linux-kernel - Re: [PATCH] rcu: ftrace: avoid tracing a few functions executed in multi_cpu

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Date:   Sat, 23 Apr 2022 17:43:14 +0800
From:   patrick wang <patrick.wang.shcn@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     paulmck@...nel.org, frederic@...nel.org, quic_neeraju@...cinc.com,
        josh@...htriplett.org, mathieu.desnoyers@...icios.com,
        jiangshanlai@...il.com, joel@...lfernandes.org,
        rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: ftrace: avoid tracing a few functions executed in multi_cpu_stop()

On Fri, Apr 22, 2022 at 11:52 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Fri, 22 Apr 2022 18:45:46 +0800
> patrick wang <patrick.wang.shcn@...il.com> wrote:
>
> > Yes, and not just RISC-V. It's arch-independent. It's the internal change of
> > stop machine implementation.
> >
> > ----------------------------------------------------------------
> > Former stop machine wait loop:
> > do {
> >     cpu_relax(); => macro
> >     ...
> > } while (curstate != STOPMACHINE_EXIT);
> > -----------------------------------------------------------------
> > Current stop machine wait loop:
> > do {
> >     stop_machine_yield(cpumask); => function (notraced)
> >     ...
> >     touch_nmi_watchdog(); => function (notraced, inside calls also notraced)
> >     ...
> >     rcu_momentary_dyntick_idle(); => function (notraced, inside calls traced)
> > } while (curstate != MULTI_STOP_EXIT);
> > ------------------------------------------------------------------
>
> That makes much more sense. Can you add that to the change log.
>

Sure, I will rewrite the log message. And thank you for the comments
and advices.

Thanks,
Patrick


> Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
>
> -- Steve