Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe

[Steven Rostedt <rostedt@goodmis.org>]

On Sat, 11 Dec 2021 23:00:32 +0800
Xiangyang Zhang <xyz.sun.ok@gmail.com> wrote:

> The 'nmissed' column of the 'kprobe_profile' file for kretprobe is
> always zero, because 'nmissed' for kretprobe is maintained in
> 'tk->rp.nmissed' but not in 'tk->rp.kp.nmissed'
> 
> Fixes: c31ffb3ff633 ("tracing/kprobes: Factor out struct trace_probe")
> Signed-off-by: Xiangyang Zhang <xyz.sun.ok@gmail.com>
> ---
>  kernel/trace/trace_kprobe.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index d10c01948e68..2b9de6826e94 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1175,15 +1175,17 @@ static int probes_profile_seq_show(struct seq_file *m, void *v)
>  {
>  	struct dyn_event *ev = v;
>  	struct trace_kprobe *tk;
> +	unsigned long nmissed = 0;

No need to initialize this to zero, the first use is an assignment.

>  
>  	if (!is_trace_kprobe(ev))
>  		return 0;
>  
>  	tk = to_trace_kprobe(ev);
> +	nmissed = tk->rp.handler ? tk->rp.nmissed : tk->rp.kp.nmissed;
>  	seq_printf(m, "  %-44s %15lu %15lu\n",
>  		   trace_probe_name(&tk->tp),
>  		   trace_kprobe_nhit(tk),
> -		   tk->rp.kp.nmissed);
> +		   nmissed);

Masami, what's your thoughts on this patch?

-- Steve

>  
>  	return 0;
>  }