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

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Date:   Tue, 25 Oct 2016 10:29:27 +0200
From:   Sebastian Frias <sf84@...oste.net>
To:     Thomas Gleixner <tglx@...utronix.de>, Mason <slash.tmp@...e.fr>
Cc:     Marc Zyngier <marc.zyngier@....com>,
        Jason Cooper <jason@...edaemon.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Disabling an interrupt in the handler locks the system up

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