linux-kernel - Re: [patch 6/8] arm: ns9xxx: Remove private irq flow handler

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Message-ID: <20110203075623.GB30452@pengutronix.de>
Date:	Thu, 3 Feb 2011 08:56:23 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [patch 6/8] arm: ns9xxx: Remove private irq flow handler

Hi Thomas,

On Wed, Feb 02, 2011 at 09:41:27PM -0000, Thomas Gleixner wrote:
> handle_prio_irq is almost identical with handle_fasteoi_irq. The
> subtle differences are
> 
> 1) The handler checks for IRQ_DISABLED after the device handler has
>    been called. In case it's set it masks the interrupt.
> 
> 2) When the handler sees IRQ_DISABLED on entry it masks the interupt
>    in the same way as handle_fastoei_irq, but does not set the
>    IRQ_PENDING flag.
> 
> 3) Instead of gracefully handling a recursive interrupt it crashes the
>    kernel.
> 
> #1 is just relevant when a device handler calls disable_irq_nosync()
>    and it does not matter whether we mask the interrupt right away or
>    not. We handle lazy masking for disable_irq anyway, so there is no
>    real reason to have this extra mask in place.
> 
> #2 will prevent the resend of a pending interrupt, which can result in
>    lost interrupts for edge type interrupts. For level type interrupts
>    the resend is a noop in the generic code. According to the
>    datasheet all interrupts are level type, so marking them as such
>    will result in the exact same behaviour as the private
>    handle_prio_irq implementation.
> 
> #3 is just stupid. Crashing the kernel instead of handling a problem
>    gracefully is just wrong. With the current semantics- all handlers
>    run with interrupts disabled - this is even more wrong.
> 
> Rename ack to eoi, remove the unused mask_ack, switch to
> handle_fasteoi_irq and remove the private function.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>
> Cc: linux-arm-kernel@...ts.infradead.org
I have no access to a ns9xxx machine, but this looks sane.

Acked-by: Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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