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

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Date:	Mon, 20 May 2013 14:23:37 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Borislav Petkov <bp@...en8.de>
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 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?

Regards,
Michael Wang

> 
> Hmmm.
> 

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