Re: [BUG 4.15-rc7] IRQ matrix management errors

[Thomas Gleixner]

On Tue, 16 Jan 2018, Thomas Gleixner wrote:
> On Tue, 16 Jan 2018, Keith Busch wrote:
> 
> > This is all way over my head, but the part that obviously shows
> > something's gone wrong:
> > 
> >   kworker/u674:3-1421  [028] d...   335.307051: irq_matrix_reserve_managed: 
> > bit=56 cpu=0 online=1 avl=86 alloc=116 managed=3 online_maps=112 
> > global_avl=22084, global_rsvd=157, total_alloc=570
> >   kworker/u674:3-1421  [028] d...   335.307053: irq_matrix_remove_managed: 
> > bit=56 cpu=0 online=1 avl=87 alloc=116 managed=2 online_maps=112 
> > global_avl=22085, global_rsvd=157, total_alloc=570
> >   kworker/u674:3-1421  [028] ....   335.307054: vector_reserve_managed: 
> > irq=45 ret=-28
> >   kworker/u674:3-1421  [028] ....   335.307054: vector_setup: irq=45 
> > is_legacy=0 ret=-28
> >   kworker/u674:3-1421  [028] d...   335.307055: vector_teardown: irq=45 
> > is_managed=1 has_reserved=0
> > 
> > Which leads me to x86_vector_alloc_irqs goto error:
> > 
> > error:
> >     x86_vector_free_irqs(domain, virq, i + 1);
> > 
> > The last parameter looks weird. It's the nr_irqs, and since we failed and
> > bailed, I would think we'd need to subtract 1 rather than add 1. Adding
> > 1 would doublely remove the failed one, and remove the next one that
> > was never setup, right?
> 
> Right. That's fishy. Let me stare at it.

What we want is s/i + 1/i/

That's correct because x86_vector_free_irqs() does:

       for (i = 0; i < nr; i++)
           ....

So if we fail at the first irq, then the loop will do nothing. Failing on
the second will free the first ....

Fix below.

Thanks,

        tglx

8<----------------------
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index f8b03bb8e725..3cc471beb50b 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -542,14 +542,17 @@ static int x86_vector_alloc_irqs(struct irq_domain 
*domain, unsigned int virq,
 
                err = assign_irq_vector_policy(irqd, info);
                trace_vector_setup(virq + i, false, err);
-               if (err)
+               if (err) {
+                       irqd->chip_data = NULL;
+                       free_apic_chip_data(apicd);
                        goto error;
+               }
        }
 
        return 0;
 
 error:
-       x86_vector_free_irqs(domain, virq, i + 1);
+       x86_vector_free_irqs(domain, virq, i);
        return err;
 }