Re: [IPX]: Fix checksum computation.

[Joe Perches <joe@xxxxxxxxxxx>]

On Thu, 2003-10-30 at 19:43, Linux Kernel Mailing List wrote:
> ChangeSet 1.1399, 2003/10/30 19:43:04-08:00, davem@xxxxxxxxxxxxxx
>       [IPX]: Fix checksum computation.
> diff -Nru a/net/appletalk/ddp.c b/net/appletalk/ddp.c
> --- a/net/appletalk/ddp.c     Fri Oct 31 12:06:06 2003
> +++ b/net/appletalk/ddp.c     Fri Oct 31 12:06:06 2003
> @@ -937,9 +937,13 @@
>  {
>       /* This ought to be unwrapped neatly. I'll trust gcc for now */
>       while (len--) {
> -             sum += *data++;
> +             sum += *data;
>               sum <<= 1;
> -             sum = ((sum >> 16) + sum) & 0xFFFF;
> +             if (sum & 0x10000) {
> +                     sum++;
> +                     sum &= 0xffff;
> +             }
> +             data++;
>       }
>       return sum;
>  }

This change didn't appear on this list for comment,
it just appeared in the source.

Why is this a "fix"?  Performance?
It seems more like someone's idea of code neatening.

If this is done, why not if (unlikely())