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SubjectRe: [PATCH] sched: fix divide by zero at {thread_group,task}_times
On Wed, Aug 08, 2012 at 10:08:20PM +0200, Peter Zijlstra wrote:
> On Wed, 2012-08-08 at 21:50 +0200, Mike Galbraith wrote:
> > 32bit built do_div()
> > and div64_u64() both sucked equally compared to 64bit
>
> /me peeks at div64_u64 fallback implementation and sees why, it still
> does a single div, it does some neat fls tricks.
>
> Ok, no point in avoiding this then..
>
> I did the below little edit, no point in mixing the old and new
> primitives.. those __force things annoy me, but I guess otherwise we'll
> upset sparse.

Yeah, __force is needed for sparse, since we marked cputime_t with
__nocast (by commit 648616343cdbe904c585a6c12e323d3b3c72e46f, which btw
looks like very nice cleanup at whole).

> Index: linux-2.6/kernel/sched/core.c
> ===================================================================
> --- linux-2.6.orig/kernel/sched/core.c
> +++ linux-2.6/kernel/sched/core.c
> @@ -3149,7 +3149,7 @@ static cputime_t scale_utime(cputime_t u
> temp *= (__force u64) utime;
>
> if (sizeof(cputime_t) == 4)
> - do_div(temp, (__force u32) total);
> + temp = div_u64(temp, (__force u32) total);
> else
> temp = div64_u64(temp, (__force u64) total);

Is this or will be queued (I do not see it queued anywhere)? Or should
I repost with above change?

Thanks
Stanislaw


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