linux-kernel - Re: x86/mce merge, integration hickup + crash, design thoughts

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Date:	Wed, 14 Jan 2009 10:02:21 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: x86/mce merge, integration hickup + crash, design thoughts

On Wed, 2009-01-14 at 01:45 +0800, Ingo Molnar wrote:
> * Andi Kleen <ak@...ux.intel.com> wrote:
> 
> > Ingo Molnar wrote:
> >
> >>>> A far more useful design for handling MCE events would be to feed 
> >>>> them into printk logging.
> >>> If there's ASCII logging it should be separate from normal printk.
> >>
> >> Well, why? 
> >
> > Mostly because the problem is not a kernel issue. Especially large 
> > systems with a lot of memory can generate a lot of corrected events (one 
> > bit flips in DIMMs are not that uncommon) and it's not good to mix that 
> > all up into other kernel messages. It also makes it more clear that it's 
> > not a kernel problem, but a hardware problem. I've got feedback over the 
> > years that confirm this sight.
> 
> Is your argument that syslog is not suitable for the logging of hw events?
> 
> If that is your argument then the answer is to extend syslog with those 
> aspects, instead of widening the quirky /dev based mce ABIs to achieve 
> something similar.

In current /dev based mce ABI implementation, syslog is used for logging
hw events, not though printk, but through /dev/mcelog and /sbin/mcelog.

For uncorrected MCE, they should be logged via printk. But for corrected
MCE, there could be thousands/millions ones (imagining you have a DIMM
with one data pin corrupted). I don't think it's a good idea to blend
these hardware events with other kernel software events in printk.

Best Regards,
Huang Ying


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