On Wed, Aug 01, 2018 at 08:33:23AM +0200, Hannes Reinecke wrote:
> On 07/31/2018 05:07 PM, Varun Prakash wrote:
> > If number of interrupt vectors are more than num_online_cpus()
> > then pci_alloc_irq_vectors_affinity() assigns cpumask based
> > on num_possible_cpus() to the remaining vectors because of
> > this interrupt does not generate for these vectors.
> >
> > This patch fixes this issue by using pci_alloc_irq_vectors()
> > instead of pci_alloc_irq_vectors_affinity().
> >
> > Signed-off-by: Varun Prakash <[email protected]>
> > ---
> > drivers/scsi/csiostor/csio_isr.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> >
> > - cnt = pci_alloc_irq_vectors_affinity(hw->pdev, min, cnt,
> > - PCI_IRQ_MSIX | PCI_IRQ_AFFINITY, &desc);
> > + cnt = pci_alloc_irq_vectors(hw->pdev, min, cnt, PCI_IRQ_MSIX);
> > if (cnt < 0)
> > return cnt;
> >
> >
> Hmm.
> That patch (and the reasoning leading up to it) really sound dodgy.
> I'd rather fix the interrupt affinity code to handle this case correctly.
Yes, it is better to fix the affinity assignment code, I posted
this patch to start a discussion on this issue.
I can confirm that if number of interrupt vectors are more than
num_online cpus() then pci_alloc_irq_vectors_affinity() assigns
cpumask based on cpu_possible_mask to the remaining vectors.
Following is the logic for creating affinity masks
struct cpumask *
irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
{
...
/* Spread on present CPUs starting from affd->pre_vectors */
usedvecs = irq_build_affinity_masks(affd, curvec, affvecs,
node_to_cpumask, cpu_present_mask,
nmsk, masks);
/*
* Spread on non present CPUs starting from the next vector to be
* handled. If the spreading of present CPUs already exhausted the
* vector space, assign the non present CPUs to the already spread
* out vectors.
*/
if (usedvecs >= affvecs)
curvec = affd->pre_vectors;
else
curvec = affd->pre_vectors + usedvecs;
cpumask_andnot(npresmsk, cpu_possible_mask, cpu_present_mask);
usedvecs += irq_build_affinity_masks(affd, curvec, affvecs,
node_to_cpumask, npresmsk,
nmsk, masks);
...
}
> Thomas, can you help here?
>
