linux-kernel - Re: Disabling an interrupt in the handler locks the system up

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Message-ID: <580A60ED.3030307@free.fr>
Date:   Fri, 21 Oct 2016 20:39:41 +0200
From:   Mason <slash.tmp@...e.fr>
To:     Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Sebastian Frias <sf84@...oste.net>
Subject: Re: Disabling an interrupt in the handler locks the system up

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@...22 {
>> 			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

http://lxr.free-electrons.com/source/drivers/irqchip/irq-tango.c

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

Which call-back handles enabling/disabling interrupts?

Regards.