linux-kernel - Re: [PATCH] warn about shared irqs requesting IRQF_DISABLED registered with setup

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Message-ID: <20091128200344.GA1272@pengutronix.de>
Date:	Sat, 28 Nov 2009 21:03:44 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>, Nicolas Pitre <nico@...vell.com>,
	Eric Miao <eric.y.miao@...il.com>,
	John Stultz <johnstul@...ibm.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] warn about shared irqs requesting IRQF_DISABLED
	registered with setup_irq

On Fri, Nov 27, 2009 at 11:18:00PM +0100, Thomas Gleixner wrote:
> On Fri, 27 Nov 2009, Uwe Kleine-König wrote:
> 
> > IRQF_DISABLED is not guaranteed on shared irqs.  There is already a
> > warning in place for irqs registered with request_irq (introduced in
> > 470c66239ef03).  Move it to __setup_irq, this way it triggers for both
> > request_irq and setup_irq.
> > 
> > One irq that is now warned about is the timer tick on at91 (ARCH=arm).
> 
> And how does that help ? The interrupt is shared between the timer and
> the debug port. There is nothing you can do about that.
> 
> The interupt handlers are called in order of setup. The AT91 timer
> irq is set up first and if that's not the case then it needs to be
> fixed and the only way to catch it is in the affected interrupt
> handler.
Russell already suggests to save (and restore) irqs in the handler
before (and after resp.) calling the clockevent functions.

Should it use the raw_ variants?
 
> Applying your patch does not change the hardware and will just result
> in useless, annoying and confusing dmesg warnings.
My patch wasn't mainly to help in the at91 case.  I just thought that a
warning that is triggered with request_irq and request_threaded_irq
shouldn't be skipped when using setup_irq.

Maybe the warning should only be printed if there's a mismatch between
different actions of the same irq regarding IRQF_DISABLED?!

I will prepare a patch for both (i.e. fixing the at91 ISRs and the
warning about IRQF_DISABLED | IRQF_SHARED) but probably only on Monday.
 
Best regards
Uwe

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