linux-kernel - RE: [v2 PATCH 1/3] panic: Change nmi

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Date:	Thu, 3 Mar 2016 01:28:53 +0000
From:	河合英宏 / KAWAI，HIDEHIRO 
	<hidehiro.kawai.ez@...achi.com>
To:	"'Borislav Petkov'" <bp@...en8.de>,
	Michal Hocko <mhocko@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Mingarelli <thomas.mingarelli@....com>,
	Wim Van Sebroeck <wim@...ana.be>,
	Corey Minyard <minyard@....org>,
	Javi Merino <javi.merino@....com>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	"Vitaly Kuznetsov" <vkuznets@...hat.com>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Gobinda Charan Maji <gobinda.cemk07@...il.com>,
	Tejun Heo <tj@...nel.org>,
	Nicolas Iooss <nicolas.iooss_linux@....org>,
	"openipmi-developer@...ts.sourceforge.net" 
	<openipmi-developer@...ts.sourceforge.net>,
	Borislav Petkov <bp@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Guenter Roeck <linux@...ck-us.net>
Subject: RE: [v2 PATCH 1/3] panic: Change nmi_panic from macro to function

Hi,

> From: Borislav Petkov [mailto:bp@...en8.de]
> On Wed, Mar 02, 2016 at 02:18:24PM +0100, Michal Hocko wrote:
> > On Wed 02-03-16 19:36:26, Hidehiro Kawai wrote:
> > [...]
> > > +void nmi_panic(struct pt_regs *regs, const char *fmt, ...)
> >
> > Do we really need vargs? All the current users seem to be OK with a
> > simple string. This makes the code slightly more complicated without any
> > apparent reason.
> 
> I was just wondering the exactly same thing...
> 
> The contra-arg would be that in case someone wants to do nmi_panic()
> with more than a string, then it won't work.

It's not necessary to use vargs at this point, and passing a simple
string is OK for me.  Even if someone wants to use vargs, we can modify
nmi_panic() without any changes in caller side.  So, I'll remove it.

> The question is, does nmi_panic() even need to dump something more than
> regs and a string?

Hmm, printing regs, especially for RIP, would be useful for hang-up
cases, but I don't want to do much things in nmi_panic() as long as
it is already done by current callers.  nmi_panic() can be called
concurrently on multiple CPUs, so it also needs another serialization
to print something.

By the way, I have a patch set to safely leave important information
by kexec's purgatory...but no one is interested in?
http://thread.gmane.org/gmane.linux.kernel.kexec/15382

Regards,
--
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group