linux-kernel - Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache

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Date:	Tue, 17 Jul 2012 10:11:56 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Pekka Enberg <penberg@...nel.org>
cc:	David Rientjes <rientjes@...gle.com>,
	Shuah Khan <shuah.khan@...com>, glommer@...allels.com,
	js1304@...il.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	shuahkhan@...il.com
Subject: Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache_create()

On Tue, 17 Jul 2012, Pekka Enberg wrote:

> Well, even SLUB checks for !name in mainline so that's definitely
> worth including unconditionally. Furthermore, the size related checks
> certainly make sense and I don't see any harm in having them as well.

There is a WARN_ON() there and then it returns NULL!!! Crazy. Causes a
NULL pointer dereference later in the caller?

> As for "in_interrupt()", I really don't see the point in keeping that
> around. We could push it down to mm/slab.c in "__kmem_cache_create()"
> if we wanted to.

Ok we could do that but I guess we are in the discussion of how much
checking should be done for a production kernel.

I think these checks are way out of hand. We cannot afford to
consistently check parameters to all kernel functions in production. We
will only do these checks in a select manner if these values could
result in serious difficult to debug problems. The checks in slab look
like debugging code that someone needed for a specific debugging scenario.

I can understand that we would keep that in for development but not for
production. Maybe I am a bit biased but my prod kernels need to have
minimal memory footprint due to excessive code size causing regressions.

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