linux-kernel - Re: [v5] Coccinelle: semantic code search for missing put

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Date:   Fri, 15 Feb 2019 14:54:27 +0100
From:   Markus Elfring <Markus.Elfring@....de>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Wen Yang <wen.yang99@....com.cn>,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>,
        Yi Wang <wang.yi59@....com.cn>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Wen Yang <yellowriver2010@...mail.com>,
        Cheng Shengyu <cheng.shengyu@....com.cn>,
        cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [v5] Coccinelle: semantic code search for missing put_device()

>> Does the first SmPL when specification include the case that a call
>> of the function “put_device” can occur within a branch of an if statement?
>
> It does include that,

Thanks for this acknowledgement.

So it seems that you find my interpretation of this bit of SmPL code appropriate.

> but there is another execution path where the put device is not present.

It is tried to find such cases.

> But given the test in the if in the when code,
> on that execution path id is NULL, an so there is no need to put it.

I would like to point out that the function “put_device” belongs also to
the category of functions which tolerate the passing of null pointers.
https://elixir.bootlin.com/linux/v5.0-rc6/source/drivers/base/core.c#L2053
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/core.c?id=cb5b020a8d38f77209d0472a0fea755299a8ec78#n2053

Have we got still different software development opinions about the need
for an extra pointer check in the “second” SmPL when specification?

Regards,
Markus