Re: [PATCH 1/2] can: bcm: registration process optimization in bcm_module_init()

[Oliver Hartkopp]

On 09.09.22 05:58, Ziyang Xuan (William) wrote:
> > On 9/8/22 13:14, Ziyang Xuan (William) wrote:
> > > > Just another reference which make it clear that the reordering of function calls in your patch is likely not correct:
> > > >
> > > > https://elixir.bootlin.com/linux/v5.19.7/source/net/packet/af_packet.c#L4734
> > > >
> > > > static int __init packet_init(void)
> > > > {
> > > >           int rc;
> > > >
> > > >           rc = proto_register(&packet_proto, 0);
> > > >           if (rc)
> > > >                   goto out;
> > > >           rc = sock_register(&packet_family_ops);
> > > >           if (rc)
> > > >                   goto out_proto;
> > > >           rc = register_pernet_subsys(&packet_net_ops);
> > > >           if (rc)
> > > >                   goto out_sock;
> > > >           rc = register_netdevice_notifier(&packet_netdev_notifier);
> > > >           if (rc)
> > > >                   goto out_pernet;
> > > >
> > > >           return 0;
> > > >
> > > > out_pernet:
> > > >           unregister_pernet_subsys(&packet_net_ops);
> > > > out_sock:
> > > >           sock_unregister(PF_PACKET);
> > > > out_proto:
> > > >           proto_unregister(&packet_proto);
> > > > out:
> > > >           return rc;
> > > > }

> Yes，all these socket operations need time, most likely, register_netdevice_notifier() and register_pernet_subsys() had been done.
> But it maybe not for some reasons, for example, cpu# that runs {raw,bcm}_module_init() is stuck temporary,
> or pernet_ops_rwsem lock competition in register_netdevice_notifier() and register_pernet_subsys().
>
> If the condition which I pointed happens, I think my solution can solve.

No, I don't think so.

We need to maintain the exact order which is depicted in the af_packet.c 
code from above as the notifier call references the sock pointer.

Regards,
Oliver