On Thu, Jun 05, 2014 at 10:12:16AM -0700, David Daney wrote:
> >vim +84 kernel/trace/trace_benchmark.c
> >
> > 78 if (bm_cnt > 1) {
> > 79 /*
> > 80 * Apply Welford's method to calculate standard deviation:
> > 81 * s^2 = 1 / (n * (n-1)) * (n * \Sum (x_i)^2 - (\Sum x_i)^2)
> > 82 */
> > 83 stddev = (u64)bm_cnt * bm_totalsq - bm_total * bm_total;
> > > 84 do_div(stddev, bm_cnt);
> > > 85 do_div(stddev, bm_cnt - 1);
> > 86 } else
> > 87 stddev = 0;
> > 88
> >
> >
> >
> >Is there something special with do_div in mips that I should be aware
> >of?
>
> Yes. MIPS is using the implementation in asm-generic/div64.h,
> which per the comments in that file has a useless pointer compare to
> find just this type of issue.
And it's not the only warning it's picking up.
> Ralf: As a side note, while looking at
> arch/mips/include/asm/div64.h, I saw that the implementation of
> __div64_32 in that file will be unused, and is also completely
> broken due to the first parameter never being used.
Seems I broke c21004cd5b4cb7d479514d470a62366e8307412c "MIPS: Rewrite
<asm/div64.h> to work with gcc 4.4.0." Took only five years until
somebody noticed ...
Ralf
