From mboxrd@z Thu Jan  1 00:00:00 1970
From: Johannes Berg <johannes@sipsolutions.net>
Date: Mon, 01 Dec 2014 20:29:05 +0000
Subject: Re: net-PA Semi: Deletion of unnecessary checks before the function call "pci_dev_put"
Message-Id: <1417465745.28610.0.camel@sipsolutions.net>
List-Id: <kernel-janitors.vger.kernel.org>
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To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: Lino Sanfilippo <LinoSanfilippo@gmx.de>, Olof Johansson <olof@lixom.net>, netdev@vger.kernel.org, backports@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>, kernel-janitors@vger.kernel.org, Julia Lawall <julia.lawall@lip6.fr>, "Luis R. Rodriguez" <mcgrof@suse.com>

On Mon, 2014-12-01 at 02:34 +0100, SF Markus Elfring wrote:

> > Some of those NULL pointer checks on input parameters may have been
> > added subsequently to functions. So there may be older kernel versions
> > out there in which those checks dont exists in some cases. If some of
> > the now "cleaned up" code is backported to such a kernel chances are
> > good that those missing checks are overseen. And then neither caller nor
> > callee is doing the NULL pointer check.

> I assume that a few backporters can tell you more about their corresponding
> software development experiences.
> http://www.do-not-panic.com/2014/04/automatic-linux-kernel-backporting-with-coccinelle.html

In such cases we just provide an appropriate wrapper and replace callers
of the original function by callers of the wrapper, typically with a
#define.

So this kind of evolution is no problem for the (automated) backports
using the backports project - although it can be difficult to detect
such a thing is needed.

johannes