netdev - Re: [PATCH net-next v4 11/12] docs: net: document new locking reality

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Message-ID: <20250218185323.70f61e4f@kernel.org>
Date: Tue, 18 Feb 2025 18:53:23 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, Saeed Mahameed <saeed@...nel.org>
Subject: Re: [PATCH net-next v4 11/12] docs: net: document new locking
 reality

On Mon, 17 Feb 2025 18:09:47 -0800 Stanislav Fomichev wrote:
> +RTNL and netdev instance lock
> +=============================
> +
> +Historically, all networking control operations were protected by a single
> +global lock known as RTNL. There is an ongoing effort to replace this global

I think RTNL stands for RouTeNetLink. RTNL -> rtnl_lock here?

> +lock with separate locks for each network namespace. The netdev instance lock
> +represents another step towards making the locking mechanism more granular.

Reads a bit like the per-netns and instance locks are related.
Maybe rephrase as:

  lock with separate locks for each network namespace. Additionally, properties
  of individual netdev are increasingly protected by per-netdev locks.

> +For device drivers that implement shaping or queue management APIs, all control
> +operations will be performed under the netdev instance lock. Currently, this
> +instance lock is acquired within the context of RTNL. In the future, there will
> +be an option for individual drivers to opt out of using RTNL and instead
> +perform their control operations directly under the netdev instance lock.
> +
> +Devices drivers are encouraged to rely on the instance lock where possible.