linux-kernel - Re: [PATCH] rcu: Fix incorrect judgment condition in show_rcu_nocb

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Date:   Wed, 25 May 2022 17:26:52 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Zqiang <qiang1.zhang@...el.com>, <paulmck@...nel.org>,
        <frederic@...nel.org>
CC:     <rcu@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rcu: Fix incorrect judgment condition in
 show_rcu_nocb_state()



On 5/25/2022 9:04 AM, Zqiang wrote:
> When check the 'rdp->nocb_cb_kthread' tasks exists, if is true, however
> the output is the cpu where 'rdp->nocb_gp_kthread' is located. this
> ensure that the tasks in the judgment condition and the tasks of the
> cpu where the output tasks are located are the same tasks.
> 
> Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> ---
>   kernel/rcu/tree_nocb.h | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
> index fa8e4f82e60c..f4ee81d119c8 100644
> --- a/kernel/rcu/tree_nocb.h
> +++ b/kernel/rcu/tree_nocb.h
> @@ -1438,8 +1438,8 @@ static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
>   		(long)rdp->nocb_gp_seq,
>   		rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
>   		rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
> -		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> -		show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
> +		rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> +		show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
>   }
>   
>   /* Dump out nocb kthread state for the specified rcu_data structure. */
> @@ -1483,7 +1483,7 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
>   		".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
>   		rcu_segcblist_n_cbs(&rdp->cblist),
>   		rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
> -		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
> +		rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
>   		show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
>   

Nice !!
Reviewed-by: quic_mojha@...cinc.com

-Mukesh

>   	/* It is OK for GP kthreads to have GP state. */