[RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED_CEC after a soft-offline?

[RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED_CEC after a soft-offline?

[Kyle Meyer]

Hi Boris and Tony,

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?

Thanks,
Kyle Meyer

RE: [RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED_CEC after a soft-offline?

[Luck, Tony]

> 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.

-Tony

Re: [RFC] RAS/CEC: Should cec_notifier() set MCE_HANDLED_CEC after a soft-offline?

[Kyle Meyer]

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