Re: [dpdk-dev] [PATCH v2] ethdev: complete closing of port

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 10/10/18 11:39 AM, Thomas Monjalon wrote:
> 10/10/2018 09:50, Andrew Rybchenko:
>> On 10/10/18 10:44 AM, Thomas Monjalon wrote:
>>> 10/10/2018 08:15, Andrew Rybchenko:
>>>> On 10/10/18 1:17 AM, Thomas Monjalon wrote:
>>>>> After closing a port, it cannot be restarted.
>>>>> So there is no reason to not free all associated resources.
>>>>>
>>>>> The last step was done with rte_eth_dev_detach() which is deprecated.
>>>>> Instead of blindly removing the associated rte_device, the driver should
>>>>> check if no more port (ethdev, cryptodev, etc) is open for the device.
>>>>>
>>>>> The last ethdev freeing (dev_private and final release), which were done
>>>>> by rte_eth_dev_detach(), are now done at the end of rte_eth_dev_close().
>>>>>
>>>>> If the driver is trying to free the port again, the function
>>>>> rte_eth_dev_release_port() will abort with -ENODEV error.
>>>>>
>>>>> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
>>>>> ---
>>>>>     lib/librte_ethdev/rte_ethdev.c | 6 ++++++
>>>>>     lib/librte_ethdev/rte_ethdev.h | 3 +--
>>>>>     2 files changed, 7 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
>>>>> index ed83e5954..3062dc711 100644
>>>>> --- a/lib/librte_ethdev/rte_ethdev.c
>>>>> +++ b/lib/librte_ethdev/rte_ethdev.c
>>>>> @@ -506,6 +506,8 @@ rte_eth_dev_release_port(struct rte_eth_dev *eth_dev)
>>>>>     {
>>>>>     	if (eth_dev == NULL)
>>>>>     		return -EINVAL;
>>>>> +	if (eth_dev->state == RTE_ETH_DEV_UNUSED)
>>>>> +		return -ENODEV;
>>>>>     
>>>>>     	rte_eth_dev_shared_data_prepare();
>>>>>     
>>>>> @@ -1441,6 +1443,10 @@ rte_eth_dev_close(uint16_t port_id)
>>>>>     	dev->data->nb_tx_queues = 0;
>>>>>     	rte_free(dev->data->tx_queues);
>>>>>     	dev->data->tx_queues = NULL;
>>>>> +
>>>>> +	rte_free(dev->data->dev_private);
>>>> It is used by, for example, PCI device uninit functions.
>>>> What does guarantee that uninit is done and we can free the private data.
>>> The state of the port is set to UNUSED and the name is NULL.
>>> So nobody should try to use it anymore.
>>> There are already some checks before calling uninit functions.
>>> For instance, in rte_eth_dev_pci_generic_remove(),
>>> rte_eth_dev_allocated() will return NULL and won't call uninit function.
>> The questions are:
>> Is application allowed to call the function? When?
>> Who calls uninit in this case? (What does guarantee that uninit is done
>> before close)
> So far, everything is allowed:
> 	- The application can close a port and remove the rte_device later.

If the patch is applied, close frees dev_private which is used by uninit.
So, uninit must be done first. Who does it?
(it looks like I'm missing something obvious, but still can't find it)

> 	- The application can remove the rte_device and expect the PMD is closing
> 		associated ports.
>
> In other words, when rte_device is removed, the ports should be closed
> by the PMD, except if the application has already closed the ports.
> It means ethdev port close is optional, but EAL removal is always required.
> The behaviour is not changed.
>
> If we want to go further, we could change the behaviour of the close op,
> by asking the PMD to remove the rte_device automatically if all associated
> ports are closed. It would allow the application to manage only ports
> at ethdev layer without bothering with low-level EAL management.
> We can think about it as a planned change for next releases.
>
>