Re: [PATCH] x86/apic: Avoid infinite loop in io_apic_level_ack_pending()

[Jason Andryuk <jason.andryuk@xxxxxxx>]

On 2025-09-05 03:39, Jan Beulich wrote:
> On 04.09.2025 23:51, Jason Andryuk wrote:
> > io_apic_level_ack_pending() will end up in an infinite loop if
> > entry->pin == -1.  entry does not change, so it will keep reading -1.
> >
> > Switched to breaking out of the loop.
> >
> > Fixes: f821102450a1 ("x86: IRQ Migration logic enhancement.")
> > Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
> > ---
> > Noticed during code inspection.
> Well spotted, just that ...
>
> > --- a/xen/arch/x86/io_apic.c
> > +++ b/xen/arch/x86/io_apic.c
> > @@ -1715,7 +1715,7 @@ static bool io_apic_level_ack_pending(unsigned int irq)
> >   
> >           pin = entry->pin;
> >           if (pin == -1)
> > -            continue;
> > +            break;
> ... we shouldn't terminate the loop here, but rather continue with the next
> entry in the list (if any). Hence presumably why "continue" was used, without
> achieving the intended effect.
Ok, makes sense.  Though after the sending the patch, I was wondering if 
it was an unreachable condition, and we should not end up here with pin 
== -1.
Thanks,
Jason