Re: [Patch v5 2/7] acpi,memory-hotplug: deal with eject request in hotplug queue

[Wen Congyang <wency@cn.fujitsu.com>]

At 11/16/2012 07:32 AM, David Rientjes Wrote:
> On Thu, 15 Nov 2012, Wen Congyang wrote:
> 
>> The memory device can be removed by 2 ways:
>> 1. send eject request by SCI
>> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
>>
>> We handle the 1st case in the module acpi_memhotplug, and handle
>> the 2nd case in ACPI eject notification. This 2 events may happen
>> at the same time, so we may touch acpi_memory_device.res_list at
>> the same time. This patch reimplements memory-hotremove support
>> through an ACPI eject notification. Now the memory device is
>> offlined and hotremoved only in the function acpi_memory_device_remove()
>> which is protected by device_lock().
>>
> 
> You mean it's protected by device_lock() before calling the remove() 
> function for eject?

Yes. We call device_release_driver() to unbind the device from the driver
(the memory will be offlined/removed when it is unbound from the driver).

we call device_lock() in device_release_driver(), so we only unbind it
from the driver once.

Thanks
Wen Congyang

> 
>> CC: David Rientjes <rientjes@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> CC: Len Brown <len.brown@intel.com>
>> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>> CC: Paul Mackerras <paulus@samba.org>
>> CC: Christoph Lameter <cl@linux.com>
>> Cc: Minchan Kim <minchan.kim@gmail.com>
>> CC: Andrew Morton <akpm@linux-foundation.org>
>> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> CC: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> CC: Rafael J. Wysocki <rjw@sisk.pl>
>> CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>> ---
>>  drivers/acpi/acpi_memhotplug.c | 87 +++++-------------------------------------
>>  1 file changed, 9 insertions(+), 78 deletions(-)
>>
>> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
>> index 2918be1..6e12042 100644
>> --- a/drivers/acpi/acpi_memhotplug.c
>> +++ b/drivers/acpi/acpi_memhotplug.c
>> @@ -272,40 +272,6 @@ static int acpi_memory_enable_device(struct acpi_memory_device *mem_device)
>>  	return 0;
>>  }
>>  
>> -static int acpi_memory_powerdown_device(struct acpi_memory_device *mem_device)
>> -{
>> -	acpi_status status;
>> -	struct acpi_object_list arg_list;
>> -	union acpi_object arg;
>> -	unsigned long long current_status;
>> -
>> -
>> -	/* Issue the _EJ0 command */
>> -	arg_list.count = 1;
>> -	arg_list.pointer = &arg;
>> -	arg.type = ACPI_TYPE_INTEGER;
>> -	arg.integer.value = 1;
>> -	status = acpi_evaluate_object(mem_device->device->handle,
>> -				      "_EJ0", &arg_list, NULL);
>> -	/* Return on _EJ0 failure */
>> -	if (ACPI_FAILURE(status)) {
>> -		ACPI_EXCEPTION((AE_INFO, status, "_EJ0 failed"));
>> -		return -ENODEV;
>> -	}
>> -
>> -	/* Evalute _STA to check if the device is disabled */
>> -	status = acpi_evaluate_integer(mem_device->device->handle, "_STA",
>> -				       NULL, &current_status);
>> -	if (ACPI_FAILURE(status))
>> -		return -ENODEV;
>> -
>> -	/* Check for device status.  Device should be disabled */
>> -	if (current_status & ACPI_STA_DEVICE_ENABLED)
>> -		return -EINVAL;
>> -
>> -	return 0;
>> -}
>> -
>>  static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
>>  {
>>  	int result;
>> @@ -325,34 +291,11 @@ static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
>>  	return 0;
>>  }
>>  
>> -static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
>> -{
>> -	int result;
>> -
>> -	/*
>> -	 * Ask the VM to offline this memory range.
>> -	 * Note: Assume that this function returns zero on success
>> -	 */
>> -	result = acpi_memory_remove_memory(mem_device);
>> -	if (result)
>> -		return result;
>> -
>> -	/* Power-off and eject the device */
>> -	result = acpi_memory_powerdown_device(mem_device);
>> -	if (result) {
>> -		/* Set the status of the device to invalid */
>> -		mem_device->state = MEMORY_INVALID_STATE;
>> -		return result;
>> -	}
>> -
>> -	mem_device->state = MEMORY_POWER_OFF_STATE;
>> -	return result;
>> -}
>> -
>>  static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
>>  {
>>  	struct acpi_memory_device *mem_device;
>>  	struct acpi_device *device;
>> +	struct acpi_eject_event *ej_event = NULL;
>>  	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
>>  
>>  	switch (event) {
>> @@ -394,31 +337,19 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
>>  			break;
>>  		}
>>  
>> -		/*
>> -		 * Currently disabling memory device from kernel mode
>> -		 * TBD: Can also be disabled from user mode scripts
>> -		 * TBD: Can also be disabled by Callback registration
>> -		 *      with generic sysfs driver
>> -		 */
>> -		if (acpi_memory_disable_device(mem_device)) {
>> -			printk(KERN_ERR PREFIX "Disable memory device\n");
>> -			/*
>> -			 * If _EJ0 was called but failed, _OST is not
>> -			 * necessary.
>> -			 */
>> -			if (mem_device->state == MEMORY_INVALID_STATE)
>> -				return;
>> -
>> +		ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
>> +		if (!ej_event) {
>> +			pr_err(PREFIX "No memory, dropping EJECT\n");
>>  			break;
>>  		}
>>  
>> -		/*
>> -		 * TBD: Invoke acpi_bus_remove to cleanup data structures
>> -		 */
>> +		ej_event->handle = handle;
>> +		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
>> +		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
>> +					(void *)ej_event);
>>  
>> -		/* _EJ0 succeeded; _OST is not necessary */
>> +		/* eject is performed asynchronously */
>>  		return;
>> -
>>  	default:
>>  		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
>>  				  "Unsupported event [0x%x]\n", event));
>