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Date: Mon, 01 Dec 2014 02:34:37 +0100
From: SF Markus Elfring <elfring@users.sourceforge.net>
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To: Lino Sanfilippo <LinoSanfilippo@gmx.de>,
	Olof Johansson <olof@lixom.net>, netdev@vger.kernel.org,
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CC: LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org,
	Julia Lawall <julia.lawall@lip6.fr>,
	"Luis R. Rodriguez" <mcgrof@suse.com>
Subject: Re: net-PA Semi: Deletion of unnecessary checks before the function
 call "pci_dev_put"
References: <5307CAA2.8060406@users.sourceforge.net> <alpine.DEB.2.02.1402212321410.2043@localhost6.localdomain6> <530A086E.8010901@users.sourceforge.net> <alpine.DEB.2.02.1402231635510.1985@localhost6.localdomain6> <530A72AA.3000601@users.sourceforge.net> <alpine.DEB.2.02.1402240658210.2090@localhost6.localdomain6> <530B5FB6.6010207@users.sourceforge.net> <alpine.DEB.2.10.1402241710370.2074@hadrien> <530C5E18.1020800@users.sourceforge.net> <alpine.DEB.2.10.1402251014170.2080@hadrien> <530CD2C4.4050903@users.sourceforge.net> <alpine.DEB.2.10.1402251840450.7035@hadrien> <530CF8FF.8080600@users.sourceforge.net> <alpine.DEB.2.02.1402252117150.2047@localhost6.localdomain6> <530DD06F.4090703@users.sourceforge.net> <alpine.DEB.2.02.1402262129250.2221@localhost6.localdomain6> <5317A59D.4@users.sourceforge.net> <547A09B1.9090102@users.sourceforge.net> <547B579F.10709@gmx.de>
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> I know there has been some criticism about those kind of "code
> improvements" already but i would like to point out just one more thing:
> 
> 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 guess that the Coccinelle software can also help you in this use case.
How do you think about to shield against "unwanted" or unexpected collateral
evolutions with additional inline functions?

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

Regards,
Markus