Re: [-mm patch] kernel/sched{,_fair}.c: make code static

Ingo Molnar
2007-06-06T07:30:42Z

* Andrew Morton <akpm@linux-foundation.org> wrote:

> > Signed-off-by: Adrian Bunk <bunk@stusta.de>
> >
> > ---
> >
> > BTW: Please don't #include C files in sched.c
>
> Yeah.

In this case it's not that bad. It makes the source quite a bit cleaner
and avoids having to create artificial interfaces, global functions,
etc. between the .o's.

> > -long div64_s(s64 divident, unsigned long divisor)
> > +static long div64_s(s64 divident, unsigned long divisor)
>
> "divident" does appear to be a word, but I suspect "dividend" was
> intended.

yeah indeed - fixed.

> Why is this function lurking in the CPU scheduler rather than in
> lib/somewhere.c?
>
> Doesn't an unsigned divide give the same result as a signed one?

no! 0xfffffff0 / 2 is 0x7fffffff when the division is unsigned, and
7ffffff8 (== -8) when signed. On x86 the silicon only offers us unsigned
64-bit division, so we first have to make '+16' out of -16, then divide
by 2, and turn the +4 into -4. (On x86_64 there's no such problem,
there's an idiv and a div 64-bit instruction as well, and gcc picks the
right one depending on the type of the variable.)

i think Roman has recently done a nice cleanup patch that introduces
this? I'll change CFS to use that interface once it's upstream.

Ingo