linux-kernel - Re: [Bug fix PATCH] numa, cpu hotplug: Change links of CPU and node when changing node number by onlining CPU

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Date:	Fri, 19 Apr 2013 10:17:01 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
CC:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [Bug fix PATCH] numa, cpu hotplug: Change links of CPU and node
 when changing node number by onlining CPU

2013/04/19 1:32, KOSAKI Motohiro wrote:
>>   #ifdef CONFIG_HOTPLUG_CPU
>> +static void change_cpu_under_node(struct cpu *cpu,
>> +                       unsigned int from_nid, unsigned int to_nid)
>> +{
>> +       int cpuid = cpu->dev.id;
>> +       unregister_cpu_under_node(cpuid, from_nid);
>> +       register_cpu_under_node(cpuid, to_nid);
>> +       cpu->node_id = to_nid;
>> +}
>> +
>

> Where is stub for !CONFIG_HOTPLUG_CPU?

This function is called by only store_online(). And the store_online() is
defined only when CONFIG_HOTPLUG_CPU enables. Thus change_cpu_under_node()
is not necessary for !CONFIG_HOTPLUG_CPU.

>
>
>>   static ssize_t show_online(struct device *dev,
>>                             struct device_attribute *attr,
>>                             char *buf)
>> @@ -39,17 +48,23 @@ static ssize_t __ref store_online(struct device *dev,
>>                                    const char *buf, size_t count)
>>   {
>>          struct cpu *cpu = container_of(dev, struct cpu, dev);
>> +       int num = cpu->dev.id;
>

> "num" is wrong name. cpuid may be better.

I'll update it.

>
>
>> +       int from_nid, to_nid;
>>          ssize_t ret;
>>
>>          cpu_hotplug_driver_lock();
>>          switch (buf[0]) {
>>          case '0':
>> -               ret = cpu_down(cpu->dev.id);
>> +               ret = cpu_down(num);
>>                  if (!ret)
>>                          kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
>>                  break;
>>          case '1':
>> -               ret = cpu_up(cpu->dev.id);
>> +               from_nid = cpu_to_node(num);
>> +               ret = cpu_up(num);
>> +               to_nid = cpu_to_node(num);
>> +               if (from_nid != to_nid)
>> +                       change_cpu_under_node(cpu, from_nid, to_nid);
>
> You need to add several comments. this code is not straightforward.

O.K. I'll update it.

Thanks,
Yasuaki Ishimatsu


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