Messages in this thread | | | Date | Wed, 27 Oct 2010 10:01:45 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC IRQ] genirq: fix handle_nested_irq for lazy disable |
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On Tue, 26 Oct 2010, adharmap@codeaurora.org wrote:
> From: Abhijeet Dharmapurikar <adharmap@codeaurora.org> > > When lazy disabling is implemented and an interrupt is disabled the > genirq code ends up marking it as IRQ_DISABLED in the descriptor. > The interrupt stays enabled in the controller. If the interrupt > fires after disabling, the flow handlers namely handle_level_irq and > handle_edge_irq mask the interrupt in the controller. > > This is not the case with handle_nested_irq. The interrupt stays enabled in > the controller and if it were a level interrupt it keeps firing only to be > ignored by handle_nested_irq. > > Update handle_nested_irq to mask such an interrupt. > > Change-Id: Id0fa3280c49a36aa8b8db1d5cc20472bf5e53c5f > Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org> > --- > This problem shows up on my hardware because the interrupt controller is > over a slow bus and it doesnt deactivate the interrupt line to the processor > until an ack or mask operation is carried out for each of its active > interrupts. > > I could have updated the interrupt controller thread itself to check if the > interrupt is marked IRQ_DISABLED but didn't seem right to take the > desc->lock in there. Instead updating handle_nested_irq to handle this > seemed like the right thing to do. > > kernel/irq/chip.c | 10 +++++++++- > 1 files changed, 9 insertions(+), 1 deletions(-) > > 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?
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.
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().
One possible solution would be to change handle_nested_irq() to return int. So we could return 0 for the normal case and some sensible error code when the irq is disabled, so the caller can deal with it. Either that or we need a separate nested function for level irqs which then can implement the mask logic.
Thanks,
tglx
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