linux-kernel - Re: [PATCH net-next 1/3] net: netpoll: Defer skb

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Message-ID: <20241031182647.3fbb2ac4@kernel.org>
Date: Thu, 31 Oct 2024 18:26:47 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: horms@...nel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, thepacketgeek@...il.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, davej@...emonkey.org.uk, vlad.wing@...il.com,
 max@...sevol.com, kernel-team@...a.com, jiri@...nulli.us, jv@...sburgh.net,
 andy@...yhouse.net, aehkn@...hub.one, Rik van Riel <riel@...riel.com>, Al
 Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH net-next 1/3] net: netpoll: Defer skb_pool population
 until setup success

On Fri, 25 Oct 2024 07:20:18 -0700 Breno Leitao wrote:
> The current implementation has a flaw where it populates the skb_pool
> with 32 SKBs before calling __netpoll_setup(). If the setup fails, the
> skb_pool buffer will persist indefinitely and never be cleaned up.
> 
> This change moves the skb_pool population to after the successful
> completion of __netpoll_setup(), ensuring that the buffers are not
> unnecessarily retained. Additionally, this modification alleviates rtnl
> lock pressure by allowing the buffer filling to occur outside of the
> lock.

arguably if the setup succeeds there would now be a window of time
where np is active but pool is empty.