create sysfs link from acpi device to sysdev for cpu

Sys I/F under acpi device node and sysdev device node are both
needed for cpu hot-removal. User space need this link so that
they know they are poking the sys I/F for the same cpu.
http://bugzilla.kernel.org/show_bug.cgi?id=9772

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

drivers/acpi/processor_core.c

@@ -621,7 +621,7 @@ static int __cpuinit acpi_processor_start(struct acpi_device *device)
 	int result = 0;
 	acpi_status status = AE_OK;
 	struct acpi_processor *pr;
-
+	struct sys_device *sysdev;
 
 	pr = acpi_driver_data(device);
 
@@ -652,6 +652,10 @@ static int __cpuinit acpi_processor_start(struct acpi_device *device)
 	if (result)
 		goto end;
 
+	sysdev = get_cpu_sysdev(pr->id);
+	if (sysfs_create_link(&device->dev.kobj, &sysdev->kobj, "sysdev"))
+		return -EFAULT;
+
 	status = acpi_install_notify_handler(pr->handle, ACPI_DEVICE_NOTIFY,
 					     acpi_processor_notify, pr);
 
@@ -810,6 +814,8 @@ static int acpi_processor_remove(struct acpi_device *device, int type)
 	status = acpi_remove_notify_handler(pr->handle, ACPI_DEVICE_NOTIFY,
 					    acpi_processor_notify);
 
+	sysfs_remove_link(&device->dev.kobj, "sysdev");
+
 	acpi_processor_remove_fs(device);
 
 	if (pr->cdev) {