linux-kernel - RE: [PATCH 4/4] x86, mce: Have MCE persistent event off by default for now

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Date:	Wed, 4 May 2011 14:40:37 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Borislav Petkov <bp@...64.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	EDAC devel <linux-edac@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Petkov, Borislav" <Borislav.Petkov@....com>
Subject: RE: [PATCH 4/4] x86, mce: Have MCE persistent event off by default
 for now

> Yes, i definitely think a gateway to printk would be useful, so that the system 
> can log MCE events the syslog way as well. This probably makes sense for 
> persistent events in general, not just MCE events.

s/as well/instead/ ??? If the persistent event mechanism is correctly feeding
data to a mart daemon, I don't think we need any printk() chatter. It is only
if this is not working that we'd want to see some console logging.

I agree that this isn't just a property of the MCE persistent event - other
persistent events would very likely want a way to shout for help if the events
are piling up with no listener.

> printk itself could become a persistent event. (Transparently and without 
> breaking compatible syslogd/klogd functionality.)

Someone from Google was very skeptical of printk() remaining stable from
release to release ... a big issue when you have some heavy duty infrastructure
trying to parse and consume these messages.  We should really consider such
stuff a user visible ABI, and thus not subject to random breakage - which
is a radical departure from our current attitude to printk().

-Tony
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