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

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Message-ID: <alpine.LFD.2.00.1004030046160.32352@localhost.localdomain>
Date:	Sat, 3 Apr 2010 00:51:20 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Pavel Machek <pavel@....cz>
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

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.

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

Thanks,

	tglx

 
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