linux-kernel - Re: [RFC][PATCH 02/13 v2] ftrace: Consolidate arch dependent functions with list function

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Date:	Fri, 15 Jun 2012 12:02:45 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [RFC][PATCH 02/13 v2] ftrace: Consolidate arch dependent functions
 with list function

(2012/06/13 7:43), Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@...hat.com>
> 
> As the function tracer starts to get more features, the support for
> theses features will spread out throughout the different architectures
> over time. These features boil down to what each arch does in the
> mcount trampoline (the ftrace_caller).
> 
> Currently there's two features that are not the same throughout the
> archs.
> 
>  1) Support to stop function tracing before the callback
>  2) passing of the ftrace ops
> 
> Both of these require placing an indirect function to support the
> features if the mcount trampoline does not.
> 
> On a side note, for all architectures, when more than one callback
> is registered to the function tracer, an intermediate 'list' function
> is called by the mcount trampoline to iterate through the callbacks
> that are registered.
> 
> Instead of making a separate function for each of these features,
> and requiring several indirect calls, just use the single 'list' function
> as the intermediate, to handle all cases. If an arch does not support
> the 'stop function tracing' or the passing of ftrace ops, just force
> it to use the list function that will handle the features required.

Ah, I see. so even if the arch doesn't support passing ftrace_ops in
mcount trampoline, this ensures that the correct ftrace_ops should
be passed to the handlers.

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thank you,


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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