[PATCH] can: ctucanfd: ctucan_err_interrupt(): do not emit info messages on Arbitration Lost or CAN Bus Error IRQs

[PATCH] can: ctucanfd: ctucan_err_interrupt(): do not emit info messages on Arbitration Lost or CAN Bus Error IRQs

[Marc Kleine-Budde]

Since commit e74bae899529 ("can: ctucanfd: handle bus error interrupts")
CAN bus error interrupts are properly handled.

With activated CAN Bus Error reporting, Arbitration Lost (ALI) and Bus Error
(BEI) interrupts are enabled. These can occur at a very high rate (~10kHz).

To avoid flooding the system, don't emit a netdev_info() for these.

Fixes: e74bae899529 ("can: ctucanfd: handle bus error interrupts")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/ctucanfd/ctucanfd_base.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c
index 07d4aa43c700..9aec18681fc5 100644
--- a/drivers/net/can/ctucanfd/ctucanfd_base.c
+++ b/drivers/net/can/ctucanfd/ctucanfd_base.c
@@ -884,8 +884,6 @@ static void ctucan_err_interrupt(struct net_device *ndev, u32 isr)
 
 	/* Check for Arbitration Lost interrupt */
 	if (FIELD_GET(REG_INT_STAT_ALI, isr)) {
-		if (dologerr)
-			netdev_info(ndev, "arbitration lost\n");
 		priv->can.can_stats.arbitration_lost++;
 		if (skb) {
 			cf->can_id |= CAN_ERR_LOSTARB;
@@ -895,7 +893,6 @@ static void ctucan_err_interrupt(struct net_device *ndev, u32 isr)
 
 	/* Check for Bus Error interrupt */
 	if (FIELD_GET(REG_INT_STAT_BEI, isr)) {
-		netdev_info(ndev, "bus error\n");
 		priv->can.can_stats.bus_error++;
 		stats->rx_errors++;
 		if (skb) {

---
base-commit: cd0784790d921ff4f7438d3b7ccda86068c8b766
change-id: 20260805-ctucanfd-silence-can-bus-error-messages-5c5bcd6860f8

Best regards,
--  
Marc Kleine-Budde <mkl@pengutronix.de>

Re: [PATCH] can: ctucanfd: ctucan_err_interrupt(): do not emit info messages on Arbitration Lost or CAN Bus Error IRQs

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Unconditional evaluation of the global `net_ratelimit()` in a high-frequency (10kHz) interrupt handler exhausts the global network ratelimit token bucket and causes lock contention, effectively silencing rate-limited messages across the entire networking subsystem. Furthermore, the generic `netdev_info` print at the top of the function still executes for these noisy interrupts, meaning the patch fails to completely fix the log flooding it aimed to resolve.
--

--- Patch [1]: [PATCH] can: ctucanfd: ctucan_err_interrupt(): do not emit info messages on Arbitration Lost or CAN Bus Error IRQs ---
commit 5e775ed40c20c9c562c6441b9b627d0ada3f07fd
Author: Marc Kleine-Budde <mkl@pengutronix.de>

can: ctucanfd: ctucan_err_interrupt(): do not emit info messages on Arbitration Lost or CAN Bus Error IRQs

With CAN Bus Error reporting enabled, Arbitration Lost and Bus Error
interrupts can occur at a very high rate (~10kHz). To avoid flooding the
system, this commit stops emitting specific netdev_info messages for these
interrupts.

> diff --git a/drivers/net/can/ctucanfd/ctucanfd_base.c b/drivers/net/can/ctucanfd/ctucanfd_base.c
> index 07d4aa43c700a..9aec18681fc54 100644
> --- a/drivers/net/can/ctucanfd/ctucanfd_base.c
> +++ b/drivers/net/can/ctucanfd/ctucanfd_base.c
> @@ -884,8 +884,6 @@ static void ctucan_err_interrupt(struct net_device *ndev, u32 isr)

[Severity: High]
This isn't a bug introduced by this patch, but does calling net_ratelimit()
unconditionally at the top of this function exhaust the global rate limit
token bucket?

Looking at ctucan_err_interrupt() earlier in this file:

	int dologerr = net_ratelimit();

	ctucan_get_rec_tec(priv, &bec);
	state = ctucan_read_fault_state(priv);
	err_capt_alc = ctucan_read32(priv, CTUCANFD_ERR_CAPT);

	if (dologerr)
		netdev_info(ndev, "%s: ISR = 0x%08x...

Since ALI and BEI interrupts can still occur at ~10kHz and trigger this
handler, won't this still drain the shared ratelimit budget and cause lock
contention on net_ratelimit_state.lock for the rest of the networking
subsystem?

Also, since the generic netdev_info log statement above is still executed
for these noisy interrupts, does this patch completely fix the log flooding
it aims to resolve?

>  
>  	/* Check for Arbitration Lost interrupt */
>  	if (FIELD_GET(REG_INT_STAT_ALI, isr)) {
> -		if (dologerr)
> -			netdev_info(ndev, "arbitration lost\n");
>  		priv->can.can_stats.arbitration_lost++;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260806-ctucanfd-silence-can-bus-error-messages-v1-1-70eff67debfd@pengutronix.de?part=1