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

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Message-ID: <CALW65jasGOz_EKHPhKPNQf3i0Sxr1DQyBWBeXm=bbKRdDusAKg@mail.gmail.com>
Date: Fri, 27 Jun 2025 11:58:58 +0800
From: Qingfang Deng <dqfext@...il.com>
To: Guillaume Nault <gnault@...hat.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, 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 12:23 AM Guillaume Nault <gnault@...hat.com> wrote:
> That doesn't look right. Several PPP Rx features are stateful
> (multilink, compression, etc.) and the current implementations
> currently don't take any precaution when updating the shared states.
>
> For example, see how bsd_decompress() (in bsd_comp.c) updates db->*
> fields all over the place. This db variable comes from ppp->rc_state,
> which is passed as parameter of the ppp->rcomp->decompress() call in
> ppp_decompress_frame().
>
> I think a lot of work would be needed before we could allow
> ppp_do_recv() to run concurrently on the same struct ppp.

Right. I think we can grab a write lock where it updates struct ppp.