[Xen-devel] Re: Crash in __pirq_guest_eoi()

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

 >>> On 03.09.10 at 20:33, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> I'm seeing a crash in:
> 
> static void __pirq_guest_eoi(struct domain *d, int pirq)
> {
>     struct irq_desc         *desc;
>     irq_guest_action_t *action;
>     cpumask_t           cpu_eoi_map;
>     int                 irq;
> 
>     ASSERT(local_irq_is_enabled());
>     desc = domain_spin_lock_irq_desc(d, pirq, NULL);
>     if ( desc == NULL )
>         return;
> 
>     action = (irq_guest_action_t *)desc->action;
>     irq = desc - irq_desc;
> 
>     if ( action->ack_type == ACKTYPE_NONE )
>     {
> 
> where action is NULL.

Any more precise information on the conditions under which this
happens? Like trying to EOI a bad pirq?

> I'm playing around with the pvops kernel's handling of pirq interrupts,
> so the kernel is probably misbehaving, but it would be nice if Xen
> didn't keep crashing on me.
> 
> I guess this is the right fix/workaround?

No. You can't return without releasing the lock acquired a couple of
lines earlier. And it seems bogus in the first place that you could get
there and find action being NULL, so it'd seem to be a workaround
at best.

Jan

> diff -r d37dc6401a1f xen/arch/x86/irq.c
> --- a/xen/arch/x86/irq.c      Thu Sep 02 17:44:46 2010 +0100
> +++ b/xen/arch/x86/irq.c      Fri Sep 03 11:33:15 2010 -0700
> @@ -1028,6 +1028,9 @@
>      action = (irq_guest_action_t *)desc->action;
>      irq = desc - irq_desc;
>  
> +    if ( action == NULL )
> +     return;
> +
>      if ( action->ack_type == ACKTYPE_NONE )
>      {
>          ASSERT(!test_bit(pirq, d->pirq_mask));
> 
>     J




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