Re: dst_ifdown breaks infiniband?

["Michael S. Tsirkin" <mst@dev.mellanox.co.il>]

> Quoting Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>:
> Subject: Re: dst_ifdown breaks infiniband?
> 
> Hello!
> 
> > If a device driver sets neigh_destructor in neigh_params, this could
> > get called after the device has been unregistered and the driver module
> > removed.
> 
> It is the same problem: if dst->neighbour holds neighbour, it should
> not hold device. parms->dev is not supposed to be used after
> neigh_parms_release(). F.e. set parms->dev to NULL to catch bad references.

Yes. I fixed that - simply checking that neighbour->dev is a
loopback device is sufficient to detect the fact that
the device is being unregistered.

> Do you search for a way to find real inifiniband device in
> ipoib_neigh_destructor()?

No, not anymore.

> I guess you will not be able.

I agree it's not possible.

> The problem is logical: if destructor needs device, neighbour entry
> _somehow_ have to hold reference to the device (via neigh->dev, neigh->parms,
> whatever). Hence, if we hold neighbour entry, unregister cannot be completed.
> Therefore, destructor cannot refer to device. Q.E.D. :-)
> 
> Seems, releasing dst->neighbour is inevitable.

infiniband sets parm->neigh_destructor, and I search for a way to prevent
this destructor from being called after the module has been unloaded.
Ideas?

-- 
MST