From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] tcp_lp: use 64-bit arithmetic instead of 32-bit
Date: Thu, 1 Feb 2018 00:32:36 +0000
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References: <20180201002407.GA1608@embeddedgus>
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Cc: "Wong Hoi Sing, Edison" <hswong3i@gmail.com>,
        "Hung Hing Lun, Mike" <hlhung3i@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        "Gustavo A. R. Silva" <garsilva@embeddedor.com>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
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On Wed, 31 Jan 2018 18:24:07 -0600
"Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote:

> Cast to s64 some variables and a macro in order to give the
> compiler complete information about the proper arithmetic to
> use. Notice that these elements are used in contexts that
> expect expressions of type s64 (64 bits, signed).
> 
> Currently such expression are being evaluated using 32-bit
> arithmetic.

The question you need to ask is 'can it overflow 32bit maths', otherwise
you are potentially making the system do extra work for no reason.

Alan