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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        rostedt <rostedt@goodmis.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        paulmck <paulmck@kernel.org>,
        "Joel Fernandes\, Google" <joel@joelfernandes.org>,
        Frederic Weisbecker <frederic@kernel.org>
Subject: Re: Instrumentation and RCU
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Date:   Tue, 10 Mar 2020 19:31:38 +0100
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Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
> ----- On Mar 10, 2020, at 12:48 PM, Thomas Gleixner tglx@linutronix.de wrote:
>> How do you "fix" that when you can't reach the tracepoint because you
>> trip over a breakpoint and then while trying to fixup that stuff you hit
>> another one?
>
> I may still be missing something, but if the fixup code (AFAIU the code performing
> the out-of-line single-stepping of the original instruction) belongs to a section
> hidden from instrumentation, it should not be an issue.

Sure, but what guarantees that on the way there is nothing which might
call into instrumentable code? Nothing, really.

That's why I want the explicit sections which can be analyzed by
tools. Humans (including me) are really bad at it was demonstrated
several times.

Thanks,

        tglx