linux-kernel - Re: On trace_*_rcuidle functions in modules

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Message-ID: <CALAqxLX2UDQ7=dvzMoP6g-rYzw9dBebrynMfo4Gnv=SzaqhE=g@mail.gmail.com>
Date:   Wed, 15 Apr 2020 17:06:24 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Todd Kjos <tkjos@...gle.com>, Stephen Boyd <sboyd@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: On trace_*_rcuidle functions in modules

On Wed, Apr 15, 2020 at 3:51 PM Steven Rostedt <rostedt@...dmis.org> wrote:
> I was about to suggest a patch, but that has already been written...
>
> 313c8c16ee62b ("PM / CPU: replace raw_notifier with atomic_notifier")
>
> Which surrounds the notifier callbacks with rcu_irq_enter_irqson()
>
> Which means that if John moves the code to use the notifier, then he could
> also remove the _rcuidle(), because RCU will be watching.

So you're saying the recent change to move to using trace_*_rcuidle()
was unnecessary?

Or is there a different notifier then cpu_pm_register_notifier() that
the driver should be using (that one seems to be using
atomic_notifier_chain_register())?

thanks
-john