linux-kernel - Re: [PATCH V2] Driver cpu: update online when cpu

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Date:	Mon, 27 Oct 2014 22:38:56 +0100
From:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:	Neil Zhang <zhangwm@...vell.com>, linux-kernel@...r.kernel.org
CC:	gregkh@...uxfoundation.org, "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH V2] Driver cpu: update online when cpu_up/down besides
 sysfs

On 10/27/2014 3:59 AM, Neil Zhang wrote:
> The current per-cpu offline info won't be updated when we use
> any other method besides sysfs to call cpu_up/down.
> Thus the cpu/online can't reflect the real online status.
>
> This patch is going to fix the issue introduced by commit
> 0902a9044fa5b7a0456ea4daacec2c2b3189ba8c (Driver core:
> Use generic offline/online for CPU offline/online)
>
> CC: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Tested-by: Dan Streetman <ddstreet@...e.org>
> Signed-off-by: Neil Zhang <zhangwm@...vell.com>

Oh dear, no.

Please first tell me what exactly the problem you're seeing is.

> ---
>   drivers/base/cpu.c |   25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
>
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 006b1bc..9d61824 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -418,10 +418,35 @@ static void __init cpu_dev_register_generic(void)
>   #endif
>   }
>   
> +static int device_hotplug_notifier(struct notifier_block *nfb,
> +				      unsigned long action, void *hcpu)
> +{
> +	unsigned int cpu = (unsigned long)hcpu;
> +	struct device *dev = get_cpu_device(cpu);
> +	int ret;
> +
> +	switch (action & ~CPU_TASKS_FROZEN) {
> +	case CPU_ONLINE:
> +		dev->offline = false;
> +		ret = NOTIFY_OK;
> +		break;
> +	case CPU_DYING:
> +		dev->offline = true;
> +		ret = NOTIFY_OK;
> +		break;
> +	default:
> +		ret = NOTIFY_DONE;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>   void __init cpu_dev_init(void)
>   {
>   	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
>   		panic("Failed to register CPU subsystem");
>   
>   	cpu_dev_register_generic();
> +	cpu_notifier(device_hotplug_notifier, 0);
>   }

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