Philippe Gerum wrote:
> On Thu, 2007-10-04 at 11:34 +0200, Philippe Gerum wrote:
> > > Well, this trace also reveals a second bug that can cause nasty priority
> > > inversion: a high-prio domains executes when a fasteoi-IRQ arrives for a
> > > low-prio domain. This will now block all IRQs until the low-prio domain
> > > was able to run its IRQ handler completely. Thus we must _mask_ fasteoi
> > > IRQs for low-prio domains while high-prio ones are running!
> > >
> >
> > This code was actually there up to 2.6.17-1.5-02, and was removed at
> > some point in the 2.6.19 series, due to some severe conflicts with the
> > vanilla IO-APIC support which used to be a hell of a moving target at
> > that time. I guess it's time to bring this code back.
> >
>
> Does the following work for you?
>
> diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
> index 2ae79e9..517937b 100644
> --- a/arch/i386/kernel/io_apic.c
> +++ b/arch/i386/kernel/io_apic.c
> @@ -2022,6 +2022,8 @@ static void ack_ioapic_quirk_irq(unsigned int irq)
> __unmask_and_level_IO_APIC_irq(irq);
> spin_unlock(&ioapic_lock);
> }
> +
> + __mask_IO_APIC_irq(irq);
> }
>
> static int ioapic_retrigger_irq(unsigned int irq)
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index ba497a7..1560b4a 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -422,8 +422,13 @@ handle_fasteoi_irq(unsigned int irq, struct irq_desc
> *desc)
>
> spin_lock(&desc->lock);
> desc->status &= ~IRQ_INPROGRESS;
> +#ifdef CONFIG_IPIPE
> + desc->chip->unmask(irq);
> +out:
> +#else
> out:
> desc->chip->eoi(irq);
> +#endif
>
> spin_unlock(&desc->lock);
> }
> @@ -533,11 +538,12 @@ void fastcall __ipipe_end_level_irq(unsigned irq,
> struct irq_desc *desc)
>
> void fastcall __ipipe_ack_fasteoi_irq(unsigned irq, struct irq_desc *desc)
> {
> + desc->chip->eoi(irq);
> }
>
> void fastcall __ipipe_end_fasteoi_irq(unsigned irq, struct irq_desc *desc)
> {
> - desc->chip->eoi(irq);
> + desc->chip->unmask(irq);
> }
>
> void fastcall __ipipe_ack_edge_irq(unsigned irq, struct irq_desc *desc)
FWIW, this patche fixes my known-to-crash I-pipe 2.6.20 configuration.
--
Gilles Chanteperdrix.
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