Re: 2.6.23-rc2: WARNING: at kernel/irq/resend.c:70check_irq_resend()

From: Ingo Molnar
Date: Fri Aug 10 2007 - 04:56:41 EST



* Jarek Poplawski <jarkao2@xxxxx> wrote:

> > > [...] 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.)
>
> Not exactly so... I've send modified version of your software-resend
> patch, and it seems to work OK.

ah, i completely missed that! Thanks :-)

this changes the picture completely and makes the IO-APIC/local-APIC hw
retrigger code/logic the main suspect. I think you right that it's quite
bogus to hw-retrigger level irqs, and that could be confusing the
IO-APIC (or the local APIC, or both).

and i think i see why my first sw-resend patch didnt do the trick:

> > - if (!desc->chip || !desc->chip->retrigger ||
> > - !desc->chip->retrigger(irq)) {
> > + if (desc->handle_irq == handle_edge_irq) {
> > + if (desc->chip->retrigger)
> > + desc->chip->retrigger(irq);
> > + return;
> > + }
> > #ifdef CONFIG_HARDIRQS_SW_RESEND

we used the hw-resend method unconditionally, right?

Ingo
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