linux-kernel - Re: [PATCH net 1/2] net: ravb: Fix missing rtnl lock in suspend path

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Message-ID: <20250123153817.398ee16f@kmaincent-XPS-13-7390>
Date: Thu, 23 Jan 2025 15:38:17 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Claudiu Beznea <claudiu.beznea@...on.dev>
Cc: Paul Barker <paul.barker.ct@...renesas.com>, Niklas Söderlund <niklas.soderlund@...natech.se>, 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>, Mikhail Ulyanov
 <mikhail.ulyanov@...entembedded.com>, Sergei Shtylyov
 <sergei.shtylyov@...entembedded.com>, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, Niklas Söderlund
 <niklas.soderlund+renesas@...natech.se>, Claudiu Beznea
 <claudiu.beznea.uj@...renesas.com>, netdev@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ravb: Fix missing rtnl lock in suspend
 path

On Thu, 23 Jan 2025 16:17:58 +0200
Claudiu Beznea <claudiu.beznea@...on.dev> wrote:

> On 23.01.2025 16:08, Kory Maincent wrote:
> > On Thu, 23 Jan 2025 13:33:30 +0200
> > Claudiu Beznea <claudiu.beznea@...on.dev> wrote:
> >   
> >> Hi, Kory,
> >>
> >> On 22.01.2025 18:19, Kory Maincent wrote:  
>  [...]  
> >   
> >>
> >> I've test it. Looks good.
> >>
> >> Thank you for your patch. However, I think this could be simplified. The
> >> locking scheme looks complicated to me. E.g., this one works too:
> >>
> >> diff --git a/drivers/net/ethernet/renesas/ravb_main.c
> >> b/drivers/net/ethernet/renesas/ravb_main.c
> >> index bc395294a32d..cfe4f0f364f3 100644
> >> --- a/drivers/net/ethernet/renesas/ravb_main.c
> >> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> >> @@ -3217,10 +3217,16 @@ static int ravb_suspend(struct device *dev)
> >>
> >>         netif_device_detach(ndev);
> >>
> >> -       if (priv->wol_enabled)
> >> -               return ravb_wol_setup(ndev);
> >> +       if (priv->wol_enabled) {
> >> +               rtnl_lock();
> >> +               ret = ravb_wol_setup(ndev);
> >> +               rtnl_unlock();
> >> +               return ret;
> >> +       }  
> > 
> > What happen if wol_enabled flag changes it state between the rtnl_lock and
> > the if condition? We will be in the wrong path.  
> 
> wol_enabled flag can't change in this suspend phase. The user space tasks
> are fronzen when ravb_suspend() is called.

Oh ok, I don't now the suspend path but if it can't conflict we can got for your
proposition.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com