Re: Disabling an interrupt in the handler locks the system up

From: Mason
Date: Fri Oct 21 2016 - 14:40:13 EST

On 21/10/2016 19:46, Marc Zyngier wrote:

> On 21/10/16 17:37, Mason wrote:
>> On my platform, one HW block pulls the interrupt line high
>> as long as it remains idle, and low when it is busy.
>> The device tree node is:
>> test@22222 {
>> compatible = "vendor,testme";
>> interrupts = <23 IRQ_TYPE_LEVEL_HIGH>;
>> };
> I assume that this is for the sake of the discussion, and that you do
> not actually intend to put together such a monstrosity.

It's just missing a reg properties to be a valid node, right?

>> I wrote a minimal driver which registers the irq.
>> And in the interrupt handler, I disable said irq.
>> Since the irq is IRQ_TYPE_LEVEL_HIGH, it will fire as soon as
>> it is registered (because the block is idle).
>> Here is the code I've been running, request_irq doesn't return.
> [...]
>> And here's what I get when I try to load the module:
>> (I'm using the default CONFIG_RCU_CPU_STALL_TIMEOUT=21)
> [...]
>> Are we not supposed to disable the irq in the handler?
> You can. It then depends on what your interrupt controller does to
> actually ensure that the interrupt is disabled. Only you can trace it on
> your HW to find out.

I'm using an upstream driver on v4.9-rc1

Given that the system locks up, is it possible there is a bug
in the driver?

Which call-back handles enabling/disabling interrupts?