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Date: Wed, 5 Oct 2011 21:22:10 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Fenghua Yu <fenghua.yu@intel.com>
cc: Ingo Molnar <mingo@elte.hu>, H Peter Anvin <hpa@zytor.com>,
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Subject: Re: [PATCH 7/8] kernel/power/main.c: Not suspend/resume if CPU0 is
 offlined
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On Wed, 5 Oct 2011, Fenghua Yu wrote:

> From: Fenghua Yu <fenghua.yu@intel.com>
> 
> System resumes from CPU0 on today's x86 BIOS. Don't suspend/resume if CPU0 is
> offlined and bsp_hotpluggable is 1.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
>  kernel/power/main.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index 6c601f8..33ffb6a 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -12,6 +12,7 @@
>  #include <linux/string.h>
>  #include <linux/resume-trace.h>
>  #include <linux/workqueue.h>
> +#include <linux/cpu.h>
>  
>  #include "power.h"
>  
> @@ -178,6 +179,14 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	int len;
>  	int error = -EINVAL;
>  
> +#ifdef CONFIG_HOTPLUG_CPU
> +	if (bsp_hotpluggable && cpumask_first(cpu_online_mask) != 0) {
> +		printk(KERN_WARNING "Because CPU0 is offlined, system can't suspend/resume.\n");
> +
> +		return -ENODEV;
> +	}
> +#endif

Oh yes, we enforce that for all architectures no matter what.

This is a x86 restriction and the cpu hotplug architecture code can
veto unplugging.

Thanks,

	tglx