Re: [PATCH v3 1/7] x86/topology.c: Support functions for BSPonline/offline
From: Konrad Rzeszutek Wilk
Date: Fri Nov 11 2011 - 13:24:42 EST
On Wed, Nov 09, 2011 at 04:34:11PM -0800, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@xxxxxxxxx>
>
> By default, BSP can't be hotpluggable because bsp_hotpluggable is 0. Kernel
> parameter bsp_hotplug can enable BSP hotplug feature.
>
> Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> ---
> arch/x86/kernel/topology.c | 24 +++++++++++++++++-------
> 1 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index 76ee977..a3fc939 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -35,18 +35,28 @@
> static DEFINE_PER_CPU(struct x86_cpu, cpu_devices);
>
> #ifdef CONFIG_HOTPLUG_CPU
> +
> +static int bsp_hotpluggable;
__read_mostly
> +
> +static int __init enable_bsp_hotplug(char *str)
> +{
> + bsp_hotpluggable = 1;
> + return 1;
> +}
> +
> +__setup("bsp_hotplug", enable_bsp_hotplug);
> +
> int __ref arch_register_cpu(int num)
> {
> /*
> - * CPU0 cannot be offlined due to several
> - * restrictions and assumptions in kernel. This basically
> - * doesn't add a control file, one cannot attempt to offline
> - * BSP.
> + * Resume from suspend/hibernate depends on BSP. PIC interrupts depend
> + * on BSP.
> *
> - * Also certain PCI quirks require not to enable hotplug control
> - * for all CPU's.
> + * If the BSP depencies are under control, one can tell kernel to
> + * enable BSP hotplug. This basically adds a control file and
> + * one can attempt to offline BSP.
> */
> - if (num)
> + if (num || bsp_hotpluggable)
> per_cpu(cpu_devices, num).cpu.hotpluggable = 1;
>
> return register_cpu(&per_cpu(cpu_devices, num).cpu, num);
> --
> 1.6.0.3
>
> --
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