linux-kernel - Re: [RFC][PATCH 07/14] fgraph: Add new fgraph_ops structure to enable function graph hooks

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Message-Id: <20181126203049.88df7c2cafed2b30a9d02bb9@kernel.org>
Date:   Mon, 26 Nov 2018 20:30:49 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Andy Lutomirski <luto@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC][PATCH 07/14] fgraph: Add new fgraph_ops structure to
 enable function graph hooks

On Wed, 21 Nov 2018 20:27:15 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> Currently the registering of function graph is to pass in a entry and return
> function. We need to have a way to associate those functions together where
> the entry can determine to run the return hook. Having a structure that
> contains both functions will facilitate the process of converting the code
> to be able to do such.
> 
> This is similar to the way function hooks are enabled (it passes in
> ftrace_ops). Instead of passing in the functions to use, a single structure
> is passed in to the registering function.
> 
> The unregister function is now passed in the fgraph_ops handle. When we
> allow more than one callback to the function graph hooks, this will let the
> system know which one to remove.
> 
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  include/linux/ftrace.h               | 24 +++++++++++++++++-------
>  kernel/trace/fgraph.c                |  9 ++++-----
>  kernel/trace/ftrace.c                | 10 +++++++---
>  kernel/trace/trace_functions_graph.c | 21 ++++++++++++++++-----
>  kernel/trace/trace_irqsoff.c         | 10 +++++++---
>  kernel/trace/trace_sched_wakeup.c    | 10 +++++++---
>  kernel/trace/trace_selftest.c        |  8 ++++++--
>  7 files changed, 64 insertions(+), 28 deletions(-)
> 
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index f98063e273e5..477ff9412d26 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -749,6 +749,18 @@ typedef int (*trace_func_graph_ent_t)(struct ftrace_graph_ent *); /* entry */
>  
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  
> +struct fgraph_ops {
> +	trace_func_graph_ent_t		entryfunc;
> +	trace_func_graph_ret_t		retfunc;

> +	struct fgraph_ops __rcu		*next;
> +	unsigned long			flags;
> +	void				*private;
> +#ifdef CONFIG_DYNAMIC_FTRACE
> +	struct ftrace_ops_hash		local_hash;
> +	struct ftrace_ops_hash		*func_hash;
> +#endif

Hmm, can we introduce these fields when we actually use it?

BTW, would you have any idea for using private field?

Thank you,




-- 
Masami Hiramatsu <mhiramat@...nel.org>