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

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Message-ID: <20121023131428.GA26756@x1.osrc.amd.com>
Date:	Tue, 23 Oct 2012 15:14:28 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Miao Xie <miaox@...fujitsu.com>
Cc:	Tang Chen <tangchen@...fujitsu.com>, tony.luck@...el.com,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.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 Tue, Oct 23, 2012 at 06:34:33PM +0800, Miao Xie wrote:
> So we add this WARN_ON_ONCE(), it can tell the developers that there
> is something wrong in the code if it is triggered.

First of all, the WARN_ON_ONCE will fire only once during system
lifetime (well, doh, of course) which diminishes debuggability
significantly and then, the only other place which deals with
CPU_POST_DEAD is kernel/stop_machine.c:cpu_stop_cpu_callback.

So, just to sum up and finish this fruitless discussion:
cmci_rediscover() correctly ignores the dying cpu and there's
*absolutely* no need to warn.

If you still think there is, you have to come up with a concrete example
and a way for others to reproduce it. Then we can talk.

End of story.

-- 
Regards/Gruss,
Boris.
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