linux-kernel - Re: [PATCH v2 1/5] printk/nmi: Generic solution for safe printk in NMI

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Message-ID: <20151204165744.GD20935@pathway.suse.cz>
Date:	Fri, 4 Dec 2015 17:57:44 +0100
From:	Petr Mladek <pmladek@...e.com>
To:	Jiri Kosina <jikos@...nel.org>
Cc:	kbuild test robot <lkp@...el.com>, kbuild-all@...org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-cris-kernel@...s.com, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
	David Howells <dhowells@...hat.com>,
	Koichi Yasutake <yasutake.koichi@...panasonic.com>,
	linux-am33-list@...hat.com
Subject: Re: [PATCH v2 1/5] printk/nmi: Generic solution for safe printk in
 NMI

On Wed 2015-12-02 00:24:49, Jiri Kosina wrote:
> On Fri, 27 Nov 2015, Petr Mladek wrote:
> 
> > MN10300 has its own implementation for entering and exiting NMI 
> > handlers. It does not call nmi_enter() and nmi_exit(). Please, find 
> > below an updated patch that adds printk_nmi_enter() and 
> > printk_nmi_exit() to the custom entry points. Then we could add HAVE_NMI 
> > to arch/mn10300/Kconfig and avoid the above warning.
> 
> Hmm, so what exactly would go wrong if MN10300 (whatever that architecture 
> is) would call nmi_enter() and nmi_exit() at the places where it's 
> starting and finishing NMI handler?
> 
> >From a cursory look, it seems like most (if not all) of the things called 
> from nmi_{enter,exit}() would be nops there anyway.

Good point. Max mentioned in the other main that the NMI handler
should follow the NMI ruler. I do not why it could not work.
In fact, it might improve things, e.g. nmi_enter() blocks
recursive NMIs.

I think that it will move it into a separate patch, thought.

Best Regards,
Petr
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