Date: Wed, 14 Dec 2005 17:20:19 -0800 (PST)
From: Zwane Mwaikambo <zwane@arm.linux.org.uk>
To: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>
cc: Gerd Knorr <kraxel@suse.de>,
       Xen merge mainline list <xen-merge@lists.xensource.com>,
       linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-merge] Re: [patch] SMP alternatives for i386
In-Reply-To: <865100f9f39bd64c72af67447023b1cd@cl.cam.ac.uk>
Message-ID: <Pine.LNX.4.64.0512141706091.1678@montezuma.fsmlabs.com>
References: <439EE742.5040909@suse.de> <Pine.LNX.4.64.0512141129090.1678@montezuma.fsmlabs.com>
 <865100f9f39bd64c72af67447023b1cd@cl.cam.ac.uk>
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Hello Keir,

On Wed, 14 Dec 2005, Keir Fraser wrote:

> >  	fixup_irqs(map);
> >  	/* It's now safe to remove this processor from the online map */
> >  	cpu_clear(cpu, cpu_online_map);
> > +
> > +	if (1 == num_online_cpus())
> > +		alternatives_smp_switch(0);
> >  	return 0;
> >  }
> > 
> > Is that really safe there? Ideally you want to do the switch when the
> > processor going offline is no longer executing kernel code.
> 
> Perhaps that check belongs at the end of __cpu_die()? That's where it lives in
> xen's smpboot.c.

Yes indeed, end of __cpu_die would be perfect for x86 too as that's where 
CPU_DEAD acknowledge is checked.

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