linux-kernel - Re: [PATCH 1/2] workqueue: Use normal rcu

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Date:   Fri, 22 Mar 2019 10:43:34 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/2] workqueue: Use normal rcu

Hello,

On Thu, Mar 21, 2019 at 09:59:35PM +0100, Sebastian Andrzej Siewior wrote:
> On 2019-03-13 17:55:47 [+0100], To linux-kernel@...r.kernel.org wrote:
> > From: Thomas Gleixner <tglx@...utronix.de>
> > 
> > There is no need for sched_rcu. The undocumented reason why sched_rcu
> > is used is to avoid a few explicit rcu_read_lock()/unlock() pairs by
> > the fact that sched_rcu reader side critical sections are also protected
> > by preempt or irq disabled regions.
> > 
> > Replace rcu_read_lock_sched with rcu_read_lock and acquire the RCU lock
> > where it is not yet explicit acquired. Replace local_irq_disable() with
> > rcu_read_lock(). Update asserts.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > [bigeasy: mangle changelog a little]
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> 
> A gentle ping.

We can switch but it doesn't really say why we'd want to.  Can you
please explain why this is better?

Thanks.

-- 
tejun