netdev - Re: [PATCH net-next v2 1/1] ppp: Replace per-CPU recursion counter with lock-owner field

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Message-ID: <20250714200139.tgfgVP1L@linutronix.de>
Date: Mon, 14 Jul 2025 22:01:39 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Guillaume Nault <gnault@...hat.com>
Cc: netdev@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	linux-ppp@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Clark Williams <clrkwllms@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net-next v2 1/1] ppp: Replace per-CPU recursion counter
 with lock-owner field

On 2025-07-14 18:10:47 [+0200], Guillaume Nault wrote:
> On Thu, Jul 10, 2025 at 06:24:03PM +0200, Sebastian Andrzej Siewior wrote:
> > The per-CPU variable ppp::xmit_recursion is protecting against recursion
> > due to wrong configuration of the ppp channels. The per-CPU variable
> 
> I'd rather say that it's the ppp unit that is badly configured: it's
> the ppp unit that can creates the loop (as it creates a networking
> interface).

I can reword this.

> > index def84e87e05b2..0edc916e0a411 100644
> > --- a/drivers/net/ppp/ppp_generic.c
> > +++ b/drivers/net/ppp/ppp_generic.c
> > @@ -119,6 +119,11 @@ struct ppp_link_stats {
> >  	u64 tx_bytes;
> >  };
> >  
> > +struct ppp_xmit_recursion {
> > +	struct task_struct *owner;
> > +	local_lock_t bh_lock;
> > +};
> > +
> 
> This hunk conflicts with latest changes in net-next.

Thank you.

> Apart from the two minor comments above, the patch looks good to me.
> Thanks!

Okay. As of the people involved while this detection was added and
polished, do you have an opinion on v1?
	https://lore.kernel.org/all/20250627105013.Qtv54bEk@linutronix.de/

Sebastian