linux-kernel - Re: [patch 3/3] genirq: introduce IRQF_ALLOW_NESTED flag for request

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Date:	Tue, 16 Mar 2010 09:36:59 +0100
From:	Marc Zyngier <maz@...terjones.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	<akpm@...ux-foundation.org>, Ingo Molnar <mingo@...e.hu>,
	<joachim.eastwood@...ron.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 3/3] genirq: introduce IRQF_ALLOW_NESTED flag for request_irq()

On Sat, 13 Mar 2010 20:56:19 +0100 (CET), Thomas Gleixner
<tglx@...utronix.de> wrote:

Hi Thomas,

> In general I have no objections, but one thing bothers me. We have no
> way to let a driver know whether it runs in a nested threaded context
> or in hard irq context. There might be (future) drivers which would be
> happy to know that to apply context dependent optimizations etc.
> 
> What about a new function which solves your problem and returns that
> information ? Something along the line:
> 
> int request_any_context_irq(....)
> {
> 	...
> 	if (desc->status & IRQ_NESTED_THREAD) {
> 	   	ret = request_threaded_irq();
> 		if (!ret)
> 			ret = IRQ_IS_NESTED;
> 
> 	} else {
> 		.....
> 			ret = IRQ_IS_NONTHREADED;
> 		else
> 			ret = IRQ_IS_THREADED;
> 
> 	}
> 	...
> 	return ret;
> }
> 
> You get the idea, right ?
> 
> It's a bit more code, but less magic and more flexible for further use
> cases.

What about the attached (sorry, webmail crap) patch? I deliberately left
IS_THREADED out of the picture, as I have the feeling that the caller has
to know if it really wants a threaded handler, and I couldn't see a way to
guess its intent.

Please note that this patch has only been compile-tested, as I'm traveling
for the rest of the week and don't have access to my boards.

Thanks,

        M.
-- 
Who you jivin' with that Cosmik Debris?
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