linux-kernel - Re: [PATCH tip/core/rcu 03/15] rcu: Drive TASKS

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Message-Id: <20170725191923.GV3730@linux.vnet.ibm.com>
Date:   Tue, 25 Jul 2017 12:19:23 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com
Subject: Re: [PATCH tip/core/rcu 03/15] rcu: Drive TASKS_RCU directly off of
 PREEMPT

On Tue, Jul 25, 2017 at 02:14:05PM -0400, Steven Rostedt wrote:
> On Mon, 24 Jul 2017 14:44:32 -0700
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> 
> > The actual use of TASKS_RCU is only when PREEMPT, otherwise RCU-sched
> > is used instead.  This commit therefore makes synchronize_rcu_tasks()
> > and call_rcu_tasks() available always, but mapped to synchronize_sched()
> > and call_rcu_sched(), respectively, when !PREEMPT.  This approach also
> > allows some #ifdefs to be removed from rcutorture.
> 
> Hmm, I'll need to update ftrace. I believe I call synchronize_sched()
> twice with !PREEMPT then.

Does this mean that synchronize_rcu_tasks() should invoke
synchronize_sched() twice?  Easy change to make, if so.

							Thanx, Paul