Re: [PATCH rdma-next] bnxt_re: Rely on Kconfig to keep module dependency

[Leon Romanovsky <leon@kernel.org>]

On Wed, Mar 24, 2021 at 02:35:56PM -0300, Jason Gunthorpe wrote:
> On Wed, Mar 24, 2021 at 10:54:58PM +0530, Devesh Sharma wrote:
> > On Wed, Mar 24, 2021 at 10:26 PM Jason Gunthorpe <jgg@nvidia.com> wrote:
> > >
> > > On Wed, Mar 24, 2021 at 10:00:05PM +0530, Devesh Sharma wrote:
> > >
> > > > > > > -static void bnxt_re_dev_unprobe(struct net_device *netdev,
> > > > > > > -                           struct bnxt_en_dev *en_dev)
> > > > > > > -{
> > > > > > > -   dev_put(netdev);
> > > > > > > -   module_put(en_dev->pdev->driver->driver.owner);
> > > > > > > -}
> > > > > >
> > > > > > And you are right to be wondering WTF is this
> > > >
> > > > Still trying to understand but what's the big idea here may be I can help.
> > >
> > > A driver should not have module put things like the above
> > >
> > > It should not be accessing ->driver without holding the device_lock()
> > >
> > > Basically it is all nonsense coding, Leon suggests to delete it and he
> > > is probably right.
> > >
> > > Can you explain what it thinks it is doing?
> > That F'ed up  code is trying to prevent a situation where someone
> > tries to remove the bnxt_en driver while bnxt_re driver is using it.
> > All because bnxt_re driver is at the mercy of bnxt_en drive and there
> > is not symbole dependence, Do you suggest anything to prevent that
> > unload of bnxt_en other than doing this jargon.
> 
> Well, the module put says nothing about the validity of the 'struct
> bnxt' and related it extracted from the netdev - you should have a
> mechanism that prevents that from going invalid which in turn will
> ensure the function pointers you want to touch are still valid
> too. (as the struct containing function pointers must become invalid
> before the module unloads)
> 
> Probably the netdev refcount does that already but I always forget the
> exact point during unregister that it waits on that...
> 
> As far as strict module dependencies go, replace the pointless
> brp->ulp_probe function pointer with an actual call to
> bnxt_ulp_probe() and you get the same effect as the module_get.

Yeah, I'll update it.

Thanks

> 
> Jason