Re: net: macb: can macb use __napi_schedule_irqoff() instead of __napi_schedule()

[Heiner Kallweit]

On 11.01.2021 20:45, Paul Thomas wrote:
> Hello, recently I was doing a lot of tracing/profiling to understand
> an issue we were having. Anyway, during this I ran across
> __napi_schedule_irqoff() where the comment in dev.c says "Variant of
> __napi_schedule() assuming hard irqs are masked".
> 
> It looks like the queue_writel(queue, IDR, bp->rx_intr_mask); call
> just before the __napi_schedule() call in macb_main.c is doing this
> hard irq masking? So could it change to be like this?
> 
It's unsafe under forced irq threading. There has been a number of
discussions about this topic in the past.

> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -1616,7 +1623,7 @@ static irqreturn_t macb_interrupt(int irq, void *dev_id)
> 
>                         if (napi_schedule_prep(&queue->napi)) {
>                                 netdev_vdbg(bp->dev, "scheduling RX softirq\n");
> -                               __napi_schedule(&queue->napi);
> +                               __napi_schedule_irqoff(&queue->napi);
>                         }
>                 }
> 
> -Paul
>