Re: [PATCH] failsafe: fix segfault on hotplug event

[Luc Pelletier <lucp.at.work@gmail.com>]

Hi Konstantin,

> It is not recommended way to update rte_eth_fp_ops[] contents directly.
> There are eth_dev_fp_ops_setup()/ eth_dev_fp_ops_reset() that supposed
> to be used for that.

Good to know. I see another fix that was made in a different PMD that
does exactly the same thing:

https://github.com/DPDK/dpdk/commit/bcd68b68415172815e55fc67cf3947c0433baf74

CC'ing the authors for awareness.

> About the fix itself - while it might help till some extent,
> I think it will not remove the problem completely.
> There still remain a race-condition between rte_eth_rx_burst() and failsafe_eth_rmv_event_callback().
> Right now DPDK doesn't support switching PMD fast-ops functions (or updating rxq/txq data)
> on the fly.

Thanks for the information. This is very helpful.

Are you saying that the previous code also had that same race
condition? It was only updating the rte_eth_dev structure, but I
assume the problem would have been the same since rte_eth_rx_burst()
in DPDK versions <=20 use the function pointers in rte_eth_dev, not
rte_eth_fp_ops.

Can you think of a possible solution to this problem? I'm happy to
provide a patch to properly fix the problem. Having your guidance
would be extremely helpful.

Thanks!