From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Borislav Petkov <bp@alien8.de>
Subject: Re: sched: Unexpected reschedule of offline CPU#2!
Date: Mon, 29 Jul 2019 12:13:49 +0200 [thread overview]
Message-ID: <20190729101349.GX31381@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1907291156170.1791@nanos.tec.linutronix.de>
On Mon, Jul 29, 2019 at 11:58:24AM +0200, Thomas Gleixner wrote:
> On Mon, 29 Jul 2019, Peter Zijlstra wrote:
> > On Sat, Jul 27, 2019 at 09:44:50AM -0700, Guenter Roeck wrote:
> > > [ 61.348866] Call Trace:
> > > [ 61.349392] kick_ilb+0x90/0xa0
> > > [ 61.349629] trigger_load_balance+0xf0/0x5c0
> > > [ 61.349859] ? check_preempt_wakeup+0x1b0/0x1b0
> > > [ 61.350057] scheduler_tick+0xa7/0xd0
> >
> > kick_ilb() iterates nohz.idle_cpus_mask to find itself an idle_cpu().
> >
> > idle_cpus_mask() is set from nohz_balance_enter_idle() and cleared from
> > nohz_balance_exit_idle(). nohz_balance_enter_idle() is called from
> > __tick_nohz_idle_stop_tick() when entering nohz idle, this includes the
> > cpu_is_offline() clause of the idle loop.
> >
> > However, when offline, cpu_active() should also be false, and this
> > function should no-op.
>
> Ha. That reboot mess is not clearing cpu active as it's not going through
> the regular cpu hotplug path. It's using reboot IPI which 'stops' the cpus
> dead in their tracks after clearing cpu online....
$string-of-cock-compliant-curses
What a trainwreck...
So if it doesn't play by the normal rules; how does it expect to work?
So what do we do? 'Fix' reboot or extend the rules?
next prev parent reply other threads:[~2019-07-29 10:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-27 16:44 sched: Unexpected reschedule of offline CPU#2! Guenter Roeck
2019-07-29 9:35 ` Peter Zijlstra
2019-07-29 9:58 ` Thomas Gleixner
2019-07-29 10:13 ` Peter Zijlstra [this message]
2019-07-29 10:38 ` Thomas Gleixner
2019-07-29 10:47 ` Peter Zijlstra
2019-07-29 20:50 ` Guenter Roeck
2019-08-16 10:22 ` Thomas Gleixner
2019-08-16 19:32 ` Guenter Roeck
2019-08-17 20:21 ` Thomas Gleixner
2021-07-27 8:00 ` Henning Schild
2021-07-27 8:46 ` Jan Kiszka
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