pgdat, x)				\
> +({									\
> +	struct pglist_data  __attribute__ ((unused))			\
> +				*__alloc_bootmem_node__pgdat = (pgdat);	\
> +	__alloc_bootmem_node(NODE_DATA(0), (x), PAGE_SIZE, 0);		\
> +})
>  #endif /* CONFIG_NEED_MULTIPLE_NODES */
>  

Can these be switched to functions, or do they actually need to be macros?


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