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Date:   Tue, 19 May 2020 18:23:56 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        "Paul E. McKenney" <paulmck@kernel.org>,
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        Zhao Yakui <yakui.zhao@intel.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: Re: [patch V6 02/37] tracing/hwlat: Split ftrace_nmi_enter/exit()
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On Sat, 16 May 2020 01:45:49 +0200
Thomas Gleixner <tglx@linutronix.de> wrote:

> The hardware latency tracer calls into timekeeping and ends up in
> various instrumentable functions which is problematic vs. the kprobe
> handling especially the text poke machinery. It's invoked from
> nmi_enter/exit(), i.e. non-instrumentable code.
> 
> Split it into two parts:
> 
>  1) NMI counter, only invoked on nmi_enter() and noinstr safe
> 
>  2) NMI timestamping, to be invoked from instrumentable code
> 
> Move it into the rcu is watching regions of nmi_enter/exit() even
> if there is no actual RCU dependency right now but there is also
> no point in having it early.
> 
> The actual split of nmi_enter/exit() is done in a separate step.
> 
> Requested-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve