linux-kernel - Re: [patch 1/2] genirq: Run irq handlers with interrupts disabled

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Date:	Sat, 3 Apr 2010 06:45:20 +0200
From:	Pavel Machek <pavel@....cz>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...l.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	David Miller <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [patch 1/2] genirq: Run irq handlers with interrupts disabled

On Sat 2010-04-03 00:51:20, Thomas Gleixner wrote:
> Pavel,
> 
> On Fri, 2 Apr 2010, Pavel Machek wrote:
> 
> > On Fri 2010-04-02 22:42:51, Thomas Gleixner wrote:
> > > On Fri, 2 Apr 2010, Pavel Machek wrote:
> > > 
> > > > On Wed 2010-03-31 13:16:37, Thomas Gleixner wrote:
> > > > > On Tue, 30 Mar 2010, Andi Kleen wrote:
> > > > > 
> > > > > > > Why not simply force IRQF_DISABLED for all MSI interrupts. That still
> > > > > > > allows nesting for non MSI ones, but it limits the chance of throwing
> > > > > > > up reasonably well. That's a two liner.
> > > > > > > 
> > > > > > > Can you please test whether it resolves the issue at hand ?
> > > > > > 
> > > > > > Sorry for the late answer. Got confirmation that this patch
> > > > > > fixes the test case. Thanks.
> > > > > 
> > > > > Ok, I'll push it linus wards and cc stable. I think thats the least
> > > > > intrusive safe bet we can have right now.
> > > > 
> > > > stable? I'd say thats way too intrusive for -stable...
> > > 
> > > So we better let the possible stack overruns unaddressed ?
> > 
> > -stable should have no regressions, first and foremost. And this is
> > pretty certain to introduce some, at least on low-powered system with
> > serial ports.
> 
> I think you misunderstood what I'm going to push. The patch merily
> forces IRQF_DISABLED for MSI(X) based interrupts. So that does not
> affect low powered systems in any way.
> 
> It only affects high end systems where Dave Miller already said he did
> the IRQF_DISABLED magic already in some NIC drivers just to prevent
> that.

Oops, yes, I did; lost in all the mails.

> So I think your fear of regressions for low-powered systems is
> completely unsubstantiated.

Yep. Sorry for the noise.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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