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    Subject[PATCH v7 06/18] perf ftrace: add option '--inherit' to trace children processes
    Date
    This adds an option '--inherit' to allow us trace children
    processes spawned by our target.

    Signed-off-by: Changbin Du <changbin.du@gmail.com>

    ---
    v2: option name '--trace-children' -> '--inherit'.
    ---
    tools/perf/Documentation/perf-ftrace.txt | 3 ++
    tools/perf/builtin-ftrace.c | 38 ++++++++++++++++++++++++
    2 files changed, 41 insertions(+)

    diff --git a/tools/perf/Documentation/perf-ftrace.txt b/tools/perf/Documentation/perf-ftrace.txt
    index dcac0d75a0e5..3eee073a7042 100644
    --- a/tools/perf/Documentation/perf-ftrace.txt
    +++ b/tools/perf/Documentation/perf-ftrace.txt
    @@ -57,6 +57,9 @@ OPTIONS
    Set the size of per-cpu tracing buffer, <size> is expected to
    be a number with appended unit character - B/K/M/G.

    +--inherit::
    + Trace children processes spawned by our target.
    +
    -T::
    --trace-funcs=::
    Only trace functions given by the argument. Multiple functions
    diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
    index 6ce626a2d0d1..765ebd56e05f 100644
    --- a/tools/perf/builtin-ftrace.c
    +++ b/tools/perf/builtin-ftrace.c
    @@ -39,6 +39,7 @@ struct perf_ftrace {
    struct list_head nograph_funcs;
    int graph_depth;
    unsigned long percpu_buffer_size;
    + bool inherit;
    };

    struct filter_entry {
    @@ -180,9 +181,27 @@ static int write_tracing_file_int(const char *name, int value)
    return 0;
    }

    +static int write_tracing_option_file(const char *name, const char *val)
    +{
    + char *file;
    + int ret;
    +
    + if (asprintf(&file, "options/%s", name) < 0)
    + return -1;
    +
    + ret = __write_tracing_file(file, val, false);
    + free(file);
    + return ret;
    +}
    +
    static int reset_tracing_cpu(void);
    static void reset_tracing_filters(void);

    +static void reset_tracing_options(struct perf_ftrace *ftrace __maybe_unused)
    +{
    + write_tracing_option_file("function-fork", "0");
    +}
    +
    static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
    {
    if (write_tracing_file("tracing_on", "0") < 0)
    @@ -201,6 +220,7 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
    return -1;

    reset_tracing_filters();
    + reset_tracing_options(ftrace);
    return 0;
    }

    @@ -339,6 +359,17 @@ static int set_tracing_percpu_buffer_size(struct perf_ftrace *ftrace)
    return 0;
    }

    +static int set_tracing_trace_inherit(struct perf_ftrace *ftrace)
    +{
    + if (!ftrace->inherit)
    + return 0;
    +
    + if (write_tracing_option_file("function-fork", "1") < 0)
    + return -1;
    +
    + return 0;
    +}
    +
    static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
    {
    char *trace_file;
    @@ -408,6 +439,11 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
    goto out_reset;
    }

    + if (set_tracing_trace_inherit(ftrace) < 0) {
    + pr_err("failed to set tracing option function-fork\n");
    + goto out_reset;
    + }
    +
    if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
    pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
    goto out_reset;
    @@ -600,6 +636,8 @@ int cmd_ftrace(int argc, const char **argv)
    "Max depth for function graph tracer"),
    OPT_CALLBACK('m', "buffer-size", &ftrace.percpu_buffer_size, "size",
    "size of per cpu buffer", parse_buffer_size),
    + OPT_BOOLEAN(0, "inherit", &ftrace.inherit,
    + "trace children processes"),
    OPT_END()
    };

    --
    2.25.1
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