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    SubjectRe: [PATCH net-next] devlink: Require devlink lock during device reload
    Sun, Nov 14, 2021 at 07:19:02AM CET, leon@kernel.org wrote:
    >On Fri, Nov 12, 2021 at 08:38:56AM +0100, Jiri Pirko wrote:
    >> Thu, Nov 11, 2021 at 01:17:52PM CET, leon@kernel.org wrote:
    >> >On Thu, Nov 11, 2021 at 01:05:11PM +0100, Jiri Pirko wrote:
    >> >> Tue, Nov 09, 2021 at 07:24:27PM CET, jgg@nvidia.com wrote:
    >> >> >On Tue, Nov 09, 2021 at 08:20:42AM -0800, Jakub Kicinski wrote:
    >> >> >> On Tue, 9 Nov 2021 11:33:35 -0400 Jason Gunthorpe wrote:
    >> >> >> > > > 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.
    >> >> >> >
    >> >> >> > My fear is this reload during net ns destruction is devlink uAPI now
    >> >> >> > and, yes it may be only a symptom, but the root cause may be unfixable
    >> >> >> > uAPI constraints.
    >> >> >>
    >> >> >> If I'm reading this right it locks up 100% of the time, what is a uAPI
    >> >> >> for? DoS? ;)
    >> >> >>
    >> >> >> Hence my questions about the actual use cases.
    >> >> >
    >> >> >Removing namespace support from devlink would solve the crasher. I
    >> >> >certainly didn't feel bold enough to suggest such a thing :)
    >> >> >
    >> >> >If no other devlink driver cares about this it is probably the best
    >> >> >idea.
    >> >>
    >> >> Devlink namespace support is not generic, not related to any driver.
    >> >
    >> >What do you mean?
    >> >
    >> >devlink_pernet_pre_exit() calls to devlink reload, which means that only
    >> >drivers that support reload care about it. The reload is driver thing.
    >>
    >> However, Jason was talking about "namespace support removal from
    >> devlink"..
    >
    >The code that sparkles deadlocks is in devlink_pernet_pre_exit() and
    >this will be nice to remove. I just don't know if it is possible to do
    >without ripping whole namespace support from devlink.

    As discussed offline, the non-standard mlx5/IB usage of network
    namespaces requires non standard mlx5/IB workaround. Does not make any
    sense to remove the devlink net namespace support removal.


    >
    >Thanks
    >
    >>
    >>
    >> >
    >> >Thanks
    >> >
    >> >>
    >> >> >
    >> >> >Jason

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