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

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Message-ID: <20190408151037.GH1975820@devbig004.ftw2.facebook.com>
Date:   Mon, 8 Apr 2019 08:10:37 -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, Sebastian.

On Fri, Apr 05, 2019 at 04:42:18PM +0200, Sebastian Andrzej Siewior wrote:
> On 2019-03-22 18:59:23 [+0100], To Tejun Heo wrote:
> > On 2019-03-22 10:43:34 [-0700], Tejun Heo wrote:
> > > Hello,
> Hi,
> 
> > > We can switch but it doesn't really say why we'd want to.  Can you
> > > please explain why this is better?
> > 
> > there is this undocumented part. Avoiding the sched RCU means also we
> > are more preemptible which is good :) Especially on -RT where we can't
> > disable preemption across the whole critical section.
> > 
> > Is this good enough?
> 
> a gentle ping.

Heh, yeah, sorry about dragging my feet on it.  The patchset itself
doesn't actually improve the upstream kernel (except for the obvious
bug fix where it's using the wrong call_rcu right now), so I've been
constantly on the fence.  At the same time, it doesn't really worsen
anything either.  Imma look through the patches once more later today.

Thanks.

-- 
tejun