linux-kernel - Re: [PATCH v4 3/3] tracing/ftrace: Add support to record and display tgid

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Date:   Mon, 26 Jun 2017 20:16:20 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Michael Sartain <mikesart@...il.com>,
        Joel Fernandes <joelaf@...gle.com>, kernel-team@...roid.com,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v4 3/3] tracing/ftrace: Add support to record and display tgid

Hi Steven,

Please drop this patch (3/3) for now because the new allocation
rearrangement we made to (1/3) will not work with this patch because
flag_changed is called before the allocation failure case. Also TGIDs
for event tracing is the main use case for my series, the function
tracer isn't the main use case so I can post a proper version of this
patch later once we get the main pieces in.

1/3 and 2/3 are still good to go, following are you patchwork links to them

1/3: https://patchwork.kernel.org/patch/9810685/
2/3: https://patchwork.kernel.org/patch/9808641/

Incase its confusing, please let me know and I can just send you both
these patches again.

Thanks,
Joel


On Sun, Jun 25, 2017 at 10:38 PM, Joel Fernandes <joelaf@...gle.com> wrote:
> Make function tracer able to record tgid if/when record-tgid is enabled.
>
> Cc: kernel-team@...roid.com
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Tested-by: Michael Sartain <mikesart@...il.com>
> Signed-off-by: Joel Fernandes <joelaf@...gle.com>
> ---
>  kernel/trace/trace_functions.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index a3bddbfd0874..d6bdc38ab273 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -27,6 +27,7 @@ static void
>  function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
>                           struct ftrace_ops *op, struct pt_regs *pt_regs);
>  static struct tracer_flags func_flags;
> +static bool tgid_recorded;
>
>  /* Our option */
>  enum {
> @@ -104,6 +105,11 @@ static int function_trace_init(struct trace_array *tr)
>         put_cpu();
>
>         tracing_start_cmdline_record();
> +
> +       if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
> +               tgid_recorded = true;
> +               tracing_start_tgid_record();
> +       }
>         tracing_start_function_trace(tr);
>         return 0;
>  }
> @@ -112,6 +118,10 @@ static void function_trace_reset(struct trace_array *tr)
>  {
>         tracing_stop_function_trace(tr);
>         tracing_stop_cmdline_record();
> +       if (tgid_recorded) {
> +               tracing_stop_tgid_record();
> +               tgid_recorded = false;
> +       }
>         ftrace_reset_array_ops(tr);
>  }
>
> @@ -252,6 +262,21 @@ func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
>         return 0;
>  }
>
> +static int
> +func_tracer_flag_changed(struct trace_array *tr, unsigned int mask,
> +                        int enabled)
> +{
> +       if (mask == TRACE_ITER_RECORD_TGID) {
> +               tgid_recorded = !!enabled;
> +               if (enabled)
> +                       tracing_start_tgid_record();
> +               else
> +                       tracing_stop_tgid_record();
> +       }
> +
> +       return 0;
> +}
> +
>  static struct tracer function_trace __tracer_data =
>  {
>         .name           = "function",
> @@ -260,6 +285,7 @@ static struct tracer function_trace __tracer_data =
>         .start          = function_trace_start,
>         .flags          = &func_flags,
>         .set_flag       = func_set_flag,
> +       .flag_changed   = func_tracer_flag_changed,
>         .allow_instances = true,
>  #ifdef CONFIG_FTRACE_SELFTEST
>         .selftest       = trace_selftest_startup_function,
> --
> 2.13.1.611.g7e3b11ae1-goog
>