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Date:   Fri, 25 Mar 2022 09:49:52 -0700
From:   Jakub Kicinski <>
To:     Johannes Berg <>
Cc:     William McVicker <>,,
        Marek Szyprowski <>,
        Kalle Valo <>,
        "David S. Miller" <>,,
        Amitkumar Karwar <>,
        Ganapathi Bhat <>,
        Xinming Hu <>,,
        Paolo Abeni <>
Subject: Re: [BUG] deadlock in nl80211_vendor_cmd

On Fri, 25 Mar 2022 13:04:23 +0100 Johannes Berg wrote:
> So we can avoid the potential deadlock in cfg80211 in a few ways:
>  1) export rtnl_lock_unregistering_all() or maybe a variant after
>     refactoring the two versions, to allow cfg80211 to use it, that way
>     netdev_run_todo() can never have a non-empty todo list
>  2) export __rtnl_unlock() so cfg80211 can avoid running
>     netdev_run_todo() in the unlock, personally I like this less because
>     it might encourage random drivers to use it
>  3) completely rework cfg80211's locking, adding a separate mutex for
>     the wiphy list so we don't need to acquire the RTNL at all here
>     (unless the ops need it, but there's no issue if we don't drop it),
>     something like
> I think I'm happy with 3) now (even if it took a couple of hours), so I
> think we can go with it, just need to go through all the possibilities.

I like 3) as well. FWIW a few places (e.g. mlx5, devlink, I think I've
seen more) had been converting to xarray for managing the "registered"
objects. It may be worth looking into if you're re-doing things, anyway.

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