linux-kernel - Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send

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Message-ID: <20130520064727.GD12690@pd.tnic>
Date:	Mon, 20 May 2013 08:47:27 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	Tejun Heo <tj@...nel.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123
 native_smp_send_reschedule, round 2

On Mon, May 20, 2013 at 02:23:37PM +0800, Michael Wang wrote:
> On 05/20/2013 12:50 PM, Borislav Petkov wrote:
> > On Mon, May 20, 2013 at 11:16:33AM +0800, Michael Wang wrote:
> >> I suppose the reason is that the cpu we passed to
> >> mod_delayed_work_on() has a chance to become offline before we
> >> disabled irq, what about check it before send resched ipi? like:
> > 
> > I think this is only addressing the symptoms - what we should be doing
> > instead is asking ourselves why are we even scheduling work on a cpu if
> > the machine goes offline?
> > 
> > I don't know though who should be responsible for killing all that
> > work - the workqueue itself or the guy who created it, i.e. cpufreq
> > governor...
> 
> So there are two questions here:
> 1. Is gov_queue_work() want to queue the work on offline cpu?
> 2. Is mod_delayed_work_on() allow offline cpu?
> 
> I guess both should be false?

Well, if we don't allow queueing work on a cpu which goes offline, i.e.
#2, the problem should be solved.

Tejun?

Here are the splats: http://marc.info/?l=linux-kernel&m=136879901425951

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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