linux-kernel - Re: [PATCH net-next] ppp: remove rwlock usage

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Message-ID: <CALW65jZToqXjwgO15vi8TWYnXyS_cY96r7V=k8gQwpSRP2TzEw@mail.gmail.com>
Date: Mon, 4 Aug 2025 17:29:32 +0800
From: Qingfang Deng <dqfext@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: 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] ppp: remove rwlock usage

Hi Eric,

On Mon, Aug 4, 2025 at 3:36 PM Eric Dumazet <edumazet@...gle.com> wrote:
> For all your patch :
>
> Since the spinlock is now only used from the control path in process
> context, what is the reason you use _bh() suffix
> blocking BH while holding it ?
>
> Also, a mere rcu_read_lock() is enough for ppp_dev_name() and
> ppp_unit_number() : No need to disable BH there.

You're right. I will drop the _bh suffix in a later patch.

>
> > +       synchronize_rcu();
> > +
> >         if (ppp) {
>
> You probably could move the synchronize_rcu() here, there is no need
> to call it if ppp is NULL

Got it.

>
> >                 /* remove it from the ppp unit's list */
> >                 ppp_lock(ppp);