linux-kernel - Re: net-PA Semi: Deletion of unnecessary checks before the function call "pci_dev

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Date:	Mon, 01 Dec 2014 21:29:05 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:	Lino Sanfilippo <LinoSanfilippo@....de>,
	Olof Johansson <olof@...om.net>, netdev@...r.kernel.org,
	backports@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>,
	"Luis R. Rodriguez" <mcgrof@...e.com>
Subject: Re: net-PA Semi: Deletion of unnecessary checks before the function
 call "pci_dev_put"

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

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