Disabling an interrupt in the handler locks the system up

[Mason]

On 25/10/2016 10:29, Sebastian Frias wrote:

> On 10/24/2016 06:55 PM, Thomas Gleixner wrote:
>
>> On Mon, 24 Oct 2016, Mason wrote:
>>
>>> For the record, setting the IRQ_DISABLE_UNLAZY flag for this device
>>> makes the system lock-up disappear.
>>
>> The way how lazy irq disabling works is:
>>
>> 1) Interrupt is marked disabled in software, but the hardware is not masked
>>
>> 2) If the interrupt fires befor the interrupt is reenabled, then it's
>>    masked at the hardware level in the low level interrupt flow handler.
> 
> Would you mind explaining what is the intention behind?
> Because it does not seem obvious why there isn't a direct map between
> "disable_irq*()" and "mask_irq()"

I had a similar, but slightly different question:

What is the difference between struct irq_chip's

 * @irq_shutdown:	shut down the interrupt (defaults to ->disable if NULL)
 * @irq_disable:	disable the interrupt
 * @irq_mask:		mask an interrupt source

(enable seems to default to unmask, but disable does not default to mask)

Regards.