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

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Message-Id: <20211013233244.46341468a06ba43895b99c0e@kernel.org>
Date:   Wed, 13 Oct 2021 23:32:44 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.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 20:15:59 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Wed, 13 Oct 2021 07:46:11 +0900
> Masami Hiramatsu <mhiramat@...nel.org> wrote:
> 
> > The first argument check should be optional. If the event name matches and
> > the system name is NULL but argc == 0, it should return true.
> > (please consider it is a wild card like "-:*/EVENT *")
> > So if the argc == 0 please skip below and check the event name and
> > the system name.
> 
> OK, so I'll make them all optional, but at least, if they are supplied,
> they will be checked.
> 
> That is, you can't add the options if you don't add the event as well. But
> if you do add the event, then it should work.
> 
> Basically, we have the following:
> 
>  # echo 'e:hrstate timer/hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
>  # cat dynamic_events
> eprobes/hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8
> 
> Then the following should work:
> 
>   # echo '-:hrstate timer/hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
>   # echo '-:eprobes/hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
>   # echo '-:eprobes/hrstate timer.hrtimer_cancel' >> dynamic_events
>   # echo '-:eprobes/hrstate' >> dynamic_events

Agreed.

> 
> But the following will not work:
> 
>   # echo '-:hrstate state=+0x38($hrtimer):u8' >> dynamic_events
>   # echo '-:hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
>   # echo '-:hrstate timer.hrtimer_cancel' >> dynamic_events

The first one is agreed. But the rest 2 cases should work because it just omits the
group name. At least {k,u}probe events work.

> Should this work?
> 
>   # echo '-:hrstate' >> dynamic_events

Yes. In this case, all dynamic events which have "hrstate" event name are removed.

Thank you,

> 
> -- Steve


-- 
Masami Hiramatsu <mhiramat@...nel.org>