[Intel-wired-lan] [PATCH net] igc: remove napi_synchronize() in igc_down()

[Intel-wired-lan] [PATCH net] igc: remove napi_synchronize() in igc_down()

[David Carlier]

When an AF_XDP zero-copy application is killed abruptly, the XSK pool is
torn down but NAPI keeps polling. igc_clean_rx_irq_zc() then returns the
full budget on every poll, so napi_complete_done() never clears
NAPI_STATE_SCHED.

igc_down() calls napi_synchronize() before napi_disable(), so it spins
forever waiting for that bit and the interface never goes down. Drop the
napi_synchronize() and let napi_disable() do the job -- it sets
NAPI_STATE_DISABLE, which forces the stuck poll to complete. Reorder it
ahead of igc_set_queue_napi() so the NAPI mapping is cleared only after
polling has stopped, matching the recent igb fix b1e067240379.

Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 2c9e2dfd8499..b3883a5a7d7a 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -5352,9 +5352,8 @@ void igc_down(struct igc_adapter *adapter)
 
 	for (i = 0; i < adapter->num_q_vectors; i++) {
 		if (adapter->q_vector[i]) {
-			napi_synchronize(&adapter->q_vector[i]->napi);
-			igc_set_queue_napi(adapter, i, NULL);
 			napi_disable(&adapter->q_vector[i]->napi);
+			igc_set_queue_napi(adapter, i, NULL);
 		}
 	}
 
-- 
2.53.0

Re: [Intel-wired-lan] [PATCH net] igc: remove napi_synchronize() in igc_down()

[Maciej Fijalkowski]

On Sun, Jul 12, 2026 at 02:22:42PM +0100, David Carlier wrote:
> When an AF_XDP zero-copy application is killed abruptly, the XSK pool is
> torn down but NAPI keeps polling. igc_clean_rx_irq_zc() then returns the
> full budget on every poll, so napi_complete_done() never clears
> NAPI_STATE_SCHED.
> 
> igc_down() calls napi_synchronize() before napi_disable(), so it spins
> forever waiting for that bit and the interface never goes down. Drop the
> napi_synchronize() and let napi_disable() do the job -- it sets
> NAPI_STATE_DISABLE, which forces the stuck poll to complete. Reorder it
> ahead of igc_set_queue_napi() so the NAPI mapping is cleared only after
> polling has stopped, matching the recent igb fix b1e067240379.
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: David Carlier <devnexen@gmail.com>

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

This is a mirror of what Alex Dvoretsky did on igb, correct? Did you
reproduce the same issue on your side or is it a blind shot at this
driver?

Regardless, I think it's a correct thing to do, but some clarification
would be nice.

> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 2c9e2dfd8499..b3883a5a7d7a 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -5352,9 +5352,8 @@ void igc_down(struct igc_adapter *adapter)
>  
>  	for (i = 0; i < adapter->num_q_vectors; i++) {
>  		if (adapter->q_vector[i]) {
> -			napi_synchronize(&adapter->q_vector[i]->napi);
> -			igc_set_queue_napi(adapter, i, NULL);
>  			napi_disable(&adapter->q_vector[i]->napi);
> +			igc_set_queue_napi(adapter, i, NULL);
>  		}
>  	}
>  
> -- 
> 2.53.0
>