Messages in this thread | | | Date | Tue, 9 Nov 2021 07:07:02 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH net-next] devlink: Require devlink lock during device reload |
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On Tue, 9 Nov 2021 10:43:58 -0400 Jason Gunthorpe wrote: > This becomes all entangled in the aux device stuff we did before.
So entangled in fact that neither of you is willing to elucidate the exact need ;)
> devlink reload is defined, for reasons unrelated to netns, to do a > complete restart of the aux devices below the devlink. This happens > necessarily during actual reconfiguration operations, for instance. > > So we have a situation, which seems like bad design, where reload is > also triggered by net namespace change that has nothing to do with > reconfiguring.
Agreed, it is somewhat uncomfortable that the same callback achieves two things. As clear as the need for reload-for-reset is (reconfig, recovery etc.) I'm not as clear on reload for netns.
The main use case for reload for netns is placing a VF in a namespace, for a container to use. Is that right? I've not seen use cases requiring the PF to be moved, are there any?
devlink now lives in a networking namespace yet it spans such namespaces (thru global notifiers). I think we need to define what it means for devlink to live in a namespace. Is it just about the configuration / notification channel? Or do we expect proper isolation?
Jiri?
> In this case the per-net-ns becomes a BKL that gets > held across way too much stuff as it recuses down the reload path, > through aux devices, into the driver core and beyond. > > When I looked at trying to fix this from the RDMA side I could not > find any remedy that didn't involve some kind of change in netdev > land. The drivers must be able to register/unregister notifiers in > their struct device_driver probe/remove functions. > > I once sketched out fixing this by removing the need to hold the > per_net_rwsem just for list iteration, which in turn avoids holding it > over the devlink reload paths. It seemed like a reasonable step toward > finer grained locking.
Seems to me the locking is just a symptom.
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