linux-kernel - Re: [PATCH v2] rcu: ftrace: avoid tracing a few functions executed in stop machine

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Date:   Tue, 26 Apr 2022 18:32:04 +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 v2] rcu: ftrace: avoid tracing a few functions executed in
 stop machine

On Mon, Apr 25, 2022 at 10:56 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Sat, 23 Apr 2022 18:28:44 +0800
> Patrick Wang <patrick.wang.shcn@...il.com> wrote:
>
> > Signed-off-by: Patrick Wang <patrick.wang.shcn@...il.com>
> > ---
> > v1->v2:
> >  - Modify log message.
> >
> >  kernel/rcu/tree_plugin.h | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index c8ba0fe17267..971bb6a00ede 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -460,7 +460,7 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
> >   * be quite short, for example, in the case of the call from
> >   * rcu_read_unlock_special().
> >   */
> > -static void
> > +notrace static void
>
> I'm fine with the change, but to be consistent with the rest of the kernel,
> static needs to come before notrace.
>
> Either:
>
>  static notrace void
>
> or even (some places have):
>
>   static void notrace
>
> but "static" should always be first.
>

Thank you for the detailed advice. I will move "notrace" to behind "static".

Thanks,
Patrick

>
>
> >  rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
> >  {
> >       bool empty_exp;
> > @@ -581,7 +581,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
> >   * is disabled.  This function cannot be expected to understand these
> >   * nuances, so the caller must handle them.
> >   */
> > -static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
> > +notrace static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
> >  {
> >       return (__this_cpu_read(rcu_data.cpu_no_qs.b.exp) ||
> >               READ_ONCE(t->rcu_read_unlock_special.s)) &&
> > @@ -595,7 +595,7 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
> >   * evaluate safety in terms of interrupt, softirq, and preemption
> >   * disabling.
> >   */
> > -static void rcu_preempt_deferred_qs(struct task_struct *t)
> > +notrace static void rcu_preempt_deferred_qs(struct task_struct *t)
> >  {
> >       unsigned long flags;
> >
>