Re: [Xen-merge] Re: [patch] SMP alternatives for i386

[Keir Fraser <Keir.Fraser@cl.cam.ac.uk>]

On 14 Dec 2005, at 19:35, Zwane Mwaikambo wrote:

> diff -urN -x 'build-*' -x '*~' -x Make -x scripts 
> linux-2.6.15-rc5/arch/i386/kernel/smpboot.c 
> work-2.6.15-rc5/arch/i386/kernel/smpboot.c
> --- linux-2.6.15-rc5/arch/i386/kernel/smpboot.c	2005-12-06 
> 17:00:36.000000000 +0100
> +++ work-2.6.15-rc5/arch/i386/kernel/smpboot.c	2005-12-06 
> 17:06:48.000000000 +0100
> @@ -1351,6 +1352,9 @@
>  	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.

 -- Keir

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