Message-ID: <50867FCD.9010907@cn.fujitsu.com>
Date: Tue, 23 Oct 2012 19:30:21 +0800
From: Tang Chen <tangchen@cn.fujitsu.com>
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To: Borislav Petkov <bp@alien8.de>, tony.luck@intel.com, tglx@linutronix.de,
        mingo@redhat.com, hpa@zytor.com, miaox@cn.fujitsu.com,
        laijs@cn.fujitsu.com, wency@cn.fujitsu.com, x86@kernel.org,
        linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] Replace if statement with WARN_ON_ONCE() in cmci_rediscover().
References: <1350625528-1385-1-git-send-email-tangchen@cn.fujitsu.com> <1350625528-1385-2-git-send-email-tangchen@cn.fujitsu.com> <20121019164045.GE11958@aftab.osrc.amd.com> <5084AB10.7010807@cn.fujitsu.com> <20121022101442.GB8352@liondog.tnic> <50860711.10807@cn.fujitsu.com> <20121023095234.GA22715@liondog.tnic>
In-Reply-To: <20121023095234.GA22715@liondog.tnic>
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On 10/23/2012 05:52 PM, Borislav Petkov wrote:
> On Tue, Oct 23, 2012 at 10:55:13AM +0800, Tang Chen wrote:
>> So, how about warn once, and continue:
>> 	if (cpu == dying) {
>> 		WARN_ON_ONCE(cpu == dying);
>> 		continue;
>> 	}
>>
>> or, use BUG_ON() instead ?
>
> Let me ask you again, but I want you to think real hard this time:
>
> "Why do we need to warn? What good would that bring us?"

Hi,

First of all, I do think I was answering your question. As I said
before, if an online cpu == dying here, there must be something wrong.
Am I right here ?

If so, I think the "good" is obvious. If we don't output anything when
an online cpu == dying, nobody will know this happens. The kernel is in
wrong state, but nobody knows that, I don't see any good.

Actually, I used BUG_ON() in my v1 patch. So I dropped the if statement.
But Tejun asked me to use WARN_ON_ONCE(). And I forgot to add the if
statement.
Please refer to https://lkml.org/lkml/2012/10/16/528

And again, the "good" is inform user the kernel is in wrong state.

Thanks. :)


>

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