On Wed, 2012-11-21 at 16:19 +0200, Alex Lyakas wrote:
> Hi,
> I was advised to turn off irqbalance and reproduced this issue, but
> the failure is in a different place now. Now request_threaded_irq()
> fails with EBUSY.
> According to the code, this can only happen on the path:
> request_threaded_irq() -> __setup_irq()
> Now in setup irq, the only place where EBUSY can show up for us is here:
> ...
> raw_spin_lock_irqsave(&desc->lock, flags);
> old_ptr = &desc->action;
> old = *old_ptr;
> if (old) {
> /*
> * Can't share interrupts unless both agree to and are
> * the same type (level, edge, polarity). So both flag
> * fields must have IRQF_SHARED set and the bits which
> * set the trigger type must match. Also all must
> * agree on ONESHOT.
> */
> if (!((old->flags & new->flags) & IRQF_SHARED) ||
> ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK) ||
> ((old->flags ^ new->flags) & IRQF_ONESHOT)) {
> old_name = old->name;
> goto mismatch;
> }
>
> /* All handlers must agree on per-cpuness */
> if ((old->flags & IRQF_PERCPU) !=
> (new->flags & IRQF_PERCPU))
> goto mismatch;
>
> KVM calls request_threaded_irq() with flags==0, so can it be that
> different KVM processes request the same IRQ?
Shouldn't be possible, irqs are allocated from a bitmap protected by a
mutex, see __irq_alloc_descs
> How different KVM
> processes spawned simultaneously agree between them on IRQ numbers?
They don't, MSI/X vectors are not currently share-able. Can you show
that you're actually getting duplicate irq vectors? Thanks,
Alex
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