linux-kernel - Re: [PATCH] rcu: per-cpu rcuc kthread are created only when rcutree.use

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Date:   Mon, 3 Jan 2022 14:17:11 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Zqiang <qiang1.zhang@...el.com>, frederic@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu: per-cpu rcuc kthread are created only when
 rcutree.use_softirq=0

On 2022-01-01 08:44:26 [-0800], Paul E. McKenney wrote:
> On Wed, Dec 29, 2021 at 12:05:10AM +0800, Zqiang wrote:
> > In non-RT kernel, if the RCU_BOOST is enabled, the per-cpu rcuc
> > kthread will be created, however under the rcutree.use_softirq=1,
> > the RCU core processing only in softirq context, the rcuc kthread
> > doesn't do anything, so remove RCU_BOOST interference.
> > 
> > Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> 
> Looks sane to me, but adding Sebastian on CC for his thoughts.

Yes, it makes sense. invoke_rcu_core_kthread() is only invoked for
!use_softirq so it makes to create the threads based on this condition.

Acked-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

> 							Thanx, Paul

Sebastian