linux-kernel - Re: [PATCH 4.0-rc1 v17 5/6] x86/nmi: Use common printk functions

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Date:	Thu, 05 Mar 2015 12:29:57 +0000
From:	Daniel Thompson <daniel.thompson@...aro.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Russell King <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	John Stultz <john.stultz@...aro.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	patches@...aro.org, linaro-kernel@...ts.linaro.org,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Dirk Behme <dirk.behme@...bosch.com>,
	Daniel Drake <drake@...lessm.com>,
	Dmitry Pervushin <dpervushin@...il.com>,
	Tim Sander <tim@...eglstein.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH 4.0-rc1 v17 5/6] x86/nmi: Use common printk functions

On Thu, 2015-03-05 at 01:54 +0100, Ingo Molnar wrote:
> * Daniel Thompson <daniel.thompson@...aro.org> wrote:
> 
> > Much of the code sitting in arch/x86/kernel/apic/hw_nmi.c to support 
> > safe all-cpu backtracing from NMI has been copied to printk.c to 
> > make it accessible to other architectures.
> > 
> > Port the x86 NMI backtrace to the generic code.
> 
> Is there any difference between the generic and the x86 code as they 
> stand today?

Shouldn't be any user observable change but there are some changes,
mostly due to review comments.

1. The seq_buf structures are initialized at boot and *after* they
   are consumed (originally they were initialized just before use).

2. The generic code doesn't maintain an equivalent of backtrace_mask
   (which was essentially a copy of cpus_online made when backtracing
   was requested) and instead iterates using for_each_possible_cpu()
   to initialize and dump the seq_buf:s.

Daniel.

PS
The main piece that git code motion tracking should follow if I squashed
the generic and x86 patches together would be nmi_vprintk(). I suspect
most of the rest would be missed as the code copies is in pretty small
fragments.

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