linux-kernel - Re: [PATCH] genirq: handle_fasteoi_irq vs IRQ_INPROGRESS && IRQ

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Message-ID: <20070821112157.GA20396@ff.dom.local>
Date:	Tue, 21 Aug 2007 13:21:57 +0200
From:	Jarek Poplawski <jarkao2@...pl>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq: handle_fasteoi_irq vs IRQ_INPROGRESS && IRQ_DISABLED

On Tue, Aug 21, 2007 at 12:35:27PM +0200, Jarek Poplawski wrote:
> On Tue, Aug 21, 2007 at 11:17:00AM +0200, Jarek Poplawski wrote:
> > 
> > Hi,
> > 
> > I've still some doubts about these irq handlers and I hope somebody
> > could explain some of these (despite my problems with earlier such
> > explanations, sorry...):
> > 
> > 1. According to some well-known Intel's manual (vol.3A page 8-41)
> > lapic can interrupt irq handler dispatching higher-priority irq; it
> > seems, such an event is possible during handle_IRQ_event, and would
> > be treated by "common" handlers with IRQ_INPROGRESS; but:
> 
> OOPS!!! Of course, I got this wrong again: this IRQ_INPROGRESS is
> for another irq... Sorry!
> 
> But, then, it seems such IRQ_INPROGRESS shouldn't be possible at all
> with properly working lapic? Or do I miss something...

I see... So, it's possible for handle_level_irq and handle_edge_irq
because of this early acking. (Then unmasking should work OK and my
1.a is invalid.)

But handle_fasteoi_irq? If it really needs IRQ_INPROGRESS check, this
patch, and maybe something more, seems needed too.

Jarek P.
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