linux-kernel - Re: [PATCH v2 1/2] Replace if statement with WARN_ON_ONCE() in cmci

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Date:	Tue, 23 Oct 2012 10:55:13 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Borislav Petkov <bp@...en8.de>, Borislav Petkov <bp@...64.org>,
	tony.luck@...el.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, miaox@...fujitsu.com, laijs@...fujitsu.com,
	wency@...fujitsu.com, x86@...nel.org, linux-edac@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] Replace if statement with WARN_ON_ONCE() in cmci_rediscover().

On 10/22/2012 06:14 PM, Borislav Petkov wrote:
> On Mon, Oct 22, 2012 at 10:10:24AM +0800, Tang Chen wrote:
>> I don't why before we just jumped over it. But I think if we have an
>> online cpu == dying here, it must be wrong. So I think we should warn
>> it, not just jump over it.
>
> Why do we need to warn? What good would that bring us?
>
> AFAICT, the check in cmci_rediscover is there to make sure we absolutely
> don't rediscover on the dying cpu. I think it is a safety precaution in
> concurrency scenarios between cpu hotplug and mce code.

Well, I see. I dropped the if statement. :)

So, how about warn once, and continue:
	if (cpu == dying) {
		WARN_ON_ONCE(cpu == dying);
		continue;
	}

or, use BUG_ON() instead ?

>
> Thanks.
>

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