linux-kernel - Re: rcu: enable rcu_normal_after

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Message-Id: <20181108161225.GK4170@linux.ibm.com>
Date:   Thu, 8 Nov 2018 08:12:25 -0800
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     lcapitulino@...hat.com, julia@...com,
        linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: rcu: enable rcu_normal_after_boot by default for RT

On Thu, Nov 08, 2018 at 04:52:26PM +0100, Sebastian Andrzej Siewior wrote:
> On 2018-11-01 16:02:35 [-0700], Paul E. McKenney wrote:
> > > The forcing of an expedited grace period is an expensive and very
> > > RT-application unfriendly operation, as it forcibly preempts all running
> > > tasks on CPUs which are preventing the gp from expiring.
> > > 
> > > By default, as a policy decision, disable the expediting of grace
> > > periods (after boot) on configurations which enable PREEMPT_RT_FULL.
> > > 
> > > Suggested-by: Luiz Capitulino <lcapitulino@...hat.com>
> > > Signed-off-by: Julia Cartwright <julia@...com>
> > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> > 
> > In case it matters:
> > 
> > Acked-by: Paul E. McKenney <paulmck@...ux.ibm.com>
> > 
> > Alternatively, any reason that I should not pull this into -rcu?

> because we don't have CONFIG_PREEMPT_RT_FULL yet.

Fair enough.  This particular case works without CONFIG_PREEMPT_RT_FULL
defined, but up to you guys.

							Thanx, Paul