* [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
@ 2021-12-11 15:00 Xiangyang Zhang
2022-01-05 19:15 ` Steven Rostedt
0 siblings, 1 reply; 6+ messages in thread
From: Xiangyang Zhang @ 2021-12-11 15:00 UTC (permalink / raw)
To: rostedt, mingo
Cc: masami.hiramatsu.pt, oleg, namhyung.kim, linux-kernel, xyz.sun.ok
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;
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);
return 0;
}
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
2021-12-11 15:00 [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe Xiangyang Zhang
@ 2022-01-05 19:15 ` Steven Rostedt
2022-01-05 19:22 ` Steven Rostedt
0 siblings, 1 reply; 6+ messages in thread
From: Steven Rostedt @ 2022-01-05 19:15 UTC (permalink / raw)
To: Xiangyang Zhang
Cc: mingo, masami.hiramatsu.pt, oleg, namhyung.kim, linux-kernel
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;
> }
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
2022-01-05 19:15 ` Steven Rostedt
@ 2022-01-05 19:22 ` Steven Rostedt
2022-01-05 22:32 ` Masami Hiramatsu
0 siblings, 1 reply; 6+ messages in thread
From: Steven Rostedt @ 2022-01-05 19:22 UTC (permalink / raw)
To: Xiangyang Zhang; +Cc: mingo, Masami Hiramatsu, oleg, namhyung.kim, linux-kernel
Resending again, this time with Masami's working email address.
On Wed, 5 Jan 2022 14:15:56 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> 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;
> > }
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
2022-01-05 19:22 ` Steven Rostedt
@ 2022-01-05 22:32 ` Masami Hiramatsu
2022-01-05 23:10 ` Steven Rostedt
0 siblings, 1 reply; 6+ messages in thread
From: Masami Hiramatsu @ 2022-01-05 22:32 UTC (permalink / raw)
To: Steven Rostedt
Cc: Xiangyang Zhang, mingo, Masami Hiramatsu, oleg, namhyung.kim,
linux-kernel
On Wed, 5 Jan 2022 14:22:08 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> Resending again, this time with Masami's working email address.
>
> On Wed, 5 Jan 2022 14:15:56 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > 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?
OK, this is a good catch :), but there are 2 issues.
1. kretprobe can be skipped by 2 reasons, shortage of kretprobe_instance which
is counted by rp.nmissed, and kprobe itself is missed by some reason (this
can be happen if KPROBE_EVENTS_ON_NOTRACE=n. Thus, better solution is to show
'tk->rp.nmissed + tk->rp.kp.nmissed'.
2. the commit c31ffb3ff633 is not actual commit which introduce this issue.
this was introduced by 4a846b443b4e ("tracing/kprobes: Cleanup kprobe tracer code.")
'git blame' tells you the commit which changes that line, but that can be just
a refactoring (renaming). I recommend you to search the correct one by 'git log -p'.
Thank you,
> >
> > -- Steve
> >
> > >
> > > return 0;
> > > }
> >
>
--
Masami Hiramatsu <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
2022-01-05 22:32 ` Masami Hiramatsu
@ 2022-01-05 23:10 ` Steven Rostedt
2022-01-06 2:14 ` xy zhang
0 siblings, 1 reply; 6+ messages in thread
From: Steven Rostedt @ 2022-01-05 23:10 UTC (permalink / raw)
To: Masami Hiramatsu; +Cc: Xiangyang Zhang, mingo, oleg, namhyung.kim, linux-kernel
On Thu, 6 Jan 2022 07:32:03 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:
> OK, this is a good catch :), but there are 2 issues.
>
> 1. kretprobe can be skipped by 2 reasons, shortage of kretprobe_instance which
> is counted by rp.nmissed, and kprobe itself is missed by some reason (this
> can be happen if KPROBE_EVENTS_ON_NOTRACE=n. Thus, better solution is to show
> 'tk->rp.nmissed + tk->rp.kp.nmissed'.
>
> 2. the commit c31ffb3ff633 is not actual commit which introduce this issue.
> this was introduced by 4a846b443b4e ("tracing/kprobes: Cleanup kprobe tracer code.")
>
> 'git blame' tells you the commit which changes that line, but that can be just
> a refactoring (renaming). I recommend you to search the correct one by 'git log -p'.
Masami, thanks for the review.
Xiangyang, can you please send a v2 with Masami's suggestions?
-- Steve
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe
2022-01-05 23:10 ` Steven Rostedt
@ 2022-01-06 2:14 ` xy zhang
0 siblings, 0 replies; 6+ messages in thread
From: xy zhang @ 2022-01-06 2:14 UTC (permalink / raw)
To: Steven Rostedt; +Cc: Masami Hiramatsu, mingo, oleg, namhyung.kim, linux-kernel
ok, I will send a v2 patch later
On Thu, Jan 6, 2022 at 7:10 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Thu, 6 Jan 2022 07:32:03 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > OK, this is a good catch :), but there are 2 issues.
> >
> > 1. kretprobe can be skipped by 2 reasons, shortage of kretprobe_instance which
> > is counted by rp.nmissed, and kprobe itself is missed by some reason (this
> > can be happen if KPROBE_EVENTS_ON_NOTRACE=n. Thus, better solution is to show
> > 'tk->rp.nmissed + tk->rp.kp.nmissed'.
> >
> > 2. the commit c31ffb3ff633 is not actual commit which introduce this issue.
> > this was introduced by 4a846b443b4e ("tracing/kprobes: Cleanup kprobe tracer code.")
> >
> > 'git blame' tells you the commit which changes that line, but that can be just
> > a refactoring (renaming). I recommend you to search the correct one by 'git log -p'.
>
> Masami, thanks for the review.
>
> Xiangyang, can you please send a v2 with Masami's suggestions?
>
> -- Steve
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-12-11 15:00 [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe Xiangyang Zhang
2022-01-05 19:15 ` Steven Rostedt
2022-01-05 19:22 ` Steven Rostedt
2022-01-05 22:32 ` Masami Hiramatsu
2022-01-05 23:10 ` Steven Rostedt
2022-01-06 2:14 ` xy zhang
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