linux-kernel - Re: [PATCH] include/linux/slab.h: new KFREE() macro.

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Date:	Mon, 8 Jan 2007 03:39:30 -0500
From:	"Sumit Narayan" <talk2sumit@...il.com>
To:	"Amit Choudhary" <amit2030@...oo.com>
Cc:	"Pekka Enberg" <penberg@...helsinki.fi>,
	"Hua Zhong" <hzhong@...il.com>,
	"Christoph Hellwig" <hch@...radead.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] include/linux/slab.h: new KFREE() macro.

Asking for KFREE is as silly as asking for a macro to check if kmalloc
succeeded for a pointer, else return ENOMEM.

#define CKMALLOC(p,x) \
   do {   \
       p = kmalloc(x, GFP_KERNEL); \
       if(!p) return -ENOMEM; \
    } while(0)


On 1/8/07, Amit Choudhary <amit2030@...oo.com> wrote:
>
> --- Pekka Enberg <penberg@...helsinki.fi> wrote:
>
> > On 1/8/07, Hua Zhong <hzhong@...il.com> wrote:
> > > > And as I explained, it can result in longer code too. So, why
> > > > keep this value around. Why not re-initialize it to NULL.
> > >
> > > Because initialization increases code size.
> >
> > And it also effectively blocks the slab debugging code from doing its
> > job detecting double-frees.
> >
>
> Man, so you do want someone to set 'x' to NULL after freeing it, so that the slab debugging code
> can catch double frees. If you set it to NULL then double free is harmless. So, you want something
> harmful in the system and then debug it with the slab debugging code. Man, doesn't make sense to
> me.
>
> -Amit
>
>
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