linux-kernel - Re: [PATCH v3] acpi: Fix CPU hot removal problem

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Date:	Thu, 15 Sep 2011 09:35:34 +0800
From:	"canquan.shen" <shencanquan@...wei.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	len.brown@...el.com,
	"shemminger@...tta.com" <shemminger@...tta.com>,
	"yakui.zhao@...el.com" <yakui.zhao@...el.com>,
	"xiaowei.yang@...wei.com" <xiaowei.yang@...wei.com>,
	hanweidong <hanweidong@...wei.com>, linqiangmin@...wei.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v3] acpi: Fix CPU hot removal problem

On 2011/9/14 22:14, Bjorn Helgaas wrote:
> On Tue, Sep 13, 2011 at 8:18 PM, canquan.shen<shencanquan@...wei.com>  wrote:
>> We run linux as a guest in Xen environment. When we used the xen tools
>> (xm vcpu-set<n>) to hot add and remove vcpu to and from the guest, we
>> encountered the failure on vcpu removal. We found the reason is that it
>> didn't go to really remove cpu in the cpu removal code path.
>>
>> This patch adds acpi_bus_trim in acpi_process_hotplug_notify to fix this
>> issue. With this patch, it works fine for us.
>>
>> Signed-off-by: Shen canquan<shencanquan@...wei.com>
>> ---
>>   drivers/acpi/processor_driver.c |    7 +++++++
>>   1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/acpi/processor_driver.c
>> b/drivers/acpi/processor_driver.c
>> index a4e0f1b..0856ef8 100644
>> --- a/drivers/acpi/processor_driver.c
>> +++ b/drivers/acpi/processor_driver.c
>> @@ -677,6 +677,13 @@ static void acpi_processor_hotplug_notify(acpi_handle
>> handle,
>>                                     "Driver data is NULL, dropping EJECT\n");
>>                         return;
>>                 }
>> +               ACPI_DEBUG_PRINT((ACPI_DB_INFO,
>> +                       "Hot-removing processor device %s\n",
>> +                       dev_name(&device->dev)));
>> +               if (acpi_bus_trim(device, 1)) {
>> +                       printk(KERN_ERR "ACPI: Removing device failed!\n");
>
> We can do better than that.  Nobody ever looks at ACPI_DEBUG_PRINT info.
>
>      u32 id;
>      ...
>      id = pr->id;
>      if (acpi_bus_trim(device, 1))
>          printk(KERN_ERR PREFIX "Failed to remove CPU %d\n", id);
>
> (No "return" needed here.  In fact, the "return" at the bottom of
> acpi_processor_hotplug_notify() is also superfluous.  You could remove
> it at the same time.)
>
> .
>

Thanks for your suggestion. I will modify it and resend the patch.

--
Canquan.shen


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