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SubjectRe: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
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;
> }

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