Messages in this thread | | | Date | Thu, 30 Oct 2014 16:59:02 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/3] genirq: Add support for priority-drop/deactivate interrupt controllers |
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On Thu, 30 Oct 2014, Marc Zyngier wrote: > So I actually implemented this, and did hit another snag: per cpu interrupts. > They don't use the startup/shutdown methods, and reproducing the above logic > on a per-cpu basis is not very pretty.
Hmm. Have not looked at the percpu stuff yet.
> /** > + * handle_spliteoi_irq - irq handler for 2-phase-eoi controllers > + * @irq: the interrupt number > + * @desc: the interrupt description structure for this irq > + * > + * This relies on mask being a very cheap operation, and on > + * unmask performing both unmask+EOI. This avoids additional > + * operations for threaded interrupts (typically ARM's GICv2/v3). > + */ > +void > +handle_spliteoi_irq(unsigned int irq, struct irq_desc *desc) > +{ > + raw_spin_lock(&desc->lock); > + > + if (!irq_may_run(desc)) > + goto out; > + > + desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING); > + kstat_incr_irqs_this_cpu(irq, desc); > + > + /* Mark the IRQ as in progress */ > + mask_irq(desc); > + > + /* > + * If it's disabled or no action available > + * then just get out of here: > + */ > + if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) { > + desc->istate |= IRQS_PENDING; > + goto out_unmask;
If this handler is used with the lazy disable approach then this goto causes an irq storm if the interrupt stays active (LEVEL).
So this relies on irq_disable() actually disabling the interrupt at the hardware level. That really wants a big fat comment if we take this approach.
Now there is another issue. Assume the following:
CPU 0 CPU 1 handle_spliteoi_irq() mask_irq(); handle_event(); wake_thread(); return;
run_thread() call_handler(); disable_irq() irq_disable() finalize_oneshot() if (disabled) return;
So that particular interrupt gets never acknowledged with a write to DIR.
What happens if you enable it again at the hardware level via enable_irq()? Is it still in dropped priority mode and waits for the write to DIR forever? That's what I tried to avoid with my approach.
Thanks,
tglx
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