Disabling an interrupt in the handler locks the system up

[Sebastian Frias]

Hi Thomas,

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()"

Thanks in advance.
Best regards,

Sebastian