[dpdk-dev] [PATCH v3 28/29] ethdev: reset all when releasing a port

[Ferruh Yigit]

On 9/29/2020 5:02 PM, Thomas Monjalon wrote:
> 29/09/2020 17:50, Ferruh Yigit:
>> On 9/29/2020 12:58 PM, Wang, Haiyue wrote:
>>> From: Thomas Monjalon <thomas at monjalon.net>
>>>> 29/09/2020 12:26, Maxime Coquelin:
>>>>> On 9/29/20 1:14 AM, Thomas Monjalon wrote:
>>>>>> The function rte_eth_dev_release_port() was resetting partially
>>>>>> the struct rte_eth_dev. The drivers were completing it
>>>>>> with more pointers set to NULL in the close or remove operations.
>>>>>>
>>>>>> A full memset is done so most of those assignments become useless.
>>>> [...]
>>>>> With this patch, I get following segfault at init time with Virtio PMD:
>>>>>
>>>>>           Program received signal SIGSEGV, Segmentation fault.
>>>>>           0x0000000000854c9b in rte_eth_dev_callback_register (port_id=32,
>>>>>               event=RTE_ETH_EVENT_UNKNOWN, cb_fn=0x4b24de
>>>>> <eth_event_callback>,
>>>>>               cb_arg=0x0) at ../lib/librte_ethdev/rte_ethdev.c:4042
>>>>>           4042
>>>>> TAILQ_INSERT_TAIL(&(dev->link_intr_cbs),
>>>>
>>>> Yes this is because after closing a port, everything is resetted,
>>>> including .link_intr_cbs which is set only once in a constructor:
>>>> http://git.dpdk.org/dpdk/commit/?id=9ec0b3869d8
>>>>
>>>> I can change this patch to selectively set pointers to NULL.
>>>>
>>>> Or if we prefer a big memset 0, we need to rework how RTE_ETH_ALL
>>>> is managed to register a callback for any event.
>>>> Instead of setting the callback for all ports, we could have
>>>> a special catch-call callback list which is called for all events.
>>>> This way we could revert initializing .link_intr_cbs in eth_dev_get().
>>>>
>>>>
>>>
>>> Move 'struct rte_eth_dev_cb_list link_intr_cbs' to the end of 'struct rte_eth_dev',
>>> and starting from link_intr_cbs, these members will be kept after closed ? :-)
>>>
>>> memset(eth_dev, 0, offsetof(struct rte_eth_dev, link_intr_cbs));
>>>
>>
>> This is similar version of a previous patch:
>> https://patches.dpdk.org/patch/65795/
> 
> I forgot this patch :)
> 
>> That one is also waiting because I remember it was not safe for hotplug.
> 
> I don't think there is a safety issue.
> It makes harder to play with dangling pointers, which is good.
> Note: the .device pointer was already resetted by
> rte_eth_dev_pci_generic_remove(), and generalized in patch 1.
> 

As far as I remember, resetting '.device' in the 'close()' was causing some 
issues on hot remove. Yes patch one already does it, I will test the hot remove 
after close with it.

>> Instead of a big memset, I am for selectively set pointers to NULL.
> 
> I will prepare the patch with selective resets.
> 
>