From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, hpa@zytor.com,
paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org,
khilman@linaro.org, tglx@linutronix.de, axboe@fb.com,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:timers/nohz] nohz: Move full nohz kick to its own IPI
Date: Mon, 5 May 2014 17:34:08 +0200 [thread overview]
Message-ID: <20140505153405.GD2099@localhost.localdomain> (raw)
In-Reply-To: <20140505151228.GR26782@laptop.programming.kicks-ass.net>
On Mon, May 05, 2014 at 05:12:28PM +0200, Peter Zijlstra wrote:
> > Note the current ordering:
> >
> > cmpxchg(&qsd->pending, 0, 1) get ipi
> > csd_lock(qsd->csd) xchg(&qsd->pending, 1)
> > send ipi csd_unlock(qsd->csd)
> >
> >
> > So there shouldn't be racing updaters. Also ipi sender shouldn't
> > race with ipi receiver, the update shouldn't always eventually see
> > the unlock happening.
>
> Yeah, I've not spotted how this particular train wreck happens either.
>
> The problem is reproduction, it took me 9 hours to confirm I could
> reproduce the problem on my machine. So how long to I run it with this
> patch reverted to show its gone..
Maybe it could be favoured cpu hotplug. Anyway converting to irq_work should
fix it.
next prev parent reply other threads:[~2014-05-05 15:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <tip-72aacf0259bb7d53b7a3b5b2f7bf982acaa52b61@git.kernel.org>
2014-05-05 12:37 ` [tip:timers/nohz] nohz: Move full nohz kick to its own IPI Peter Zijlstra
2014-05-05 13:31 ` Peter Zijlstra
2014-05-05 15:04 ` Frederic Weisbecker
2014-05-05 15:12 ` Peter Zijlstra
2014-05-05 15:34 ` Frederic Weisbecker [this message]
2014-05-07 15:17 ` Peter Zijlstra
2014-05-07 15:29 ` Frederic Weisbecker
2014-05-07 15:37 ` Peter Zijlstra
2014-05-07 16:05 ` Frederic Weisbecker
2014-05-07 16:13 ` Peter Zijlstra
2014-05-07 19:07 ` Ingo Molnar
2014-05-09 15:10 ` Frederic Weisbecker
2014-05-11 5:34 ` Ingo Molnar
2014-05-05 14:52 ` Frederic Weisbecker
2014-05-05 14:58 ` Peter Zijlstra
2014-05-05 15:06 ` Frederic Weisbecker
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