linux-kernel - Re: Hardware Error Kernel Mini-Summit

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Date:	Wed, 19 May 2010 00:29:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Borislav Petkov <bp@...64.org>, "Luck, Tony" <tony.luck@...el.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	"Young, Brent" <brent.young@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Matt Domsch <Matt_Domsch@...l.com>,
	Doug Thompson <dougthompson@...ssion.com>,
	Joe Perches <joe@...ches.com>,
	"bluesmoke-devel@...ts.sourceforge.net" 
	<bluesmoke-devel@...ts.sourceforge.net>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Edac Mailing List <linux-edac@...r.kernel.org>
Subject: Re: Hardware Error Kernel Mini-Summit


* Eric W. Biederman <ebiederm@...ssion.com> wrote:

> > [...]
> >
> > Concerning critical errors, there we bypass the perf 
> > subsystem and execute the smallest amount of code 
> > possible while trying to shutdown gracefully if the 
> > error type allows that.
> >
> > These are the rough ideas at least...
> 
> Can someone please tell me why everyone is eager to 
> squirrel correctable error reports away and not report 
> them in dmesg? aka syslog.
> 
> I have had on several occasions a machine with memory 
> errors that mcelog or the BIOS was eating the error 
> reports and not putting them anywhere a normal human 
> being would look.

That's possible too - the TRACE_EVENT() of MCE events, 
beyond the record format, also includes a human-readable 
ASCII output format string:

 # tail -1 /debug/tracing/events/mce/mce_record/format

 print fmt: "CPU: %d, MCGc/s: %llx/%llx, MC%d: %016Lx, 
 ADDR/MISC: %016Lx/%016Lx, RIP: %02x:<%016Lx>, TSC: %llx, 
 PROCESSOR: %u:%x, TIME: %llu, SOCKET: %u, APIC: %x", 
 REC->cpu, REC->mcgcap, REC->mcgstatus, REC->bank, 
 REC->status, REC->addr, REC->misc, REC->cs, REC->ip, 
 REC->tsc, REC->cpuvendor, REC->cpuid, REC->walltime, 
 REC->socketid, REC->apicid

Which could be used to printk events.

Cheers,

	Ingo
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