From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Peter Xu <peterx@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
linux-kernel@vger.kernel.org,
Nitesh Narayan Lal <nitesh@redhat.com>
Subject: Re: [patch 1/2] nohz: only wakeup a single target cpu when kicking a task
Date: Thu, 8 Oct 2020 21:48:19 +0200 [thread overview]
Message-ID: <20201008194819.GA86389@lothringen> (raw)
In-Reply-To: <20201008152844.GB2628@hirez.programming.kicks-ass.net>
On Thu, Oct 08, 2020 at 05:28:44PM +0200, Peter Zijlstra wrote:
> On Thu, Oct 08, 2020 at 10:59:40AM -0400, Peter Xu wrote:
> > On Wed, Oct 07, 2020 at 03:01:52PM -0300, Marcelo Tosatti wrote:
> > > +static void tick_nohz_kick_task(struct task_struct *tsk)
> > > +{
> > > + int cpu = task_cpu(tsk);
> > > +
> > > + /*
> > > + * If the task concurrently migrates to another cpu,
> > > + * we guarantee it sees the new tick dependency upon
> > > + * schedule.
> > > + *
> > > + *
> > > + * set_task_cpu(p, cpu);
> > > + * STORE p->cpu = @cpu
> > > + * __schedule() (switch to task 'p')
> > > + * LOCK rq->lock
> > > + * smp_mb__after_spin_lock() STORE p->tick_dep_mask
> > > + * tick_nohz_task_switch() smp_mb() (atomic_fetch_or())
> > > + * LOAD p->tick_dep_mask LOAD p->cpu
> > > + */
> > > +
> > > + preempt_disable();
> >
> > Pure question: is preempt_disable() required here? Same question to
> > tick_nohz_full_kick_all().
>
> I think it serializes against hotplug.
Exactly!
Thanks.
next prev parent reply other threads:[~2020-10-08 19:48 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 18:01 [patch 0/2] nohz_full: only wakeup target CPUs when notifying new tick dependency (v2) Marcelo Tosatti
2020-10-07 18:01 ` [patch 1/2] nohz: only wakeup a single target cpu when kicking a task Marcelo Tosatti
2020-10-08 12:22 ` Peter Zijlstra
2020-10-08 17:54 ` Marcelo Tosatti
2020-10-08 19:54 ` Frederic Weisbecker
2020-10-13 17:13 ` Marcelo Tosatti
2020-10-14 8:33 ` Peter Zijlstra
2020-10-14 23:40 ` Frederic Weisbecker
2020-10-15 10:12 ` Peter Zijlstra
2020-10-26 14:42 ` Frederic Weisbecker
2020-10-20 18:52 ` Marcelo Tosatti
2020-10-22 12:53 ` Frederic Weisbecker
2020-10-08 14:59 ` Peter Xu
2020-10-08 15:28 ` Peter Zijlstra
2020-10-08 19:16 ` Peter Xu
2020-10-08 19:48 ` Frederic Weisbecker [this message]
2020-10-08 17:43 ` Marcelo Tosatti
2020-10-07 18:01 ` [patch 2/2] nohz: change signal tick dependency to wakeup CPUs of member tasks Marcelo Tosatti
2020-10-08 12:35 ` Peter Zijlstra
2020-10-08 18:04 ` Marcelo Tosatti
2020-10-08 19:11 [patch 0/2] nohz_full: only wakeup target CPUs when notifying new tick dependency (v3) Marcelo Tosatti
2020-10-08 19:11 ` [patch 1/2] nohz: only wakeup a single target cpu when kicking a task Marcelo Tosatti
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