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From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Kevin Shanahan <kevin@shanahan.id.au>,
	Siegfried Metz <frame@mailbox.org>,
	linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com,
	len.brown@intel.com, rjw@rjwysocki.net, diego.viola@gmail.com,
	rui.zhang@intel.com, viktor_jaegerskuepper@freenet.de
Subject: Re: REGRESSION: boot stalls on several old dual core Intel CPUs
Date: Mon, 3 Sep 2018 10:54:23 +0200	[thread overview]
Message-ID: <20180903085423.GU24124@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.21.1809030937230.1349@nanos.tec.linutronix.de>

On Mon, Sep 03, 2018 at 09:38:15AM +0200, Thomas Gleixner wrote:
> On Mon, 3 Sep 2018, Peter Zijlstra wrote:
> > On Sat, Sep 01, 2018 at 11:51:26AM +0930, Kevin Shanahan wrote:
> > > commit 01548f4d3e8e94caf323a4f664eb347fd34a34ab
> > > Author: Martin Schwidefsky <schwidefsky@de.ibm.com>
> > > Date:   Tue Aug 18 17:09:42 2009 +0200
> > > 
> > >     clocksource: Avoid clocksource watchdog circular locking dependency
> > > 
> > >     stop_machine from a multithreaded workqueue is not allowed because
> > >     of a circular locking dependency between cpu_down and the workqueue
> > >     execution. Use a kernel thread to do the clocksource downgrade.
> > 
> > I cannot find stop_machine usage there; either it went away or I need to
> > like wake up.
> 
> timekeeping_notify() which is involved in switching clock source uses stomp
> machine.

ARGH... OK, lemme see if I can come up with something other than
endlessly spawning that kthread.

A special purpose kthread_worker would make more sense than that.

  reply	other threads:[~2018-09-03  8:54 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-30 10:55 REGRESSION: boot stalls on several old dual core Intel CPUs Siegfried Metz
2018-08-30 13:04 ` Peter Zijlstra
2018-08-30 13:48   ` Peter Zijlstra
2018-09-01  2:21   ` Kevin Shanahan
2018-09-03  7:25     ` Peter Zijlstra
2018-09-03  7:38       ` Thomas Gleixner
2018-09-03  8:54         ` Peter Zijlstra [this message]
2018-09-03  9:33           ` Peter Zijlstra
2018-09-03 11:30             ` Viktor Jägersküpper
2018-09-03 12:34             ` Kevin Shanahan
2018-09-03 21:34             ` Siegfried Metz
2018-09-04 13:44             ` Niklas Cassel
2018-09-05  8:41               ` [PATCH] clocksource: Revert "Remove kthread" Peter Zijlstra
2018-09-06 10:46                 ` [tip:timers/urgent] " tip-bot for Peter Zijlstra
2018-09-06 21:42                 ` tip-bot for Peter Zijlstra

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