Re: [PATCH] ACPI: Add ACPI CPU hot-remove support

[Jiang Liu <liuj97@gmail.com>]

Hi Toshi,
	I think a better solution here is to send a notification to acpid
daemon instead of directly ejecting the physical processor in kernel by
apci hotplug work thread. The daemon should do:
	1) check whether user policy allows to remove the physical processor
	2) resolve any dependency issues, such as some memory/IOHs may have
	dependency on the processor.
	3) Remove all devices on the physical processor through sysfs.
	4) Power off the physical processor through sysfs.

	If we rely on the acpi hotplug work thread to do the hard work, it
may block the work thread for a very long time and it won't respond to other
hotplug events.
	Thanks!
	Gerry
On 06/29/2012 10:51 PM, Toshi Kani wrote:
> Added CPU hot-remove support through an ACPI eject notification.
> It calls acpi_bus_hot_remove_device(), which shares the same code
> path with the sysfs eject operation.  acpi_os_hotplug_execute()
> serializes hot-remove operations between ACPI hot-remove and sysfs
> eject requests.
> 
> Signed-off-by: Toshi Kani <toshi.kani@hp.com>
> 
> ---
> This patch applies on top of the patchset below.
> 
> [PATCH v6 0/6] ACPI: Add _OST support for ACPI hotplug
> http://marc.info/?l=linux-acpi&m=134074381322973&w=2
> 
> ---
>  drivers/acpi/processor_driver.c |   27 +++++++++++++++++----------
>  1 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
> index f9fa1b2..a6f6bde 100644
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -699,8 +699,8 @@ int acpi_processor_device_add(acpi_handle handle, struct acpi_device **device)
>  static void acpi_processor_hotplug_notify(acpi_handle handle,
>  					  u32 event, void *data)
>  {
> -	struct acpi_processor *pr;
>  	struct acpi_device *device = NULL;
> +	struct acpi_eject_event *ej_event = NULL;
>  	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
>  	int result;
>  
> @@ -732,20 +732,27 @@ static void acpi_processor_hotplug_notify(acpi_handle handle,
>  				  "received ACPI_NOTIFY_EJECT_REQUEST\n"));
>  
>  		if (acpi_bus_get_device(handle, &device)) {
> -			printk(KERN_ERR PREFIX
> -				    "Device don't exist, dropping EJECT\n");
> +			pr_err(PREFIX "Device don't exist, dropping EJECT\n");
>  			break;
>  		}
> -		pr = acpi_driver_data(device);
> -		if (!pr) {
> -			printk(KERN_ERR PREFIX
> -				    "Driver data is NULL, dropping EJECT\n");
> +		if (!acpi_driver_data(device)) {
> +			pr_err(PREFIX "Driver data is NULL, dropping EJECT\n");
>  			break;
>  		}
>  
> -		/* REVISIT: update when eject is supported */
> -		ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
> -		break;
> +		ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
> +		if (!ej_event) {
> +			pr_err(PREFIX "No memory, dropping EJECT\n");
> +			break;
> +		}
> +
> +		ej_event->handle = handle;
> +		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
> +		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
> +					(void *)ej_event);
> +
> +		/* eject is performed asynchronously */
> +		return;
>  
>  	default:
>  		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
>