linux-kernel - Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache

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Message-ID: <20070321175413.GC455@lazybastard.org>
Date:	Wed, 21 Mar 2007 18:54:13 +0100
From:	Jörn Engel <joern@...ybastard.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jarek Poplawski <jarkao2@...pl>,
	Eric Dumazet <dada1@...mosbay.com>, mpm@...enic.com,
	Christoph Lameter <clameter@....com>,
	"ast@...dv.de" <ast@...dv.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slab: deal with NULL pointers passed to kmem_cache_free

On Wed, 21 March 2007 08:30:27 -0800, Andrew Morton wrote:
> On Wed, 21 Mar 2007 16:41:19 +0200 "Pekka Enberg" <penberg@...helsinki.fi> wrote:
> 
> > Yeah, I'll try to sneak a patch past Andrew.
> 
> That would be sneaky.
> 
> Thing is, such a patch would amount to adding a test-for-NULL to codepaths
> which we *know* do not need it.  There is no point in doing that.

How about two patches, one renaming kmem_cache_free to
kmem_cache_free_fast or __kmem_cache_free or whatever pleases you most,
the second adding kmem_cache_free with a NULL check.

The point is that the easiest way to use kmem_cache_free should be the
safest, but not necessarily the fastest.  Existing well-tuned and
NULL-aware code paths can remain fast, random new code will be safe.

Jörn

-- 
Joern's library part 14:
http://www.sandpile.org/
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