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SubjectRe: irq/affinity: Fix extra vecs calculation
Hi,

Something is wrong with this patch. We run CRIU tests for upstream kernels.
And we found that a kernel with this patch can't be booted.

https://travis-ci.org/avagin/linux/builds/223557750

We don't have access to console logs and I can't reproduce this issue on
my nodes. I tired to revert this patch and everything works as expected.

https://travis-ci.org/avagin/linux/builds/223594172

Here is another report about this patch
https://lkml.org/lkml/2017/4/16/344

Thanks,
Andrei

On Thu, Apr 13, 2017 at 01:28:12PM -0400, Keith Busch wrote:
> This fixes a math error calculating the extra_vecs. The error assumed
> only 1 cpu per vector, but the value needs to account for the actual
> number of cpus per vector in order to get the correct remainder for
> extra CPU assignment.
>
> Fixes: 7bf8222b9bd0 ("irq/affinity: Fix CPU spread for unbalanced nodes")
> Reported-by: Xiaolong Ye <xiaolong.ye@intel.com>
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
> kernel/irq/affinity.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
> index dc52911..d052947 100644
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -108,7 +108,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
> vecs_to_assign = min(vecs_per_node, ncpus);
>
> /* Account for rounding errors */
> - extra_vecs = ncpus - vecs_to_assign;
> + extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
>
> for (v = 0; curvec < last_affv && v < vecs_to_assign;
> curvec++, v++) {

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