linux-kernel - Re: [PATCH] tracepoint: Allow livepatch module add trace event

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Message-ID: <CAFA-uR_Bhc8fdBXajKzSSXQ1Cf_iLirK0gS+TovPM9G7MLv=dg@mail.gmail.com>
Date:   Fri, 23 Dec 2022 12:52:18 +0800
From:   Jianlin Lv <iecedge@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        alison.schofield@...el.com, davidgow@...gle.com,
        thunder.leizhen@...wei.com, jianlv@...y.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracepoint: Allow livepatch module add trace event

On Tue, Nov 15, 2022 at 11:17 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 16 Nov 2022 00:07:07 +0900
> Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:
>
> > BTW, now the kprobe_ftrace_handler() uses ftrace_test_recursion_trylock()
> > to avoid ftrace recursion, is that OK for this case?
>
> Note, the ftrace_test_recursion_trylock() only prevents "same context"
> recursion. That is, it will not let normal context recurse into normal
> context, or interrupt context recurse into interrupt context.
>
> It has the logic of breaking up into 4 levels:
>
>  1. normal
>  2. softirq
>  3. irq
>  4. NMI
>
> It allows the high levels to recurse into lower levels
>  (e.g. irq context into normal context)
>
> Thus, the code within the ftrace_test_recursion_trylock() must itself be
> re-entrant to handle being called from different contexts.
>
> -- Steve

hi, Steve
Any other comments for code changes?
Is it possible for this patch to be merged?

Regards,
Jianlin