linux-kernel - Re: [PATCH 2/2] rcu/tree: Clarify comments about FQS loop reporting quiescent states

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Date:   Wed, 29 Jul 2020 23:25:19 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Neeraj Upadhyay <neeraju@...eaurora.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, rcu <rcu@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 2/2] rcu/tree: Clarify comments about FQS loop reporting
 quiescent states

On Wed, Jul 29, 2020 at 11:02 PM Joel Fernandes (Google)
<joel@...lfernandes.org> wrote:
>
> At least since v4.19, the FQS loop no longer reports quiescent states

I meant here, "FQS loop no longer reports quiescent states for offline CPUs."

Sorry,

 - Joel


> unless it is a dire situation where an offlined CPU failed to report
> a quiescent state. Let us clarify the comment in rcu_gp_init() inorder
> to keep the comment current.
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
>  kernel/rcu/tree.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 1e51962b565b..929568ff5989 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1701,8 +1701,8 @@ static bool rcu_gp_init(void)
>
>         /*
>          * Apply per-leaf buffered online and offline operations to the
> -        * rcu_node tree.  Note that this new grace period need not wait
> -        * for subsequent online CPUs, and that quiescent-state forcing
> +        * rcu_node tree.  Note that this new grace period need not wait for
> +        * subsequent online CPUs, and that RCU hooks in CPU offlining path
>          * will handle subsequent offline CPUs.
>          */
>         rcu_state.gp_state = RCU_GP_ONOFF;
> --
> 2.28.0.rc0.142.g3c755180ce-goog
>