linux-kernel - Re: [PATCH] scsi:NCR5380: remove same check condition in NCR5380

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Message-ID: <alpine.DEB.2.20.1808031146090.3871@hadrien>
Date:   Fri, 3 Aug 2018 11:52:45 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
cc:     Finn Thain <fthain@...egraphics.com.au>,
        zhong jiang <zhongjiang@...wei.com>,
        Michael Schmitz <schmitzmic@...il.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        John Garry <john.garry@...wei.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scsi:NCR5380: remove same check condition in
 NCR5380_select



On Fri, 3 Aug 2018, Andy Shevchenko wrote:

> On Fri, Aug 3, 2018 at 5:24 AM, Finn Thain <fthain@...egraphics.com.au> wrote:
> > On Thu, 2 Aug 2018, zhong jiang wrote:
> >
> >> The same check condition is redundant, so remove one of them.
> >>
> >
> > If you are trying to find redundant code, your coccinelle script is
> > dangerously flawed.
>
> These days too many coccinelle helpers make people think they are
> doing right "clean ups" when in the practice they bring the
> regressions.
>
> Julia, is possible by coccinelle to distinguish memory accesses versus
> I/O? At least it would increase robustness in some cases.

With make coccicheck, the semantic patch should already emit the warning:

//# A common source of false positives is when the argument performs a side
//# effect.

I can modify the rule so that it doesn't report on code that involves
function calls.  It could lose some desirable warnings, where the function
call is just a wrapper for eg extracting some field, but it is probably
safer in practice.

julia