linux-kernel - Re: [NAK] Re: [PATCH -v2 9/9] ACPI, APEI, Generic Hardware Error Source POLL/IRQ/NMI notification type support

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Message-ID: <20101026100329.GB16552@elte.hu>
Date:	Tue, 26 Oct 2010 12:03:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Borislav Petkov <petkovbb@...glemail.com>,
	"H. Peter Anvin" <hpa@...or.com>, Don Zickus <dzickus@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	"Luck, Tony" <tony.luck@...el.com>
Subject: Re: [NAK] Re: [PATCH -v2 9/9] ACPI, APEI, Generic Hardware Error
 Source POLL/IRQ/NMI notification type support


* Huang Ying <ying.huang@...el.com> wrote:

> On Tue, 2010-10-26 at 15:55 +0800, Ingo Molnar wrote:
> > * Huang Ying <ying.huang@...el.com> wrote:
> > 
> > > On Tue, 2010-10-26 at 15:22 +0800, Ingo Molnar wrote:
> > > > * Thomas Gleixner <tglx@...utronix.de> wrote:
> > > > 
> > > > > >From Kconfig:
> > > > > 
> > > > >   EDAC is designed to report errors in the core system.
> > > > >   These are low-level errors that are reported in the CPU or
> > > > >   supporting chipset or other subsystems:
> > > > >   memory errors, cache errors, PCI errors, thermal throttling, etc..
> > > > >   If unsure, select 'Y'.
> > > > > 
> > > > > So please explain why your error reporting is so different from the above that it 
> > > > > justifies a separate facility. And you better come up with a real good explanation 
> > > > > other than we looked at EDAC and it did not fit our needs.
> > > > 
> > > > Btw., it's not just about EDAC - the firmware can store Linux events 
> > > > persistently (beyond allowing the firmware to insert its own RAS events), that 
> > > > is obviously _hugely_ useful for kernel debugging in general. We could inject 
> > > > debugging events there and recover them after a crash, etc.
> > > 
> > > Yes. It can be used by other kernel subsystems other than RAS. A kernel API is 
> > > provided already. The design of the kernel API makes it easy to be used by various 
> > > kernel subsystems. As the first step, we plan to support saving kernel log before 
> > > panic and reading it back after reboot.
> > 
> > And that's the problem: we have good facilities already that deal with similar 
> > things. We have NMI-safe event logging, event enumeration, dump-on-panic code 
> > and all sorts of goodies there.
> 
> We have provided an in-kernel API for ERST now. And we plan to implement a 
> kmsg_dumper with ERST. And maybe implement some output support (maybe via some 
> /dev/kmsg extension) for kmsg_dumper if necessary.

So my argument/objection was:

 " You are introducing a bad ABI here, amongst other problems. Please work with the
   people who are maintaining sane RAS/event/error reporting ABIs and facilities.
   You should have done that to begin with. "

and your answer to that is:

 " Hey, we plan to introduce another ad-hoc ABI as well! "

... do you really not see the glaring disconnect?

	Ingo
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