Re: [dpdk-dev] [PATCH 20.05] ethdev: clear struct on releasing port

[Thomas Monjalon <thomas@monjalon.net>]

13/02/2020 17:05, Ferruh Yigit:
> On 2/13/2020 3:27 PM, Thomas Monjalon wrote:
> > 13/02/2020 16:16, Ferruh Yigit:
> >> On 2/13/2020 2:33 PM, Thomas Monjalon wrote:
> >>> The function rte_eth_dev_release_port() is called by drivers
> >>> when closing or removing a device.
> >>> Its main usage should be via rte_eth_dev_close() by up-to-date
> >>> drivers which are compliant with RTE_ETH_DEV_CLOSE_REMOVE flag.
> >>>
> >>> When a port is released, the data (rte_eth_dev_data) are cleared,
> >>> but the pointers in rte_eth_dev were not cleared.
> >>> It may cause issues with code paths trying to use dangling pointers
> >>> (e.g. the .device pointer which may reference a removed rte_device).
> >>> Everything is now cleared to 0 when releasing.
> >>> The state is explicitly set to RTE_ETH_DEV_UNUSED which is 0 anyway.
> >>>
> >>> Using this patch may reveal bugs in some code paths:
> >>> 	- device pointer must be saved before closing a port if needed
> >>
> >> Is this saving should be done in application code or will be done by ethdev?
> > 
> > by the application
> > From ethdev point of view, when a port is closed, there is nothing more to do next.
> > 
> 
> That sound reasonable from ethdev perspective, but it will push dealing with
> rte_device level details to the application.
> 
> Like this change will be forcing each application to store the rte_device
> pointer before close(), in case device can be detached later.

Yes
I think PMDs could release rte_device when closing the last port of the device.
I am not sure what is the benefit of explicit detach.
That's something we should discuss, agree and write in the API doc.