# Re: \[PATCH net\] net: lantiq: disable interrupt before sheduling NAPI

- From: Hauke Mehrtens \<hauke@hauke-m.de\>
- Date: 2021-06-08 21:33:49 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/06/1407626
- Thread: https://ratatoskr.run/netdev/2021/06/1407602/t.md

```text
On 6/8/21 11:21 PM, Aleksander Jan Bajkowski wrote:
> This patch fixes TX hangs with threaded NAPI enabled. The scheduled
> NAPI seems to be executed in parallel with the interrupt on second
> thread. Sometimes it happens that ltq_dma_disable_irq() is executed
> after xrx200_tx_housekeeping(). The symptom is that TX interrupts
> are disabled in the DMA controller. As a result, the TX hangs after
> a few seconds of the iperf test. Scheduling NAPI after disabling
> interrupts fixes this issue.
>
> Tested on Lantiq xRX200 (BT Home Hub 5A).
>
> Fixes: 9423361da523 ("net: lantiq: Disable IRQs only if NAPI gets scheduled ")
> Signed-off-by: Aleksander Jan Bajkowski <redacted>

Acked-by: Hauke Mehrtens <hauke@hauke-m.de>

> ---
>   drivers/net/ethernet/lantiq_xrx200.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/lantiq_xrx200.c b/drivers/net/ethernet/lantiq_xrx200.c
> index 36dc3e5f6218..0e10d8aeffe1 100644
> --- a/drivers/net/ethernet/lantiq_xrx200.c
> +++ b/drivers/net/ethernet/lantiq_xrx200.c
> @@ -352,8 +352,8 @@ static irqreturn_t xrx200_dma_irq(int irq, void *ptr)
>   	struct xrx200_chan *ch = ptr;
>   
>   	if (napi_schedule_prep(&ch->napi)) {
> -		__napi_schedule(&ch->napi);
>   		ltq_dma_disable_irq(&ch->dma);
> +		__napi_schedule(&ch->napi);
>   	}
>   
>   	ltq_dma_ack_irq(&ch->dma);
>

```