Date: Fri, 18 Mar 2016 11:03:06 +0100
From: Petr Mladek <pmladek@suse.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>, kbuild test robot <lkp@intel.com>,
        kbuild-all@01.org, Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Russell King <rmk+kernel@arm.linux.org.uk>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        linux-arm-kernel@lists.infradead.org,
        adi-buildroot-devel@lists.sourceforge.net, linux-cris-kernel@axis.com,
        linux-mips@linux-mips.org, linuxppc-dev@lists.ozlabs.org,
        linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
        sparclinux@vger.kernel.org, David Howells <dhowells@redhat.com>,
        Koichi Yasutake <yasutake.koichi@jp.panasonic.com>,
        linux-am33-list@redhat.com
Subject: Re: [PATCH v2 1/5] printk/nmi: Generic solution for safe printk in
 NMI
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On Thu 2016-03-17 12:35:27, Andrew Morton wrote:
> On Fri, 4 Dec 2015 17:57:44 +0100 Petr Mladek <pmladek@suse.com> wrote:
> 
> > 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.
> > 
> 
> I've sort of lost the plot on this patchset.
> 
> I know Daniel had concerns (resolved?).  Sergey lost the ability to
> perform backtraces and has a proposed fix ("printk/nmi: restore
> printk_func in nmi_panic") but that wasn't fully resolved and I didn't
> merge anything.  I'm not sure what Jan's thinking is on it all.
> 
> So... I'll retain 
> 
> printk-nmi-generic-solution-for-safe-printk-in-nmi.patch
> printk-nmi-use-irq-work-only-when-ready.patch
> printk-nmi-warn-when-some-message-has-been-lost-in-nmi-context.patch
> printk-nmi-increase-the-size-of-nmi-buffer-and-make-it-configurable.patch
> 
> in -mm for now.  Perhaps I should drop them all and we start again
> after -rc1?

Please, drop it for now. I'll send an updated version that will better
handle Daniel's concerns after rc1.

I thought that it had already been decided. You wanted to remove the patchset
in favour of "improvements to the nmi_backtrace code" by Chris Metcalf, see
http://thread.gmane.org/gmane.linux.ports.arm.kernel/482845/focus=483002

Best Regards,
Petr