linux-kernel - Re: [PATCH 1/11] kernel/kfifo.c: trivial: use BUG

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Date:	Tue, 2 Aug 2011 13:33:35 +0200
From:	Andrea Righi <arighi@...eler.com>
To:	Julia Lawall <julia@...u.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, trivial@...nel.org,
	kernel-janitors@...r.kernel.org,
	Stefani Seibold <stefani@...bold.net>,
	"Ira W. Snyder" <iws@...o.caltech.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/11] kernel/kfifo.c: trivial: use BUG_ON

On Tue, Aug 02, 2011 at 12:34:54PM +0200, Julia Lawall wrote:
> From: Julia Lawall <julia@...u.dk>
> 
> Use BUG_ON(x) rather than if(x) BUG();
> 
> The semantic patch that fixes this problem is as follows:
> (http://coccinelle.lip6.fr/)
> 
> // <smpl>
> @@ identifier x; @@
> -if (x) BUG();
> +BUG_ON(x);
> 
> @@ identifier x; @@
> -if (!x) BUG();
> +BUG_ON(!x);
> // </smpl>
> 
> Signed-off-by: Julia Lawall <julia@...u.dk>
> 

The patch looks good. However, I think we should just get rid of the
BUG_ON() there. If nents is 0, setup_sgl_buf() would just returns 0 and
nothing critical will happen.

Also consider that in __kfifo_dma_in_prepare(), the equivalent of
__kfifo_dma_in_prepare_r() when recsize is 0, we don't check nents at
all.

-Andrea

> ---
>  kernel/kfifo.c |    6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff -u -p a/kernel/kfifo.c b/kernel/kfifo.c
> --- a/kernel/kfifo.c
> +++ b/kernel/kfifo.c
> @@ -562,8 +562,7 @@ EXPORT_SYMBOL(__kfifo_to_user_r);
>  unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
>  	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
>  {
> -	if (!nents)
> -		BUG();
> +	BUG_ON(!nents);
>  
>  	len = __kfifo_max_r(len, recsize);
>  
> @@ -586,8 +585,7 @@ EXPORT_SYMBOL(__kfifo_dma_in_finish_r);
>  unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
>  	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)
>  {
> -	if (!nents)
> -		BUG();
> +	BUG_ON(!nents);
>  
>  	len = __kfifo_max_r(len, recsize);
>  
--
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