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

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Date:	Sat, 28 Nov 2009 22:50:02 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.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 Sat, 28 Nov 2009, Uwe Kleine-König wrote:

> 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.

What about analysing the code and verifying that the setup order is
correct ?

Adding save/restore_irq just because you have no clue what the code
does is utter nonsense.

Thanks,

	tglx