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

Masami Hiramatsu
2024-12-25T14:23:29Z

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>