linux-kernel - Re: linux-4.14-rc1/arch/powerpc/perf/hv-24x7.c:541: bad condition ?

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Message-ID: <87y3p8b9iv.fsf@concordia.ellerman.id.au>
Date:   Thu, 21 Sep 2017 21:01:28 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     cody@...yps.com
Cc:     David Binderman <dcb314@...mail.com>,
        "benh\@kernel.crashing.org" <benh@...nel.crashing.org>,
        "paulus\@samba.org" <paulus@...ba.org>,
        "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: linux-4.14-rc1/arch/powerpc/perf/hv-24x7.c:541: bad condition ?

[ + Cody in case he's still interested]

Michael Ellerman <mpe@...erman.id.au> writes:
> David Binderman <dcb314@...mail.com> writes:
>
>> Hello there,
>>
>> linux-4.14-rc1/arch/powerpc/perf/hv-24x7.c:543]: (warning) Identical condition 's1<s2', second condition is always false
>>
>> Source code is
>>
>>     if (s1 < s2)
>>         return 1;
>>     if (s2 > s1)
>>         return -1;
>>
>> Suggest code rework.
>
> Um thanks.
>
> It's trying to implement a sort comparison returning -1, 0, 1.
>
> So it's pretty obviously wrong, but also harmless AFAICS, because it's
> just an optimisation before doing a full comparison using memcmp().
>
> So yeah we should fix it, but not an actual bug AFAICS.
>
> cheers