Re: [PATCH v2 3/4] ftrace: Have funcgraph-args take affect during tracing

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Mon, 23 Dec 2024 15:13:50 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt <rostedt@goodmis.org>
> 
> Currently, when function_graph is started, it looks at the option
> funcgraph-args, and if it is set, it will enable tracing of the arguments.
> 
> But if tracing is already running, and the user enables funcgraph-args, it
> will have no effect. Instead, it should enable argument tracing when it is
> enabled, even if it means disabling the function graph tracing for a short
> time in order to do the transition.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>


> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/trace_functions_graph.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index c8eda9bebdf4..d1ee001f5a8e 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -469,7 +469,7 @@ static int graph_trace_init(struct trace_array *tr)
>  	else
>  		tr->gops->retfunc = trace_graph_return;
>  
> -	/* Make gops functions are visible before we start tracing */
> +	/* Make gops functions visible before we start tracing */
>  	smp_mb();
>  
>  	ret = register_ftrace_graph(tr->gops);
> @@ -480,6 +480,28 @@ static int graph_trace_init(struct trace_array *tr)
>  	return 0;
>  }
>  
> +static int ftrace_graph_trace_args(struct trace_array *tr, int set)
> +{
> +	trace_func_graph_ent_t entry;
> +
> +	if (set)
> +		entry = trace_graph_entry_args;
> +	else
> +		entry = trace_graph_entry;
> +
> +	/* See if there's any changes */
> +	if (tr->gops->entryfunc == entry)
> +		return 0;
> +
> +	unregister_ftrace_graph(tr->gops);
> +
> +	tr->gops->entryfunc = entry;
> +
> +	/* Make gops functions visible before we start tracing */
> +	smp_mb();
> +	return register_ftrace_graph(tr->gops);
> +}
> +
>  static void graph_trace_reset(struct trace_array *tr)
>  {
>  	tracing_stop_cmdline_record();
> @@ -1609,6 +1631,9 @@ func_graph_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
>  	if (bit == TRACE_GRAPH_GRAPH_TIME)
>  		ftrace_graph_graph_time_control(set);
>  
> +	if (bit == TRACE_GRAPH_ARGS)
> +		return ftrace_graph_trace_args(tr, set);
> +
>  	return 0;
>  }
>  
> -- 
> 2.45.2
> 
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>