linux-kernel - Re: [PATCH] tracing: Skip software disabled event at __synth_event_trace

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Message-ID: <1581523405.8740.10.camel@kernel.org>
Date:   Wed, 12 Feb 2020 10:03:25 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     artem.bityutskiy@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH] tracing: Skip software disabled event at
 __synth_event_trace_end()

Hi Masami,

You're right, this is a bug, thanks for sending the patch to fix it.

Tom

Reviewed-by: Tom Zanussi <zanussi@...nel.org>


On Wed, 2020-02-12 at 14:54 +0900, Masami Hiramatsu wrote:
> When the synthetic event is software disabled,
> __synth_event_trace_start() does not allocate an event buffer.
> In this case __synth_event_trace_end() also should not commit
> the buffer.
> 
> Check the trace_state->disabled at __synth_event_trace_end()
> and if it is disabled, skip it.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_events_hist.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/trace_events_hist.c
> b/kernel/trace/trace_events_hist.c
> index 483b3fd1094f..781e4b55e117 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1847,6 +1847,9 @@ __synth_event_trace_start(struct
> trace_event_file *file,
>  static inline void
>  __synth_event_trace_end(struct synth_event_trace_state *trace_state)
>  {
> +	if (trace_state->disabled)
> +		return;
> +
>  	trace_event_buffer_commit(&trace_state->fbuffer);
>  
>  	ring_buffer_nest_end(trace_state->buffer);
>