linux-kernel - Re: [PATCH 0/3] tracing: Fix some selftest issues

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Date: Mon, 10 Jun 2024 15:49:49 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Tom Zanussi <tom.zanussi@...ux.intel.com>, LKML
 <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] tracing: Fix some selftest issues

On Mon, 10 Jun 2024 11:10:01 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> > But you don't explain what exactly the conflict is. What about those
> > events causes kprobe selftests to fail?  
> 
> I also found another problem on these modules. These modules get trace
> event file references to prevent removing probes. Therefore, if we
> embed these modules, we can not remove these events forever!
> 
>         /*
>          * Now get the gen_kprobe_test event file.  We need to prevent
>          * the instance and event from disappearing from underneath
>          * us, which trace_get_event_file() does (though in this case
>          * we're using the top-level instance which never goes away).
>          */
>         gen_kprobe_test = trace_get_event_file(NULL, "kprobes",
>                                                "gen_kprobe_test");
>         if (IS_ERR(gen_kprobe_test)) {
>                 ret = PTR_ERR(gen_kprobe_test);
>                 goto delete;
>         }
> 
> This means most ftracetest fails because we can not clean up the
> tracing state by removing dynamic events, which are installed while
> booting.
> Note that these references (locks) will be removed when the module
> is unloaded.

I'm fine if you want to force these as modules. Just make sure the change
log lists all the issues of them not being modules.

-- Steve