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

[Bjorn Helgaas]

> äé: [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@xxxxxxxxxx>
> ---
> Âdrivers/acpi/processor_driver.c | Â Â2 ++
> Â1 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,
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â "Driver data is NULL, dropping EJECT\n");
> Â Â Â Â Â Â Â Â Â Â Â Â return;
> Â Â Â Â Â Â Â Â }
> +
> + Â Â Â Â Â Â Â kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
> Â Â Â Â Â Â Â Â break;
> Â Â Â Â default:
> Â Â Â Â Â Â Â Â 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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