From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: tnt@246tNt.com, manfred@colorfullife.com,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
paulus@samba.org, akpm@linux-foundation.org
Subject: Re: [PATCH] prevent powerpc from invoking irq handlers on offline CPUs
Date: Sun, 31 Aug 2008 22:00:04 -0700 [thread overview]
Message-ID: <20080901050003.GN7015@linux.vnet.ibm.com> (raw)
In-Reply-To: <1220238880.13010.4.camel@pasglop>
On Mon, Sep 01, 2008 at 01:14:40PM +1000, Benjamin Herrenschmidt wrote:
> On Sun, 2008-08-31 at 19:06 -0700, Paul E. McKenney wrote:
> > On Mon, Sep 01, 2008 at 10:34:44AM +1000, Benjamin Herrenschmidt wrote:
> > > On Sun, 2008-08-31 at 10:31 -0700, Paul E. McKenney wrote:
> > > > Make powerpc refrain from clearing a given to-be-offlined CPU's bit in the
> > > > cpu_online_mask until it has processed pending irqs. This change
> > > > prevents other CPUs from being blindsided by an apparently offline CPU
> > > > nevertheless changing globally visible state.
> > > >
> > > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > > > ---
> > >
> > > Sounds reasonable... the only possible worry here is if somebody tries
> > > an IPI ... The IPI code will and the target CPU mask with the online
> > > map, so it may try to send to the to-be-offlined CPU and timeout, no ?
> >
> > OK. Do we need separate IPI and online masks?
>
> Shouldn't we already have routed all interrupts to other CPUs anyway ?
>
> IE. The affinity of all interrupts should have been updated. So the
> only thing we're going to get here are possibly IPIs and decrementer,
> I don't see it being a big deal making sure we test we are online when
> receiving it.
It did look to me that the CPU removed itself from the interrupt queue
before re-enabling interrupts, so makes sense to me...
Thanx, Paul
prev parent reply other threads:[~2008-09-01 5:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-31 17:31 [PATCH] prevent powerpc from invoking irq handlers on offline CPUs Paul E. McKenney
2008-09-01 0:34 ` Benjamin Herrenschmidt
2008-09-01 2:06 ` Paul E. McKenney
2008-09-01 3:14 ` Benjamin Herrenschmidt
2008-09-01 5:00 ` Paul E. McKenney [this message]
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