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

Jianlin Lv
2022-12-23T04:52:37Z

On Tue, Nov 15, 2022 at 11:17 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 16 Nov 2022 00:07:07 +0900
> Masami Hiramatsu (Google) <mhiramat@kernel.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