linux-kernel - Re: [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init

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Message-ID: <784b10f0-45c4-4038-97b1-e20cacd3709b@paulmck-laptop>
Date: Mon, 5 Jan 2026 13:34:06 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Zqiang <qiang.zhang@...ux.dev>
Cc: frederic@...nel.org, neeraj.upadhyay@...nel.org, joelagnelf@...dia.com,
	boqun.feng@...il.com, urezki@...il.com, rcu@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in
 cblist_init_generic()

On Mon, Jan 05, 2026 at 09:19:51AM +0800, Zqiang wrote:
> The cblist_init_generic() is executed during the CPU early boot
> phase due to commit:30ef09635b9e ("rcu-tasks: Initialize callback
> lists at rcu_init() time"), at this time, only one boot CPU is
> online and the irq is disabled. this commit therefore use routine
> assignment replace of smp_store_release() and WRITE_ONCE() in the
> cblist_init_generic().
> 
> Signed-off-by: Zqiang <qiang.zhang@...ux.dev>

Very good!

Reviewed-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  kernel/rcu/tasks.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 76f952196a29..c736900317cd 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -290,9 +290,9 @@ static void cblist_init_generic(struct rcu_tasks *rtp)
>  	shift = ilog2(rcu_task_cpu_ids / lim);
>  	if (((rcu_task_cpu_ids - 1) >> shift) >= lim)
>  		shift++;
> -	WRITE_ONCE(rtp->percpu_enqueue_shift, shift);
> -	WRITE_ONCE(rtp->percpu_dequeue_lim, lim);
> -	smp_store_release(&rtp->percpu_enqueue_lim, lim);
> +	rtp->percpu_enqueue_shift = shift;
> +	rtp->percpu_dequeue_lim = lim;
> +	rtp->percpu_enqueue_lim = lim;
>  
>  	pr_info("%s: Setting shift to %d and lim to %d rcu_task_cb_adjust=%d rcu_task_cpu_ids=%d.\n",
>  			rtp->name, data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim),
> -- 
> 2.48.1
>