Re: [RFC PATCH tip/master 1/3] trace: kprobes: Show sum of probe/retprobe nmissed count

[Alban Crequy]

On Wed, Mar 29, 2017 at 7:22 AM, Masami Hiramatsu  wrote:
> Show sum of probe and retprobe nmissed count in
> kprobe_profile, since retprobe can be missed even
> if the kprobe itself succeeeded.
> This explains user why their return probe didn't hit
> sometimes.
>
> Signed-off-by: Masami Hiramatsu 

I tested this patch with my kretprobe on "inet_csk_accept" when there
are many processes waiting in the accept() syscall. I can now
successfully see the nmissed counter in
/sys/kernel/debug/tracing/kprobe_profile being incremented when the
kretprobe is missed.

Tested-by: Alban Crequy 


> ---
>  kernel/trace/trace_kprobe.c |2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 013f4e7..bbdc3de 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -896,7 +896,7 @@ static int probes_profile_seq_show(struct seq_file *m, 
> void *v)
> seq_printf(m, "  %-44s %15lu %15lu\n",
>trace_event_name(>tp.call),
>trace_kprobe_nhit(tk),
> -  tk->rp.kp.nmissed);
> +  tk->rp.kp.nmissed + tk->rp.nmissed);
>
> return 0;
>  }
>

[RFC PATCH tip/master 1/3] trace: kprobes: Show sum of probe/retprobe nmissed count

[Masami Hiramatsu]

Show sum of probe and retprobe nmissed count in
kprobe_profile, since retprobe can be missed even
if the kprobe itself succeeeded.
This explains user why their return probe didn't hit
sometimes.

Signed-off-by: Masami Hiramatsu 
---
 kernel/trace/trace_kprobe.c |2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 013f4e7..bbdc3de 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -896,7 +896,7 @@ static int probes_profile_seq_show(struct seq_file *m, void 
*v)
seq_printf(m, "  %-44s %15lu %15lu\n",
   trace_event_name(>tp.call),
   trace_kprobe_nhit(tk),
-  tk->rp.kp.nmissed);
+  tk->rp.kp.nmissed + tk->rp.nmissed);
 
return 0;
 }