linux-kernel - Re: [PATCH v2] tracing: Fix event probe removal from dynamic events

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Date:   Tue, 12 Oct 2021 12:03:10 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tom Zanussi <zanussi@...nel.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Yordan Karadzhov <y.karadz@...il.com>
Subject: Re: [PATCH v2] tracing: Fix event probe removal from dynamic events

On Tue, 12 Oct 2021 23:31:07 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Hmm, this seems something wrong. Via dynamic_events interface, all the
> events must be parsed equaly. If you have to pass the attached "system/event"
> that's something wrong. The dynamic_events interface will accept 
> 
> -:[GROUP/]EVENT [optional arguments]
> 
> Or
> 
> !e:[GROUP/]EVENT [optional arguments]
> 
> What did you expect other that these syntax?

But there are non "optional arguments".

To create the event probe, we need to send:

  e:[GROUP/]EVENT system/event [optional arguments]

Where the "system/event" is what we attach to. Similar to adding a function
or address to kprobes. Do you not need to add that for deleting a kprobe?

That is, if I create a kprobe with:

  p:myprobe schedule > dynamic_events

To remove it, don't we need to have:

  -:myprobe schedule >> dynamic_events

?

-- Steve