netdev - Re: [PATCH net-next 1/3] ppp: convert rlock to rwlock to improve RX concurrency

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Message-ID: <CALW65jarGfgtkSJ3pdNTxgDpjzN-K_unqz3GWqH=BHdhmHKMug@mail.gmail.com>
Date: Fri, 27 Jun 2025 17:23:47 +0800
From: Qingfang Deng <dqfext@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Guillaume Nault <gnault@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	linux-ppp@...r.kernel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] ppp: convert rlock to rwlock to improve RX concurrency

On Fri, Jun 27, 2025 at 2:50 PM Eric Dumazet <edumazet@...gle.com> wrote:
> tldr: network maintainers do not want rwlock back.
>
> If you really care about concurrency, do not use rwlock, because it is
> more expensive than a spinlock and very problematic.
>
> Instead use RCU for readers, and spinlock for the parts needing exclusion.
>
> Adding rwlock in network fast path is almost always a very bad choice.
>
> Take a look at commit 0daf07e527095e6 for gory details.

Thanks for the info, I'll see how to refactor it using RCU instead.