From: Boqun Feng <boqun.feng@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
oleg@redhat.com, joel@joelfernandes.org
Subject: Re: [PATCH tip/core/rcu 2/2] rcu: Make expedited GPs handle CPU 0 being offline
Date: Tue, 26 Jun 2018 18:44:47 +0800 [thread overview]
Message-ID: <20180626104447.GG9125@tardis> (raw)
In-Reply-To: <20180626093820.GG2494@hirez.programming.kicks-ass.net>
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On Tue, Jun 26, 2018 at 11:38:20AM +0200, Peter Zijlstra wrote:
> On Mon, Jun 25, 2018 at 03:43:32PM -0700, Paul E. McKenney wrote:
> > + preempt_disable();
> > + for_each_leaf_node_possible_cpu(rnp, cpu) {
> > + if (cpu_is_offline(cpu)) /* Preemption disabled. */
> > + continue;
>
> Create for_each_node_online_cpu() instead? Seems a bit pointless to
> iterate possible mask only to then check it against the online mask.
> Just iterate the online mask directly.
>
> Or better yet, write this as:
>
> preempt_disable();
> cpu = cpumask_next(rnp->grplo - 1, cpu_online_mask);
> if (cpu > rnp->grphi)
> cpu = WORK_CPU_UNBOUND;
> queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);
> preempt_enable();
>
> Which is what it appears to be doing.
>
Make sense! Thanks ;-)
Applied this and running a TREE03 rcutorture. If all go well, I will
send the updated patch.
Regards,
Boqun
> > + queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);
> > + rnp->exp_need_flush = true;
> > + break;
> > + }
> > + preempt_enable();
> > + if (!rnp->exp_need_flush) { /* All offline, report QSes. */
> > + queue_work(rcu_par_gp_wq, &rnp->rew.rew_work);
> > + rnp->exp_need_flush = true;
> > + }
> > }
> >
> > /* Wait for workqueue jobs (if any) to complete. */
> > --
> > 2.17.1
> >
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next prev parent reply other threads:[~2018-06-26 10:40 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-25 22:43 [PATCH tip/core/rcu 0/2] Expedited grace-period changes for v4.19 Paul E. McKenney
2018-06-25 22:43 ` [PATCH tip/core/rcu 1/2] rcu: Make expedited grace period use direct call on last leaf Paul E. McKenney
2018-06-25 22:43 ` [PATCH tip/core/rcu 2/2] rcu: Make expedited GPs handle CPU 0 being offline Paul E. McKenney
2018-06-26 9:38 ` Peter Zijlstra
2018-06-26 10:44 ` Boqun Feng [this message]
2018-06-26 11:46 ` Boqun Feng
2018-06-26 12:31 ` Paul E. McKenney
2018-06-26 19:27 ` Paul E. McKenney
2018-06-27 2:42 ` Boqun Feng
2018-06-27 16:15 ` Paul E. McKenney
2018-06-28 16:52 ` Paul E. McKenney
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