linux-kernel - Re: Re : [PATCH] acpi: Fix hot cpu remove problem on acpi subsystem

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Date:	Mon, 5 Sep 2011 22:19:09 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Shen Canquan <shencanquan@...wei.com>
Cc:	"lenb@...nel.org" <lenb@...nel.org>,
	"rui.zhao@...el.com" <rui.zhao@...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>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: Re : [PATCH] acpi: Fix hot cpu remove problem on acpi subsystem

> 主题: [PATCH] acpi: Fix hot cpu remove problem on acpi subsystem
>
> In Xen virtualization environment, When I used xen tools (xm vcpu-set vcpu_number ) to test the vcpu add and remove, I found it is failure on vcpu remove, I found the reason is that nothing to do when cpu remove in acpi_processor_hotplug_notify function, so I add the code of send the OFFLINE message to udev and add the rule of udev. it is ok on vcpu remove.
> Signed-off-by: Shen canquan <shencanquan@...wei.com>
> ---
>  drivers/acpi/processor_driver.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index a4e0f1b..a1c564f 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -677,6 +677,8 @@ static void acpi_processor_hotplug_notify(acpi_handle handle,
>                                     "Driver data is NULL, dropping EJECT\n");
>                         return;
>                 }
> +
> +               kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
>                 break;
>         default:
>                 ACPI_DEBUG_PRINT((ACPI_DB_INFO,

The processor driver used to generate ONLINE and OFFLINE messages.  I
removed them with c1815e0740.  According to the changelog, the driver
core still generates KOBJ_ADD and KOBJ_REMOVE events.

Could you fix the Xen vcpu add/remove problem by looking for
ADD/REMOVE events rather than ONLINE/OFFLINE?

I removed ONLINE/OFFLINE because I think hotplug should be handled in
the ACPI core, not in the drivers.  Removing ONLINE/OFFLINE got rid of
one small piece of driver-specific hotplug handling.  Obviously,
there's still a lot to do.

If using ADD/REMOVE is not sufficient, what is the justification for
needing both REMOVE and OFFLINE, and how would they be different?

Bjorn
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