linux-kernel - Re: [patch/rfc 1/2] GENIRQ: add handle_threaded

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Message-ID: <20090318120056.GG24947@scadufax.research.nokia.com>
Date:	Wed, 18 Mar 2009 14:00:56 +0200
From:	Felipe Balbi <felipe.balbi@...ia.com>
To:	ext David Brownell <david-b@...bell.net>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"me@...ipebalbi.com" <me@...ipebalbi.com>,
	"dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
	"sameo@...nedhand.com" <sameo@...nedhand.com>
Subject: Re: [patch/rfc 1/2] GENIRQ: add handle_threaded_irq() flow handler

Hi,

On Wed, Mar 18, 2009 at 03:19:47AM +0100, David Brownell wrote:

[..]

> @@ -295,6 +295,67 @@ static inline void mask_ack_irq(struct i
>  }
>  
>  /**
> + *	handle_threaded_irq - flow handler reusing current irq thread
> + *	@irq:	the interrupt number
> + *	@desc:	the interrupt description structure for this irq
> + *	Context: irq thread, with IRQs enabled
> + *
> + *	IRQ threads which demultiplex IRQs may use this flow handler
> + *	to chain those demultiplexed IRQs to subsidiary handlers, when
> + *	all that IRQ dispatch logic must run in sleeping contexts.
> + *
> + *	Examples include some multifunction I2C and SPI based devices
> + *	(where access to registers, including ones involved in IRQ
> + *	dispatching, requires sleeping) that have multiple independent
> + *	maskable interupts.
> + *
> + *	The irq thread using this flow handler must handle any ack,
> + *	clear, mask or unmask issues needed.
> + */
> +void
> +handle_threaded_irq(unsigned int irq, struct irq_desc *desc)
> +{
> +	struct irqaction *action;
> +	irqreturn_t action_ret;
> +
> +	spin_lock_irq(&desc->lock);
> +
> +	if (unlikely(desc->status & IRQ_INPROGRESS))
> +		goto out_unlock;
> +	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
> +	kstat_incr_irqs_this_cpu(irq, desc);
> +
> +	action = desc->action;
> +	if (unlikely(!action || (desc->status & IRQ_DISABLED)))
> +		goto out_unlock;

you say below irqs are always enabled so this branch is something we
never want to happen. How about adding a WARN() then ?

-- 
balbi
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