Re: [PATCH] irq/affinity: fix irq_create_affinity_masks for the pre_vectors case

[Thomas Gleixner]

On Tue, 15 Nov 2016, Christoph Hellwig wrote:

> Adjust the exit condition for assigning the affinity vectors to take the
> pre_vectors into account.  Otherwise the last vector will get a cpu mask
> for all CPUs by accidentally hitting the post_vectors case.
> 
> Signed-off-by: Christoph Hellwig <h...@lst.de>
> ---
>  kernel/irq/affinity.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
> index 17360bd..2ca420a 100644
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -107,7 +107,9 @@ irq_create_affinity_masks(int nvecs, const struct 
> irq_affinity *affd)
>               /* Calculate the number of cpus per vector */
>               ncpus = cpumask_weight(nmsk);
>  
> -             for (v = 0; curvec < affv && v < vecs_to_assign; curvec++, v++) 
> {
> +             for (v = 0;
> +                  curvec < affd->pre_vectors + affv && v < vecs_to_assign;
> +                  curvec++, v++) {
>                       cpus_per_vec = ncpus / vecs_to_assign;
>  
>                       /* Account for extra vectors to compensate rounding 
> errors */

We have the same exit condition in the (affv <= nodes) case and further
down in the outer loop. So the complete patch should be something like
this:

--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -61,6 +61,7 @@ irq_create_affinity_masks(int nvecs, con
 {
        int n, nodes, vecs_per_node, cpus_per_vec, extra_vecs, curvec;
        int affv = nvecs - affd->pre_vectors - affd->post_vectors;
+       int last_affv = affv + affd->pre_vectors;
        nodemask_t nodemsk = NODE_MASK_NONE;
        struct cpumask *masks;
        cpumask_var_t nmsk;
@@ -87,7 +88,7 @@ irq_create_affinity_masks(int nvecs, con
        if (affv <= nodes) {
                for_each_node_mask(n, nodemsk) {
                        cpumask_copy(masks + curvec, cpumask_of_node(n));
-                       if (++curvec == affv)
+                       if (++curvec == last_affv)
                                break;
                }
                goto done;
@@ -107,7 +108,8 @@ irq_create_affinity_masks(int nvecs, con
                /* Calculate the number of cpus per vector */
                ncpus = cpumask_weight(nmsk);
 
-               for (v = 0; curvec < affv && v < vecs_to_assign; curvec++, v++) 
{
+               for (v = 0; curvec < last_affv && v < vecs_to_assign;
+                    curvec++, v++) {
                        cpus_per_vec = ncpus / vecs_to_assign;
 
                        /* Account for extra vectors to compensate rounding 
errors */
@@ -119,7 +121,7 @@ irq_create_affinity_masks(int nvecs, con
                        irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
                }
 
-               if (curvec >= affv)
+               if (curvec >= last_affv)
                        break;
        }