Re: [PATCH 1/11] kernel/kfifo.c: trivial: use BUG_ON

From: Julia Lawall
Date: Tue Aug 02 2011 - 07:53:05 EST


On Tue, 2 Aug 2011, Andrea Righi wrote:

> On Tue, Aug 02, 2011 at 12:34:54PM +0200, Julia Lawall wrote:
> > From: Julia Lawall <julia@xxxxxxx>
> >
> > 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@xxxxxxx>
> >
>
> 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.

I don't know the code at all. Indeed, I'm not sure to see any uses of eg
__kfifo_dma_in_prepare_r, except in demo code. But that would imply
returning 0 for two different reasons: asking for nothing and being out of
space.

julia

> 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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