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

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Date:	Tue, 2 Aug 2011 14:03:29 +0200
From:	Andrea Righi <andrea@...terlinux.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 01:52:49PM +0200, Julia Lawall wrote:
> 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@...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.
> 
> 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

Right. But I'd prefer to return nothing also when asking nothing rather
than crashing the kernel.

-Andrea
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