linux-kernel - Re: [PATCH] drivers: base: update cpu offline info when do hotplug

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Date:	Thu, 23 Oct 2014 10:05:27 -0400
From:	Dan Streetman <ddstreet@...e.org>
To:	Neil Zhang <zhangwm@...vell.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] drivers: base: update cpu offline info when do hotplug

On Tue, Oct 21, 2014 at 9:02 AM, Dan Streetman <ddstreet@...e.org> wrote:
> On Sun, Oct 19, 2014 at 11:29 PM, Neil Zhang <zhangwm@...vell.com> wrote:
>> The current per-cpu offline info won't be updated if it is
>> hotplugged in/out by a kernel governer.
>> Let's update it via cpu notifier.
>>
>> Signed-off-by: Neil Zhang <zhangwm@...vell.com>
>> ---
>>  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;
>
> one thing i just thought of here, since dev->offline is getting set
> here, can you remove it being set in drivers/base/core.c at
> device_online() and device_offline() ?  That's probably redundant now
> right?

sorry ignore that; device_on|offline() is common code, not cpu-specific.

>
>
>> +               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);
>>  }
>> --
>> 1.7.9.5
>>
>> --
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