linux-kernel - Re: [PATCH v2] can: m_can: apply rate-limiting to lost msg in rx

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Message-ID: <ku5336aidq5j24dswy5egbuse6a6jpfmf5j7ochenifxzy7he7@lth6f55c4nz4>
Date: Fri, 11 Jul 2025 09:58:53 +0000
From: Sean Nyekjaer <sean@...nix.com>
To: Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Chandrasekar Ramakrishnan <rcsekar@...sung.com>, Vincent Mailhol <mailhol.vincent@...adoo.fr>, Fengguang Wu <fengguang.wu@...el.com>, Varka Bhadram <varkabhadram@...il.com>, Dong Aisheng <b29396@...escale.com>, linux-can@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] can: m_can: apply rate-limiting to lost msg in rx

Hi,

On Fri, Jul 11, 2025 at 11:33:35AM +0100, Marc Kleine-Budde wrote:
> On 30.06.2025 09:52:44, Sean Nyekjaer wrote:
> > Wrap the "msg lost in rxf0" error in m_can_handle_lost_msg() with
> > a call to net_ratelimit() to prevent flooding the kernel log
> > with repeated debug messages.
> >
> > Fixes: e0d1f4816f2a ("can: m_can: add Bosch M_CAN controller support")
> > Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
> > Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> > ---
> > Changes in v2:
> > - Changed to dbg msg
> > - Link to v1: https://lore.kernel.org/r/20250620-mcan_ratelimit-v1-1-e747ee30f71f@geanix.com
> > ---
> >  drivers/net/can/m_can/m_can.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> > index 6c656bfdb3235e1f5d6405c49b07b821ddacc1b9..9f43111609d364c01c6df10489fc4708deab9fbb 100644
> > --- a/drivers/net/can/m_can/m_can.c
> > +++ b/drivers/net/can/m_can/m_can.c
> > @@ -665,7 +665,8 @@ static int m_can_handle_lost_msg(struct net_device *dev)
> >  	struct can_frame *frame;
> >  	u32 timestamp = 0;
> >
> > -	netdev_err(dev, "msg lost in rxf0\n");
> > +	if (net_ratelimit())
> > +		netdev_dbg(dev, "msg lost in rxf0\n");
> 
> This has some subtle side effects. Even if debugging is not enabled, you
> will still get the "... output lines suppressed due to ratelimiting"
> message, which is IMHO very confusing :)

Indeed yes :)

> 
> What about replacing the netdev_err() by netdev_dbg()?
> 
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -665,7 +665,7 @@ static int m_can_handle_lost_msg(struct net_device *dev)
>         struct can_frame *frame;
>         u32 timestamp = 0;
> 
> -       netdev_err(dev, "msg lost in rxf0\n");
> +       netdev_dbg(dev, "msg lost in rxf0\n");
> 
>         stats->rx_errors++;
>         stats->rx_over_errors++;
> 

Yeah that will do. V3 or?

/Sean