linux-kernel - Re: [PATCH 3/7] rcu: trace_rcu

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Date:   Tue, 15 Oct 2019 20:40:47 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     20191015102402.1978-1-laijs@...ux.alibaba.com
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org
Subject: Re: [PATCH 3/7] rcu: trace_rcu_utilization() paired

On Tue, Oct 15, 2019 at 10:28:45AM +0000, Lai Jiangshan wrote:
> The notations include "Start" and "End", it is better
> when there are paired.
> 
> Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> ---
>  kernel/rcu/tree.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index c351fc280945..7830d5a06e69 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2484,8 +2484,8 @@ static void rcu_cpu_kthread(unsigned int cpu)
>  	char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
>  	int spincnt;
>  
> +	trace_rcu_utilization(TPS("Start CPU kthread@..._run"));
>  	for (spincnt = 0; spincnt < 10; spincnt++) {
> -		trace_rcu_utilization(TPS("Start CPU kthread@..._run"));
>  		local_bh_disable();
>  		*statusp = RCU_KTHREAD_RUNNING;
>  		local_irq_disable();

This one is good -- great catch, by the way!

> @@ -2501,6 +2501,7 @@ static void rcu_cpu_kthread(unsigned int cpu)
>  			return;
>  		}
>  	}
> +	trace_rcu_utilization(TPS("End CPU kthread@..._run"));
>  	*statusp = RCU_KTHREAD_YIELDING;
>  	trace_rcu_utilization(TPS("Start CPU kthread@..._yield"));

But here the addition of "rcu_run" is redundant with the pre-existing
rcu_yield.

So I folded the first hunk into the previous patch and dropped this
one.

As always, please let me know if I am missing something.

							Thanx, Paul

>  	schedule_timeout_interruptible(2);
> -- 
> 2.20.1
>