linux-kernel - Re: 2.6.23-rc2: WARNING: at kernel/irq/resend.c:70 check_irq

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Message-ID: <20070810083050.GA4545@elte.hu>
Date:	Fri, 10 Aug 2007 10:30:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jarek Poplawski <jarkao2@...pl>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	John Stoffel <john@...ffel.org>, linux-kernel@...r.kernel.org,
	shemminger@...ux-foundation.org, vignaud@...dmail.fr,
	marcin.slusarz@...il.com, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	linux-net@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: 2.6.23-rc2: WARNING: at kernel/irq/resend.c:70
	check_irq_resend()

* Jarek Poplawski <jarkao2@...pl> wrote:

> > Hmm. This solution is still just pampering over the real problem. 
> > The delayed disable just re-sends level interrupts unnecessarily. I 
> > have a fix (needs some testing) for this, which I send out tomorrow, 
> > when I'm really back from vacation.
> > 
> > But suppressing the resend is not fixing the driver problem. The 
> > problem can show up with spurious interrupts and with interrupts on 
> > a shared PCI interrupt line at any time. It just might take weeks 
> > instead of minutes.
> 
> Doesn't it look like a little change of mind? [...]

what change of mind do you mean exactly?

> [...] Well, there are probably (but need more testing) two other 
> solutions: _SW_RESEND and disabling without delay for levels only...

IIRC Marcin tested software-resend and it didnt fix the hang. That 
strongly points in the direction of a driver bug (or a genirq bug) being 
made more prominent by the genirq change - not any hardware detail such 
as the APIC vector-retrigger sequence.

While we'd like to see the suspected driver bug (or any higher level 
genirq bug) fixed, we'll undo the effect of the genirq change (because 
it is causing a regression). We'll also add a separate, optional 
irq-debugging feature that generates high-rate interrupts on any shared 
irq line. (and thus artificially stresses the robustness of the driver 
and the genirq layer against spurious interrupts.)

	Ingo
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