From: "Paul E. McKenney" <paulmck@kernel.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Frederic Weisbecker <frederic@kernel.org>, rcu@vger.kernel.org
Subject: Re: [BUG] Random intermittent boost failures (Was Re: [BUG] TREE04..)
Date: Thu, 14 Sep 2023 04:11:26 -0700 [thread overview]
Message-ID: <fe78cd08-1b2c-4ab0-bbf7-8d324b4fa77f@paulmck-laptop> (raw)
In-Reply-To: <CAEXW_YQpgjXexpHfGGJS5_VoVUvb+ZXp7pkOdm8NGo+Z4iJAKA@mail.gmail.com>
On Wed, Sep 13, 2023 at 04:30:20PM -0400, Joel Fernandes wrote:
> On Mon, Sep 11, 2023 at 4:16 AM Paul E. McKenney <paulmck@kernel.org> wrote:
> [..]
> > > I am digging deeper to see why the rcu_preempt thread cannot be pushed out
> > > and then I'll also look at why is it being pushed out in the first place.
> > >
> > > At least I have a strong repro now running 5 instances of TREE03 in parallel
> > > for several hours.
> >
> > Very good! Then why not boot with rcutorture.onoff_interval=0 and see if
> > the problem still occurs? If yes, then there is definitely some reason
> > other than CPU hotplug that makes this happen.
>
> Hi Paul,
> So looks so far like onoff_interval=0 makes the issue disappear. So
> likely hotplug related. I am ok with doing the cpus_read_lock during
> boost testing and seeing if that fixes it. If it does, I can move on
> to the next thing in my backlog.
>
> What do you think? Or should I spend more time root-causing it? It is
> most like runaway RT threads combined with the CPU hotplug threads,
> making scheduling of the rcu_preempt thread not happen. But I can't
> say for sure without more/better tracing (Speaking of better tracing,
> I am adding core-dump support to rcutorture, but it is not there yet).
This would not be the first time rcutorture has had trouble with those
threads, so I am for adding the cpus_read_lock().
Additional root-causing might be helpful, but then again, you might
have higher priority things to worry about. ;-)
Thanx, Paul
next prev parent reply other threads:[~2023-09-14 11:11 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-10 20:14 [BUG] Random intermittent boost failures (Was Re: [BUG] TREE04..) Joel Fernandes
2023-09-10 21:16 ` Paul E. McKenney
2023-09-10 23:37 ` Joel Fernandes
2023-09-11 2:27 ` Joel Fernandes
2023-09-11 8:16 ` Paul E. McKenney
2023-09-11 13:17 ` Joel Fernandes
2023-09-11 13:49 ` Paul E. McKenney
2023-09-11 16:18 ` Joel Fernandes
2023-09-13 20:30 ` Joel Fernandes
2023-09-14 11:11 ` Paul E. McKenney [this message]
2023-09-14 13:13 ` Joel Fernandes
2023-09-14 15:23 ` Paul E. McKenney
2023-09-14 18:56 ` Joel Fernandes
2023-09-14 21:53 ` Joel Fernandes
2023-09-15 0:13 ` Joel Fernandes
2023-09-15 11:33 ` Joel Fernandes
2023-09-15 14:53 ` Paul E. McKenney
2023-09-15 16:37 ` Joel Fernandes
2023-09-15 16:57 ` Paul E. McKenney
2023-09-15 21:14 ` Joel Fernandes
2023-09-18 6:05 ` Paul E. McKenney
2023-09-15 14:48 ` Paul E. McKenney
2023-09-15 14:45 ` Paul E. McKenney
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