> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Tuesday, October 20, 2020 12:31 AM
>
> On Mon, Oct 19, 2020 at 01:23:23PM +0000, Parav Pandit wrote:
> > > > - err = register_netdevice_notifier(&dev->port[port_num].roce.nb);
> > > > + err = register_netdevice_notifier_net(mlx5_core_net(dev->mdev),
> > > > + &dev->port[port_num].roce.nb);
> > >
> > > This looks racy, what lock needs to be held to keep *mlx5_core_net()
> stable?
> >
> > mlx5_core_net() cannot be accessed outside of mlx5 driver's load, unload,
> reload path.
> >
> > When this is getting executed, devlink cannot be executing reload.
> > This is guarded by devlink_reload_enable/disable calls done by mlx5 core.
>
> A comment that devlink_reload_enable/disable() must be held would be
> helpful
>
Yes. will add.
> > >
> > > > if (err) {
> > > > dev->port[port_num].roce.nb.notifier_call = NULL;
> > > > return err;
> > > > @@ -3335,7 +3336,8 @@ static int mlx5_add_netdev_notifier(struct
> > > >mlx5_ib_dev *dev, u8 port_num) static void
> > > >mlx5_remove_netdev_notifier(struct mlx5_ib_dev *dev, u8 port_num)
> {
> > > > if (dev->port[port_num].roce.nb.notifier_call) {
> > > > - unregister_netdevice_notifier(&dev-
> > > >port[port_num].roce.nb);
> > > > + unregister_netdevice_notifier_net(mlx5_core_net(dev-
> > > >mdev),
> > > > + &dev-
> > > >port[port_num].roce.nb);
> > >
> > > This seems dangerous too, what if the mlx5_core_net changed before
> > > we get here?
> >
> > When I inspected driver, code, I am not aware of any code flow where
> > this can change before reaching here, because registration and
> > unregistration is done only in driver load, unload and reload path.
> > Reload can happen only after devlink_reload_enable() is done.
>
> But we enable reload right after init_one
>
> > > What are the rules for when devlink_net() changes?
> > >
> > devlink_net() changes only after unload() callback is completed in driver.
>
> You mean mlx5_devlink_reload_down ?
>
Right.
> That seems OK then
Ok. will work with Leon to add the comment.
>
> Jason
