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

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Message-ID: <20220425105600.722b1345@gandalf.local.home>
Date:   Mon, 25 Apr 2022 10:56:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Patrick Wang <patrick.wang.shcn@...il.com>
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 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.

-- Steve


>  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;
>