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

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Message-ID: <20220105181029.4fa08f6a@gandalf.local.home>
Date:   Wed, 5 Jan 2022 18:10:29 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Xiangyang Zhang <xyz.sun.ok@...il.com>, 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

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