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

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Message-ID: <5085F458.9080705@cn.fujitsu.com>
Date:	Tue, 23 Oct 2012 09:35:20 +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.

Hi Borislav,

As I said, cmci_rediscover() is only used to handle CPU_POST_DEAD event.
And is uses for_each_online_cpu to iterate all online cpus. If we get a
online cpu == dying, I think we are in a wrong situation. I think at
least, we should give a warning.

Thanks. :)

>
> Thanks.
>

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