linux-kernel - Re: [PATCH] prevent ia64 from invoking irq handlers on offline CPUs

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Message-ID: <20080831175100.GD7015@linux.vnet.ibm.com>
Date:	Sun, 31 Aug 2008 10:51:00 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	linux-kernel@...r.kernel.org, tony.luck@...el.com, jes@....com,
	manfred@...orfullife.com, akpm@...ux-foundation.org
Subject: Re: [PATCH] prevent ia64 from invoking irq handlers on offline CPUs

On Sun, Aug 31, 2008 at 07:46:33PM +0200, Vegard Nossum wrote:
> On Sun, Aug 31, 2008 at 7:28 PM, Paul E. McKenney
> <paulmck@...ux.vnet.ibm.com> wrote:
> > Make ia64 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@...ux.vnet.ibm.com>
> > ---
> >
> >  smpboot.c |    3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
> > index bcea81e..7a90f42 100644
> > --- a/arch/ia64/kernel/smpboot.c
> > +++ b/arch/ia64/kernel/smpboot.c
> > @@ -741,8 +741,6 @@ int __cpu_disable(void)
> >                        return -EBUSY;
> >        }
> >
> > -       cpu_clear(cpu, cpu_online_map);
> > -
> >        if (migrate_platform_irqs(cpu)) {
> >                cpu_set(cpu, cpu_online_map);
> >                return (-EBUSY);
> > @@ -751,6 +749,7 @@ int __cpu_disable(void)
> >        remove_siblinginfo(cpu);
> >        cpu_clear(cpu, cpu_online_map);
> >        fixup_irqs();
> > +       cpu_clear(cpu, cpu_online_map);
> >        local_flush_tlb_all();
> >        cpu_clear(cpu, cpu_callin_map);
> >        return 0;
> 
> Hm. Maybe my eyes are going bad. But isn't that now clearing the cpu
> both before and after calling fixup_irqs()?

I don't believe so...  I removed the earlier one and added the later
one.  Or is there another one hidden somewhere that I missed?

							Thanx, Paul
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