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

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Date:   Thu, 6 Jan 2022 10:14:00 +0800
From:   xy zhang <xyz.sun.ok@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>, mingo@...hat.com,
        oleg@...hat.com, namhyung.kim@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/kprobes: 'nmissed' not showed correctly for kretprobe

ok, I will send a v2 patch later

On Thu, Jan 6, 2022 at 7:10 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Thu, 6 Jan 2022 07:32:03 +0900
> Masami Hiramatsu <mhiramat@...nel.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