rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()

[PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()

Posted by Zqiang 1 day, 19 hours ago

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@linux.dev>
---
 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

Re: [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()

Posted by Paul E. McKenney 23 hours ago

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@linux.dev>

Very good!

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