Re: [RFC IRQ] genirq: fix handle_nested_irq for lazy disable

[Abhijeet Dharmapurikar]

Thomas Gleixner wrote:
> > diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> > index baa5c4a..35ccc41 100644
> > --- a/kernel/irq/chip.c
> > +++ b/kernel/irq/chip.c
> > @@ -419,6 +419,7 @@ void handle_nested_irq(unsigned int irq)
> >  {
> >  	struct irq_desc *desc = irq_to_desc(irq);
> >  	struct irqaction *action;
> > +	int mask_this_irq = 0;
> >  	irqreturn_t action_ret;
> >  
> >  	might_sleep();
> > @@ -428,8 +429,10 @@ void handle_nested_irq(unsigned int irq)
> >  	kstat_incr_irqs_this_cpu(irq, desc);
> >  
> >  	action = desc->action;
> > -	if (unlikely(!action || (desc->status & IRQ_DISABLED)))
> > +	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
> > +		mask_this_irq = 1;
> >  		goto out_unlock;
> > +	}
> >  
> >  	desc->status |= IRQ_INPROGRESS;
> >  	raw_spin_unlock_irq(&desc->lock);e
> > @@ -443,6 +446,11 @@ void handle_nested_irq(unsigned int irq)
> >  
> >  out_unlock:
> >  	raw_spin_unlock_irq(&desc->lock);
> > +	if (unlikely(mask_this_irq)) {
> > +		chip_bus_lock(irq, desc);
> > +		desc->chip->mask(irq);
>
> That does not work with current mainline due to the irq_chip changes,
> can you please respin against linus latest?
Sure will address this in the next patch.
> Also there is no requirement for irq_chip instances to implement the
> mask function, so this might crash the kernel for innocent users of
> that infrastructure. mask_irq() is your friend.
Thanks, this one too.
> Aside of that this wont work for edge triggered interrupts, as you'd
> loose the edge, so this needs more thought and a thorough look at the
> users of handle_nested_irq().

I didn't understand this though. This patch will mask the interrupt in 
the controller even if it were edge. My interrupt controller latches
edges and wants a mask (or an ack) to be executed to deactivate the line 
summary line. Do you mean that I should mark the interrupt IRQ_PENDING 
if it were an edge before masking it? If not, can you please explain.

Thanks,
Abhijeet
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