[rds-devel] [PATCH RFC RFC] rds: Use NETDEV_UNREGISTER in rds_tcp_dev_event() (then kill NETDEV_UNREGISTER_FINAL)
Sowmini Varadhan
sowmini.varadhan at oracle.com
Fri Mar 16 06:00:08 PDT 2018
On (03/16/18 15:38), Kirill Tkhai wrote:
>
> 467fa15356acf by Sowmini Varadhan added NETDEV_UNREGISTER_FINAL dependence
> with the commentary:
>
> /* rds-tcp registers as a pernet subys, so the ->exit will only
> * get invoked after network acitivity has quiesced. We need to
> * clean up all sockets to quiesce network activity, and use
> * the unregistration of the per-net loopback device as a trigger
> * to start that cleanup.
> */
>
> It seems all the protocols pernet subsystems meet this situation, but they
> solve it in generic way. What does rds so specific have?
The difference with rds is this: most consumers of netns associate
a net_device with the netns, and cleanup of the netns state
happens as part of the net_device teardown without the constraint
above. rds-tcp does has a netns tied to listening socket, not
to a specific network interface (net_device) so it registers
as a pernet-subsys. But this means that cleanup has to be
cone carefully (see comments in net_namespace.h before
register_pernet_subsys)
For rds-tcp, we need to be able to do the right thing in both of these
cases
1. modprobe -r rds-tcp (cleanup of rds-tcp state should happen in
every namespace, including init_net)
2. netns delete (rds_tcp.ko should remain loaded for other namespaces)
> This commit makes event handler to iterate rds_tcp_conn_list and
> kill them. If we change the stage to NETDEV_UNREGISTER, what will change?
The above two cases need to work correctly.
> Can unregistered loopback device on dead net add new items to rds_tcp_conn_list?
> How it's possible?
I dont understand the question- no unregistered loopback devices
cannot add items.
fwiw, I had asked questions about this (netns per net_device
vs netns for module) on the netdev list a few years ago, I can
try to hunt down that thread for you later (nobody replied to
it, but maybe it will help answer your questions).
--Sowmini
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