Re: Hardware Error Kernel Mini-Summit

From: Ingo Molnar
Date: Tue May 18 2010 - 18:00:37 EST

* Tony Luck <tony.luck@xxxxxxxxx> wrote:

> > This gives us a broad platform to add various RAS
> > events as well, beyond raw hardware events: we could
> > for example events for various system anomalies such
> > as lockup messages, kernel warnings/oopses, IOMMU
> > exceptions - maybe even pure software concepts such as
> > fatal segmentation fault events, etc. etc.
> This looks like sticky ground. I can see the event
> mechanism passing data to a user daemon working well for
> all kinds of corrected and minor errors. But when you
> start talking about lockups and fatal errors things get
> a lot trickier. Often the main concern at this point is
> error containment. Making sure that the flaky data
> doesn't become visible (saved to storage, transmitted to
> the network, etc.). [...]

I was pointing beyond the narrow hardware (memory) error
point of view, towards a more generic 'system health'

In the broader view it may makes sense to for example
define policy over excessive number of segfaults on a
server system (where excessive segfaults are an anomaly),
or a suspiciously large number of soft IO errors, etc.

But yes, of course, when it comes to hard memory errors,
those take precedence, and handling them (and
saving/propagating information about them while we still
can) is a priority.

> [...] Getting from a machine check handler through some
> context switches (and page faults etc.) to a user level
> daemon before the error gets recorded looks to be really
> hard.

As Boris mentioned it too, critical policy action can and
will be done straight in the kernel.

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