linux-kernel - Re: [RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED

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Message-ID: <ZvxDRzW6_5dn2_X6@hpe.com>
Date: Tue, 1 Oct 2024 13:45:27 -0500
From: Kyle Meyer <kyle.meyer@....com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: "bp@...en8.de" <bp@...en8.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED_CEC after a
 soft-offline?

On Tue, Oct 01, 2024 at 06:24:19PM +0000, Luck, Tony wrote:
> > I noticed CEC should indicate whether it took action to log or handle an error
> > by setting MCE_HANDLED_CEC (commit 1de08dc) and that EDAC and dev-mcelog should
> > skip errors that have been processed by CEC (commit 23ba710).
> >
> > cec_notifier() does not set MCE_HANDLED_CEC when the offlining threshold
> > is reached in cec_add_elem() because the return code is not zero. Is that
> > intentional?
> 
> Kyle,
> 
> It seems a bit murky. You are right that cec_add_elem() appears to expect three
> different actions from its caller based on the return value being <0, 0, >0. But
> cec_notifier() only has two actions (0 and !0).
> 
> But I think this may be OK. The main purpose of CEC is to avoid over-reacting
> to simple corrected memory errors. Many (most?) are due to particle bit flips and
> no action is needed. So setting MCE_HANDLED_CEC for the case where CEC
> counted the error, but took no action feels like the right thing to do.
> 
> Conversely, if action was taken (because this was an error that repeated
> enough to hit the threshold) the we do want mcelog/EDAC to give additional
> reporting.

That makes sense. Thank you for the explanation.

Thanks,
Kyle Meyer