Hi Vincent,
Oh ok I didn't know this facility. I'm pushing a new patch that includes it. Thanks for that!
FYI the frequency and number of these notifications means net_ratelimit() may not be enough in the long run.
— Stéphane
De : Vincent Mailhol <vincent.mailhol@xxxxxxxxx>
Envoyé : vendredi 16 février 2024 02:37
À : Stéphane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
Cc : linux-can Mailing List <linux-can@xxxxxxxxxxxxxxx>
Objet : Re: [PATCH 3/3] can: peak_usb: fix potential kernel log flooding
Hi Stéphane,
On Fri. 16 Feb. 2024 at 00:27, Stephane Grosjean
<s.grosjean@xxxxxxxxxxxxxxx> wrote:
> In rare cases of very high bus load, the firmware can generate messages
> warning that the receive cache capacity is about to be exceeded.
> This modification prevents the driver from flooding the kernel log with
> messages and memory dumps that are far too verbose in such cases,
> by limiting their production to once per session.
>
> Signed-off-by: Stephane Grosjean <s.grosjean@xxxxxxxxxxxxxxx>
> ---
> drivers/net/can/usb/peak_usb/pcan_usb_fd.c | 36 ++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
> index a1c339716776..d444ff0fa7cc 100644
> --- a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
> +++ b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
> @@ -70,6 +70,7 @@ struct pcan_usb_fd_if {
> struct pcan_usb_fd_device {
> struct peak_usb_device dev;
> struct can_berr_counter bec;
> + bool rx_cache_warn_handled;
> struct pcan_usb_fd_if *usb_if;
> u8 *cmd_buffer_addr;
> };
> @@ -667,6 +668,28 @@ static int pcan_usb_fd_decode_error(struct pcan_usb_fd_if *usb_if,
> return 0;
> }
>
> +/* Handle uCAN Rx cache warning messages.
> + *
> + * Such messages SHOULD NOT occur. If they do, then this might come from
> + * massive PING host flooding that prevents PCAN-USB Pro FD HW v4 to handle
> + * CAN traffic anymore. In this case, the driver itself manages the display of
> + * the warning message.
> + */
> +static void pcan_usb_fd_handle_rx_cache_warn(struct peak_usb_device *dev,
> + struct pucan_msg *rx_msg)
> +{
> + struct pcan_usb_fd_device *pdev =
> + container_of(dev, struct pcan_usb_fd_device, dev);
> +
> + if (pdev->rx_cache_warn_handled)
> + return;
> +
> + netdev_warn(dev->netdev,
> + "Rx cache size warning! Possible loss of frames\n");
Did you consider using netdev_warn_once?
https://elixir.bootlin.com/linux/v6.7/source/include/net/net_debug.h#L46
This seems to do pretty much what you want.
FYI, the net_ratelimit() may also be helpful here:
if (net_ratelimit())
netdev_warn(...);
> + pdev->rx_cache_warn_handled = true;
> +}
> +
> /* handle uCAN overrun message */
> static int pcan_usb_fd_decode_overrun(struct pcan_usb_fd_if *usb_if,
> struct pucan_msg *rx_msg)
> @@ -768,6 +791,14 @@ static int pcan_usb_fd_decode_buf(struct peak_usb_device *dev, struct urb *urb)
> goto fail;
> break;
>
> + case PUCAN_MSG_CACHE_CRITICAL:
> + pcan_usb_fd_handle_rx_cache_warn(dev, rx_msg);
> +
> + /* Rx cache warning means possible overrun cases in
> + * the device.
> + */
> + fallthrough;
> +
> case PCAN_UFD_MSG_OVERRUN:
> err = pcan_usb_fd_decode_overrun(usb_if, rx_msg);
> if (err < 0)
> @@ -885,6 +916,11 @@ static int pcan_usb_fd_start(struct peak_usb_device *dev)
> pdev->bec.txerr = 0;
> pdev->bec.rxerr = 0;
>
> + /* warn of a cache problem only once per session, to avoid flooding
> + * the kernel log.
> + */
> + pdev->rx_cache_warn_handled = false;
> +
> return err;
> }
--
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