Re: [PATCH v2 1/2] net/failsafe: fix removed sub-device cleanup

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

Hello Matan,

On Mon, May 21, 2018 at 07:48:03PM +0000, Matan Azrad wrote:
> The fail-safe PMD registers to RMV event for each removable sub-device
> port in order to cleanup the sub-device resources and switch the Tx
> sub-device directly when it is plugged-out.
> 
> During removal time, the fail-safe PMD stops and closes the sub-device
> but it doesn't unregister the LSC and RMV callbacks of the sub-device
> port.
> 
> It can lead the callbacks to be called for a port which is no more
> associated with the fail-safe sub-device, because there is not a
> guarantee that a sub-device gets the same port ID for each plug-in
> process. This port, for example, may belong to another sub-device of a
> different fail-safe device.
> 
> Unregister the LSC and RMV callbacks for sub-devices which are not
> used.
> 
> Fixes: 598fb8aec6f6 ("net/failsafe: support device removal")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Matan Azrad <matan@mellanox.com>
> ---
>  drivers/net/failsafe/failsafe_ether.c   | 22 ++++++++++++++++++++++
>  drivers/net/failsafe/failsafe_ops.c     |  5 +++++
>  drivers/net/failsafe/failsafe_private.h |  5 +++++
>  3 files changed, 32 insertions(+)
> 
> V2:
> Improve the commit log and add code comments for the new sub-dev fields (Ophir suggestion).
> 
> 
> diff --git a/drivers/net/failsafe/failsafe_ether.c b/drivers/net/failsafe/failsafe_ether.c
> index 733e95d..2bbee82 100644
> --- a/drivers/net/failsafe/failsafe_ether.c
> +++ b/drivers/net/failsafe/failsafe_ether.c
> @@ -260,6 +260,7 @@
>  		sdev->state = DEV_ACTIVE;
>  		/* fallthrough */
>  	case DEV_ACTIVE:
> +		failsafe_eth_dev_unregister_callbacks(sdev);
>  		rte_eth_dev_close(PORT_ID(sdev));
>  		sdev->state = DEV_PROBED;
>  		/* fallthrough */
> @@ -321,6 +322,27 @@
>  }
>  
>  void
> +failsafe_eth_dev_unregister_callbacks(struct sub_device *sdev)
> +{
> +	if (sdev == NULL)
> +		return;
> +	if (sdev->rmv_callback) {
> +		rte_eth_dev_callback_unregister(PORT_ID(sdev),
> +					RTE_ETH_EVENT_INTR_RMV,
> +					failsafe_eth_rmv_event_callback,
> +					sdev);
> +		sdev->rmv_callback = 0;

I agree with Ophir here, either the return value should not be ignored,
and rmv_callback should only be set to 0 on success, or a proper
justification (and an accompanying comment) should be given.

The issue I could see is that even on error, there won't be a process to
try again unregistering the callback.

Maybe this could be added in failsafe_dev_remove()? Something like

FOREACH_SUBDEV(sdev, i, dev) {
    if (sdev->rmv_callback && sdev->state <= DEV_PROBED)
        if (rte_eth_dev_callback_unregister(...) == 0)
            sdev->rmv_callback = 0;
    /* same for lsc_callback */
}

Does it make sense to you? Do you think this is necessary, or should we
ignore this?

Thanks,
-- 
Gaëtan Rivet
6WIND