linux-kernel - Re: [PATCH -v2 2/2] x86, MCE: Drop the default decoding notifier

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Date:	Tue, 26 Apr 2011 14:06:39 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Borislav Petkov <bp@...64.org>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	EDAC devel <linux-edac@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Nagananda Chumbalkar <Nagananda.Chumbalkar@...com>,
	Russ Anderson <rja@....com>
Subject: Re: [PATCH -v2 2/2] x86, MCE: Drop the default decoding notifier

Borislav Petkov <bp@...64.org> writes:

> On Mon, Apr 25, 2011 at 03:40:11PM -0400, Eric W. Biederman wrote:
>> > From: Borislav Petkov <borislav.petkov@....com>
>> > Date: Wed, 13 Apr 2011 14:32:06 +0200
>> > Subject: [PATCH -v2.1 2/2] x86, MCE: Drop the default decoding notifier
>> >
>> > The default notifier doesn't make a lot of sense to call in the
>> > correctable errors case. Drop it and emit the mcelog decoding hint only
>> > in the uncorrectable errors case and when no notifier is registered.
>> > Also, limit issuing the "mcelog --ascii" message in the rare case when
>> > we dump unreported CEs before panicking.
>> >
>> > While at it, remove unused old x86_mce_decode_callback from the
>> > header.
>> 
>> Can we please print something if we please log something in the
>> case of a correctable error, when we only report it via mcelog?
>> 
>> I have a stupid recent intel cpu here that hits that case and without
>> the default x86_mce_decode_callback I wouldn't have even known that I am
>> getting something like 50 correctable errors an hour on one of my
>> machines.  In particular I am it hits so often I am seeing:
>> "mce_notify_irq: 2 callbacks suppressed".  I need to get those dimms
>> replaced soon because in a new product I simply can't imagine that many
>> correctable errors.
>
> Isn't there a mcelog daemon or something that polls /dev/mcelog and
> tells you about those DRAM ECCs in some log file where you're supposed
> to look? :)

On fedora 14 there is a cron job that writes to /var/log/mcelog, and
does not go through syslog.  But you have to be proactive and look
there.  If the people who work on this code can't even remember
where to look I can't imagine how anyone else can remember.
Which is why I object to the removal of the one printk that told
me something was broken on my machine.

So far from what I have seen /dev/mcelog and the userspace mcelog is
over complicated and near useless.  It seems to focused around the
notion that "This is not a software problem, please do not bug
Andi Kleen about it"

Well it is a hardware problem so I do need to RMA that hardware.
Sigh.

Eric

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