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Message-ID: <4fa0229e-630b-4b6e-8882-3d8a5793a9dd@linaro.org>
Date: Wed, 11 Sep 2024 10:45:16 +0100
From: James Clark <james.clark@...aro.org>
To: Changbin Du <changbin.du@...wei.com>
Cc: Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
"Liang, Kan" <kan.liang@...ux.intel.com>, linux-perf-users@...r.kernel.org,
linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] perf ftrace: Detect whether ftrace is enabled on system
On 10/09/2024 04:36, Changbin Du wrote:
> To make error messages more accurate, this change detects whether ftrace is
> enabled on system by checking trace file "set_ftrace_pid".
>
> Before:
> ~ # perf ftrace
> failed to reset ftrace
>
> After:
> ~ # perf ftrace
> ftrace is not supported on this system
>
> Signed-off-by: Changbin Du <changbin.du@...wei.com>
> ---
> tools/perf/builtin-ftrace.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index eb30c8eca488..e1dc2768bc0f 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -1112,6 +1112,24 @@ static int parse_graph_tracer_opts(const struct option *opt,
> return 0;
> }
>
> +static bool is_ftrace_supported(void)
> +{
> + char *file;
> + bool supported = false;
> +
> + file = get_tracing_file("set_ftrace_pid");
> + if (!file) {
> + pr_debug("cannot get tracing file set_ftrace_pid\n");
> + return false;
> + }
> +
> + if (!access(file, F_OK))
> + supported = true;
> +
> + put_tracing_file(file);
> + return supported;
> +}
> +
> enum perf_ftrace_subcommand {
> PERF_FTRACE_NONE,
> PERF_FTRACE_TRACE,
> @@ -1254,6 +1272,12 @@ int cmd_ftrace(int argc, const char **argv)
> goto out_delete_filters;
> }
>
> + if (!is_ftrace_supported()) {
> + pr_err("ftrace is not supported on this system\n");
> + ret = -ENOTSUP;
> + goto out_delete_filters;
> + }
> +
Very minor nit, but you could probably put this earlier next to
check_ftrace_capable(). It didn't look like it used any of the config or
parsing results.
Either way:
Reviewed-by: James Clark <james.clark@...aro.org>
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