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Date: Thu, 24 Jul 2008 18:31:51 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Martin Wilck <martin.wilck@fujitsu-siemens.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "H. Peter Anvin" <hpa@zytor.com>,
       "Wichert, Gerhard" <Gerhard.Wichert@fujitsu-siemens.com>,
       "Maciej W. Rozycki" <macro@linux-mips.org>
Subject: Re: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe
Message-ID: <20080724143151.GA32422@lenovo>
References: <48885DDC.9010003@fujitsu-siemens.com> <20080724111631.GA3432@lenovo> <48886E6D.1030005@fujitsu-siemens.com> <20080724120512.GA21804@lenovo> <488889B6.9070707@fujitsu-siemens.com>
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[Martin Wilck - Thu, Jul 24, 2008 at 03:55:02PM +0200]
> Cyrill Gorcunov wrote:
>
>> yes, it will issue some effects but it's better then stuck there.
>> More over in 'case of SMI flood with current patch you don't get
>> error message printed i think so you better add max iteration
>> counter so user will see on console (or whatever) that he is got
>> problems.
>>                 - Cyrill -
>
> I disagree. If you have a system that generates SMIs in this extreme  
> frequency, you're better off stuck than running on such an unstable  
> system. The user _will_ see messages on the console if this happens.  
> Note that apparently there are few people who have trouble with this. We  
> did see problems, but never had more than 1 SMI disturbing the  
> calibration procedure.
>
> Anyway, here is another patch that defines max iteration counts. I  
> haven't added a "Signed-off:" line, because I prefer the original 
> version.
>
> Martin
>

yes, Martin, it'll be written on console (just forgot it's not interrupt
driven). I've Cc'ed Maciej in previous message so we should better wait
for his opinion I think. For me the almost ideal solution could be like -
lets user to choose what he wants. I mean you even could add some boot
param to specify behaviour on a such case like panic on SMI flood during
calibration. yes - if we got smi flood we have serious troubles anyway but
i don't think that being just stuck is good choise. And that is why I do like
much more _this_ patch. Anyway - thanks!

		- Cyrill -
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