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

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Message-ID: <20100322060343.3487e32c@taxman.wild-wind.fr.eu.org>
Date:	Mon, 22 Mar 2010 06:03:43 +0000
From:	Marc Zyngier <maz@...terjones.org>
To:	Marc Zyngier <maz@...terjones.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, <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 Tue, 16 Mar 2010 09:36:59 +0100
Marc Zyngier <maz@...terjones.org> wrote:

> 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.

Any comment on this?

Thanks,

	M.
-- 
I'm the slime oozin' out from your TV set...
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