Dear Paul,

Thanks for your comments.

On Mon, Jun 22, 2026 at 05:59:53PM +0200, Paul Menzel wrote: 

Am 22.06.26 um 06:13 schrieb Ding Meng via Intel-wired-lan:

quoted

When CONFIG_NET_RX_BUSY_POLL is deactivated, fetching RX HW timestamps
from the NIC no longer works as expected.

Maybe paste some logs/errors, so it can be easier found by people with the
same issue.

Will do.
 

quoted

This occurs because disabling CONFIG_NET_RX_BUSY_POLL disables the
SKB NAPI mapping in __skb_mark_napi_id(). Consequently, get_timestamp()
fails to perform its driver lookup, and the igc driver's struct
net_device_ops::ndo_get_tstamp is never invoked.

Instead, get_timestamp() falls back to use shhwtstamps(skb)->hwtstamp,
a field that the driver has not populated.

Fix this by populating the hwtstamp field with the correct timestamp
in the default timer when CONFIG_NET_RX_BUSY_POLL is disabled.

Maybe detail, why the adapter needs to be passed now.

Also, please describe a test case to check the change.

Will do.

quoted

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 8ac16808023..1da8d7aa76d 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c

@@ -1992,7 +1992,26 @@ static struct sk_buff *igc_build_skb(struct igc_ring *rx_ring,
  	return skb;
  }
-static struct sk_buff *igc_construct_skb(struct igc_ring *rx_ring,
+static void igc_construct_skb_timestamps(struct igc_adapter *adapter,
+					 struct sk_buff *skb,
+					 struct igc_xdp_buff *ctx)
+{
+	if (!ctx->rx_ts)
+		return;
+#ifdef CONFIG_NET_RX_BUSY_POLL

Is there a way to do this in C instead of the pre-processor. That way all
the code gets build tested. (Is there a config with disabled
NET_RX_BUSY_POLL?)

 
How about defining a function to replace the pre-processor:

static inline bool is_net_rx_busy_poll()
{
#ifdef CONFIG_NET_RX_BUSY_POLL
        return true;
#else
        return false;
#endif
}

CONFIG_PREEMPT_RT=y && CONFIG_NETCONSOLE=y will cause NET_RX_BUSY_POLL
disabled.


Kind regards,
 
Ding Meng