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    SubjectRe: [PATCH net-next] devlink: Require devlink lock during device reload
    On Mon, 15 Nov 2021 11:09:31 -0400 Jason Gunthorpe wrote:
    > On Mon, Nov 15, 2021 at 03:42:58PM +0100, Jiri Pirko wrote:
    > > >Sorry, I don't agree that registering a net notifier in an aux device
    > > >probe function is non-standard or wrong.
    > >
    > > Listening to events which happen in different namespaces and react to
    > > them is the non-standard behaviour which I refered to. If you would not
    > > need to do it, you could just use netns notofier which would solve your
    > > issue. You know it.
    >
    > Huh?
    >
    > It calls the bog standard
    >
    > register_netdevice_notifier()
    >
    > Like hundreds of other drivers do from their probe functions
    >
    > Which does:
    >
    > int register_netdevice_notifier(struct notifier_block *nb)
    > {
    > struct net *net;
    > int err;
    >
    > /* Close race with setup_net() and cleanup_net() */
    > down_write(&pernet_ops_rwsem);
    >
    > And deadlocks because devlink hols the pernet_ops_rwsem when it
    > triggers reload in some paths.
    >
    > There is nothing wrong with a driver doing this standard pattern.
    >
    > There is only one place in the entire kernel calling the per-ns
    > register_netdevice_notifier_dev_net() and it is burred inside another
    > part of mlx5 for some reason..
    >
    > I believe Parav already looked at using that in rdma and it didn't
    > work for some reason I've forgotten.
    >
    > It is not that we care about events in different namespaces, it is
    > that rdma, like everything else, doesn't care about namespaces and
    > wants events from the netdev no matter where it is located.

    devlink now allows drivers to be net ns-aware, and they should
    obey if they declare support. Can we add a flag / capability
    to devlink and make it an explicit opt-in for drivers who care?

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