linux-kernel - Re: irq 16: nobody cared

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Date:	Mon, 22 Apr 2013 06:16:44 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>, x86-ml <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>, tiwai@...e.de,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: irq 16: nobody cared

On Mon, Apr 22, 2013 at 11:18:47AM +0200, Borislav Petkov wrote:
> On Mon, Apr 22, 2013 at 10:01:36AM +0200, Ingo Molnar wrote:
> > Hm, this really smells like a workaround: treating the symptom, not
> > the cause.
> 
> Well, I just tested Takashi's add missing synchronize_irq() to the
> suspend path of snd_hda_intel and it doesn't help.
> 
> So it could be an issue with this driver or only this hw/driver can
> exacerbate RCU this much to trigger the spurious irq machinery.
> 
> > How can an increase in grace-periods break drivers and suspend? Do we
> > understand exactly what happens there?
> 
> I'd rather look into Paul's direction here. :)

I believe that we need both -- a fix that prevents the stray irq for
normal CONFIG_RCU_FAST_NO_HZ grace periods and also expediting grace
periods during suspend/resume.  I am greedy that way.  ;-)

						Thanx, Paul

> > If we do, can we fix that instead of tweaking the RCU timeouts?
> 
> Well, I was under the impression yesterday that we actually want
> to switch to expedited grace periods for suspend/resume *anyway*,
> regardless of drivers.
> 
> Paul?
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --
> 

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