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

[Matan Azrad <matan@mellanox.com>]

Hi Gaetan

From: Gaëtan Rivet
> 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?

The RMV\LSC event callbacks are called from the host thread and also the removal process is running from the host thread so I think EAGAIN is not expected in the removal time.
Other error (EINVAL) may return again every attempt and probably points to another critical issue.

Is a code comment for the above enough? Or you think we still need to check it?


> Thanks,
> --
> Gaëtan Rivet
> 6WIND