From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>,
KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
Gilad Ben-Yossef <gilad@benyossef.com>,
linux-kernel@vger.kernel.org, Chris Metcalf <cmetcalf@tilera.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Frederic Weisbecker <fweisbec@gmail.com>,
linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>,
Matt Mackall <mpm@selenic.com>,
Sasha Levin <levinsasha928@gmail.com>,
Rik van Riel <riel@redhat.com>, Andi Kleen <andi@firstfloor.org>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH v5 7/8] mm: Only IPI CPUs to drain local pages if they exist
Date: Sat, 7 Jan 2012 09:05:06 -0800 [thread overview]
Message-ID: <20120107170506.GA29261@linux.vnet.ibm.com> (raw)
In-Reply-To: <20120107165201.GA23939@linux.vnet.ibm.com>
On Sat, Jan 07, 2012 at 08:52:01AM -0800, Paul E. McKenney wrote:
> On Thu, Jan 05, 2012 at 04:17:39PM +0000, Mel Gorman wrote:
> > On Thu, Jan 05, 2012 at 02:40:11PM +0000, Russell King - ARM Linux wrote:
> > > On Thu, Jan 05, 2012 at 02:20:17PM +0000, Mel Gorman wrote:
>
> [ . . . ]
>
> > > I've been chasing that patch and getting no replies what so
> > > ever from folk like Peter, Thomas and Ingo.
> > >
> > > The problem affects all IPI-raising functions, which mask with
> > > cpu_online_mask directly.
> >
> > Actually, in one sense I'm glad to hear it because from my brief
> > poking around, I was having trouble understanding why we were always
> > safe from sending IPIs to CPUs in the process of being offlined.
>
> The trick is to disable preemption (not interrupts!) across the IPI, which
> prevents CPU-hotplug's stop_machine() from running. You also have to
> have checked that the CPU is online within this same preemption-disabled
> section of code. This means that the outgoing CPU has to accept IPIs
> even after its CPU_DOWN_PREPARE notifier has been called -- right up
> to the stop_machine() call to take_cpu_down().
Of course, another trick is to hold the CPU-hotplug lock across the IPI,
but this is quite a bit more heavy-weight than disabling preemption.
Thanx, Paul
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next prev parent reply other threads:[~2012-01-07 17:05 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1325499859-2262-1-git-send-email-gilad@benyossef.com>
2012-01-02 10:24 ` [PATCH v5 1/8] smp: Introduce a generic on_each_cpu_mask function Gilad Ben-Yossef
2012-01-03 7:51 ` Michal Nazarewicz
2012-01-03 8:12 ` Gilad Ben-Yossef
2012-01-03 8:57 ` Michal Nazarewicz
2012-01-03 22:26 ` Andrew Morton
2012-01-05 13:17 ` Michal Nazarewicz
2012-01-08 16:04 ` Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 2/8] arm: Move arm over to generic on_each_cpu_mask Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 3/8] tile: Move tile to use " Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 4/8] smp: Add func to IPI cpus based on parameter func Gilad Ben-Yossef
2012-01-03 22:34 ` Andrew Morton
2012-01-08 16:09 ` Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 5/8] slub: Only IPI CPUs that have per cpu obj to flush Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 6/8] fs: only send IPI to invalidate LRU BH when needed Gilad Ben-Yossef
2012-01-02 10:24 ` [PATCH v5 7/8] mm: Only IPI CPUs to drain local pages if they exist Gilad Ben-Yossef
2012-01-03 17:45 ` KOSAKI Motohiro
2012-01-03 18:58 ` Gilad Ben-Yossef
2012-01-03 22:02 ` KOSAKI Motohiro
2012-01-05 14:20 ` Mel Gorman
2012-01-05 14:40 ` Russell King - ARM Linux
2012-01-05 15:24 ` Peter Zijlstra
2012-01-05 16:17 ` Mel Gorman
2012-01-05 16:35 ` Russell King - ARM Linux
2012-01-05 18:35 ` Paul E. McKenney
2012-01-05 22:21 ` Mel Gorman
2012-01-06 6:06 ` Srivatsa S. Bhat
2012-01-06 10:46 ` Mel Gorman
2012-01-06 13:28 ` Greg KH
2012-01-06 14:09 ` Mel Gorman
2012-01-05 22:06 ` Andrew Morton
2012-01-05 22:31 ` Mel Gorman
2012-01-05 23:19 ` Andrew Morton
2012-01-09 17:25 ` Mel Gorman
2012-01-07 16:52 ` Paul E. McKenney
2012-01-07 17:05 ` Paul E. McKenney [this message]
2012-01-05 15:54 ` Mel Gorman
2012-01-08 16:01 ` Gilad Ben-Yossef
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