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

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Message-ID: <20130510153148.GA9358@somewhere>
Date:	Fri, 10 May 2013 17:31:50 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Ingo Molnar <mingo@...nel.org>, Jiri Kosina <jkosina@...e.cz>,
	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123
 native_smp_send_reschedule

On Fri, May 10, 2013 at 11:45:56AM +0200, Borislav Petkov wrote:
> On Fri, May 10, 2013 at 11:37:29AM +0200, Ingo Molnar wrote:
> > The pattern I use in such cases is:
> > 
> > 	if (WARN_ONCE(!cpu_online(cpu))) {
> > 		printk("%d %d\n", cpu, smp_processor_id());
> > 		dump_stack();
> > 	}
> 
> Cool, and WARN_ONCE dumps stack already so:
> 
> 	if (WARN_ONCE(!cpu_online(cpu)))
> 		printk("%d %d\n", cpu, smp_processor_id());

Even better:

 	if (WARN_ONCE(!cpu_online(cpu)))
 		printk_once("%d %d\n", cpu, smp_processor_id());

So the printk doesn't flood after the first case.

> 
> Nice.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --
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