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Re: [PATCH -v5 08/11] tracing: not trace mips_timecounter_init() in MIPS

To: Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH -v5 08/11] tracing: not trace mips_timecounter_init() in MIPS
From: Wu Zhangjin <wuzhangjin@gmail.com>
Date: Tue, 03 Nov 2009 09:34:25 +0800
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, Thomas Gleixner <tglx@linutronix.de>, Ralf Baechle <ralf@linux-mips.org>, Nicholas Mc Guire <der.herr@hofr.at>, Richard Sandiford <rdsandiford@googlemail.com>, David Daney <ddaney@caviumnetworks.com>, Adam Nemet <anemet@caviumnetworks.com>, Patrik Kluba <kpajko79@gmail.com>
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Hi,

On Mon, 2009-11-02 at 22:43 +0100, Frederic Weisbecker wrote:
[...]
> > > > -static inline u64 mips_timecounter_read(void)
> > > > +static inline u64 notrace mips_timecounter_read(void)
> > > 
> > > 
> > > You don't need to set notrace functions, unless their addresses
> > > are referenced somewhere, which unfortunately might happen
> > > for some functions but this is rare.
> > > 
> > 
> > Okay, Will remove it.
> 
> 
> 
> Oops, a word has escaped from my above sentence. I wanted to say:
> 
> "You don't need to set notrace to inline functions" :)
> 
> 

Thanks ;)

I have got your meaning at that time, and have removed them with inline
functions.

> > > But I would rather see a __mips_notrace on these two core functions.
> > 
> > What about this: __arch_notrace? If the arch need this, define it,
> > otherwise, ignore it! if only graph tracer need it, define it in "#ifdef
> > CONFIG_FUNCTION_GRAPH_TRACER ... #endif".
> 
> The problem is that archs may want to disable tracing on different
> places.
> For example mips wants to disable tracing in timecounter_read_delta,
> but another arch may want to disable tracing somewhere else.
> 
> We'll then have several unrelated __arch_notrace. One that is relevant
> for mips, another that is relevant for arch_foo, but all of them will
> apply for all arch that have defined a __arch_notrace.
> 
> It's true that __mips_notrace is not very elegant as it looks like
> a specific arch annotation intruder.
> 
> But at least that gives us a per arch filter granularity.
> 
> If only static ftrace could disappear, we could keep only dynamic
> ftrace and we would then be able to filter dynamically.
> But I'm not sure it's a good idea for archs integration.
> 

Got it.

Thanks & Regards,
        Wu Zhangjin


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