Re: [PATCH net-next] netdevsim: Register and unregister devlink traps on probe/remove device

Jakub Kicinski
2021-10-27T19:28:32Z

On Wed, 27 Oct 2021 22:15:41 +0300 Leon Romanovsky wrote:
> One of the outcomes is that such chain usually prevents from us to ensure
> proper locking annotation.
>
> Let's take as an example devlink_trap_policers_register().
> In some drivers, it is called before device_register() and we don't need
> any locks at all, because we are in initialization flow.
>
> In mlxsw, it is called during devlink reload, and we don't really need to
> lock it too, because we were supposed to lock everything for the reload.
>
> However, for the mlxsw, we created devlink_trap_policers_register() to be
> dynamic, so we must lock devlink->lock, as we don't know how other users
> of this API will use it.
>
> In the reality, no one uses it dynamically except mlxsw and we stuck
> with function that calls to useless lock without us able to properly
> annotate it with an invitation to misuse.
>
> It is an example of layering problem, there are many more subtle issues
> like this that require some cabal knowledge of proper locks to make it
> is safe.

Now that you made me express my opinion I started feeling attached to
my way of thinking :) Let me try to convert devlink core, netdevsim and
nfp to devlink instance locking and see how far I can get...