* [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()
@ 2026-01-05 1:19 Zqiang
2026-01-05 21:34 ` Paul E. McKenney
2026-02-25 16:00 ` Joel Fernandes
0 siblings, 2 replies; 3+ messages in thread
From: Zqiang @ 2026-01-05 1:19 UTC (permalink / raw)
To: paulmck, frederic, neeraj.upadhyay, joelagnelf, boqun.feng,
urezki
Cc: qiang.zhang, rcu, linux-kernel
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()
2026-01-05 1:19 [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic() Zqiang
@ 2026-01-05 21:34 ` Paul E. McKenney
2026-02-25 16:00 ` Joel Fernandes
1 sibling, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2026-01-05 21:34 UTC (permalink / raw)
To: Zqiang
Cc: frederic, neeraj.upadhyay, joelagnelf, boqun.feng, urezki, rcu,
linux-kernel
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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()
2026-01-05 1:19 [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic() Zqiang
2026-01-05 21:34 ` Paul E. McKenney
@ 2026-02-25 16:00 ` Joel Fernandes
1 sibling, 0 replies; 3+ messages in thread
From: Joel Fernandes @ 2026-02-25 16:00 UTC (permalink / raw)
To: Zqiang
Cc: paulmck, frederic, neeraj.upadhyay, boqun.feng, urezki, rcu,
linux-kernel
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>
Applied for 7.1 with Paul's tag. Thanks!
--
Joel Fernandes
> ---
> 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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-01-05 1:19 [PATCH v2] rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic() Zqiang
2026-01-05 21:34 ` Paul E. McKenney
2026-02-25 16:00 ` Joel Fernandes
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