[PATCH 4.0-rc1 v17 4/6] printk: Simple implementation for NMI backtracing

Daniel Thompson daniel.thompson at linaro.org
Wed Mar 4 08:33:06 PST 2015

On Wed, 2015-03-04 at 11:20 -0500, Steven Rostedt wrote:
> On Wed, 04 Mar 2015 08:13:21 -0800
> Joe Perches <joe at perches.com> wrote:
> > On Wed, 2015-03-04 at 10:12 +0000, Daniel Thompson wrote:
> > > Currently there is a quite a pile of code sitting in
> > > arch/x86/kernel/apic/hw_nmi.c to support safe all-cpu backtracing from NMI.
> > > The code is inaccessible to backtrace implementations for other
> > > architectures, which is a shame because they would probably like to be
> > > safe too.
> > > 
> > > Copy this code into printk. We'll port the x86 NMI backtrace to it in a
> > > later patch.
> > 
> > I think this would be better as a separate file
> > rather than increasing the bulk of printk.c
> > 
> I agree, as printk already has its own directory. Perhaps a
> "nmi_backtrace.c"?

I agree on moving the code. However, after Thomas' review I made sure
all the external symbols were prefixed printk_nmi and, as a result of
the same review I started using CONFIG_PRINTK_NMI to enable/disable the
feature). For that reason I'm much more inclined to name it
"printk_nmi.c". Any objections?

I know it is a somewhat generic name but I'll move the comment text that
commences "This is not a generic printk() implementation and must be
used with great care. In particular..." to the top of the file to make
clear the limitations of this code.


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